MSS SP 43 butt welding fittings are wrought or fabricated for low pressure, corrosion resistant applications. The fittings include 90° & 45° long radius elbows, straight and reducing tees, lap joint stub ends, caps, 180° long radius returns, concentric and eccentric reducers. MSS Sp 43 covers fittings made for use with schedule 5S and 10S pipe, for all nominal pipe sizes(NPS) listed in ASME B36.19, except that short pattern stub ends can be used with SCH 40S pipe.

As MSS SP 43 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.

Pressure Ratings, Sizes & End Preparation

MSS SP 43 butt welding fittings are not pressure rated; however, they must be capable of withstanding 30% of allowable pressure rating of the pipe with which they are marked. It’s sized from NPS 1/2 (DN 15) to NPS 24 (DN 600). The fittings shall be furnished with ends cut square for wall thickness 0.12 inch or less. For wall thickness > 0.12 inch, they shall be beveled at 37.5°[±2.5°], with root face 0.06 inch (±0.03 inch).

Materials, Heat Treatment & Welding

The standard materials of MSS SP 43 cover austenitic stainless steel Types 304/ 304L, 316/ 316L, 317/ 317L, 321 and 347. The fittings can also be made of nonferrous metals such as titanium Gr.1, Gr.2, Gr.3, Gr.5, Gr.7, Gr.12; Inconel 600, Inconel 625, Hastelloy C-276, Hastelloy C-22, Monel 400, Incoloy 800, Incoloy 825/ 925, Alloy 31, Alloy 20, etc. Proper heat treatment shall be conducted based on specific material to insure maximum corrosion resistance. All fittings shall have welders, welding operators, and welding procedures qualified under the provisions of ASME BPVC Section IX.

MSS SP 43: Dimensions & Tolerances

MSS SP 43 Fittings: Dimension & Drawing
90° & 45° L/R Elbows	Straight Tees	Reducing Tees
Stub Ends and Caps	180° L/R Returns	Conc. & Ecc. Reducers

*Click to view the specific dimensions & drawings for each specific fitting.

NPS	1/2"~1-1/2"	2"~3-1/2"	4"	5"~8"	10"~18"	20"~24"
Outside Diameter	+0.03 -0.03	+0.03 -0.03	+0.03 -0.03	+0.06 -0.03	+0.09 -0.03	+0.12 -0.03
Wall Thickness	Not less than 87.5% of nominal thickness specified by ASME B36.19

*These tolerances are applicable for all fittings.