MSS SP-97

Covers — reinforced branch fittings:

• Buttwelding outlets (Weldolets) designed for Standard (STD), Extra Strong (XS), and Schedule 160 wall thicknesses.
• Socket-welding (Sockolets) and threaded outlets (Threadolets) for Class 3000 and 6000 pressure ratings.
• Fittings are specifically contoured and designated to match specific run pipe sizes (e.g., a 10" x 2" Weldolet is contoured to fit perfectly on a 10" pipe).

Does NOT cover (exclusions) — the following are governed elsewhere:

• Standard factory-made tees (B16.9).
• Unreinforced branch connections (stub-ins/stub-ons) where the pipe is simply welded directly to the header.
• Extruded outlets or sweep-olets often used in pipeline codes.

SP-97 fittings mathematically solve one of the most tedious piping engineering problems:

• Integral Reinforcement (Area Replacement) — When a hole is cut into a pressurized pipe to make a branch, the pipe wall is severely weakened. ASME B31.3 requires complex "Area Replacement" calculations to prove the joint is safe, and often requires the welder to fabricate and weld an external reinforcement pad (re-pad) around the hole. SP-97 fittings are forged with a massive amount of extra steel built directly into the body. This "integral reinforcement" automatically satisfies the B31.3 Area Replacement rules, completely eliminating the need for calculations or re-pads.
• Base Contour — The base of the fitting is meticulously machined to perfectly match the outside diameter curvature of the intended run pipe.

Olets (the generic industry term for SP-97 fittings) are heavily preferred over standard tees for creating branch connections, especially when the branch pipe is at least two sizes smaller than the main header pipe (e.g., branching a 2-inch line off a 10-inch header).

They offer immense fabrication advantages: they require significantly less welding than installing a standard B16.9 reducing tee (only one weld to the header, versus three separate pipe cuts and welds required to install a tee). This saves massive amounts of fabrication time, labor, and non-destructive testing (NDT) costs, while inherently satisfying the stringent pressure design codes.