General Introduction
Fittings include butt weld pipe fittings, threaded(screwed) fittings, socket weld fittings. Since they are part of the piping system, they must match as closely as possible in specification and rating to the pipe to which the fittings are being attached. Fittings are used to make changes of flow direction, branch from a main pipe, make a reduction in line size, connect pipes from two or a plurality of directions, and close a pipeline, etc. Butt weld pipe fittings are furnished with butt-welding ends for pipeline connection. They are manufactured and classified according to their wall thickness. Both threaded(screwed) fittings and socket weld fittings perform the same basic function as butt-welding fittings. They are commonly seen for installations using fittings 4″ and smaller.
Fittings may be manufactured from casting, bar, rod, forging, plate, sheet, strip, pipe, and tube by cold or hot forming process. Especially, cast fittings are typically used on low pressure and low temperature lines such as air, water, or condensate. Line containing high pressure and temperature mediums, which may be subject to movement and vibration, require fittings made from forgings.
Designation & Specification of Fittings
Sizes: 1/2″(DN 15) ~ 160″(DN 4000); Schedule No.: SCH 5(SCH 5S), SCH 10(SCH 10S), SCH 20, SCH 30, STD, SCH 40(SCH 40S) SCH 60, XS, SCH 80(SCH 80S), SCH 100. SCH 120, SCH 140, SCH 160, XXS; Wall Thickness: 0.2 mm ~ 110 mm; Pressure Ratings: Class 2000, Class 3000, Class 6000, Class 9000.
Types of Fittings
There are many types of fittings categorized on the basis of function and shape: elbow, tee, reducer, cross, end cap, return, bend, lateral tee, coupling, nipple, swage nipple, street elbow, plug, weld outlet, threaded outlet, lateral outlet, nipolet, socket outlet, half coupling, bushing, union, insert, welding boss, flanged weld outlet, etc.
Typical Standards for Fittings
- Butt Weld Pipe Fittings: ASME B16.9, ASME B16.49, ASME B16.28, MSS SP 43, MSS SP 75, JIS B2311, JIS B2312, JIS B1213, EN 10253-1, EN 10253-2, EN 10253-3, EN 10253-4, DIN 2605, DIN 2615, DIN 2616, DIN 2617, GOST 17379, GOST 17375, GOST 30753, GOST 17378.
- Threaded/Screwed, or Socket Weld Fittings: ASME B16.11, MSS SP 83, MSS SP 95, MSS SP 97, JIS B2316, JIS B2302, BS 3799.