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pipingdesigners.com Training Seminar

Section - I

A: ValvesBy: Anton Dooley

A valve is a mechanical device that regulates the flow of fluids (either gases, fluidised solids, slurries or liquids)by opening, closing, or partially obstructing various passageways.

Valves are used in a myriad of industrial, military, commercial, and residential applications. There are manydifferent types of valves:

Ball valve, which is good for on/off control;

Butterfly valve, particularly in large pipes;

Gate valve, mainly for on/off control;

Globe valve, which is good for regulating flow;

check valve or Non-return valve, allows the fluid to pass in one direction only;

A pressure relief valveor safety valve operates automatically at a set differential pressure to correct apotentially dangerous situation, typically over-pressure.

High purity valves, are flow control devices that meet the industry criteria for purity of materials and design.

Section - I

A1: Articles related to Valves

Valve TestingBy: United Valve (http://www.unitedvalve.com/art-valve_testing.htm)

THE INCREASE IN GLOBALLY SOURCED PRODUCTS AND MUCH-REDUCED DOMESTIC MANUFACTURING HASCAUSED EVERYONE IN THE VALVE SUPPLY CHAIN TO REQUEST AND REQUIRE MORE TESTING. HERES A LOOK

AT SOME OF THE MOST COMMON VALVE TESTING STANDARDS IN USE TODAY ..... (read more ......)

Why Valve Qualification Programs?

By: United Valve (http://www.unitedvalve.com/art-valve_qualification_06.htm)

As the valve world continues to turn and tilt its production towards new countries and their untestedmanufacturing plants, the potential backlash is a rise in quality issues. In decades past, when bottom-dollarpricing was not the chief procurement driver, higher quality cast steel valves, produced in the United States,Great Britain, and Japan could be counted upon. Unfortunately, the global economic realities of the past 10years have caused many of these companies to either cease production in their native countries or go out of

business altogether. ..... (read more ......)

The Ever-Popular Gate ValveBy: United Valve (http://www.unitedvalve.com/art-gate-valve.htm)

This low-tech valve may not have changed much in the last 100 years, but the gate valve plays a major role invirtually every refinery, chemical plant and industrial facility in the world.
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The most popular style of valve in the world of flow control is the gate valve. They are the on/off switches ofthe fluid control industry and they are found in every refinery, chemical plant, power plant and industrialfacility. Gate valves exist for one primary purpose- to stop flow. Because of this, they are often referred to asstop or block valves. Gate valves are manufactured in a wide range of sizes- from through 144. .....(read more ......)

The Gate Valves Long HistoryBy: United Valve (http://www.unitedvalve.com/art-gate-valve-history.htm)

The ubiquitous gate valve has a long history of serving the flow control industry in the United States. From itshumble beginnings during the middle of the 19th century, to its universal usage today, the gate valve hassoldiered on behind the scenes of Americas industrial pageantry.

The first valve patent in America was for a gate valve. It was issued in 1839 to New Haven resident, Charley W.Peckham. Although Mr. Peckham s patent was for a sluice gate valve, it was a gate valve nonetheless. Itwasnt until 1840 that the first gate valve as we would recognize it today was patented. It was called a stopcock and was issued to Theodore Scowden of Cincinnati, Ohio. Mr. Scowdens valve was actually aunidirectional gate valve with a primitive bolted bonnet. ..... (read more ......)

This low-tech valve may not have changed much in the last 100 years, but the gate valve plays a major role invirtually everyrefinery, chemical plant and industrial facility in the world.

The most popular style of valve in the world of flow control is the gate valve. They are the on/off switches ofthe fluidcontrol industry and they are found in every refinery, chemical plant, power plant and industrial facility. Gatevalves exist forone primary purpose- to stop flow. Because of this, they are often referred to as "stop" or "block" valves. Gatevalves aremanufactured in a wide range of sizes- from " through 144".

It is not recommended to operate gate valves in the partially open position, or to use them in throttling service.When a gatevalve is partially open, it closure element (disc or wedge) can vibrate against the seats and become scratched

causing them to lose their seating integrity.

The chief advantage of a gate valve is that it offers virtually no resistance to flow in the open position. Only afull port ball valvecan equal the gate valve's flow characteristics. Due to their symmetrical design and equilateral seating, gatevalves can beused to stop flow from either direction. They are available in every material from the shiny brass constructionof the diminutive" water valves on the hardware store shelf, to the exotic high alloy models found in nuclear powerinstallations.

Gate valves have been an important piece of fluid control equipment for over 150 years. In fact, the very firstvalve patentissued in the United States was for a "gate valve". Since those humble beginnings in the 19th century, the gatevalve hasanswered the fluid control call with relatively little basic design change.

From the outside, most gate valves look somewhat similar. However, inside there are a host of different designpossibilities.Most gate valves consist of a body and bonnet that contains a closure element, called a disc or a gate. Theclosure elementis attached to a stem that passes through the bonnet of the valve, ultimately interfacing with a handwheel orother device tooperate the stem. Pressure around the stem is contained through the use of packing material which iscompressed into apacking area or chamber.

Trim

The word "trim" is often overheard when valve professionals are talking about industrial gate valves. Trim has

nothing to dowith how slim and fit a valve is, rather it refers to the internal components of a valve that are exposed to greatstress or subject
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to a harsh combination of erosion and corrosion. In a gate valve the trim components are the stem, discseating area, bodyseats and backseat, if applicable. Common utility bronze or brass valves usually have trim parts of the samematerial as thebody and bonnet. Cast and ductile iron valves have either all iron trim components or occasionally bronze trim.The term for aniron valve with bronze trim is "iron body, bronze mounted" or IBBM for short.Because of their weldability, steel valves can be furnished with a number of different trims. Stellite, Hastelloy,

316ss, 347ss,Monel, and Alloy 20 are some of the materials regularly used for gate valve trim.

During most of the 19th century, valves were predominantly supplied with screwed end connections, even insizes as large as12" NPT. Since that time the flanged end connection has become the most popular. Other end connection typesin use todayinclude screwed, ring-type-joint (RTJ), Victaulic, Greyloc and water works "mechanical joint".

Disc Design

Gate valves can have one of two different disc designs: parallel or tapered type. Both operate on the principleof a closureelement (disc or gate) sliding into a slot in the pipeline and closing off the fluid path. The tapered disc of the

"wedge gate"valve is machined to match a pair of body seats set at the same angle, usually about 10o. If machinedcorrectly, as thetapered disc engages the seats, it locks firmly into place, stopping the flow.

Three types of wedge gates are available: solid disc, one piece flexible type, and two piece split design.

The solid wedge has been around the longest and at one time virtually all wedge gates were the solid type.Thedrawback to a solid design is that it does not have any flexibility and if there is any valve body/seat distortiondue toextreme temperature fluctuations or pipe stresses, the solid disc can become jammed in the seats. The soliddisc isstill standard on bronze, cast iron, water service and compact carbon steel valves (API 602 type). Today, soliddiscsare usually only available as special order items on large diameter gate valves.

The flexible wedge type is just that- flexible. By the addition of a groove or slot around its periphery, theflexible disccan adapt to temperature changes and adverse piping stresses without binding. The flexible design also is alittleeasier to manufacture, in that minor imperfections in the seating surface angles can be compensated for by thedisc'sflexibility. The "flex-wedge" design is by far the most common type seen on commodity gate valves used inindustrialapplications.

The split wedge type consists of a two-piece design with mating surfaces on the back side of each disc half.Thesemating surfaces allow the downward stem thrust to be uniformly transferred to the disc faces and onto theseats. This

flexible design also provides protection against jamming due to thermal expansion. A disadvantage to the splitdesignis that in "dirty" services, residue or debris can cake in between the disc halves, causing the valve to improperlyseator even jam. Split wedge designs are commonly found on stainless steel and high alloy valves, as well as manysmallbronze valves.

Wedge gates are guided by grooves or ribs cast or welded into the body of the valve. These wedge guides keepthe disc inalignment as it opens or closes and also keeps the disc from sliding against the downstream seat duringopening and closing.

The second disc design is the parallel type. Unlike the wedge type gate valve, which relies on the stem thrust to"wedge" the

disc into the seats to seal, the parallel seat valve needs some assistance to seal properly. The sealingassistance is usually in the form of a spring loaded or mechanically activated spreading action between the two


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disc halves as the valve closes fully.On most parallel seat designs the friction and sealing force is relieved as the gate disengages from the seats.

The most common use for parallel disc valves today is in the pipeline industry, where elastomer seat seals andambientoperating temperatures make valve virtually leak proof. Parallel gates are also used in some high pressure,high temperature steam applications, to help reduce the possibility of locking the disc in the closed position dueto a radical change in temperature.

Regardless of disc design or type, the gate valve closure element must come in perfect contact with seats in thevalve body.The body seats may be welded, screwed, pressed or swaged in, or be integral with the valve body. Mostindustrial steel gatevalves utilize seat rings that are welded into the valve body. For most of the 20th century the norm wasscrewed in seat ringsin steel valves. However, advances in welding and valve repair techniques made the screwed-in rings obsolete.Seat rings andvalve discs are also often overlaid with corrosion or abrasion resistant alloys to increase their service life.

Body-Bonnet Design

Gate valves are normally available in five different body/bonnet joint designs. They are: screwed, union,

bolted-bonnet,welded-bonnet & pressure-seal.

The screwed joint is the simplest design. However it is only used for inexpensive bronze valves that rarely ifeverrequire disassembled.

The union joint is also primarily used on bronze valves, but the union design allows for easier disassembly forrepairand maintenance.

The bolted-bonnet joint is the most popular joint and it is used on the vast majority of gate valves inindustrial usetoday. Unlike threaded and union bonnet valves, the bolted-bonnet connection requires a gasket to seal thejointbetween the body and bonnet. On lower pressure valves, sheet gasket materials are used. ANSI Class 150 steelvalves usually employ a corrugated soft iron or graphite/corrugated soft iron gasket. Valves of class 300 andhigheremploy either a spiral-wound or ring joint type gasket.

The pressure-seal joint is energized by the fluid pressure in the valve body acting upon a wedge shaped,soft ironor graphite gasket wedged between the body and bonnet. On a pressure-seal valve, the higher the body cavitypressure, the greater the force on the gasket. Pressure-seal bonnets are used extensively for high-pressurehigh-temperature applications, such as the power industry. Pressure-seal valves are much lighter than theircorrespondingbolted bonnet designs. Due to the pressure energization of the seal ring, they are normally not used in pressureclasses below ANSI class 600.

Welded bonnets are a very popular body-bonnet joint for compact steel valves in sizes " through 2" andpressureclasses 800 through 2500, where disassembly is not required. The higher pressure welded-bonnet type valvesrelyon threads to handle the force generated by the body cavity pressure, while a small peripheral weld bevelactuallycontains the pressure. Like pressure-seal valves, welded-bonnet valves are much lighter than their bolted-bonnetcounterparts.

Stem Design

Three different bonnet/stem designs are predominant in gate valve construction. They are: inside screw, risingstem (ISRS),non-rising stem (NRS), and outside screw and yoke (OS&Y).


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The ISRS bonnet/stem design is the most popular design in use today on bronze valves. Due to the fact thatitexposes the stem threads to the process fluid and potential corrosion damage which could cause a stem to discfailure, the ISRS design is not used for critical service industrial applications.

The NRS type is another special purpose type that is used in applications where there is limited verticalclearanceabove the handwheel, because on an NRS valve, the stem does not rise up as the valve is opened. Most NRSvalvestoday are manufactured of either iron or bronze. Some applications such as marine use, where clearances aretight,often use NRS steel gate valves.

The most common stem/bonnet design in use on industrial valves is the OS&Y. The OS&Y design is preferredfor corrosive environments because the threads are outside the fluid containment area. It also differs fromotherdesigns in that the handwheel is attached to a bushing at the top of the valve yoke, and not to the stem itself,thus thehandwheel does not rise as the valve is opened.

Also in the gate valve family are knife and sluice gates. The bonnetless knife gate is especially suited for use inslurries such as in pulp and paper mills. Knife gates are very thin, only slightly wider than there closure element(disc). Because of their unique geometry and thin cross-section, knife gates are limited to low pressure

applications.

In appearance, the sluice gate doesn't look like it even belongs in the gate valve family, however based uponits sliding discdesign; it is characterized as a gate valve. Sluice gates are limited to very low pressures, in most cases, simplehead pressure.They are used primarily in waste water and irrigation systems.

Valve Standards

Gate valves standards are produced by several standards making organizations, for a multitude of industries.Here are some of the better known gate valve specifications:

American Petroleum Institute*API 600 "Steel Gate Valves, Flanged & Butt welding Ends", it is a companion document to ISO 10434.*API 602 "Compact Steel Gate Valves"*API 603 "Corrosion Resistant Bolted Bonnet Gate Valves"*API 6D "Specification for Pipeline Valves", it is a companion document to ISO 14314.

Manufacturers Standardization Society*SP-70 "Cast Iron Gate Valves"*SP-80 "Bronze Gate, Globe, Angle and Check Valves"*SP-81 "Stainless Steel Bonnetless, Flanged, Knife Gate Valves"

American Waterworks Association*AWWA C500 "Metal-Seated Gate Valves for Water Supply Service"*AWWA C509 "Resilient-Seated Gate Valves for Water Supply Service"*AWWA C515 "Resilient-Seated Gate Valves for Water Supply Service"

American Society of Mechanical Engineers*B16.34 "Valves- Flanged, Threaded and Welding End"

Materials of Construction

Gate valves are manufactured in virtually every metal from Aluminum to Zirconium. They are alsomanufactured in a variety of engineering plastics. The most common materials however, are steel, iron andbronze.

Bronze offers the greatest machinability and the lowest manufacturing cost. The features that make bronzeeasy to machine,its lower strength and softness, also make the valve only suitable for lower pressure applications. Thepredominant service forbronze valves is on water and utility lines where pressures are lower than about 300 psi.


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Iron valves are in between bronze and steel as far as strength goes. The iron is slightly harder to machine, butthe iron castings are relatively easy to pour. Iron for valves is commonly two types; grey or cast iron andmalleable iron. In refinery and petrochemical service iron valves are usually restricted to low pressure waterlines. The high carbon content and better rust resistance of iron valves makes them more suitable for buriedservice than steel valves.

For industrial valves, steel is the material of choice. A broad spectrum of steels are utilized for valveconstruction, from the lowest grade WCB, to the chrome/moly's. Unlike the brasses, bronzes and irons, moststeels and low alloys are readilyweldable, which makes them easier to modify, repair and in some cases even easier to manufacture. Gatevalves are alsomanufactured in a number of exotic alloys from Titanium to Zirconium.

There have been several attempts to make the gate valve obsolete and take away its market share, but theyhave only metwith limited success. The first challenger to the gate valve throne was the ball valve, which came intoprominence during themiddle part of the 20th century. Ball valves have been substituted for gate valves in many lower pressure andlowertemperature applications, but in some cases they are more expensive to manufacture and repair. Theelastomer seats of theball valve also limit them to temperatures below about 500 degrees F.

Butterfly valves have supplanted gate valves in some of the larger (48" and above) low pressure applications,such as waterworks usage. The metal-seated butterfly valve has also been successful in certain critical service applicationsthat once weresolely the realm of the gate valve, but their high initial cost and very high repair costs make them unlikely toever completelyreplace the venerable gate valve.

Gate Valve Actuation

The most common method of opening and closing (actuating) a valve is through a handwheel attached to theyoke or bonnet.This works fine on moderate size valves operating at reasonable pressures, but some severe operatingsituations call for more muscle. For example, an 18", class 1500, main steam isolating valve in a power plantoperating at 1750 psi and 1000 degrees F. requires a huge amount of torque to open under pressure. The onlysolution is remote actuation- usually in the form of an electric motor or hydraulic actuator.

Additional gate valve actuation can be provided by pneumatic cylinders. In some cases these sit directly on topof the yoke and are attached directly to the stem, to provide a quick-opening form of actuation. For additionalleverage a standard gate valve might have a manual gear operator attached to it to decrease the amount offorce required to open and close it under pressure.These devices are called bevel gears.

Repair of Gate Valves

Industrial gate valves are often used in harsh environments and sometimes these valves need to be repaired.The decision to repair or replace a valve usually is a result of comparing the replacement cost to the repaircost. When the repair cost exceeds 50-65% of the cost of a new valve, the decision is usually to replace thevalve, unless the delivery is unacceptable.

Generally speaking, all bronze valves, except for expensive cryogenic designs, are replaced rather thanrepaired. Iron valves,except for the largest sizes, are also replaced rather than repaired. Steel and alloy gate valves are the mostrepaired types.Steel valves smaller than 12", class 150 are usually not repaired, unless replacements are not readily available.On the otherhand, high alloy gate valves as small as " size may be repaired because of their high cost and long lead time.

Some gate valves, such as large diameter, butt-weld end and pressure-seal types are often repaired in thefield. These fieldrepairs are often difficult and pose logistical challenges, but compared to the cost of removing them from theline and shipping them to a repair facility, field repair is more economical option.

Gate valves are still the primary choice for many service applications. Their cost of manufacture to value ratio is

still very high.On typical petrochemical and refining projects today, the percentage of gate valves on the requisition is about60-70%.


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Although science and technology has made tremendous leaps during the past 50 years, most gate valves arestill beingproduced to the same basic designs developed a hundred years ago. And until someone invents a Buck Rogerslaser valvewith no moving parts, tens of thousands of gate valves will still be manufactured each year, in plants fromSouth Carolina toSoutheast Asia.

References:

API 600 Steel Valves - Flanged & Butt welded Ends API 600 is the primary steel gate valve purchasespecification. Valvedesign and construction criteria are detailed, as well as materials and trim designations. An appendix containsinformationpertaining to pressure seal valves. ISO Standard 10434 is essentially the same as API 600, only published inthe ISOformat.

API 602 Compact Steel Gate Valves- Flanged, Threaded, Welding and Extended-Body Ends API 602 isthe 4" & smallerforged steel gate valve purchase specification. Valve design and construction criteria are detailed, as well asmaterials and

trim designations. Future versions of this document are expected to include requirements for bellows seal gatevalves.

API 603 Class 150, Cast, Corrosion-Resistant, Flanged-End Gate Valves API 603 covers light walled gatevalves in size NPS 1/2" through 24", in classes 150, 300 & 600. These valves are used in applications where thethicker API 600 casting isnot needed.

API 608 Metal Ball Valves-Flanged and Butt-Welding Ends API 608 is the purchase specification for class150 and class300 metal ball valves. Valve design and construction criteria are detailed. Important Note- ball valve workingpressures shouldbe based on seat material, not valve class.

API 609 Butterfly Valves, Lug-Type and Wafer Type API 609 is the purchase specification for butterfly

valves with lug-typeand wafer-type configurations designed for installation between ANSI B16 flanges, through Class 600.

API 598 Valve Inspection & Testing API 598 covers the testing and inspection requirements for gate, globe,check, ball,plug & butterfly valves. Steel valve pressure ratings found in ASME/ANSI B16.34 are required to determine API598 testpressures for steel valves.

API 6D Specification for Pipeline Valves (Gate, Plug, Ball and Check Valves) Specification for PipelineValves (Gate,Plug, Ball and Check Valves) API 6D is the primary standard for valves used in pipeline service, including gate,plug, ball andcheck valves. Occasionally refinery and petrochemical purchasers will reference the more stringent testingrequirements of 6D

although the valve may have built under API 600, 602, 608 or 609 design criteria.

ASME/ANSI B16.34 Steel Valves - Flanged & Butt welded Ends ASME B16.34 is the base document fromwhich steelvalve pressure/temperature ratings are derived. It also offers additional valve specification data includingnondestructiveexamination procedures for upgrading valves to Special Class. Note: Gate valves manufactured under B16.34wall thicknessminimums may not meet the minimum wall thickness requirement of API 600 & API 602 for class 150, 300 and600.

ASME/ANSI B16.10 Face-to-Face Dimensions of Ferrous Valves B16.10 lists the face to face dimensions ofall flanged andbutt-weld end valves. Screwed and socket weld end valve face-to-face dimensions are not included in thisspecification.

MSS SP-55 Quality Standard for Steel Castings for Valves, Flanges and Fittings and Other PipingComponents SP-


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55 details the visual inspection criteria for castings. This specification is listed as part of the procedure underAPI 598. NACEMR-0175 Standard Material Requirements for Sulfide Stress Cracking Resistant Metallic Materials For OilfieldEquipment MR-0175 is the "standard" for materials used in "sour" environments such as found in piping systems in manyrefineries. It listsmaterials, mechanical properties and heat treatments for metals used in Hydrogen Sulfide bearing hydrocarbonservice.

The Ever-Popular Gate Valve, By: Greg Johnson

Valve Repair, a Changing & ChallengingBusinessBy: United Valve (http://www.unitedvalve.com/art-vm_valve_repair.htm)

Who Moved my Cheese? The heck with who moved my cheese, who moved my valve repair customers! Thoseof us in the valve repair business can certainly relate to Dr. Spencer Johnsons book, Who Moved My Cheese,which deals with handling change. The way our business is rapidly changing, it feels like just about the time wefigure out what the customer needs and how best to meet that need, some new paradigm takes over in themaintenance arena and voila the rules have changed again!

In the 50s and 60s, to be successful in the valve repair business all that was required was some mechanicalability, good people skills and a nice fishing boat or a prolific deer hunting lease. Since then, we have seen theindustry morph its way through end-user AMLs, manufacturers authorizations, OEM service centers, API ValveRepair Standards, ISO 9000, preventative maintenance and run-to-failure mode. The only constant through itall has been that there are still valves being repaired. ..... (read more ......)

Valve ModificationBy: United Valve (http://www.unitedvalve.com/art-

valve_modification.htm)

In a perfect world of valve supply and demand, an end-user would be able to purchase any combination ofvalve configurations from the distributor with only a few days notice. The commonly-stocked standard trimvalves would share shelf space with the most unusual trimmed or end-configured valves. However, in this worldof globally procured commodity steel valves and just-in-time inventories, it is not a financially viable option.So in order to meet the demand for these specials in the United States, the valve modification industry wascreated. ..... (read more ......)

Valve Owners Survival KitBy: United Valve (http://www.unitedvalve.com/art-

valve_survival.htm)

Its a jungle out there, so the saying goes. Unfortunately, that jungle extends to and includes your workenvironment. And if you are responsible for some part of a chemical processing facility, the vines and beasts ofthat jungle wrap around and through the pipe racks, instrument panels and valves you call home everyworkday.

If this sounds familiar to you then you probably wont turn down a little survival help. ..... (read more ......)

Valve Repair in the 21st CenturyBy: United Valve (http://www.unitedvalve.com/art-valve_repair_21st.htm)

Once upon a time, most large refineries and chemical plants had their own valve shops, complete with a fullcompliment of experienced valve repair technicians. These service departments took care of most of the plantsrepair needs, although oftentimes valves were simply replaced rather than refurbished. ..... (read more ......)
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Valve Standards in The Petrochemical &Refining Industry

By: United Valve (http://www.unitedvalve.com/art-valve_standards.htm)

Valves in petrochemical and refining installations are subject to numerous standards and specifications issuedby many supporting organizations. Today's valve standards are dynamic documents that reflect soundengineering practice, changes in market demands and changes in technology and manufacturingprocedures. ..... (read more ......)

Section - IA2: The Ever Popular Gate Valve

By: Greg Johnson (Published with the author's kind permission)

This low-tech valve may not have changed much in the last 100 years, but the gate valve plays a major role invirtually every

refinery, chemical plant and industrial facility in the world.

The most popular style of valve in the world of flow control is the gate valve. They are the on/off switches ofthe fluidcontrol industry and they are found in every refinery, chemical plant, power plant and industrial facility. Gatevalves exist forone primary purpose- to stop flow. Because of this, they are often referred to as "stop" or "block" valves. Gatevalves aremanufactured in a wide range of sizes- from " through 144".

It is not recommended to operate gate valves in the partially open position, or to use them in throttling service.When a gatevalve is partially open, it closure element (disc or wedge) can vibrate against the seats and become scratchedcausing them to lose their seating integrity.

The chief advantage of a gate valve is that it offers virtually no resistance to flow in the open position. Only afull port ball valvecan equal the gate valve's flow characteristics. Due to their symmetrical design and equilateral seating, gatevalves can beused to stop flow from either direction. They are available in every material from the shiny brass constructionof the diminutive" water valves on the hardware store shelf, to the exotic high alloy models found in nuclear powerinstallations.

Gate valves have been an important piece of fluid control equipment for over 150 years. In fact, the very firstvalve patentissued in the United States was for a "gate valve". Since those humble beginnings in the 19th century, the gatevalve hasanswered the fluid control call with relatively little basic design change.

From the outside, most gate valves look somewhat similar. However, inside there are a host of different designpossibilities.Most gate valves consist of a body and bonnet that contains a closure element, called a disc or a gate. Theclosure elementis attached to a stem that passes through the bonnet of the valve, ultimately interfacing with a handwheel orother device tooperate the stem. Pressure around the stem is contained through the use of packing material which iscompressed into apacking area or chamber.

Trim

The word "trim" is often overheard when valve professionals are talking about industrial gate valves. Trim hasnothing to dowith how slim and fit a valve is, rather it refers to the internal components of a valve that are exposed to great

stress or subjectto a harsh combination of erosion and corrosion. In a gate valve the trim components are the stem, discseating area, body
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seats and backseat, if applicable. Common utility bronze or brass valves usually have trim parts of the samematerial as thebody and bonnet. Cast and ductile iron valves have either all iron trim components or occasionally bronze trim.The term for aniron valve with bronze trim is "iron body, bronze mounted" or IBBM for short.Because of their weldability, steel valves can be furnished with a number of different trims. Stellite, Hastelloy,316ss, 347ss,Monel, and Alloy 20 are some of the materials regularly used for gate valve trim.

During most of the 19th century, valves were predominantly supplied with screwed end connections, even insizes as large as12" NPT. Since that time the flanged end connection has become the most popular. Other end connection typesin use todayinclude screwed, ring-type-joint (RTJ), Victaulic, Greyloc and water works "mechanical joint".

Disc Design

Gate valves can have one of two different disc designs: parallel or tapered type. Both operate on the principleof a closureelement (disc or gate) sliding into a slot in the pipeline and closing off the fluid path. The tapered disc of the"wedge gate"valve is machined to match a pair of body seats set at the same angle, usually about 10o. If machined

correctly, as thetapered disc engages the seats, it locks firmly into place, stopping the flow.

Three types of wedge gates are available: solid disc, one piece flexible type, and two piece split design.

The solid wedge has been around the longest and at one time virtually all wedge gates were the solid type.Thedrawback to a solid design is that it does not have any flexibility and if there is any valve body/seat distortiondue toextreme temperature fluctuations or pipe stresses, the solid disc can become jammed in the seats. The soliddisc isstill standard on bronze, cast iron, water service and compact carbon steel valves (API 602 type). Today, soliddiscsare usually only available as special order items on large diameter gate valves.

The flexible wedge type is just that- flexible. By the addition of a groove or slot around its periphery, theflexible disccan adapt to temperature changes and adverse piping stresses without binding. The flexible design also is alittleeasier to manufacture, in that minor imperfections in the seating surface angles can be compensated for by thedisc'sflexibility. The "flex-wedge" design is by far the most common type seen on commodity gate valves used inindustrialapplications.

The split wedge type consists of a two-piece design with mating surfaces on the back side of each disc half.Thesemating surfaces allow the downward stem thrust to be uniformly transferred to the disc faces and onto theseats. Thisflexible design also provides protection against jamming due to thermal expansion. A disadvantage to the splitdesign

is that in "dirty" services, residue or debris can cake in between the disc halves, causing the valve to improperlyseator even jam. Split wedge designs are commonly found on stainless steel and high alloy valves, as well as manysmallbronze valves.

Wedge gates are guided by grooves or ribs cast or welded into the body of the valve. These wedge guides keepthe disc inalignment as it opens or closes and also keeps the disc from sliding against the downstream seat duringopening and closing.

The second disc design is the parallel type. Unlike the wedge type gate valve, which relies on the stem thrust to"wedge" thedisc into the seats to seal, the parallel seat valve needs some assistance to seal properly. The sealingassistance is usually in the form of a spring loaded or mechanically activated spreading action between the two

disc halves as the valve closes fully.On most parallel seat designs the friction and sealing force is relieved as the gate disengages from the seats.


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The most common use for parallel disc valves today is in the pipeline industry, where elastomer seat seals andambientoperating temperatures make valve virtually leak proof. Parallel gates are also used in some high pressure,high temperature steam applications, to help reduce the possibility of locking the disc in the closed position dueto a radical change in temperature.

Regardless of disc design or type, the gate valve closure element must come in perfect contact with seats in thevalve body.The body seats may be welded, screwed, pressed or swaged in, or be integral with the valve body. Mostindustrial steel gatevalves utilize seat rings that are welded into the valve body. For most of the 20th century the norm wasscrewed in seat ringsin steel valves. However, advances in welding and valve repair techniques made the screwed-in rings obsolete.Seat rings andvalve discs are also often overlaid with corrosion or abrasion resistant alloys to increase their service life.

Body-Bonnet Design

Gate valves are normally available in five different body/bonnet joint designs. They are: screwed, union,bolted-bonnet,welded-bonnet & pressure-seal.

The screwed joint is the simplest design. However it is only used for inexpensive bronze valves that rarely ifeverrequire disassembled.

The union joint is also primarily used on bronze valves, but the union design allows for easier disassembly forrepairand maintenance.

The bolted-bonnet joint is the most popular joint and it is used on the vast majority of gate valves inindustrial usetoday. Unlike threaded and union bonnet valves, the bolted-bonnet connection requires a gasket to seal thejointbetween the body and bonnet. On lower pressure valves, sheet gasket materials are used. ANSI Class 150 steelvalves usually employ a corrugated soft iron or graphite/corrugated soft iron gasket. Valves of class 300 andhigher

employ either a spiral-wound or ring joint type gasket.

The pressure-seal joint is energized by the fluid pressure in the valve body acting upon a wedge shaped,soft ironor graphite gasket wedged between the body and bonnet. On a pressure-seal valve, the higher the body cavitypressure, the greater the force on the gasket. Pressure-seal bonnets are used extensively for high-pressurehigh-temperature applications, such as the power industry. Pressure-seal valves are much lighter than theircorrespondingbolted bonnet designs. Due to the pressure energization of the seal ring, they are normally not used in pressureclasses below ANSI class 600.

Welded bonnets are a very popular body-bonnet joint for compact steel valves in sizes " through 2" andpressureclasses 800 through 2500, where disassembly is not required. The higher pressure welded-bonnet type valves

relyon threads to handle the force generated by the body cavity pressure, while a small peripheral weld bevelactuallycontains the pressure. Like pressure-seal valves, welded-bonnet valves are much lighter than their bolted-bonnetcounterparts.

Stem Design

Three different bonnet/stem designs are predominant in gate valve construction. They are: inside screw, risingstem (ISRS),non-rising stem (NRS), and outside screw and yoke (OS&Y).

The ISRS bonnet/stem design is the most popular design in use today on bronze valves. Due to the fact thatitexposes the stem threads to the process fluid and potential corrosion damage which could cause a stem to discfailure, the ISRS design is not used for critical service industrial applications.


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The NRS type is another special purpose type that is used in applications where there is limited verticalclearanceabove the handwheel, because on an NRS valve, the stem does not rise up as the valve is opened. Most NRSvalvestoday are manufactured of either iron or bronze. Some applications such as marine use, where clearances aretight,often use NRS steel gate valves.

The most common stem/bonnet design in use on industrial valves is the OS&Y. The OS&Y design is preferredfor corrosive environments because the threads are outside the fluid containment area. It also differs fromotherdesigns in that the handwheel is attached to a bushing at the top of the valve yoke, and not to the stem itself,thus thehandwheel does not rise as the valve is opened.

Also in the gate valve family are knife and sluice gates. The bonnetless knife gate is especially suited for use inslurries such as in pulp and paper mills. Knife gates are very thin, only slightly wider than there closure element(disc). Because of their unique geometry and thin cross-section, knife gates are limited to low pressureapplications.

In appearance, the sluice gate doesn't look like it even belongs in the gate valve family, however based uponits sliding discdesign; it is characterized as a gate valve. Sluice gates are limited to very low pressures, in most cases, simple

head pressure.They are used primarily in waste water and irrigation systems.

Valve Standards

Gate valves standards are produced by several standards making organizations, for a multitude of industries.Here are some of the better known gate valve specifications:

American Petroleum Institute*API 600 "Steel Gate Valves, Flanged & Butt welding Ends", it is a companion document to ISO 10434.*API 602 "Compact Steel Gate Valves"*API 603 "Corrosion Resistant Bolted Bonnet Gate Valves"*API 6D "Specification for Pipeline Valves", it is a companion document to ISO 14314.

Manufacturers Standardization Society*SP-70 "Cast Iron Gate Valves"*SP-80 "Bronze Gate, Globe, Angle and Check Valves"*SP-81 "Stainless Steel Bonnetless, Flanged, Knife Gate Valves"

American Waterworks Association*AWWA C500 "Metal-Seated Gate Valves for Water Supply Service"*AWWA C509 "Resilient-Seated Gate Valves for Water Supply Service"*AWWA C515 "Resilient-Seated Gate Valves for Water Supply Service"

American Society of Mechanical Engineers*B16.34 "Valves- Flanged, Threaded and Welding End"

Materials of Construction

Gate valves are manufactured in virtually every metal from Aluminum to Zirconium. They are alsomanufactured in a variety of engineering plastics. The most common materials however, are steel, iron andbronze.

Bronze offers the greatest machinability and the lowest manufacturing cost. The features that make bronzeeasy to machine,its lower strength and softness, also make the valve only suitable for lower pressure applications. Thepredominant service forbronze valves is on water and utility lines where pressures are lower than about 300 psi.

Iron valves are in between bronze and steel as far as strength goes. The iron is slightly harder to machine, butthe iron castings are relatively easy to pour. Iron for valves is commonly two types; grey or cast iron andmalleable iron. In refinery and petrochemical service iron valves are usually restricted to low pressure waterlines. The high carbon content and better rust resistance of iron valves makes them more suitable for buriedservice than steel valves.


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For industrial valves, steel is the material of choice. A broad spectrum of steels are utilized for valveconstruction, from the lowest grade WCB, to the chrome/moly's. Unlike the brasses, bronzes and irons, moststeels and low alloys are readilyweldable, which makes them easier to modify, repair and in some cases even easier to manufacture. Gatevalves are alsomanufactured in a number of exotic alloys from Titanium to Zirconium.

There have been several attempts to make the gate valve obsolete and take away its market share, but theyhave only metwith limited success. The first challenger to the gate valve throne was the ball valve, which came intoprominence during themiddle part of the 20th century. Ball valves have been substituted for gate valves in many lower pressure andlowertemperature applications, but in some cases they are more expensive to manufacture and repair. Theelastomer seats of theball valve also limit them to temperatures below about 500 degrees F.

Butterfly valves have supplanted gate valves in some of the larger (48" and above) low pressure applications,such as waterworks usage. The metal-seated butterfly valve has also been successful in certain critical service applicationsthat once weresolely the realm of the gate valve, but their high initial cost and very high repair costs make them unlikely toever completely

replace the venerable gate valve.

Gate Valve Actuation

The most common method of opening and closing (actuating) a valve is through a handwheel attached to theyoke or bonnet.This works fine on moderate size valves operating at reasonable pressures, but some severe operatingsituations call for more muscle. For example, an 18", class 1500, main steam isolating valve in a power plantoperating at 1750 psi and 1000 degrees F. requires a huge amount of torque to open under pressure. The onlysolution is remote actuation- usually in the form of an electric motor or hydraulic actuator.

Additional gate valve actuation can be provided by pneumatic cylinders. In some cases these sit directly on topof the yoke and are attached directly to the stem, to provide a quick-opening form of actuation. For additionalleverage a standard gate valve might have a manual gear operator attached to it to decrease the amount offorce required to open and close it under pressure.These devices are called bevel gears.

Repair of Gate Valves

Industrial gate valves are often used in harsh environments and sometimes these valves need to be repaired.The decision to repair or replace a valve usually is a result of comparing the replacement cost to the repaircost. When the repair cost exceeds 50-65% of the cost of a new valve, the decision is usually to replace thevalve, unless the delivery is unacceptable.

Generally speaking, all bronze valves, except for expensive cryogenic designs, are replaced rather thanrepaired. Iron valves,except for the largest sizes, are also replaced rather than repaired. Steel and alloy gate valves are the mostrepaired types.Steel valves smaller than 12", class 150 are usually not repaired, unless replacements are not readily available.

On the otherhand, high alloy gate valves as small as " size may be repaired because of their high cost and long lead time.

Some gate valves, such as large diameter, butt-weld end and pressure-seal types are often repaired in thefield. These fieldrepairs are often difficult and pose logistical challenges, but compared to the cost of removing them from theline and shipping them to a repair facility, field repair is more economical option.

Gate valves are still the primary choice for many service applications. Their cost of manufacture to value ratio isstill very high.On typical petrochemical and refining projects today, the percentage of gate valves on the requisition is about60-70%.Although science and technology has made tremendous leaps during the past 50 years, most gate valves arestill beingproduced to the same basic designs developed a hundred years ago. And until someone invents a Buck Rogerslaser valvewith no moving parts, tens of thousands of gate valves will still be manufactured each year, in plants fromSouth Carolina toSoutheast Asia.


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References:

API 600 Steel Valves - Flanged & Butt welded Ends API 600 is the primary steel gate valve purchasespecification. Valvedesign and construction criteria are detailed, as well as materials and trim designations. An appendix containsinformationpertaining to pressure seal valves. ISO Standard 10434 is essentially the same as API 600, only published in

the ISOformat.

API 602 Compact Steel Gate Valves- Flanged, Threaded, Welding and Extended-Body Ends API 602 isthe 4" & smallerforged steel gate valve purchase specification. Valve design and construction criteria are detailed, as well asmaterials andtrim designations. Future versions of this document are expected to include requirements for bellows seal gatevalves.

API 603 Class 150, Cast, Corrosion-Resistant, Flanged-End Gate Valves API 603 covers light walled gatevalves in size NPS 1/2" through 24", in classes 150, 300 & 600. These valves are used in applications where thethicker API 600 casting isnot needed.

API 608 Metal Ball Valves-Flanged and Butt-Welding Ends API 608 is the purchase specification for class150 and class300 metal ball valves. Valve design and construction criteria are detailed. Important Note- ball valve workingpressures shouldbe based on seat material, not valve class.

API 609 Butterfly Valves, Lug-Type and Wafer Type API 609 is the purchase specification for butterflyvalves with lug-typeand wafer-type configurations designed for installation between ANSI B16 flanges, through Class 600.

API 598 Valve Inspection & Testing API 598 covers the testing and inspection requirements for gate, globe,check, ball,plug & butterfly valves. Steel valve pressure ratings found in ASME/ANSI B16.34 are required to determine API598 testpressures for steel valves.

API 6D Specification for Pipeline Valves (Gate, Plug, Ball and Check Valves) Specification for PipelineValves (Gate,Plug, Ball and Check Valves) API 6D is the primary standard for valves used in pipeline service, including gate,plug, ball andcheck valves. Occasionally refinery and petrochemical purchasers will reference the more stringent testingrequirements of 6Dalthough the valve may have built under API 600, 602, 608 or 609 design criteria.

ASME/ANSI B16.34 Steel Valves - Flanged & Butt welded Ends ASME B16.34 is the base document fromwhich steelvalve pressure/temperature ratings are derived. It also offers additional valve specification data includingnondestructiveexamination procedures for upgrading valves to Special Class. Note: Gate valves manufactured under B16.34wall thickness

minimums may not meet the minimum wall thickness requirement of API 600 & API 602 for class 150, 300 and600.

ASME/ANSI B16.10 Face-to-Face Dimensions of Ferrous Valves B16.10 lists the face to face dimensions ofall flanged andbutt-weld end valves. Screwed and socket weld end valve face-to-face dimensions are not included in thisspecification.

MSS SP-55 Quality Standard for Steel Castings for Valves, Flanges and Fittings and Other PipingComponents SP-55 details the visual inspection criteria for castings. This specification is listed as part of the procedure underAPI 598. NACEMR-0175 Standard Material Requirements for Sulfide Stress Cracking Resistant Metallic Materials For OilfieldEquipment MR-0175 is the "standard" for materials used in "sour" environments such as found in piping systems in manyrefineries. It listsmaterials, mechanical properties and heat treatments for metals used in Hydrogen Sulfide bearing hydrocarbonservice.


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Section - IB: Pipe

By: James O. PennockDefinition:Pipe is a hollow "tube" used for conveying products and pressure. The products include fluids, gas, slurry,powders, pellets and more. The pressure is hydraulic power. We usually designate the "tube" as pipe in theapplicable line class but the definition includes any similar component designed as tubing, which is used for thesame application.

History:One of the earliest methods of conveying fluids in the history of mankind was by pipe. The earliest pipe onrecord was the use of bamboo for moving small quantities of water as a continues flow. As man progressed, hebegan using hollow logs for his piping needs. Probably the first recorded use of metal in piping systems was theuse of lead or bronze during the "Bronze" age.During the excavation at Pompeii, complete water distribution systems fabricated from lead have beenuncovered. These systems, include probably the first use of metal plug valves, are still workable.Without piping our modern civilization and their attendant conveniences could not exist. Today piping is used inalmost every aspect of our lives. Our drinking water is produced in plants full of piping and then comes to usthrough a vast network of pipes. The waste from our homes and businesses flows away through anothernetwork of pipes and is then treated in a plant full of piping. The fuel we use for travel or for heating wascollected, processed and distributed using pipe. No mater what you think about, power, food, paint, medicine,paper products, plastics, chemicals, and many more are all made in plants full of piping. Our safety is alsodependent on the piping in the fire water systems in our neighborhoods and buildings.

Materials of construction:The various kinds of material from which pipe is, or can be, made is proved to be endless; among them are themore common carbon steel, along with chromes, stainless steel, iron, brass, copper, lead, aluminum, glass,rubber and various types of plastic material. Over the years some of these materials have been combined toform lined pipe systems. These include carbon steel pipe lined with glass, carbon steel pipe that is lined withvarious plastics; carbon steel pipe lined with concrete. Each one, plain or lined has certain advantages anddisadvantages. Many things enter into making a choice of materials. Among the most important of these arecommodity, pressure, temperature, size, ease of assembly availability and economics.

Pipe sizes:Many years ago pipe was sized by its true inside diameter. i.e., a 1" pipe was actually 1" inside diameter.However, as time went on and the methods of manufacturing were improved and made more standard, andbecause it became necessary to increase wall thickness to accommodate higher pressures and temperatures, itbecame necessary to size pipe by "nominal" size rather than actual size. Because it was deemed too expensiveto have a set of thread dies for each wall thickness in the smaller sizes, the outside diameter (O.D.) was heldconstant. Thus wall thickness changes affect the internal diameter only and leave the O. D. constant forstandardized fitting engagements.Nominal size refers to the name by which we call a particular size pipe. Nominal size and actual outsidediameter of a pipe differs for size 12" and under. For sizes 14" and larger the actual outside diameter and thenominal size are identical.Pipe comes in a very wide range of sizes. It is not uncommon to see piping as small as " or as large as 66".Pipe mills can and will make almost any size for a price. This does not always prove to be the economical choicebecause odd size fittings may not be available. It is best to stick to the closest and most commercially availableor common size to meet the need.

The smaller common sizes in pipe include ", ", 1", 2", 3", 4", 6", 8" 10" and 12". The larger sizes, 14" andabove increase in 2" increments.The Nominal size pertains to calling the pipe size by name only. The actual outside diameter or O. D. is differentfor the 12" and under sizes.Example:

Nominal Size Actual O. D.

1"1-

5/16"

2" 2-3/8"

3" 3-1/2"

4" 4-1/2"


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12"12-

3/4"

14" 14"

For all pipe sizes the inside diameter varies as the wall thickness increases thus the thicker the wall, the smallerthe inside diameter.

Weight:Many years ago the only "weights" of pipe available were classed as standard weight, extra heavy and doubleextra heavy. Within the last seventy-five years or so it became increasingly evident that this system waslimited in scope and did not meet the needs of the growing state of the industry. This was the direct result ofthe increasingly higher pressures and temperatures of the commodities being handled. Consequently the use ofschedule numbers came into being. Today, both weight and schedule are the way of identifying the wallthickness.

Length:Based on common practice pipe usually can be furnished in "single random" lengths, "double random" lengths,

and under certain circumstances (pipeline work for example) in even longer lengths. A single random will runfrom about 16' to 22' in length. A double random will run from about 35' to 40' in length. Pipe can be orderedto a specified fixed length but this will cost more.

Methods of manufacture:Pipe is made two ways. It is made by taking a flat plate, called a skelp, and rolling it into a tube shape and thenwelding the two edges together to form a tube. This pipe is commonly called "welded pipe" or ERW pipe. Theother way is to take a solid bar or billet and pierce a hole through the length. This pipe is commonly calledseamless pipe.

Determining wall thickness:The wall thickness for pipe is generally covered in the piping material specifications by calling out the ScheduleNumber for a large majority of sizes. However, as pressure and temperature increase, and sometimes thecorrosion allowance, it becomes necessary to calculate the required wall thickness for a specific case. Pleasenote that generally as the specifications change into higher-pressure classes, wall thickness calculations mustbe made for smaller size pipe. Wall thicknesses are by strict adherence to the rules set forth in the code for

Pressure Piping. For more detailed information on specific pipe sizes and it's various wall thicknesses, schedulesand pipe weights see the "tools," "piping", "pipe chart" on this website

Grades:In steel pipe, the word "grade" designates divisions within different types based on carbon content ormechanical properties (tensile and yield strengths). The tensile strength is the ultimate amount of stretchingthe steel can bear without breaking. The yield strength is the maximum amount of stretching steel can bearbefore it becomes permanently deformed or before it loses its ability to return to its original shape.Grade A steel pipe has lower tensile and yield strengths than Grade B steel pipe. This is because it has a lowercarbon content. Grade A in more ductile and is better for cold bending and close coiling applications.Grade B steel pipe is better for applications where pressure, structural strength and collapse are factors. It isalso easier to machine because of its higher carbon content. It is generally accepted that Grade B welds as wellas Grade A.

Ends:Steel pipe can generally be specified with a specific end preparation at the time of purchase. Three end prepsare standard. There is plain end (PE). This would be the choice for small sizes where socket welded fittings willbe used to join pipe to pipe or pipe to fittings. This is also the default end prep if no end prep is specified. Thereis threaded end (TE). This would be the choice for small sizes where the pipe to pipe or pipe to fitting assemblyis to be threaded. There is also bevel end (BE). This would be the choice for most all 3" and larger steel pipe (orother metallic pipe) where "butt welding will be used to join pipe to pipe or pipe to fittings.

Discussion:The information given above is what you should know about pipe. There are also some things that you shouldunderstand about pipe. There is a big difference between what you know about a subject and what youunderstand about that subject.With pipe, most novice designers think that all they have to do is "draw" or "place" the pipe symbol (on thatpipe support beam symbol) in whatever CAD system they are currently using and they are done. They do notunderstand what that pipe symbol really means.That pipe is (or represents) what will be almost a living thing and as such it will have a growing problem. It will

be installed at a certain ambient temperature and then on start-up it will operate at a totally differenttemperature. That difference between the installation temperature and the operating temperature will cause thepipe to expand or contract. No matter what the designed tries to do he or she cannot stop this action. This


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expansion (or contraction) will cause stress, strain and force in both the piping system and the pipe supportsystem.This pipe will also have a weight problem. The pipe it self has a certain weight. The pipe next to it may be thesame size but it may not weight the same. This pipe may be both high pressure and high temperature. Thismeans that the wall schedule may be much thicker therefore it will weigh more. Let's say we do have two linesside by side. They are both 14", one (Line A) is a low temperature, low pressure cooling water line and theother (Line B) is a high pressure, high temperature hydrocarbon process line. The span for both lines is 25'.

Example:

ItemLine

ALine B

Pipe

weight/foot54.6 189.1

Water

weight/foot59.7 42.6

Insulation

weight/foot

0 15

Total weight

of span

2857

lbs.

6170

lbs.

This does not include any forces that may be imposed by the total piping configuration on this specific pipesupport. However, it does indicate that there must be some close coordination with the structural departmentso they do not assume that all 14" lines are equal.As for the piping designer, does this line need extra space for movement? Do either or both of these lines needa pipe guide at this specific pipe support? Does either of these lines need anchors at this specific pipe support?If an anchor is required will the anchor forces on each side of the support be the same or will the anchor farcesbe unbalanced? Both cases must be brought to the attention of the structural group.With the hot line there is normally an insulation shoe required which is added material and which changes thedimensional reference point for the centerline of this line and can cause design errors if not understood andallowed for.

For additional information about pipe see the "Standards" tab on this website.

Section - IC: Fittings (Just the basics)

By: James O. Pennock

Definition:

A fitting is a pipe item used for changing direction, branching or attaching in a piping system. There are manydifferent types of fittings and they are produced in all the same sizes and weights (schedules) as the pipe.Fittings are commonly segregated into three groups; Butt-weld, Socket-weld and Screwed. Only the mostcommon will be discussed in this article.

Materials of construction:

Like pipe, fittings are fabricated from several different types of material and usually match the material of thepipe to which they are being attached. Some fittings are Cast Iron, some are Malleable Iron, some are ForgedSteel and others are even fabricated from rolled Steel Plate. The most used materials are again common carbonsteel, along with chromes, stainless steel, iron, brass, copper, lead, aluminum, glass, rubber and various typesof plastic and plastic lined metal materials.

Fitting Types:


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Normally, fittings fall into three basic types or categories. These are In-line, On-line and Closures. The In-linefittings include elbows (Ells), Tees, Couplings and Reducers. The On-line fittings include a wide variety of "O-Let" fittings used primarily for making branch connections. The closure fittings are various types of caps andplugs used to close the end of a pipe system. We also will discuss some cases where there are alternates tothese normal categories.

Butt-Welded Fittings

Elbows (Ells):

An Elbow is a piping fitting used for changing direction. There are five basic versions of elbows. The first and byfar the most common is the 90 long radius Ell. The second is the 45 long radius Ell. The third is the 90 shortradius Ell. The fourth is the long radius reducing Ell. The fifth version is the long radius 180 Return Bend. Thebasic Butt-Weld Ell is manufactured in 90 or 45 configurations as a standard. However for special order andextra cost, the large sizes can be made in other degrees of turn.

The standard Butt-Weld elbows (90, 45 and 180 ) can be altered to meet any special angle needs of a pipingsystem. Elbows like pipe can be flame cut or machine cut to the required angle. The rough end is then groundor machine beveled to the proper angle for welding. There is normally no harm to the fitting when this is done.

The terms "Long Radius" and "Short Radius" are important to understand. "Long Radius" means that the center

to end dimension is one and a half times the nominal pipe size.

Example:

Nominal Line Size (and Center-tend of short radius Ell)

Center-to-end of longradius Ell

4" 6"

10" 15"

14" 21"

20" 30"

24" 36"

"Short Radius" means that the center to end dimension is equal to the nominal pipe size. This means that thecenter-to-end for a 4" short radius Ell is 4", for a 10" Ell the center-to-end is 10" and so on.

The long radius Ell is the default standard. All elbows shown in a system are assumed to be long radius 90 Ellsunless noted otherwise. This means that the designer must call out any and all exceptions to this rule. If the Ellis a 90 long radius Ell then the elbow symbol is all that is required. However, if the Ell is a 45 Ell then thedesigner must add the notation "45 Ell" next to the elbow symbol. If the Ell is a 90 short radius Ell then thedesigner must place the notation S. R. next to the elbow symbol. Also if the elbow has been trimmed to anyodd angle this too must be noted next to the fitting.

As stated above the 90 long radius Ell is the default standard and is the most used. The designed should usethe long radius Ell at all times unless conditions exist that force another choice. The short radius 90 Ell shouldonly be used when tight space does not allow the long radius. The 45 Ell is normally used where a simpleoffset is required for some purpose. The 180 Ell is used mostly by equipment manufacturers to form heating or

cooling coils. Return Bends are not normally required by the piping designer unless there is a requirement tofabricate a complex configuration.

The purpose of the 90 long radius Reducing Ell is to do the job of an elbow and a reducer. (Reducers will becovered later.) As such this Ell is made with one end of one size and the other end one or two line sizessmaller. The using of the reducing Ell is not cheaper; it only takes less room. The "long radius" dimension forthe 90 long radius reducing Ell is based on the size of the large end.

Because the long radius and short radius designation of the 90 Ells are based on the nominal pipe size thedesigner quickly learns the center-to-end dimensions. The center-to-end dimensions for the 45 Ell arenormally found only on a chart. However, there is a short-cut way to "know" these dimensions. You see, thesedimensions are also based on the nominal pipe size. This short-cut method works for all 45 Ells from 4" to 24"line size. You can do this in your head. You simply divide the line size in half three times. Take the answer fromthe first time and the third time and total them up. That will be the dimension for the 45 Ell fitting.

Example:


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Column #1(Line size)

Column #2(Col. #1)

Column #3(Col. #2)

Column #4(Col. #3)

Column #5 -Fittingdimension

(Total of Col. #2 &Col. #4)

4" 2" 1" " 2 "

8" 4" 2" 1" 5"10" 5" 2 " 1 " 6 "

14" 7" 3 " 1 " 8 "

20" 10" 5" 2-" 12

Tees:

The primary purpose of a Tee fitting is to make a branch from a pipe line (or run). The branch may need to bethe same size as the run or it may need to be one or more sizes smaller than the run. Because of economics(the cost of special orders) the use of Tees is normally limited to size-to-size or Straight Tee, (all threeconnections are the same size) or Reducing Tees where the branch outlet is only one size smaller than run size.Methods for making branches of other smaller sizes will be discussed later.

The dimensions of Tees are not as simple as they are for Ells. For Tees you must look them up on a fittingchart. The dimension found there is however standardized between all manufacturers. For Straight Tees thecenter-to-end dimension of both ends and for the branch outlet is the same. For Reducing Tees the center-to-end of the branch outlet is different from that of the run.

Reducers:

A Reducer is a fitting used to change the line size one or more sizes smaller (or larger). There are two versionsof Reducers. There is Concentric Reducers- where the centerline of the inlet and the outlet are the same. Thereis Eccentric Reducers- where the centerline of the inlet is different than the centerline of the outlet. With theEccentric Reducer, one side is flat. Depending on how it is installed you may have bottom flat (BF) or top flatTF). You may also have a need to have (*) side flat (*= north, south, east or west). It is about a toss-up as towhich is used more. Concentric Reducers are used mostly in situations where the reducer is in a vertical run ofpipe. Eccentric Reducers are used in horizontal runs of pipe such as pipeways or in pump suctions.

The dimensions for reducers must be looked up but are normally standardized among the manufacturers for agiven size. The length of a reducer is the same for a range of sizes (Example: The end-to-end dimension for10" x 4", 10" x 6" and 10" x 8" reducers is 7"). As you can see the length of a Reducer is very short in relationto the diameter.

Caps:

The weld Cap is a fitting used to close the end of a pipe. The closed end of the Cap is semi-elliptical in shape.The dimension of a weld cap is a look-up item. Weld caps are most often found at the bottom of a pipingconfiguration called a "Boot." A boot is a short length of pipe with a pipe Cap that is attached to the bottom ofsteam line and provides for the collection of condensate.

Alternates:

Here are a few alternates to the normal methods of doing business discussed above.

Miters:

We talked about elbows as a way to change direction. You can change direction without using elbows. Youmight do this with a Miter Ell (or Mitre, both spellings are correct). A Miter Ell is where no fitting is used. Mitersare normally used in large size/low pressure piping.

You fabricate the Miter or change in direction from pipe segments (or pieces) that are cut at specific anglesdepending on the number of pieces and welds required. This is really effective when really odd angles arerequired. Two of the pieces are the incoming pipe and the out-going pipe. There may be no middle piece orthere may be one (or more) other short middle pieces depending on the angle of the turn. A simple turn of 45might be made with a two-piece/one weld miter. Other changes in direction might be three piece/two weldmiters, three piece/two weld miters and so on. The number of welds is always one less than the number of

pieces.


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Depending on the size and schedule of the pipe a Miter might be cheaper than buying fittings. In small diameterpiping the miter is more expensive (labor costs) and there is more pressure drop through a small miter than asmall fitting. Miters are also not recommended for high temperature lines because miters are more susceptibleto overstressing.

Stub-in (Stub-on):

We talked about using Straight Tees and Reducing Tees as a way to make branches from a line. For lowpressure (or reasonably low pressure) there is another way to make branches from a line. This method usesonly pipe. It is normally used only for low pressure/low temperature applications where the branch is reducing.The ASME B31.3 (and other piping B31 Code sections) recognize two basic versions of the pipe to pipe branch.

One method is where the run pipe has a hole cut the outside diameter of the branch pipe. This opening is thenbeveled for a "full penetration weld" The branch pipe is saddle cut (with no bevel) to match the I. D. of the runpipe. They are then fitted together and welded.

The second method is where the diameter of the hole in the run pipe is the same I. D. as the I. D. of the branchpipe. This hole does not get a bevel. The end of the branch pipe is saddle cut to fit the run pipe and is thenbeveled for a full penetration weld.

With the first method, the branch pipe is inserted in the run pipe. With the second method, the branch pipe isset on the run pipe. Both are still commonly referred to as "Stub-ins"Both of these can come non-reinforced (as described above) or reinforced. The reinforced version is normallyonly required for higher stress situations. The reinforcement is a "ring" plate cut from some scrape run pipe orthe same material as the run pipe. At the center is a hole the same size as the branch pipe. If cut from flatplate it is then shaped to fit around the run pipe. The width of the ring is normally one half the diameter of thebranch pipe. The ring is intended to replace the material that was removed when the hole was cut in the runpipe. A small diameter hole (1/4" NPT) is normally drilled (and tapped) in the ring to act as a vent during thewelding process and to allow for Hydrotesting of the welds. The ring is then welded to the branch pipe and therun pipe with full penetration welds. The small hole is fitted with a plug after work is completed.

O-let fittings:

Another way to make branch connections on pipe and vessels is by using an "O-Let" fitting. An "O-Let fitting isdesigned for use on 3" and larger welded pipe. The main feature of the typical O-Let fitting is the built-up basedesign which eliminates the need of any other form of branch reinforcement. The O-let fitting is manufacturedin a number of styles.

These are:

Weld-O-Let - (common) - This fitting is best described as an odd shaped "donut." It's purpose is to make self-reinforced branch outlets on a larger (one size or more) run of pipe. The base of the common weld-o-let has asaddle shape to fit the run pipe. The outlet end of the weld-o-let has a beveled-end allowing for butt welding apipe or fitting. Weld-O-Lets come in a wide range of sizes and materials. The size call-out is normally the run(header) size by the branch size (Example: 24" x 4" WOL). It may be of some interest to know that most O-Letfittings are made with the base that covers a range of header sizes. This means that the 24" x 4" WOL will alsofit on all pipe sizes from 24" pipe to 36" pipe.

Thread-O-Let - The Thread-O-Let is made much the same as the Weld-O-Let except that the outlet is threadedto match the normal tapered pipe threads. The threaded outlet sizes are normally limited to the smaller (2" andunder) pipe sizes.

Sock-O-Let - The Sock-O-Let is also made much the same as the Weld-O-Let except that the outlet has asocket to match the socket welded piping fittings and pipe. The socket outlet sizes are normally limited to thesmaller (2" and under) pipe sizes.

Latrolet - A Latrolet is a weld on branch fitting that is attached to the run pipe at a 45 angle. The angleattachment is sometimes required on high pressure relief systems. A Latrolet may be ordered with; a Butt-weldoutlet end, a threaded outlet end or a socket weld end.

Elbowlet - The Elbowlet is made to be fitted on the back side of a long radius 90 elbow. An Elbowlet may alsobe ordered with; a Butt-weld outlet end, a threaded outlet end or a socket weld outlet end.

Nip-O-Let - A Nip-O-Let is a fitting that has the reinforced base for attaching to the run pipe and then has ashort pipe extension with a threaded or plain outlet end. The Nip-O-Let does come in a range of sizes, however

they are limited to the smaller sizes. This fitting is normally used for vent, drain and pressure gage connections.


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Flange-O-Let - This fitting is much like the Nip-O-Let but has a flanged outlet end. The purpose is the same asfor the Nip-O-Let.

Couplings: (as a branch outlet fitting)

The common pipe Coupling (to be discussed later) can also be used in the making of small size branches from alarger header or run pipe. One end of the (Threaded or Socket Weld) Coupling is shaped to match the O. D. ofthe larger pipe. This shaped end is then ground to form a beveled end which allows for a full penetration weld.

Screwed and Socket-Welded Fittings

These fittings perform the same function as the Butt-Weld fittings. There function is the same but the methodof joining and the dimensioning is different. Normally these fittings are used in sizes 1-1/2" (or 2") and smaller.Welded fittings are specified the same as the pipe, by weight, schedule or wall thickness. Screwed and Socket-

Weld fittings are specified per the pressure class.Thread engagements as well as the depths of the sockets for different pipe sizes are different and must be

looked-up on an approved dimension table.

Threaded fitting pressure classes:

125# Cast Iron 250# Cast Iron

150# Malleable Iron 300# Malleable Iron

2000# Forged Steel * 3000# Forged Steel * 6000# Forged Steel

* Most common

The Cast Iron and Malleable Iron fittings are basically used for air and water services at a low temperature andpressure. Forged fittings are normally used for higher pressures and temperatures as well as for the morecomplex commodities.The majority of the screwed fittings will have female (internal) threads per NPT (National Pipe Thread). Theexception will be the swages and the plugs - they will have male (external) threads.

Socket-Weld fittings are manufactured in two classes.

3000# Forged Steel 6000# Forged Steel

Socket-Weld fittings have a deep socket into which the pipe slips and aligns itself. The weld is then made on theouter surface of the pipe and fitting. This eliminate the need for or use of special clamps or tack welding foralignment prior to the final fit-up welding. At the bottom of the socket a 1/16" gap is left to compensate forexpansion when the weld is made. This gap is called a root-gap. The swage does not have an internal socket; itwill fit into the socket of a fitting or be butt-welded to a pipe.

The dimensions for screwed and socket-weld fittings must be looked up on a standard fitting dimension chart.There are no dimension short-cuts for these fittings.

Common Screwed an Socket-Weld fittings:

Elbows (Ells): Here again we have a fitting whose purpose is to change direction. There are only two versions.There is the 90 Ell and the 45 Ell. With the Screwed and Socket-Weld Ells there is no long radius or shortradius. They are just as they are and they cannot be "trimmed" to allow for odd angles..

Tees: The Screwed and Socket-Weld Tee fittings are used for making branches. They do come in straight andsome reducing sizes.

Swages: The Screwed and Socket-Weld Swage comes in both the concentric and the eccentric shapes. Swagesdo have an important feature that every designer needs to know and accept. Where a Butt-Weld reducer isshort relative to the diameter, the swage is very long relative the diameter. Screwed and Socket-Weld swagesare made by the same people and in some cases by the same machine. Some are then threaded and some areleft with a plain end or beveled for welding. The extra length on the Screwed Swage allows space for the pipewrench.

Caps and Plugs: Caps and Plugs are intended to provide for the closer of the end of a pipe or fitting.


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Nipples: A Nipple is a name given to a short length of pipe. It is not really a fitting in the same context as anelbow or a Tee. Nipples are cut from pipe and can be purchased in 4", 6" and 12" standard lengths. Pipe Nipplescan also be made by the piping crew in the field.

Unions: The Union is basically used as a dismantling fitting, and in many cases it is necessary for assembly.The field crew may install extra Unions at their own discretion to expedite and facilitate the construction ofsocket-weld and screwed piping.

Section - 1

D: Flanges, Gaskets & Bolts (Just thebasics) Revision 1

By: James O. Pennock

Note: This article covers ASME B 16.5 Standard Piping Flanges up to 24" NPS. Flanges larger than 24" fallunder ASME B16.47 and while they have the same attributes they will be covered at a later time.

Definition:A flange is defined as a plate type device, normally round, that is attached to the end of a pipe, fitting, valve orother object to facilitate the assembly and disassembly of a piping system. For many years the only practicalmethod of joining steel pipe had been by connecting threaded pipe ends with couplings. Improvements in thewelding of carbon steel reduced labor costs and provided a completely sealed and much stronger joint. In mostpresent day piping systems, threaded joints are usually limited to pipe sizes 2" and smaller. Larger pipe (3" andlarger) is normally joined by butt-welding of continuous pipe and fittings or by flanges at joints that mayrequire dismantling. Flanges (3" and larger) are also the default standard for connecting to most equipmentconnections and valves.

Materials of construction:Flanges are manufactured in all the different materials to match the material of the pipe and fittings to whichthey are being attached. While some flanges are made of Cast Iron. The vast majority of flanges are forgedcarbon steel.

Forged Flange Ratings:Forged steel flanges are made in seven primary ratings.

These primary ratings are as follows:o Class 150o Class 300o Class 400o Class 600o Class 900o Class 1500o Class 2500The Primary Rating is on a pressure/temperature relationship.

Example:

A Class 150 Forged Flange is used for 150 PSIG at 500 F. This same flange may also be used for 275 PSIG at100 F. This same flange could also be used at 100 PSIG at 750 F. Note the inverse relationship. When thepressure goes up, the temperature goes down and vice versa. Pressure ratings are used as a guide to safelydesign piping systems and also to standardize manufactured piping components. The same ratings hold true forscrewed and socket-weld flanges.

Cast Iron Flange Ratings:The two most common ratings for Cast Iron flanges are Class 125 and Class 250. Other flange ratings areavailable but are not as common. Cast Iron flanges are generally found associated with low pressure cast ironvalves and nozzles on cast iron equipment such as some pumps and turbines. Mating forged steel flanges tocast iron flange can pose a potential for damage to the "weaker" cast iron. The main point to remember now isthat a Class 125 Cast Iron flange will mate to a Class 150 forged steel flange, and a Class 250 Cast Iron flangewill mate to a Class 300 forged steel flange. The solution to the potential damage problem will be discussedlater in flange facings.

Flange Dimensions:A flange has many dimensions. The most critical is the "length" of the flange. This dimension will vary with each


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type of flange and will be covered in the section below covering Flange Types.All other dimensions for a flange will normally be the same across all flange types but will vary with each flangerating.

These common dimensions include:o Flange Outside Diametero Flange Thicknesso Bolt Circleo Number of Boltso Bolt Hole Sizeo Bolt Size

Bolt Hole Location:The ASME B16.5 has a standard for bolt holes that are used by all (US) manufacturers for flange sizes upthrough 24" For instance; the number of bolt holes required varies with the size and rating of the flange. Butthe number and size is the same no matter the type of flange. The bolt holes are evenly spaced around theflange on a concentric bolt circle. There will always be an even number of bolt holes, in graduations of 4 (i.e., 4,8, 12, 16, etc.).Unless specifically noted otherwise by the piping designer (and then only if for good reason) all flange bolt holesshall straddle the "natural" centerlines. This is the flange bolt hole orientation rule. This "natural" centerline rulefor flange is known, understood and followed by all responsible equipment manufacturers and pipe fabricators.

The rule is as follows:

o For a vertical flange face (the flange face in vertical and the line is horizontal) the bolt holes shall be orientedto straddle the vertical and horizontal centerlines.o For a horizontal flange face (the flange face is horizontal and the line is vertical up or vertical down) the boltholes shall be oriented to straddle the (plant) north/south centerlines.

Care must be taken to check all equipment vendor outlines to identify any flange orientations that do not matchthis rule. When an exception is found the vendor can be requested to change his bolt hole orientation. This isnot always successful and if not then the piping designer must insure that the piping fabrication documents callfor the correct orientation.This rule of bolt holes straddling the natural centerlines is sometimes referred to as "Two-Hole" the flange. Thismeans that the two of the holes straddle the centerline. To "One-Hole" a flange means that the flange has beenrotated so that one hole is right on the natural centerline. I assure you that 99.999% of the time that to "OneHole" a flange is a mistake and will add cost to the field. It also makes the piping foreman very unhappy.

Flange Types:

Weld Neck Flanges:Weld Neck Flanges are distinguished from other flange types by their long tapered hub and gentle transition ofthickness in the region of the butt weld that joins them to pipe or a fitting. A weld-neck flange is attached to apipe or a fitting with a single full penetration, "V" bevel weld. The long tapered hub provides an importantreinforcement of the flange proper from the standpoint of strength and resistance to dishing. The smoothtransition from the flange thickness

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