Pipe Fittings Codes Applicable to Industrial Piping in US Code Description ASME B31.1 Power Piping (Governs piping in Power Industries) ASME B31.3 Chemical Plant and Petroleum Refinery Piping ASME B31.4 Liquid Petroleum Transportation piping Systems ASME B31.5 Refrigeration Piping ASME B31.8 Gas Transmission and Distribution Piping Systems ASME Section III Nuclear Piping ASTM STANDARDS ASTM STANDARDS The materials of construction and testing are referred ASTM standards. Most of the ASTM standards are adapted by ASME and are specified in ASME Section II. The Section II has four parts. 1.4.1 Part-A - for ferrous materials 1.4.2 Part-B - for Non-ferrous metals and 1.4.3 Part-C - for welding materials 1.4.4 Part-D - for properties of materials Pipes Classified on the Basis of method of Manufacture 1.Seamless 2. Welded 2.1 Electric Resistance Welded (ERW) 2.2 Electric Fusion Welded (EFW) 2.3 Spiral Welded
Transcript
Pipe Fittings
Codes Applicable to Industrial Piping in US
Code Description
ASME B31.1Power Piping (Governs piping in Power Industries)
ASME B31.3Chemical Plant and Petroleum Refinery Piping
ASME B31.4Liquid Petroleum Transportation piping Systems
ASME B31.5 Refrigeration Piping
ASME B31.8Gas Transmission and Distribution Piping Systems
ASME Section III Nuclear Piping
ASTM STANDARDS
ASTM STANDARDS The materials of construction and testing are referred ASTM standards. Most of the ASTM standards are adapted by ASME and are specified in ASME Section II. The Section II has four parts.
1.4.1 Part-A - for ferrous materials1.4.2 Part-B - for Non-ferrous metals and 1.4.3 Part-C - for welding materials1.4.4 Part-D - for properties of materials
Pipes Classified on the Basis of method of Manufacture
1.Seamless2. Welded 2.1 Electric Resistance Welded (ERW) 2.2 Electric Fusion Welded (EFW) 2.3 Spiral Welded
Ser No. Description & Common use1 Pipe CS to LTCS A333 Gr 1 or 3 or 6, Sch ( ), ERW or SMLS, PE or BE, B 36.10L.P.ethylene. C12 vapour
Common Use of Alloy Carbon SteelSer No. Description & Common use1 Pipe CS to Alloy steel A335 Gr P1 or PII or P22, Size ( ), SMLS, PE or BE. B36.10, with or without IBR SHP steam, IPS line or PE plant
Common Use of SS Pipes
Ser No. Description & Common use1 Pipe SS to A312 Gr TP304 or 304L or 316 or 316L, Sch ( ), Size ( ), ERW (straight seam) or SMLS, PE or BE, B36.10 Cryogenic, HP ethylene, Acetic acid, DM water, Liquid oxygen
Superheater Materials & Allowable Temp.
Superheater materials: Material Composition Allowable
SB-407-800H Ni-Cr-Fe 1,500 Sa-213 TP 310H 25Cr 20 Ni 1,500
NON FERROUS PIPING
The non ferrous piping is used depending upon the corrosion properties and the temperature at which the fluid is handled. Special technology is involved in the fabrication of these piping. The commonly used materials are : Aluminum Alloy-20 Hastalloy Lead Monel Nickel
904 L- Cr-20, Ni-25, Mo-4, Cu-1.5 ( This is a good material for 60-70% H2 SO4)
Alloy 20 Cr-20,Cu-4, Fe-44, Mo-3,Ni-29Cupro-Nickel,70-30 Cu-69.3, Fe-0.75, Ni-30Cupro-Nickel,90-10 Cu88.8, Fe-1.25, Ni-10Ni-Hard alloy Fe-89.5,Cr-1.5, Mn-0.5, Ni-4.5, Si-0.6, C-3.4Ni-Resist Type 1 Fe 69.6,Cr-2.5, Mn-1.3, Ni-15.5, Si1.8, C-3.4,Cu-6.5,C-2.8Ni-Resist Type 2 Fe 71.9, Cr-2.5, Mn-1.0, Ni-20, Si-1. 8, C-2.8
Ser No. Description Common use
1 Pipe HDPE IS 4984, PE ( ), PN ( ) Standard – Genl – PI – UZ – 0007, Size (OD), Thk ( ), PE or SE
Domestic effluent, LPG, Natural gas (U/G or A/G)
CLASSIFICATION BASED ON END CONNECTIONS
Fittings are classified based on their end connections. They Are:
Butt Weld Ends Socket Weld Ends Threaded ends
Pipe Fittings Dimensional Standards
ANSI B 16.1 – Cast Iron Flanged End FittingsANSI B 16.3 – Malleable Iron Threaded FittingsANSI B 16.5 – Steel Flanged end FittingsANSI B 16.9 – Butt Welding end FittingsANSI B 16.11 – Socket Weld and Screwed End FittingsANSI B 16.28 – Butt Welding End Short Radius ElbowsBS 3799 – Socket Weld and Screwed End Fittings
BW FITTING MATERIALS 1 ASTM A 234 - Carbon Steel Fittings 2 ASTM A 403 - Austenitic Stainless Steel
Fittings 3 ASTM A 420 - Alloy Steel for low
temperature services.
Butt Weld fittings
Elbows: These make 900 or 450 changes of direction in the run of the pipe. The elbows normally used are “long radius” (LR) with centerline radius of curvature equal to 1 ½ times the nominal pipe size for ¾” and larger sizes. “Short radius” (SR) elbows with centerline radius of curvature equal to the nominal pipe size are also available.
Reducing elbows make a 900 change in direction with change in line size of the pipe to be attached to larger end.
Returns: A return changes direction of flow through 1800, and is used to construct heating coils, vents on tanks, etc. Long radius (LR) returns have centre to contre distance 3 times
NPS, whereas Short radius (SR) returns returns have centre to contre distance 2 times NPS.
Reducers: They join larger pipes to smaller ones. There are two types available, concentric and eccentric. The eccentric reducer is used when it is necessary to keep either the top or the bottom of the line level – offset equals ½ x (larger I.D. minus smaller I.D.)
Swages (or Swaged Nipples): These are employed to connect butt-welded piping to smaller screwed or socket-welded piping. In butt-welded lines, used as an alternative to the reducer when greater reductions in line size are required. Regular swages in concentric or eccentric form give abrupt change of line size. The ventury swage allows smoother flow.
Stub-in: It is a term for branch pipe welded directly into the side of the main pipe run. This is strictly not a fitting. This is the least expensive method of welding a full-size or reducing branch for 2” and larger. A stub-in, however, may need reinforcement.
Butt-weld tees (straight or reducing): These are used to make 900 branches from the main pipes. Straight tees, with the branch the same size as the run, are readily available. Reducing tees have branches smaller than the run. Bullhead tees have branches larger than the run, and very seldom used but can be made to special order.
Weldolets: These make 900 branch, full size or reducing, or straight pipes. Closer manifolding than the tees is made possible. These are specified by the range of the curved surfaces on which they can be welded and the branch size. For example 12” -24” x 1” . Flat-based weldolets are available for connecting to pipe caps and vessel heads.
Butt-weld elbolets: These make reducing tangent branches on long-radius and short-radius elbows.. Butt-weld latrolet makes a 450 reducing branch on straight pipes.
Sweepolets: They make 900 reducing branch from the main pipe. Primarily developed for high yield pipe used in oil and gas lines. Provides good pattern, and optimum stress distribution.
Butt-weld crosses: These provide 4-way fittings. Straight crosses are usually stock items. Reducing crosses may not be readily available. For economy, availability and to minimize the number of items in inventory, it is preferred to use tees, etc., and not crosses, except where space is restricted. Reinforcement is not needed.
Butt-weld laterals: These permit odd-angled entry into the pipe run where low resistance to flow is important. Straight laterals with branch bore equal to run bore are available in STD and XS weights. Reducing laterals and laterals at angles other than 45 degrees are available only to special order. Reinforcement is required where it is necessary to restore the strength of the joint to full strength of the pipe.
Butt-weld pipe caps: These are used to seal the open ends of pipes.
SOCKET WELD/SCREWED END FITTINGS
For Socket Weld/Screwed end fittings, four pressure classes are available. They are;
2000 # Class 3000 # Class 6000 # Class 9000 # Class
These designations represent the maximum cold non-shock working pressure of the fitting ion ponds per square inch.
Applicability of Classes of Fittings
2000 # Class
This class is applicable only for screwed fittings and is covered only in ANSI B 16.11. The corresponding pipe thickness for this class is Sch 80 or XS.
3000 # Class This class is applicable for both screwed and socket weld fittings. The corresponding pipe thickness for this class is Sch 80 or XS for socket weld end connection and Sch 160 for screwed and connection.
6000 # Class This class is also applicable for both screwed and socket weld fittings. The socket welding fitting under this class are normally used with Sch 160 pipes and screwed fittings with XXS pipes.
9000 # Class This class is applicable only for socket weld fittings and are normally used with XXS pipes.Types of threads on pipe fittings
The screwed end fittings can be with parallel threads or with taper threads. Taper threads are preferred for the fittings. These could be to NPT as covered in American Standards or to BSPT as covered in British standards or to relevant Indian Standard specifications.
SW/SCRD FITTING MATERIALS 1 ASTM A105 - Forged Carbon Steel 2 ASTM A 181 - Forged Carbon Steel for
General Purposes 3 ASTM A 182 - Forged Alloy Steel and
Stainless Steel 4 ASTM A 234 - Wrought Carbon Steel and
Alloy Steel pipe fitting for moderate and elevated temperatures 5 ASTM A 350 - Forged Alloy Steel for Low
Temperature Services
A socket weld joint is made by finishing the end flat (plain) and then inserting the pipe in the female boss of the fitting, valve, etc., and a continuous fillet weld is made around the circumference. Pipe sizes 2” and under are normally socket welded.
Full-couplings (called “coupling”): These join pipe to pipe, or to nipple, swage, etc.
Half Coupling: The half-coupling permits 90 degrees entry into a larger pipe or vessel wall. The sockolet is more practicable as shaping is necessary by grinding to fit the surface of the pipe.
Reducing Couplings (called “Socket Weld Reducer”): These join two different sizes of pipes.
Reducing Inserts: These are used for connecting small pipes to larger fittings. Socket weld reducing inserts can be made in any reduction by boring standard forged blanks.
Unions: These are used primarily for maintenance as it permits easy removal for replacement of piping, valves, etc. These are screwed joints designed for use with socket welded piping systems. Unions should be screwed tight before the ends are welded, to minimize warping of the seat.
Swaged Nipples also called “Swage”:
These depending on type join:
1. Socket-ended items of different sizes –this type of swaged nipples has both ends plain (PBE) for insertion into socket ends. (PBE stands for Plain Both Ends)
2. Socket-ended item to a larger butt-welding pipe or fitting – this type of swaged nipple has larger end bevelled (BLE) and the smaller end plain (PSE) for insertion into a socket-ended item. (BLE stands for Bevel Large End and PSE stands for Plain Small End.)
Swaged Nipples are abbreviated on drawing as “SWG NIPP”
Socket weld elbows: These make 900 and 450 changes of direction in the run of the pipe.
Tees (straight or reducing): These make a 900 branch from the main run of the pipe. Reducing tees are custom-fabricated by boring standard forged blanks.
Socket weld laterals: These make full size 450 branch from the main run of the pipe.
Socket weld crosses: These are used in the same way as butt welded crosses except these are socket welded. Reducing crosses are custom fabricated by boring forged blanks.
Sockolets: Makes a 900 branch, full size or reducing, on straight pipe. These are specified by the range of the curved surfaces on which they can be welded and the branch size. For example 3’ -6” x ¾” . Flat-based weldolets are available for connecting to pipe caps and vessel heads.
Socket weld elbolets: These make a reducing tangent branch on long-radius and short radius elbows. No reinforcing is required.
Socket weld latrolets: These make a 450 reducing branch on straight pipe. No reinforcement is required.
Socket weld Nipolets: These are variants of sockolets and has an integral plain nipple. These are primarily developed for small valve connections. No reinforcement is required.
Socket welding Caps: These seal plain ended pipes.
Threaded Fittings
The connections are exactly similar to socket weld connections of similar name except instead of socket weded ends these have threaded ends. The mating components should also be threaded to match the size of the threaded fittings.Threded Couplings:
Pipe Nipples:
Scred Unions:
Hexagonal Bushing:
Swaged Nipples:
Threaded Elbows:
Treaded Tees:
Screwed Lateral:
Screwed Cross:
Screwed Half & Full Coupling:
Threadolet, Elbowlet & Letrolet:
Nipolet:
Threaded Pipe Cap & Plug:
Flanged Joints
Flanged joints are made by bolting together twi flanges with gasket in between them to provide a seal. The surface of contact for a flange is called “flange face”. Flange faces are serrated and the gaskets conform to these serrations to provide a tortuous path for the medium to escape thus providing better sealing. However, flange faces using spiral wound gaskets are almost flat.
Types of Flanges:Weld NeckSlip-onSocket WeldScrewedReducing/ExpandingLap JointBlindOrifice
Flange Classification Based on Pressure & Temperature Ratings:
The flanges are also be classified by the pressure temperature rating in ANSI B 16.5 as below;
150 # 300 # 400 # 600 # 900 # 1500 # 2500 #
FLANGE CLASSIFICATION BASED ON FACING:
Flat face Raised face Tongue and groove Male and Female Ring type joint
ASTM A350 - Forged Alloy Steel for low temperature services
Weld Neck Flanges:
Regular welding neck (WN) flanges are used with standard butt-welding fittings and pipe. Long weldneck flanges are primarily used for vessel and equipment nozzles, and rarely for pipe. Weld-neck flanges are suitable where extreme temperature, shear, impact and vibratory stresses apply. Regularity of the bore is maintained. To suit pipes of different schedules the bore is matched to schedule of pipe. Example 4” x 300# WN Flange bored to sch 80. For Hydrocarbon Process Industries Weld-neck flanges are mandatory requirement for Chemicals and Hydrocarbon Service.
Slip-on Flanges:
Slip-on flanges are used commonly on pipes. The bore suits the pipe OD. The internal weld is slightly more subject to corrosion than the external weld. The flange has poor resistance to shock and vinration. Calculated strengths under internal pressure are about one third that of the corresponding weld-neck flange. The pipe or fitting is set back from the face of the flange a distance equal to the wall thicness -0 + 1/16”.In Process plants involving chemicals and hydrocarbons, Its use is generally confined to low pressure utility service.
Socket Weld Flanges:
A socket weld flange is very similar to a socket weld joint. The socket weld is made by finishing the pipe end and inserting it into the flange and a continuous fiilet weld is made around the circumference. Occationally a fatigue weld is added at the pipe end and flange lip base. This weld assists the joint in maintaiing its integrity.
Screwed Flanges:
Screwed (threaded) flanges are self expanatory flange joints. Both the flange and pipe are threaded to allow you to screw them together. These joints will commonly have either a tape or liquid sealer used to assist in preventing system leaks. Screwed type flanges are not generally allowed in chemical or hydrocarbon service.
Reducing Flange:
A reducing flange is suitable for changing line size, but should not be used if abrupt transition would create undesirable turbulence, as at pump connections.
Expander Flange:
Applications are the same as the weld-neck flange. Increases pipe size to first or second larger size. They are alternative to using reducer and weld-neck flanges and useful for connecting to valves, compressors and pumps.
Lap Joint (or Van Stone Flange):
It is economical if costly pipe such as stainless steel is used, as the flange can be of carbon steel and only the lap joint stub end need be of the line material. A stub-end must be used in a lap joint, and the cost of two items must be considered. If both stub and flange are of the same material they will be more rxpensive than a welding neck flange. Useful where alignment of bolt holes is difficult, as with spools to be attached to flanges nozzles of vessels as the lap joint flange is free and can be rotated for aligning with the mating flange. For vertical joints the lower flange is stopped from falling by welding small stoppers on the OD of the pipe during opeing of the flange.
Orifice Flanges:
Basically, the orifice flange is the same as standard weld-neck, slip-on and screwed flanges, except for provision of radial tapped holes in the flange ring for meter connections and additional bolts which act as jack screws to facilitate separating the flanges for inspection or replacement of orifice plates.
Gaskets:Based on the type of construction, gaskets are classified as:
Full FaceInside bolt circleSpiral wound metallicRing TypeMetal jacketed
For high temperature and high pressure applications, spiral wound metallic gaskets are used. The selection of material of construction for winding depends upon the corrosiveness and concentration of the fluid, the operating temperature and the relative cost of alternative winding materials. The most commonly used are the Austenitic stainless steel 304, 316 and 321 with Asbestos filler (now banned and now been replaced with synthetic fibers like Aramid). For very high temperatures, graphic filler is also used. Alternate winding materials also can be used depending upon the services. ANSI B 16.5 do not recommend the use of 150# rating gaskets on flanges other than welding neck type.Spiral wound gaskets are provided with carbon steel external ring known as centering ring to position the gasket. When used in vacuum services, an internal ring is also provided. The material of inner ring should be compatible with the fluid.
Gasket dimensions are covered under the following standards: API 601 – Metallic Gasket for Refinery Piping. BS 3381 – Metallic Spiral Wound Gaskets ANSI B 16.20 – Ring Joint Gaskets and grooves for steel pipe
flanges. ANSI B 16.21 – Non –metallic gaskets for pipe flanges.
Flange Bolting
Depending upon the service, pressure / temperature and the type of gasket, type of bolting is selected.
For low pressure, low temperature services, machine bolts are used and studs are used otherwise. Normally, the bolts are provided with hexagonal head, hexagonal nut and a round washer. Studs are provided with two hexagonal nuts and two washers. The length of bolts / studs required for the flange joints of all pressure classes are specified in ANSI B 16.5.
MATERIAL OF CONSTRUCTION FOR BOLTING
Bolting materials normally used are:
ASTM A 307 – Low carbon Steel Bolting Material ASTM A 320 – Allow Steel Bolting material for low temperature
service
ASTM A 193 - Alloy Steel Bolting Material for high temperature service.
ASTM A 194 – Alloy Steel nut material for high temperature service
IS 1367 – Threaded steel fasteners
The dimensional standards referred for the studs/bolts are: ANSI B 18.2.1 - Square & Hex. Head bolts ANSI B 18.2.2- Square & Hex. Nuts BS 916 - Black bolts & nuts IS 1367 - Threaded steel fasteners.
Expansion Joints:
Expansion Joints are provided in Piping Systems to compensate for the expansion and contraction of pipes due to temperature changes in order to prevent undue stresses generated in the piping system
Installation:
The necessary steps for installing all expansion joints shall be pre-planned. The installers shall be made aware of the steps as well as the installation instructions furnished by the manufacturer
Critical Phases of Expansion Joint Installation:
1. Care shall be exercised to prevent any damage to the thin bellows section, such as dents, scores, are strikes and weld spatter.
3. No movement of the expansion joint - compression, extension, offset, rotation
and especially torsion - due to piping misalignment, for example, shall be imposed which has not been anticipated and designed into the movement capability of the expansion joint. If such movements are imposed, they can result in system malfunction, damage to the bellows or other components in the system. Specifically, cycle life adjacent equipment may exceed their design limits, internal sleeve clearances may be adversely affected, and the pressure capacity and stability of the bellows may be reduced.
4. Any field pre-positioning shall be performed in accordance with specific instructions which include both the direction and magnitude of the movement.
3. Anchors, guides and pipe supports shall be installed in strict accordance with the piping system drawings. Any field variances from planned installation may affect proper functioning of the expansion joint and must be brought to the attention of a competent design authority for resolution.
5. The expansion joint, if provided with internal sleeves, shall be installed with the proper orientation with respect to flow direction6. After the anchors or other fixed points are in place and the piping is properly supported and guided, the expansion joint shipping devices should normally be removed in order to allow the expansion joint to compensate for changes in ambient temperature during the remainder for the construction phase.
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