NPT, BSP and flanges: identify the connection before ordering

Write more than the size

An enquiry that says “one-inch connection” leaves several questions open. Record the standard, whether the connection is male or female, and how the joint seals. A nominal size is a name within a connection system; it is not a complete description of the end connection.

Separate thread form from the seal

Tapered and parallel threads use different geometries. NPT and BSP designations should not be treated as substitutes. A parallel-thread connection may rely on a separate sealing surface or gasket, so identifying the thread alone can leave the joint incompletely specified. Swagelok’s identification guide checks taper, diameter and pitch, then identifies the complete end connection. Thread and end connection identification guide.

For a flange, capture the mating information

Include the flange standard and rating, nominal size, bolt pattern and sealing-face details from the drawing. Photograph the markings and mating connection if the paperwork is missing. Do not force an uncertain fitting into a plastic pump port to see whether it fits; have the connection identified before assembly.

Make the purchase line unambiguous

A useful order record contains the complete pump model, inlet and outlet connection descriptions, and the drawing or manual revision used for confirmation. If an adapter is required, list it separately with its materials and rating. This gives the installer a clear handover and reduces the risk that a convenient-looking substitute is accepted without checking the actual joint.

Use the instructions and specifications for the exact equipment configuration. This article introduces the selection discussion.