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Piping Training_Section I - Piping Components

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Piping Training Subject Index Section I - Piping Components A. Valves - By Anton Dooley This is a brief overview of different valves and their uses. B. Pipe - By: James O. Pennock This is a discussion about pipes, from their history and their uses to weights and grades. C. Fittings - By: James O. Pennock This is a discussion about fittings, the different types of fittings and their uses. D: Flanges - By: James O. Pennock - Updated - Revision 1 This article covers ASME B 16.5 Standard Piping Flanges up to 24" NPS Section II - Equipment Piping and Assembly Applications A: General Guidelines for Equipment and Piping Location, Spacing, Distances and Clearances - By: James O. Pennock This article is intended to aid both the novice and experienced piping designer with guidance for plot plan development.
Transcript
Page 1: Piping Training_Section I - Piping Components

Piping Training

Subject Index

Section I - Piping Components

A. Valves - By Anton Dooley

This is a brief overview of different valves and their uses.

B. Pipe - By: James O. Pennock

This is a discussion about pipes, from their history and their uses to weights and grades.

C. Fittings - By: James O. Pennock

This is a discussion about fittings, the different types of fittings and their uses.

D: Flanges - By: James O. Pennock - Updated - Revision 1

This article covers ASME B 16.5 Standard Piping Flanges up to 24" NPS

Section II - Equipment Piping and Assembly Applications

A: General Guidelines for Equipment and Piping Location, Spacing, Distances and Clearances - By: James O. Pennock

This article is intended to aid both the novice and experienced piping designer with guidance for plot plan development.

C1: Introduction to Vessels and Vessel Orientation - By: James O. Pennock

C2: Vertical Vessel Orientation - By: James O. Pennock

Section III - Pipe Supports

Page 2: Piping Training_Section I - Piping Components

A. Pipe Supports - Part 1, By: James O. Pennock

This is a discussion about the two basic categories of pipe supports (the primary pipe support systems, and the secondary pipe support systems).

B. Pipe Supports - Part 2, By: James O. Pennock

This is a discussion about the data requirements and the process of selection and qualification for the typical secondary pipe supports.

Section IV - Piping Stress for the Piping Designer

A. Stress Problems and Designer Stress Training - By: James O. Pennock

This discussion is an introduction to the problems found in piping caused by thermal expansion and dead weight, their relationship to the overall piping arrangement and the type of stress related training required for the piping designer.

B: The Problem with Piping "Lift-off" - By CAEPIPE

Contemporary commercial piping analysis programs deal differently with the problem of apparent lift-off of an operating pipe at a rod hanger or a one-way vertical support, such as a pipe on a support rack (... more)

Section V - Field Issues

A. Field trip guidelines - By: James O. Pennock

This discussion is about what to expect when you are asked to go to the field?

B. Defining Offsite Facilities for Process Plants - Contributed by Jadeep Choudary, Anita R. Legvold and James O. Pennock.

Some have asked questions such as: “What is Balance of Plant?”; “What is Offsites?” What is OSBL?” and “What needs to be considered when a project includes Offsites.” The purpose of this document is to aid in answering this type of question.

Section VI - Pipe Fabrication Shop Issues

A: Checking of Pipe Fabrication Shop Drawings - By: James O. Pennock

B: Pipe Fabrication Shop Assignment Questions and Problems - By: James O. Pennock

Page 3: Piping Training_Section I - Piping Components

Section VII - Management and Supervision

A: Introduction To Line Numbering - By: James O. Pennock

B: Checking, Quality Assurance and Quality Control of Piping Drawings - By: James O. Pennock

"Checking or the Quality Assurance & Quality Control (QA/QC) in process plant piping engineering and design is a grossly misunderstood activity that is performed (or should be performed) by every piping group on every process plant project deliverable."

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Page 4: Piping Training_Section I - Piping Components

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 many different 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 valve or safety valve operates automatically at a set differential pressure to correct a potentially dangerous situation, typically over-pressure.

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

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Section - I

B: Pipe By: James O. Pennock

Definition:

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 the applicable line class but the definition includes any similar component designed as tubing, which is used for the same application.

History:

Page 5: Piping Training_Section I - Piping Components

One of the earliest methods of conveying fluids in the history of mankind was by pipe. The earliest pipe on record was the use of bamboo for moving small quantities of water as a continues flow. As man progressed, he began using hollow logs for his piping needs. Probably the first recorded use of metal in piping systems was the use of lead or bronze during the "Bronze" age.

During the excavation at Pompeii, complete water distribution systems fabricated from lead have been uncovered. 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 in almost every aspect of our lives. Our drinking water is produced in plants full of piping and then comes to us through a vast network of pipes. The waste from our homes and businesses flows away through another network of pipes and is then treated in a plant full of piping. The fuel we use for travel or for heating was collected, 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 also dependent 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 the more 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 to form lined pipe systems. These include carbon steel pipe lined with glass, carbon steel pipe that is lined with various plastics; carbon steel pipe lined with concrete. Each one, plain or lined has certain advantages and disadvantages. Many things enter into making a choice of materials. Among the most important of these are commodity, 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, and because it became necessary to increase wall thickness to accommodate higher pressures and temperatures, it became necessary to size pipe by "nominal" size rather than actual size. Because it was deemed too expensive to have a set of thread dies for each wall thickness in the smaller sizes, the outside diameter (O.D.) was held constant. Thus wall thickness changes affect the internal diameter only and leave the O. D. constant for standardized fitting engagements. Nominal size refers to the name by which we call a particular size pipe. Nominal size and actual outside diameter of a pipe differs for size 12" and under. For sizes 14" and larger the actual outside diameter and the nominal size are identical.

Pipe comes in a very wide range of sizes. It is not uncommon to see piping as small as ½" 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 choice because odd size fittings may not be available. It is best to stick to the closest and most commercially available or common size to meet the need. The smaller common sizes in pipe

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include ½", ¾", 1", 2", 3", 4", 6", 8" 10" and 12". The larger sizes, 14" and above increase in 2" increments. The Nominal size pertains to calling the pipe size by name only. The actual outside diameter or O. D. is different for 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"

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 smaller the inside diameter.

Weight:

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

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 run from about 16' to 22' in length. A double random will run from about 35' to 40' in length. Pipe can be ordered to 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 then welding the two edges together to form a tube. This pipe is commonly called "welded pipe" or ERW pipe. The other way is to take a solid bar or billet and pierce a hole through the length. This pipe is commonly called seamless pipe.

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Determining wall thickness:

The wall thickness for pipe is generally covered in the piping material specifications by calling out the Schedule Number for a large majority of sizes. However, as pressure and temperature increase, and sometimes the corrosion allowance, it becomes necessary to calculate the required wall thickness for a specific case. Please note that generally as the specifications change into higher-pressure classes, wall thickness calculations must be 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, schedules and 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 or mechanical properties (tensile and yield strengths). The tensile strength is the ultimate amount of stretching the steel can bear without breaking. The yield strength is the maximum amount of stretching steel can bear before 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 lower carbon 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 is also easier to machine because of its higher carbon content. It is generally accepted that Grade B welds as well as Grade A.

Ends:

Steel pipe can generally be specified with a specific end preparation at the time of purchase. Three end preps are standard. There is plain end (PE). This would be the choice for small sizes where socket welded fittings will be used to join pipe to pipe or pipe to fittings. This is also the default end prep if no end prep is specified. There is threaded end (TE). This would be the choice for small sizes where the pipe to pipe or pipe to fitting assembly is to be threaded. There is also bevel end (BE). This would be the choice for most all 3" and larger steel pipe (or other 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 should understand about pipe. There is a big difference between what you know about a subject and what you understand about that subject.

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With pipe, most novice designers think that all they have to do is "draw" or "place" the pipe symbol (on that pipe support beam symbol) in whatever CAD system they are currently using and they are done. They do not understand 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 different temperature. That difference between the installation temperature and the operating temperature will cause the pipe to expand or contract. No matter what the designed tries to do he or she cannot stop this action. This expansion (or contraction) will cause stress, strain and force in both the piping system and the pipe support system.

This pipe will also have a weight problem. The pipe it self has a certain weight. The pipe next to it may be the same size but it may not weight the same. This pipe may be both high pressure and high temperature. This means that the wall schedule may be much thicker therefore it will weigh more. Let's say we do have two lines side by side. They are both 14", one (Line A) is a low temperature, low pressure cooling water line and the other (Line B) is a high pressure, high temperature hydrocarbon process line. The span for both lines is 25'.

Example:

Item Line A Line B

Pipe weight/foot 54.6 189.1

Water weight/foot 59.7 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 pipe support. However, it does indicate that there must be some close coordination with the structural department so 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 need a 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 farces be 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 the dimensional reference point for the centerline of this line and can cause design errors if not understood and allowed for.

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Page 9: Piping Training_Section I - Piping Components

Section - I

C: 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 many different 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 most common 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 the pipe to which they are being attached. Some fittings are Cast Iron, some are Malleable Iron, some are Forged Steel and others are even fabricated from rolled Steel Plate. The most used materials are again common carbon steel, along with chromes, stainless steel, iron, brass, copper, lead, aluminum, glass, rubber and various types of plastic and plastic lined metal materials.

Fitting Types:

Normally, fittings fall into three basic types or categories. These are In-line, On-line and Closures. The In-line fittings 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 and plugs used to close the end of a pipe system. We also will discuss some cases where there are alternates to these 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 by far the most common is the 90° long radius Ell. The second is the 45° long radius Ell. The third is the 90° short radius Ell. The fourth is the long radius reducing Ell. The fifth version is the long radius 180° Return Bend. The basic Butt-Weld Ell is manufactured in 90° or 45° configurations as a standard. However for special order and extra 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 piping system. Elbows like pipe can be flame cut or machine cut to the required angle. The rough end is then ground or machine beveled to the proper angle for welding. There is normally no harm to the fitting when this is done.

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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 long radius 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 the center-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° Ells unless noted otherwise. This means that the designer must call out any and all exceptions to this rule. If the Ell is a 90° long radius Ell then the elbow symbol is all that is required. However, if the Ell is a 45° Ell then the designer must add the notation "45° Ell" next to the elbow symbol. If the Ell is a 90° short radius Ell then the designer must place the notation S. R. next to the elbow symbol. Also if the elbow has been trimmed to any odd 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 use the long radius Ell at all times unless conditions exist that force another choice. The short radius 90° Ell should only be used when tight space does not allow the long radius. The 45° Ell is normally used where a simple offset 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 to fabricate 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 be covered later.) As such this Ell is made with one end of one size and the other end one or two line sizes smaller. The using of the reducing Ell is not cheaper; it only takes less room. The "long radius" dimension for the 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 the designer quickly learns the center-to-end dimensions. The center-to-end dimensions for the 45° Ell are normally found only on a chart. However, there is a short-cut way to "know" these dimensions. You see, these dimensions 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 from the first time and the third time and total them up. That will be the dimension for the 45° Ell fitting.

Example:Column #1 (Line size) Column #2(½ Col. #1) Column #3(½ Col. #2) Column #4(½ Col. #3)

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Column #5 -Fitting dimension

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

4" 2" 1" ½" 2 ½"

8" 4" 2" 1" 5"

10" 5" 2 ½" 1 ¼" 6 ¼"

14" 7" 3 ½" 1 ¾" 8 ¾"

20" 10" 5" 2-½" 12 ½

Tees:

The primary purpose of a Tee fitting is to make a branch from a pipe line (or run). The branch may need to be the 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 three connections 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 fitting chart. The dimension found there is however standardized between all manufacturers. For Straight Tees the center-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 versions of Reducers. There is Concentric Reducers- where the centerline of the inlet and the outlet are the same. There is Eccentric Reducers- where the centerline of the inlet is different than the centerline of the outlet. With the Eccentric Reducer, one side is flat. Depending on how it is installed you may have bottom flat (BF) or top flat TF). You may also have a need to have (*) side flat (*= north, south, east or west). It is about a toss-up as to which is used more. Concentric Reducers are used mostly in situations where the reducer is in a vertical run of pipe. 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 a given size. The length of a reducer is the same for a range of sizes (Example: The end-to-end dimension for 10" 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 relation to the diameter.

Caps:

Page 12: Piping Training_Section I - Piping Components

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 piping configuration called a "Boot." A boot is a short length of pipe with a pipe Cap that is attached to the bottom of steam 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. You might do this with a Miter Ell (or Mitre, both spellings are correct). A Miter Ell is where no fitting is used. Miters are 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 angles depending on the number of pieces and welds required. This is really effective when really odd angles are required. Two of the pieces are the incoming pipe and the out-going pipe. There may be no middle piece or there may be one (or more) other short middle pieces depending on the angle of the turn. A simple turn of 45° might be made with a two-piece/one weld miter. Other changes in direction might be three piece/two weld miters, three piece/two weld miters and so on. The number of welds is always one less than the number of pieces. Depending on the size and schedule of the pipe a Miter might be cheaper than buying fittings. In small diameter piping the miter is more expensive (labor costs) and there is more pressure drop through a small miter than a small fitting. Miters are also not recommended for high temperature lines because miters are more susceptible to overstressing.

Stub-in (Stub-on):

We talked about using Straight Tees and Reducing Tees as a way to make branches from a line. For low pressure (or reasonably low pressure) there is another way to make branches from a line. This method uses only 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 then beveled for a "full penetration weld" The branch pipe is saddle cut (with no bevel) to match the I. D. of the run pipe. 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 branch pipe. This hole does not get a bevel. The end of the branch pipe is saddle cut to fit the run pipe and is then beveled 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 is set 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 normally only required for higher stress situations. The reinforcement is a "ring" plate cut from some scrape run pipe or the same material as the run pipe. At the center is a hole the same size as the branch pipe. If cut from flat plate it is then shaped to fit around the run pipe. The width of the ring is normally one half the diameter of the branch pipe. The ring is intended to replace the material that was removed when the hole was cut in the run pipe. A small diameter hole (1/4" NPT) is normally drilled

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(and tapped) in the ring to act as a vent during the welding process and to allow for Hydrotesting of the welds. The ring is then welded to the branch pipe and the run 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 is designed for use on 3" and larger welded pipe. The main feature of the typical O-Let fitting is the built-up base design which eliminates the need of any other form of branch reinforcement. The O-let fitting is manufactured in 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 a saddle shape to fit the run pipe. The outlet end of the weld-o-let has a beveled-end allowing for butt welding a pipe 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-Let fittings are made with the base that covers a range of header sizes. This means that the 24" x 4" WOL will also fit 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 threaded to match the normal tapered pipe threads. The threaded outlet sizes are normally limited to the smaller (2" and under) 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 a socket to match the socket welded piping fittings and pipe. The socket outlet sizes are normally limited to the smaller (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 angle attachment is sometimes required on high pressure relief systems. A Latrolet may be ordered with; a Butt-weld outlet 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 also be 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 a short 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.

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

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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 a larger header or run pipe. One end of the (Threaded or Socket Weld) Coupling is shaped to match the O. D. of the 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 method of 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 and pressure. Forged fittings are normally used for higher pressures and temperatures as well as for the more complex commodities.

The majority of the screwed fittings will have female (internal) threads per NPT (National Pipe Thread). The exception 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

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Socket-Weld fittings have a deep socket into which the pipe slips and aligns itself. The weld is then made on the outer surface of the pipe and fitting. This eliminate the need for or use of special clamps or tack welding for alignment prior to the final fit-up welding. At the bottom of the socket a 1/16" gap is left to compensate for expansion when the weld is made. This gap is called a root-gap. The swage does not have an internal socket; it will 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 short radius. 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 and some reducing sizes.

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

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

Nipples: A Nipple is a name given to a short length of pipe. It is not really a fitting in the same context as an elbow or a Tee. Nipples are cut from pipe and can be purchased in 4", 6" and 12" standard lengths. Pipe Nipples can 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 of socket-weld and screwed piping.

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Section - 1

D: Flanges, Gaskets & Bolts (Just the basics) Revision 1By: James O. Pennock

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Note: This article covers ASME B 16.5 Standard Piping Flanges up to 24" NPS. Flanges larger than 24" fall under 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 or other object to facilitate the assembly and disassembly of a piping system. For many years the only practical method of joining steel pipe had been by connecting threaded pipe ends with couplings. Improvements in the welding of carbon steel reduced labor costs and provided a completely sealed and much stronger joint. In most present day piping systems, threaded joints are usually limited to pipe sizes 2" and smaller. Larger pipe (3" and larger) is normally joined by butt-welding of continuous pipe and fittings or by flanges at joints that may require dismantling. Flanges (3" and larger) are also the default standard for connecting to most equipment connections and valves.

Materials of construction:

Flanges are manufactured in all the different materials to match the material of the pipe and fittings to which they are being attached. While some flanges are made of Cast Iron. The vast majority of flanges are forged carbon steel.

Forged Flange Ratings:

Forged steel flanges are made in seven primary ratings.

These primary ratings are as follows:

o Class 150

o Class 300

o Class 400

o Class 600

o Class 900

o Class 1500

o Class 2500

The Primary Rating is on a pressure/temperature relationship.

Example:

A Class 150 Forged Flange is used for 150 PSIG at 500º F. This same flange may also be used for 275 PSIG at 100º F. This same flange could also be used at 100 PSIG at 750º F. Note the inverse relationship. When the pressure goes up, the temperature goes down and vice versa. Pressure ratings are used as a

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guide to safely design piping systems and also to standardize manufactured piping components. The same ratings hold true for screwed 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 are available but are not as common. Cast Iron flanges are generally found associated with low pressure cast iron valves and nozzles on cast iron equipment such as some pumps and turbines. Mating forged steel flanges to cast iron flange can pose a potential for damage to the "weaker" cast iron. The main point to remember now is that a Class 125 Cast Iron flange will mate to a Class 150 forged steel flange, and a Class 250 Cast Iron flange will mate to a Class 300 forged steel flange. The solution to the potential damage problem will be discussed later 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 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 flange rating.

These common dimensions include:

o Flange Outside Diameter

o Flange Thickness

o Bolt Circle

o Number of Bolts

o Bolt Hole Size

o 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 up through 24" For instance; the number of bolt holes required varies with the size and rating of the flange. But the number and size is the same no matter the type of flange. The bolt holes are evenly spaced around the flange 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 holes shall straddle the "natural" centerlines. This is the flange bolt hole orientation rule. This "natural" centerline rule for flange is known, understood and followed by all responsible equipment manufacturers and pipe fabricators.

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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 oriented to 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 bolt holes 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 match this rule. When an exception is found the vendor can be requested to change his bolt hole orientation. This is not always successful and if not then the piping designer must insure that the piping fabrication documents call for the correct orientation.

This rule of bolt holes straddling the natural centerlines is sometimes referred to as "Two-Hole" the flange. This means that the two of the holes straddle the centerline. To "One-Hole" a flange means that the flange has been rotated so that one hole is right on the natural centerline. I assure you that 99.999% of the time that to "One Hole" 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 of thickness in the region of the butt weld that joins them to pipe or a fitting. A weld-neck flange is attached to a pipe or a fitting with a single full penetration, "V" bevel weld. The long tapered hub provides an important reinforcement of the flange proper from the standpoint of strength and resistance to dishing. The smooth transition from the flange thickness to the pipe wall thickness by the taper is extremely beneficial under conditions of repeated bending caused by line expansion or other variable forces, and produces an endurance strength of welding neck flanged assemblies equivalent to that of a butt-welded joint. This type of flange is preferred for severe service conditions, whether loading conditions are substantially constant or fluctuate between wide limits.

The weld neck flange is used in each of the seven flange ratings and has the advantage of requiring only one weld to attach it to the adjacent pipe or fitting.

The key dimension for a weld neck flange is the length through the hub from the beveled end to the contact face of the flange. This "length" includes the bevel, the tapered hub, and the thickness of the plate part of the flange and the raised face. To obtain the correct dimension you must look at a correctly constructed flange dimension chart (see the "Tools" button on this website) or a flange manufacturers catalog. Electronic piping design software will normally already have the correct dimension built-in.

It is important to understand and remember that the (1/16") raised face on the Class 150 raised face and on the Class 300 raised face flanges is normally included in the length dimension. However, the ¼" raised face is not included in the chart or catalog length dimension for the Class 400 and higher pressure rated

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flanges. The raised face dimension for Class 400 flanges (and up) normally must be added to the chart or catalog length to arrive at the true total length of these higher-pressure flanges.

Slip-on Flanges:

Slip-On (SO) Flanges are preferred by some contractors, over the Weld-neck, because of the lower initial cost. However, this may be offset by the added cost of the two fillet welds required for proper installation. The strength of the slip-on flange is ample for it's rating, but its life under fatigue conditions is considered to be only one-third that of the weld-neck flange.

The slip-on flange may be attached to the end of a piece of pipe or to one or more ends of a pipefitting. The slip-on flange is positioned so the inserted end of the pipe or fitting is set back or short of the flange face by the thickness of the pipe wall plus 1/8 of an inch. This allows for a fillet weld inside the SO flange equal to the thickness of the pipe wall without doing any damage to the flange face. The back or outside of the flange is also welded with a fillet weld.

A variation of the Slip-On flange also exists. This is the Slip-On Reducing Flange. This is simply a larger (say a 14") Slip-On flange blank that, instead of the Center (pipe) hole being cut out (or drilled out) for 14" pipe it is cut out for a 6" (or some other size) pipe. The SO Reducing flange is basically used for reducing the line size where space limitations will not allow the length of a weld neck flange and reducer combination. The use of the Slip-On Reducing Flange should only be used where the flow direction is from the smaller size into the larger size.

Lap Joint Flanges:

A Lap Joint Flange is a two piece device that is much like a weld-neck flange but also like a loose slip-on flange. One piece is a sleeve called a 'Stub-end" and is shaped like a short piece of pipe with a weld bevel on one end and a narrow shoulder on the other end called the hub. The hub is the same outside diameter as the raised face (gasket contact surface) of a weld neck flange. The thickness of the hub is normally about ¼" to 3/8". The back face of the hub has a rounded transition (or inside fillet) that joins the hub to the sleeve.

The other piece of a Lap Joint Flange is the backing flange. This flange has all the same common dimensions (O.D., bolt circle, bolt hole size, etc.) as any other flange however it does not have a raised face. One side, the backside, has a slight shoulder that is square cut at the center or pipe hole. The front side has flat face and at the center hole an outside fillet to match the fillet of the "Stub-end" piece. The flange part of the Lap-joint flange assembly is slipped on to the stub-end prior to the sleeve being welded to the adjoining pipe or fitting. The flange itself is not welded or fixed in any way. It is free to spin for proper alignment with what ever it is joining to.

The "Stub-end" can normally be purchased in two lengths. There is a short version, about 3" long and a long version of about 6" long. It is prudent for the piping designer to know which version is in the piping specification.

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Because of it's two piece configuration, the Lap Joint Flange offers a way to cut cost or simplify work. The cost saving comes when the piping system requires a high cost alloy for all "wetted" parts to reduce corrosion. The sleeve or Stub-end can be the required higher cost alloy but the flange can be the lower cost forged carbon steel.

The work simplification comes into the picture where there are cases that require frequent and rapid disassembly and assembly during the operation of a plant. The ability to spin that backing flange compensates for misalignment of the bolt holes during reassembly.

Screwed (or Threaded) Flanges:

Screwed flanges look very much like a Slip-On flange in some ways. The main difference is the Screwed flange was bored out initially to match a specific pipe inside diameter. The backside of this center opening is then threaded with the proper sized tapered pipe thread. This flange is primarily used to make flanged joints where required in small sizes in threaded pipe specs

Socket Weld Flanges:

Socket Weld flanges also look very much like a Slip-On flange. Here the main difference is the Socket Weld flange was also bored out initially to match a specific pipe inside diameter. Here however, the backside of this center opening is then counter bored to form the proper size socket to take the pipe O.D. This flange is primarily used to make flanged joints where required in small sizes in socket welded pipe specs

Blind Flanges:

Blind flanges are a round plate with all the proper bolt holes but no center hole. This flange is used to provide positive closer at the ends of pipes, valves or equipment nozzles.

Flange Faces:

Face Types:

Flanges faces come in different forms. Some forms are more common and others are old and out of date forms. These old forms may be ordered but possibly only to match an existing piece of old equipment.

Flange face forms are:

o Flat Face (FF) - The Flat Face is primarily used on Cast Iron flanges. With this face the whole contact face of the flange is machined flat.

o Raised Face (RF) - The Raised Face is most common of all flange faces. The flange has a raised area machined on the flange face equal to the contact area of a gasket.

o Ring-type Joint (RTJ) - This is a form of flange face that is becoming obsolete. This type has a higher raised portion on the face into which a ring groove is then machined.

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o Tongue and Groove (T&G) - This is also a form of flange face that in becoming obsolete. With this type the flanges must be matched. One flange face has a raised ring (Tongue) machined onto the flange face while the mating flange has a matching depression (Groove) machined into it's face.

o Male-and -Female (M&F) - This is another form of flange face that is obsolete. With this type the flanges must also be matched. One flange face has an area that extends beyond the normal flange face (Male). The companion flange or mating flange has a matching depression (Female) machined into it's face.

Dissimilar flange faces such as the RTJ, T&G and the F&M shall never be bolted together. The primary reason for this is that the contact surfaces do not match and there is no gasket that has one type on one side and another type on the other side. Don't even think about it!

Flat face flanges are never to be bolted to a raised face flange. If you need to bolt a Forged steel flange to cast iron then you must call for the forged steel flange to be machined off to a flat face. For more information on this see this link to Goulds pumps

Flange Face Finish:

The part of a flange where the gasket touches is called the contact surface. This area is the most critical area to the prevention of leaks. This area of a flange must be protected from the time it is machined clear through all the various shipping, storage, fabrication and installation periods. Flange faces are machined with standard finishes. No doubt your piping material engineer could request another special finish but that would only add extra cost. The most common finish for the contact face of a flange is a concentric (or phonographic) groove. This pattern is machined into the flange face and provides the grip for the gasket.

Gaskets:

You can have Class 600 stainless steel flanges and have the bolts fully tight and if you do not have a gasket (or the proper gasket) you will have a lot of leaks. Having the gasket and the right gasket is very important. Gaskets provide the tight seal that retains the pressure and keeps the gas or liquid in the pipe. In a vacuum system it keeps the outside air from getting in. Gaskets are designed and later chosen considering all the same issues as were used to select the pipe. These include pressure, temperature, and corrosiveness of the commodity, among others. Gaskets are made of a wide range of materials. These include rubber, elastomers and graphite. The Spiral Wound gasket has a graphite or Teflon material wound with a metal strip which is then held in shape by a flat metal ring. This metal retainer ring also acts as a centering tool to insure that the casket is not misaligned or blocks the product flow.

Gaskets for Ring Type Joint flanges are simply a solid metal ring. There are two basic cross-sectional shapes for the RTJ gasket. These are "Oval" and "Hexagonal."

Bolts:

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Bolting is the final element of a complete flange joint assembly. Here again we have some variations. The most common is the Stud Bolt. Next is normally the Cap Screw. And finally we have the Machine Bolt.

Stud Bolts:

The Stud Bolt is a long threaded rod (with no head on either end) and two nuts. The Stud Bolt is used in all locations where you have two normal flanges with access to the backside of both flanges and both ends of the stud.

Cap Screws:

The Cap Screw is a fully threaded rod with a head on one end. No nut is used with the Cap Screw. The Cap Screw is normally used in all locations where a flange is being attached to a piece of equipment where there are only tapped holes (i.e.: no access to the backside). Cap Screws are also used to attach threaded-lug type wafer valves (Butterfly Valves) between a pair of flanges. For this application the length of the Cap Screw selected is critical. Two Cap Screws are used at each lug position, one from one side and one from the other side. The Cap Screw must be long enough to go through the flange, the raised face and half of the threaded lug minus 1/16 of an inch. This leaves a 1/8 inch total gap between the ends of the two cap screws when the screws are tight.

Machine Bolts:

A Machine Bolt is a rod with a hexagon head on one end and threads on some of the length. Machine Bolts are normally made of a lower strength material than Stud Bolts and are therefore considered only where low strength bolting is required. These applications most often include Cast Iron flanges.


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