Elbows, Tees and Reducers: Getting the Fitting Schedule Right

Pipe is usually ordered accurately because it is measured off drawings. Fittings are estimated, and that is where shortages appear.

Elbows

Specify the angle and the radius. A long-radius elbow creates less pressure drop and is preferred where flow matters; a short-radius elbow fits tighter spaces. Both exist in the same nominal size, so stating "90 degree elbow" alone is incomplete.

Tees

Equal tees have three ports of the same size. Reducing tees have a smaller branch, and the size convention must be written unambiguously — run size first, then branch. Ordering an equal tee where a reducing tee was needed means an extra reducer, an extra joint and a further leak path.

Reducers

Concentric reducers share a centreline and suit vertical runs. Eccentric reducers keep one side flat, which prevents air pockets in horizontal liquid lines and allows drainage. Substituting one for the other creates trapped air or standing liquid.

Union, coupling or flange

Couplings make a permanent joint. Unions and flanges allow disassembly. Place a demountable connection wherever a valve, pump or instrument will eventually need removal — retrofitting one later means cutting the line.

Check before ordering

• Nominal size and the standard the sizing follows
• Pressure class and material grade
• End type — threaded, socket, butt weld, flanged
• Thread standard where threaded, since standards are not interchangeable
• Flange facing and drilling pattern for flanged connections

Practical habit

Take off fittings from isometrics rather than estimating a percentage of pipe length, and add a small allowance for site modifications. A missing reducer stops a crew as effectively as a missing pump.