MSS SP 43 provides requirements for wrought and fabricated butt-welding fittings intended for low pressure, corrosion resistant applications. Requirements covered include pressure ratings, size, marking, materials, metal thickness, dimensions, testing, and tolerances.
This Standard Practice covers only fittings made for use with Schedule 5S or 10S pipe, for all Nominal Pipe Sizes (NPS) listed in ASME B36.19M; except that short pattern stub ends suitable for use with Schedule 40S are also shown.
PRESSURE RATINGS
3.1 Fittings covered by this Standard Practice are primarily intended for corrosion resistant applications; however, they shall have a pressure rating equal to 30% of the allowable pressure rating for comparable straight seamless pipe of the same wall and grade of material as marked on the fittings, whose ratings are determined by the applicable ASME B31 Code for Pressure Piping.
3.2 For fittings that are of the same pressure rating as the matching pipe, refer to ASME B16.9.
MARKING
Each fitting shall be marked as per MSS SP-25 to show the following:
a) Manufacturer’s name or trademark
b) “CR” followed by the material identification symbol established for the respective grade in the appropriate ASTM specifications or AISI/SAE designations
c) Manufacturer’s heat number/identification number|
d) Schedule number or nominal wall thickness designation
e) Size
Where the size of the fittings does not permit complete marking, Sections 5.1(a) and (c) are mandatory. The other marking and identification marks may be omitted in the sequence, as specified in MSS SP-25.
The required markings shall be made by any suitable method that is not injurious to the fitting.
MATERIALS
Fittings made from AISI/SAE Grade Types 304, 304L, 310, 316, 316L, 317, 317L, 321, and 347 are considered standard designations under this Standard Practice. Fittings made from other corrosion resistant material, including nonferrous materials, are acceptable by agreement between the purchaser and the manufacturer provided they meet the requirements of a recognized and applicable AISI/SAE grade designation or ASTM specification.
METAL THICKNESS
As these fittings are to match pipe, the dimensions of the welding ends must conform to established pipe standards, with regard to outside diameters and tolerances. The nominal wall thickness of the fittings shall be the same as the pipe to which it is welded; except that fittings with heavier walls may be butt-welded to lighter wall pipe, provided the heavier wall is tapered on the inside or outside to match the dimensions of the lighter pipe.
FITTING DIMENSIONS
U.S. customary (inch) dimensions for the fittings covered by this Standard Practice are given in Tables 1 through 6.
One of the principles of this Standard Practice is the maintenance of a fixed position for welding ends with reference to the center-line of the fittings or the overall dimensions, as the case may be.
Dimensions are in inches
| NPS | Outside Diameter at Bevel | Center-to-End | |
| 90° Elbows A | 45° Elbows B | ||
| 1/2 | 0.84 | 1.50 | 0.62 |
| 3/4 | 1.05 | 1.50 | 0.75 |
| 1 | 1.32 | 1.50 | 0.88 |
| 1 1/4 | 1.66 | 1.88 | 1.00 |
| 1 1/2 | 1.90 | 2.25 | 1.12 |
| 2 | 2.38 | 3.00 | 1.38 |
| 2 1/2 | 2.88 | 3.75 | 1.75 |
| 3 | 3.50 | 4.50 | 2.00 |
| 3 1/2 | 4.00 | 5.25 | 2.25 |
| 4 | 4.50 | 6.00 | 2.50 |
| 5 | 5.56 | 7.50 | 3.12 |
| 6 | 6.62 | 9.00 | 3.75 |
| 8 | 8.62 | 12.00 | 5.00 |
| 10 | 10.75 | 15.00 | 6.25 |
| 12 | 12.75 | 18.00 | 7.50 |
| 14 | 14.00 | 21.00 | 8.75 |
| 16 | 16.00 | 24.00 | 10.00 |
| 18 | 18.00 | 27.00 | 11.25 |
| 20 | 20.00 | 30.00 | 12.50 |
| 22 | 22.00 | 33.00 | 13.50 |
| 24 | 24.00 | 36.00 | 15.00 |
Dimensions are in inches
Dimensions are in inches
| NPS | Nominal O.D. at Bevel | Caps Length E | Lap-Joint-Stub-Ends(C) | |||
| Length F | Diameter of Lap G (max.) | Radius of Fillet | ||||
| A | B(max.) | |||||
| 1/2 | 0.84 | 1.00 | 2.00 | 1.38 | 0.12 | 0.03 |
| 3/4 | 1.05 | 1.00 | 2.00 | 1.69 | 0.12 | 0.03 |
| 1 | 1.32 | 1.50 | 2.00 | 2.00 | 0.12 | 0.03 |
| 1 1/4 | 1.66 | 1.50 | 2.00 | 2.50 | 0.19 | 0.03 |
| 1 1/2 | 1.90 | 1.50 | 2.00 | 2.88 | 0.25 | 0.03 |
| 2 | 2.38 | 1.50 | 2.50 | 3.62 | 0.31 | 0.03 |
| 2 1/2 | 2.88 | 1.50 | 2.50 | 4.12 | 0.31 | 0.03 |
| 3 | 3.50 | 2.00 | 2.50 | 5.00 | 0.38 | 0.03 |
| 3 1/2 | 4.00 | 2.50 | 3.00 | 5.50 | 0.38 | 0.03 |
| 4 | 4.50 | 2.50 | 3.00 | 6.19 | 0.44 | 0.03 |
| 5 | 5.56 | 3.00 | 3.00 | 7.31 | 0.44 | 0.06 |
| 6 | 6.62 | 3.50 | 3.50 | 8.50 | 0.50 | 0.06 |
| 8 | 8.62 | 4.00 | 4.00 | 10.62 | 0.50 | 0.06 |
| 10 | 10.75 | 5.00 | 5.00 | 12.75 | 0.50 | 0.06 |
| 12 | 12.75 | 6.00 | 6.00 | 15.00 | 0.50 | 0.06 |
| 14 | 14.00 | 6.50 | 6.00 | 16.25 | 0.50 | 0.06 |
| 16 | 16.00 | 7.00 | 6.00 | 18.50 | 0.50 | 0.06 |
| 18 | 18.00 | 8.00 | 6.00 | 21.00 | 0.50 | 0.06 |
| 20 | 20.00 | 9.00 | 6.00 | 23.00 | 0.50 | 0.06 |
| 24 | 24.00 | 10.50 | 6.00 | 27.25 | 0.50 | 0.06 |
| NOTES: (a)Minimum lap thickness shall not be less than nominal wall thickness (b)Contact faces of stub ends shall have a modified spiral or concentric serration. (c)These lengths and radii for use with Schedule 40S or thinner pipe. | ||||||
Dimensions are in inches
| NPS | Outside Diameter at Bevel | Center-to-Center 0 | Back-to-Face K |
| 1/2 | 0.84 | 3.00 | 1.88 |
| 3/4 | 1.05 | 3.00 | 2.00 |
| 1 | 1.32 | 3.00 | 2.19 |
| 1 1/4 | 1.66 | 3.75 | 2.75 |
| 1 1/2 | 1.90 | 4.50 | 3.25 |
| 2 | 2.38 | 6.00 | 4.19 |
| 2 1/2 | 2.88 | 7.50 | 5.19 |
| 3 | 3.50 | 9.00 | 6.25 |
| 3 1/2 | 4.00 | 10.50 | 7.25 |
| 4 | 4.50 | 12.00 | 8.25 |
| 5 | 5.56 | 15.00 | 10.31 |
| 6 | 6.62 | 18.00 | 12.31 |
| 8 | 8.62 | 24.00 | 16.31 |
| 10 | 10.75 | 30.00 | 20.38 |
| 12 | 12.75 | 36.00 | 24.38 |
| 14 | 14.00 | 42.00 | 28.00 |
| 16 | 16.00 | 48.00 | 32.00 |
| 18 | 18.00 | 54.00 | 36.00 |
| 20 | 20.00 | 60.00 | 40.00 |
| 24 | 24.00 | 72.00 | 48.00 |
Dimensions are in inches
TEST
Hydrostatic testing of fittings is not required in this Standard Practice; however, fittings shall be capable of withstanding a hydrostatic test pressure that is 1.5 times greater than the pressure rating required in Section 3.1.
TOLERANCES
Table 1 lists tolerances for the fittings covered by this Standard Practice. The location of dimensions OA and OP are illustrated in Figure 1 below and actual maximum angularity tolerances are indicated in Table 1.
| TABLE 1 Tolerances Dimensions are in inches | ||||||||||||
| NPS | All Fittings | 90°Elbows 45°Elbows Tees | Reducers Lap-Joint Stub Ends | 180°Returns | Caps | Lap-Joint Stub Ends | Angularity Tolerances (Max.) | |||||
| Outside Diameter at Welding End(a) | Wall Thickness | Center-to- End Dimension | Overall Length | Center-to- Center Dimension | Back-to- Face Dimension | Aignment of Ends | Overall Length | Fillet Radius of Lap(b) | Outside Diameter of Lap | Off Angle | Off Plane | |
| A-B-C-M | F-H | O | K | U | E | A | G | OA | OP | |||
| 1/2-1-1/2 | ±0.03 | Not less than nominal 871/2% of thickness | ±0.06 | ±0.06 | ±0.25 | ±0.25 | ±0.03 | ±0.12 | +0.00 -0.03 | +0.00 -0.03 | 0.03 | 0.06 |
| 2-3-1/2 | ±0.03 | ±0.06 | ±0.06 | ±0.25 | ±0.25 | ±0.03 | ±0.12 | +0.00 -0.03 | +0.00 -0.03 | 0.03 | 0.06 | |
| 4 | ±0.03 | ±0.06 | ±0.06 | ±0.25 | ±0.25 | ±0.03 | ±0.12 | +0.00 -0.03 | +0.00 -0.03 | 0.03 | 0.06 | |
| 5-8 | +0.06 -0.03 | ±0.06 | ±0.06 | ±0.25 | ±0.25 | ±0.03 | ±0.25 | +0.00 -0.06 | +0.00 -0.06 | 0.06 | 0.12 | |
| 10-18 | +0.09 -0.03 | ±0.09 | ±0.09 | ±0.38 | ±0.25 | ±0.06 | ±0.25 | +0.00 -0.06 | +0.00 -0.06 | 0.09 | 0.25 | |
| 20-24 | +0.12 -0.03 | ±0.09 | ±0.09 | ±0.38 | ±0.25 | ±0.06 | ±0.25 | +0.00 -0.06 | +0.00 -0.06 | 0.12 | 0.38 | |
| GENERAL NOTE: Diameter and wall hicknesses are as specifed in either ASME B36.19Mor ASME B36.10M. NOTES: (a)Out of roundness is the vector sum of plus and minus tolerance. (b)Fillet B radius is maximum(see Table 4) | ||||||||||||
WELDING BEVEL
Fittings conforming to this Standard Practice may be finished with ends cut square for wall thickness 0.12 in. or less. For wall thicknesses in excess of 0.12 in., the ends shall be beveled at 37%° ± 2%°, with root face (land) 0.06 in. ± 0.03 in. as indicated in Figure 2 below.
FINISH AND HEAT TREATMENT
The fittings shall be satisfactorily heat treated by an accepted practice, and adequately cleaned to ensure maximum corrosion resistance.
WELDING
All fittings shall have the welders, welding operators, and welding procedures qualified under the provisions of Section IX of the ASME Boiler and Pressure Vessel Code (BPVC).
ANNEX A Referenced Standards and Applicable Dates
| Standard Name | Description |
| ASME; ANSI/ASME | |
| B16.9-2018 | Factory-Made Wrought Buttwelding Fittings |
| B31.x | [Applicable] Code for Pressure Piping |
| B36.10M-2018 | Welded and Seamless Wrought Steel Pipe |
| B36.19M-2018 | Stainless Steel Pipe |
| BPVC-IX-2017 | Boiler and Pressure Vessel Code, Section IX: Welding and Brazing Qualifications |
| MSS; ANSI/MSS | |
| SP-25-2018 | Standard Marking System for Valves, Fittings, Flanges, and Unions |
| ANSI/MSS SP-25 | Standard Marking System for Valves, Fittings, Flanges, and Unions |
| ANSI/MSS SP-96 | Terminology for Valves, Fittings, and Their Related Components |
| American National | |
| ANSI/MSS SP-25 | Standard Marking System for Valves, Fittings, Flanges, and Unions |
| ANSI/MSS SP-44 | Steel Pipeline Flanges |
| ANSI/MSS SP-55 | Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components – Visual Method for Evaluation of Surface Irregularities |
| ANSI/MSS SP-58 | Pipe Hangers and Supports – Materials, Design, Manufacture, Selection, Application, and Installation |
| ANSI/MSS SP-96 | Terminology for Valves, Fittings, and Their Related Components |
| ANSI/MSS SP-114 | Corrosion Resistant Pipe Fittings Threaded and Socket Welding Class 150 and 1000 |
| ANSI/MSS SP-122 | Plastic Industrial Ball Valves |
| ANSI/MSS SP-134 | Valves for Cryogenic Service, including Requirements for Body/Bonnet Extensions |
| ANSI/MSS SP-135 | High Pressure Knife Gate Valves |
| ANSI/MSS SP-138 | Quality Standard Practice for Oxygen Cleaning of Valves and Fittings |
| ANSI/MSS SP-144 | Pressure Seal Bonnet Valves |
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