Screwed Fitting

Screwed fittings have female threads (threads inside the fitting) and socket weld fittings have an internal socket that prevents a fitting make up assembly.

From: A Practical Guide to Piping and Valves for the Oil and Gas Industry, 2021

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Pipe Fittings

Roy A. Parisher, Robert A. Rhea, in Pipe Drafting and Design (Third Edition), 2012

Screwed and Socket-Weld Fittings

Screwed and socket-weld fittings perform the same basic functions as butt-weld fittings. Like butt-weld fittings, elbows, tees, and reducers are manufactured for screwed and socket-weld applications. There are, however, a few differences that must be examined. Screwed and socket-weld fittings are normally reserved for installations where the nominal pipe size is 3″ and smaller. Screwed and socket-weld fittings are also available in cast iron, malleable iron, or forged steel. Typically, forged steel fittings are used on high pressure and temperature lines. However, low pressure and temperature lines, such as air, water, or condensate, are fabricated using either cast or malleable iron fittings.

Pipe lines containing high pressure and temperature commodities, which are subject to substantial amounts of movement and vibration, mandate fittings made of forged steel. For these reasons, forged steel screwed and socket-weld fittings are manufactured in two pressure classes—3000# and 6000#. The sizing charts, shown in Appendix A, provide the dimensional measurements for 3000# and 6000# screwed and socket-weld fittings. Figures 3.54 and 3.55 display a portion of the screwed and socket-weld fitting dimensioning charts found in Appendix A.

Figure 3.54. Screwed fittings dimensioning chart.

Figure 3.55. Socket-weld fittings dimensioning chart.

Most screwed fittings are manufactured with internal, or female, threads as defined by the American Standard and API thread guidelines. As shown in Figure 3.56, of particular concern to the pipe designer is the amount of pipe length lost during the assembly of screwed fitting configurations. When screwed fittings and threaded pipe are assembled, a certain amount of pipe length is lost as a result of the internal and external, or male, thread connecting process. Each time a threaded connection, or engagement, is made, the configuration gets shorter. The length of this engagement varies depending upon the nominal pipe size and pound rating of the fitting. The procedure to determine the actual center-to-center length of a threaded configuration is to subtract the total length of all the thread engagements from the total unassembled length of pipe and fittings. The unassembled length can be thought of as all the pieces, both fittings and pipe, being laid out end to end. From this unassembled length, the total of all the thread engagements is then subtracted to determine the total assembled length. The formula below applies the values shown in Figure 3.56 to calculate the assembled length.

Figure 3.56. Internal and external thread engagements.

AL=CE1+CE2+PL-(TE1+TE2)

Some fittings, such as plugs and swages, however, are manufactured with external threads and their assembled lengths are treated differently, as will be explained later.

The socket-weld fitting has become the fitting of choice for many fabricators because it offers greater strength at each point of connection. Even though screwed fittings can be seal-welded if necessary, strength of the fitting is decreased when the threads are cut during the manufacturing process. Socket-weld fittings can be easily fitted and welded without the need of special clamps or tack-welds, which are often required to hold a fitting in place before the final weld is made. Like screwed fitting configurations, during the assembly of socket-weld configurations, there is pipe length loss. This lost length is equal to the depth of the socket, or socket depth, and must be accounted for when calculating overall lengths of pipe runs. However, there is a slight difference from screwed pipe assemblies. On socket-weld connections, a 116 gap is factored into each socket-weld connection. Figure 3.57 provides a sectional view of two socket-weld elbows and the connecting pipe. Notice two socket depths must be subtracted from the total unassembled length of the two elbows and the piece of pipe, then ⅝″ is added back to account for the two 116 gaps, before an assembled configuration length can be determined. If a formula were applied to calculate the assembled length using the values shown in Figure 3.57, it would look like

Figure 3.57. Socket-weld fitting connections.

AL=CE1+CE2+PL-(SD1+SD2)+18

Fittings

Like butt-weld fittings, screwed and socket-weld fittings are used to make similar routings in the piping system, but only in smaller pipe sizes. Screwed and socket-weld fittings differ in size and shape, but they achieve the same purpose as butt-weld fittings. However, there are some differences. Ninety degree elbows are not available as long-radius or short-radius, and their center-to-end dimension must be found on a dimensioning chart, as no formula is available for calculating their radius length. Figure 3.58 provides examples of some screwed and socket-weld fittings.

Figure 3.58. Screwed and socket-weld fittings.

Screwed and socket-weld fittings are represented differently on drawings than their butt-weld counterparts. For example, screwed and socket-weld elbows are drawn with square corners, using short hash marks to represent the connection points of the fitting and its mating pipe. Some engineering companies even draw short ears on the hash marks to indicate a difference between screwed and socket-weld symbols (see Figure 3.59).

Figure 3.59. Screwed and socket-weld drawing symbols.

There are, however, some fittings that are unique to the screwed and socket-weld family of fittings. These fittings do not lend themselves to butt-weld applications and are manufactured solely for use in screwed and socket-weld configurations. A brief discussion of those is as follows.

Unions

The union, shown in Figure 3.60, is a fitting placed within a piping configuration that will allow the assembly to be disassembled for inspection, repair, or replacement. Manufactured for screwed and socket-weld applications, the union is represented on drawings as shown in Figure 3.61. Unions should be positioned in locations that will facilitate the easy removal of critical pieces of equipment. Figure 3.62 shows how unions are placed in a configuration to allow easy removal of a valve.

Figure 3.60. Union.

Figure 3.61. Union drawing symbols.

Figure 3.62. Positioning of unions.

Plug

The plug, like a cap, is designed to seal the end of a run of pipe. Plugs are manufactured for screwed fittings with male threads and are screwed into the end of a pipe to create a seal. Figure 3.63 shows the drawing symbols for the plug.

Figure 3.63. Plug drawing symbols.

Coupling

Although this fitting is used in butt-welding applications as a branch connection, its primary use is to connect lengths of screwed and socket-weld pipe together. Some clients may stipulate, however, that all socket-weld pipe must be connected with a butt-weld rather than a coupling.

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Leaks

Trevor Kletz, in What Went Wrong? (Fifth Edition), 2009

Publisher Summary

This chapter opens with the discussion of locations of leaks and their immediate causes. Major sources of leaks highlighted in this chapter are from tanks, lined pipes, closed valves, screwed fittings, and other weak spots in pipe work. In the case of tanks, the major causes of leaks are described such as problems in welding, plastic material tanks, and material used for lining inside the tanks. Pipes are mostly damaged by corrosion or rust, so it is necessary that places where corrosion is likely are listed for inspection, and some other places picked at random should also be inspected. A major cause of leaks listed in this chapter is surge pressure, particularly water hammer in steam mains, which has caused many failures and large leaks of steam and condensate. Some of the important features of surge pressure are also discussed in this chapter. Essentially in the case of screwed fittings, pressure tests are carried out to confirm that the equipment can withstand the test pressure and, therefore, we should assume that failure is possible and keep everyone out of the way. If we were sure the equipment would not fail, we would not need to test it. Leaks can be detected by testing at the operating pressure. This chapter provides various examples of the weakness that penetrates pipe work and is a reason for failure or major leaks.

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FLUID FLOW

A. Kayode Coker, in Ludwig's Applied Process Design for Chemical and Petrochemical Plants (Fourth Edition), Volume 1, 2007

4.9 PIPE, FITTINGS, AND VALVES

To ensure proper understanding of terminology, a brief discussion of the “piping” components of most process systems is appropriate.

The fluids considered in this chapter consist primarily of liquids, vapors, gases, and slurries. These are transported usually under pressure through circular ducts, tubes, or pipes (except for low pressure air), and these lengths of pipe are connected by fittings (screwed or threaded, butt-welded, socket-welded, or flanged) and the flow is controlled (stopped, started, or throttled) by means of valves fixed in these line systems. The components of these systems will be briefly identified in this chapter, because the calculation methods presented are for flows through these components in a system. These flows always create some degree of friction loss (pressure drop) (or loss of pressure head) which then dictates the power required to move the fluids through the piping components (Figure 4-4). (Pump power may be required for other purposes than just overcoming friction.)

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Steel Pipe

Roy A. Parisher, Robert A. Rhea, in Pipe Drafting and Design (Fourth Edition), 2022

Threaded Connections

Another common means of joining pipe is the threaded end (TE) connection. Typically used on pipe 3″ and smaller, threaded connections are often referred to as screwed pipe. With tapered grooves cut into the ends of a run of pipe, screwed pipe and screwed fittings can easily be assembled without welding or other permanent means of attachment. Screwed pipe and its mating fittings will have threads that are either male or female. Male threads are cut into the outside of a pipe or fitting, whereas female threads are cut into the inside of the fitting.

As screwed pipe and fittings are assembled, a short length of pipe is drawn into the fitting. This connection length is called a thread engagement. When drawing and dimensioning screwed pipe, a piping drafter must be aware of this lost length of pipe. As the diameter of the pipe increases, so will the length of the thread engagement. Table 2.2 provides a chart indicating the thread engagements for small bore pipes.

Table 2.2. American Standard and API Thread Engagement Dimensions.

Dimensions (in inches and millimeters)
Pipe size Thread engagement
(in.) (mm) (in.) (mm)
½″ 13 ½″ 13
¾″ 20 9/16 14
1″ 25.4 11/16 18
1½″ 38 11/16 18
2″ 50.8 ¾″ 20
2½″ 63.5 15/16 24
3″ 76.2 1″ 25.4
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Process Piping

Kenneth Storm, in Industrial Piping and Equipment Estimating Manual, 2017

1.2 Piping Section General Notes

Handling and erecting pipe—man hours to unload, store in lay down, haul, rig, and align in place.

Field handling valves—man hours to place screwed, flanged and weld end valves, and expansion joints

Field handling control valves and specialty items—man hours are two times manual valves per valve

Field erection bolt-ups—man hours per joint to bolt-up valves, expansion joints, flanged fittings, and spools

Making on screwed fittings and valves—man hours for cutting, threading, handling, and erection per connection.

General Welding Notes

Manual butt welds—wall thickness of the pipe determines man hours that will apply per joint

PWHT butt welds greater than or equal to 0.750″

PWHT craft support—man hours for craft to warp/and remove pipe insulation for stress relief

Apply percentages for welding alloys and nonferrous butt welds

Preheating and stress-relieving butt welds are not included

Olet welds—man hours are two times butt weld and include cutting, placing, and welding per connection

Stub in weld—man hours are 1.5 times butt weld and include cutting, placing, and welding per connection

Socket welds—man hours include fit up and welding per joint

Hydro test pipe—man hours to place/remove blinds, open/close valves, removal/replacement of valves and specialty items and pipe sections as required, and drain lines after testing.

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Maintenance-induced accidents and process piping problems

Roy E. Sanders, in Chemical Process Safety (Fourth Edition), 2015

Beware of other piping issues

In the fifth edition of What Went Wrong? Trevor Kletz listed a number of weak spots in chemical plant piping systems. Some of his listings are blended with my experiences as a reminder of weak places in piping systems [28].

Small diameter connections should not be less than ¾ in. on main pipe lines (and 1 in. connections are even more desirable to survive the rigors of a plant atmosphere).

The smallest nozzle connection to a storage tank or a pressure vessel should be a welded 1½ in. flanged connection.

Screwed fittings should generally be avoided except on small diameter lines containing nonhazardous materials. Every small diameter threaded fitting should have a flanged block valve upstream.

Long runs of small bore piping for instruments or of samples must be adequately supported [28].

Vents, drains, and other connections that have been abandoned or are no longer needed should be removed and the plug welded in place (if conditions allow welding) [28].

Utility stations and permanent connections to services as utility air, water, steam, nitrogen, etc., should be equipped with double block and bleeds and check valves (if there is a remote opportunity for reverse flow) [28].

Pipelines transporting hazardous materials must have routine inspections via a well-coordinated mechanical integrity program (see Chapter 12).

Expansion joints if they cannot be avoided with piping loops, must be regularly inspected for misalignment, twisting, or missing stay bolts.

Spring pipe hangers is required must be regularly inspected in a mechanical integrity program.

Be aware and inspect for corrosion under pipe supports and corrosion under insulation. Promptly handle any deficiencies.

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Centrifugal Compressors

Royce N. Brown P. E., in Compressors (Third Edition), 2005

Casing Connections

Casing inlet and outlet nozzles are normally flanged. The general preference in process service is for all casing connections to be flanged or machined and studded. On steel-cased machines, this normally is not a problem. On the smaller refrigeration compressors that are highly standardized, constructed of cast iron, and originally designed for other than process service, connections will generally have flanged inlet and outlet nozzles. However, most of the auxiliary connections on these machines will be screwed fittings. It is desirable to use standard flanges throughout the connections on the casing. However, for space reasons, on rare occasions, a nonstandard flange arrangement may become necessary. It is quite important to have the compressor vendor furnish all mating flanges and associated hardware.

Forces and moments which the compressor can accept without causing misalignment to the machine are to be specified by the vendor. Many factors go into this determination and, as one may guess, the limits are determined quite arbitrarily in most cases. With all of the many configurations a compressor can take, a single set of rules cannot fit all. Despite this, NEMA SM-23 [5] for mechanical-drive steam turbines is used as a basis. API 617 has adopted the NEMA nozzle criteria to centrifugal compressors. This works on larger steel-cased multistage compressors, but is not good for the overhung style. Moreover, the user or piping designers want a higher number to simplify piping design, while the manufacturer wants a small number to ensure good alignment and fewer customer complaints. From a user's point of view where long-term reliability is a must, the vote must go to the manufacturer. Experience shows that the lower the piping loads on the nozzles, the easier it is to maintain coupling alignment. This seems reasonable since most compressors are equipped with plates called wobble feet to provide flexibility for thermal growth. The feet will flex from pipe loads as well as from the temperature. The piping loads tend not to align themselves as well with the shaft as the temperature gradients. Even when guides and keys are used, as is customary on the larger machines, they may bind despite the fact that they are stout enough to carry the load.

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Screw threads and conventional representations

Colin H. Simmons, ... Neil Phelps, in Manual of Engineering Drawing (Fifth Edition), 2020

ISO metric threads

Fig. 17.3 shows the ISO metric thread form for a nut (internal) and for a bolt (external). In the case of the nut, the root is rounded in practice. For the mating bolt, the crest of the thread may be rounded within the maximum outline, as shown, and the root radiused to the given dimension. Both male and female threads are subject to manufacturing tolerances and for complete information reference should be made to BS 3643-1.

Fig. 17.3. ISO metric thread H = 0.86,603 P, H/4 = 0.21,651 P, (3/8)H = 0.32,476 P, (5/8) H = 0.54,127 P, where P is the pitch of the thread.

BS 3643-2 defines two series of diameters with graded pitches for general use in nuts, bolts, and screwed fittings: one series with coarse and the other with fine pitches. The extract given in Table 17.1 from the Standard gives thread sizes from 1.6 to 24 mm diameter. Note that first, second, and third choices of basic diameters are quoted, to limit the number of sizes within each range.

Table 17.1. Thread sizes from 1.6 to 24 mm diameter.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Basic major diameters choice Coarse series with graded pitches Fine series with constant pitches
1st 2nd 3rd 6 4 3 2 1.5 1.25 1 0.75 0.5 0.35 0.25 0.2
1.6 0.35 0.2
1.8 0.35 0.2
2 0.4 0.25
2.2 0.45 0.25
2.5 0.45 0.35
3 0.5 0.35
3.5 0.6 0.35
4 0.7 0.5
4.5 0.75 0.5
5 8.8 0.5
5.5 0.5
6 1 0.75
7 1 0.75
8 1.25 0.75
9 1.25 1 0.75
10 1.5 1.25 1 0.75
11 1.5 1 0.75
12 1.75 1.5 1.25 1
14 2 1.5 1.25a 1
15 1.5 1
16 2 1.5 1
17 1.5 1
18 2.5 2 1.5 1
20 2.5 2 1.5 1
22 2.5 2 1.5 1
24 3 2 1.5 1
a
The pitch of 1.25 mm for 14 mm diameter is to be used only for sparking plugs.

On a drawing, a thread will be designated in accordance with BS EN ISO 6410-1, e.g. the letter M followed by the size of the nominal diameter, the pitch required, and the thread tolerance class, i.e. M10 × 1 – 6h. The pitch is always preceded by a multiplication symbol and the tolerance class is always preceded by a short dash.

When dimensioning metric coarse threads it is not necessary to indicate the pitch as this is the default thread system. Should the reader encounter threads designated this way, e.g. M10 or M10 – 6H, it can be assumed they are of the coarse series. However, the authors advise that for completeness the pitch should always be included.

Any dimension relating to the depth or length of thread refers to the full depth or length of thread. The direction of a Right Hand thread (RH) is not generally noted; however Left Hand threads should include abbreviation ‘LH’ after the thread designation, i.e. M10 × 1 – 6h LH.

BS 3643-2 specifies the tolerances and limits of size for the tolerance classes 4H, 5H, 6H, and 7H for internal threads and 4h, 5h, 6h, and 7h for external threads. For general use, the tolerance class 6H is suitable for internal threads and tolerance class 6g for external threads.

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Measurement System Design

James E. Gallagher, in Natural Gas Measurement Handbook, 2006

General

An insulating gasket should be installed at the flange that designates the change in ownership between the two operating companies. This change in ownership should be clearly marked in accordance with governmental requirements.

Piping and fittings should be welded and coated in accordance with operator's approved specifications. Piping should be buried whenever practical to minimize maintenance costs and increase the ease of access for LACT/ACT operations and maintenance.

In selecting flowmetering equipment and piping, the owner or designer should consider any special material requirements or design code practices if the gas contains corrosive components. Hydrogen sulfide and carbon dioxide in sufficiently large concentrations are the most commonly found sour contaminants in hydrocarbon gases and require special consideration, particularly where the gas is water wet. While piping codes may require the use of special materials and control of steel hardness, good-quality standard stainless steels normally suffice for most instrument internals in sour service. Where components are welded, low-carbon stainless steels should be selected for sour service.

To minimize the possibility of fatigue failure and emissions, the appropriate operator's management should approve in writing the use of screwed fittings.

The exceptions are as follows. For instruments and sampling valves, the valve attached to the piping element shall be welded on the piping side and screwed on the instrumentation side. For ANSI 400 or less, thermowells or sample probes may employ a threaded design. The thread-o-let into which the thermowell or sample probe is inserted should be welded to the piping element. For ANSI 600 class or higher, all thermowells and sampling probes should employ a flanged design.

All valves, fittings, pipe, and equipment containing gas or liquids should comply with all requirements of the Federal Gas Pipeline Safety Regulations and all other applicable codes and standards. All valves, fittings, and pipe shall be based on a design factor of 0.50 (50% of specified minimum yield strength). All piping should be API 5L Grade B or higher seamless in accordance with the design requirements. All fittings should be ASTM A105 or higher yield strength.

Piping between the LACT/ACT and the tie-in point(s) should be designed for a maximum gas velocity of 50 fps. The exceptions to this criterion are the flowmeter tube velocity and the control valve piping, which are contained in the appropriate sections.

The amount of takeoff fittings, drains, vents, and other devices or procedures that could result in the inadvertent loss of natural gas should be minimized as much as reasonable. All of the piping, fittings, and take-offs associated with the flowmeters and the pipeline pigging facilities should be carefully reviewed by all parties to ensure accurate measurement. If a potential for loss or gain is found, remedial action should be taken as quickly as practical (bypass of the flowmeter facility).

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Piping

Ian SuttonAuthor, in Plant Design and Operations (Second Edition), 2017

Fittings

Fittings make directional changes in a piping system and connect pipes, sometimes of different sizes. The following are commonly found pipe fittings:

Elbows—usually either 90° or 45°.

Caps.

Saddles—used to form a connection between two pipes when a fitting is not already present.

Reducers/Expanders—used to either reduce or increase the pipe diameter. An expansion may be required if the fluid is a flashing liquid, i.e., one that is forming vapor as its pressure drops.

The ideal pipe joint is easily assembled, does not introduce weaknesses in the piping system, and provides a seamless flow path.

The three most typical types of joints in process piping systems are welded, threaded, and flanged. Other joints used in utility services include groove and press fit systems. Fittings can be either welded or clamped to the piping.

Welding

Welded joints provide strength equal to original pipe, do not impair flow pattern, and are resistant to corrosion. Welded joints require precise alignment, require skilled labor and equipment. Unlike flanges, they cannot be disassembled. Butt-weld joints, in which portions of pipe of equal dimensions are lined up and welded, are most common in metallic piping systems. Socket welds are also used.

Threaded Piping

Threaded joints, in which the end of a pipe or fitting is screwed into another pipe or fitting, are easy to assemble and disassemble. They are most often used in pipes with diameters of DN 50 (2 in.) or less. The pipe threads are frequently packed with a filler material referred to as “pipe dope” to prevent leakage. Pipe dope also acts as a lubricant between meshing tapered threads.

Although convenient, threaded joints have the following drawbacks:

Stress concentration at the root of the thread create weakness.

A decrease in effective wall thickness where the threads are cut.

The potential for thread disengagement if the pipe is exposed to fire.

Susceptibility to vibration and fatigue failure.

Given these problems screwed fittings should be limited to services such as the following:

With pipe that contains only cool nonhazardous fluids.

Maximum working pressure of 20 bar(g).

Nominal diameter DN 50 or smaller.

Expansion Loops/Compensators

As the temperature of the fluids in the pipe changes or as the atmospheric temperature changes, the piping system will expand or contract. The temperature of piping will also change if it is steamed out or if it is exposed to fire. Changes such as these, as well as the effect of vibration, can place an unacceptable level of stress on the piping and its fittings. One way of addressing this problem is to install expansion loops or joints, sometimes referred to as compensators, in a section of the pipe.

Broadly speaking there are three types of expansion compensator:

1.

Expansion loops

2.

Axial joints

3.

Bellows.

Expansion loops are generally preferred since they are less vulnerable to mechanical failure. However, they take up considerable space so axial or bellows compensators may have to be used.

Expansion joints used in the process industries are generally manufactured from steel, including stainless and high-grade nickel alloys. Expansion joints can also be manufactured from rubber or a polymer such as Teflon that will resist corrosion and aging. The Expansion Joint Manufacturers Association provides detailed information as to their design and operation in A Practical Guide to Expansion Joints (EJMA, 2016).

The improper design of a temporary expansion loop was a critical factor in the 1974 Flixborough disaster (BBC, 2010)―an event that was foundational in the development of process safety management systems.

Expansion loops

Fig. 4.2 is a sketch of an expansion loop. They are generally manufactured from standard pipe and elbows.

Figure 4.2. Expansion loop.

In general the height of an expansion loop will be twice its width (W in Fig. 4.2). Guidance as to the values that should be selected for W for different pipe sizes and different expansion values are provided by Engineering Toolbox (2016c).

Axial joints

Axial joints are typically used in long straight runs of pipe that do not have bends (e.g., in tunnels, trenches, and below grade). Any nonaxial movement could cause excessive strain.

Advantages of this type of joint include:

They are fabricated from the same metals as the pipe.

They are inherently robust and strong.

They do not have a catastrophic failure mode, i.e., they can leak but not rupture.

Packing can be injected into them while the line is in service.

A disadvantage, in addition to the need for a straight pipe run, is that require occasional maintenance and packing and so they need to be accessible.

Bellows

Bellows-type joints, as shown in Fig. 4.3, are used if the piping system is subject to a high level of vibration or earthquake movement. The bellows must be strong enough to handle the internal pressures of the piping system yet be flexible enough to accept axial, lateral, and angular deflections.

Figure 4.3. Bellows-type expansion joint.

Bellows-type joints require minimal maintenance. However, if they are damaged or fail for some other reason they have to be replaced. This involves shutting down the system of which the piping is a part. They can also fail catastrophically, thus creating potentially serious environmental and safety consequences. They can also be improperly used to correct for incorrect alignment of piping sections.

Small Pipe Connections

Small bore connections (less than 2 in. nominal/DN 50) such as threaded gauge connections, sample points, and nozzles are prone to fatigue failure and mechanical damage. Therefore their number should be limited, particularly if they are subject to vibration. Where possible they should be combined into a single branch using reducing tees and one piece forged fittings.

The following are general requirements for nozzle and instrument connections:

Connections smaller than 19 mm (¾ in.) should not be used.

Threaded and socket welded connections should be 6000 lb couplings, maximum size 38 mm (1½ in.). Threaded connections should not be used for hydrocarbon (including glycol mixtures), heat transfer oils, or steam service.

Flanges should be used for sizes 50 mm (2 in.) and larger. Class 150 flanges should be used, except internal or external displacement liquid level devices should have Class 300 flanges.

Potential failures are minimized by:

Installing only those connections actually needed.

Making the attachments as short as possible.

Using extra heavy pipe nipples and ¾ in. minimum diameter to the first valve off the vessel.

Using socket-weld fittings, especially between a vessel and the first valve.

Locating small bore connections such that they are protected from mechanical damage.

Minimizing the length and weight of branch assemblies.

Supporting or bracing small bore branches especially in vibrating service.

Small bore piping should be shown in full detail on the isometric drawings.

Branches should be avoided downstream of compressors, desuperheaters, and other items that can create high vibration.

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