BSP vs NPT Threads: Avoid Mismatched Fittings
BSP and NPT are different thread systems. Common BSP pipe threads use a 55-degree profile; NPT uses a 60-degree profile. Similar nominal sizes are not proof of compatibility. Identify the exact thread standard and sealing method before ordering.
Are all BSP threads tapered?
No. BSP includes parallel and tapered forms. G threads are parallel under ISO 228; ISO 7 includes R tapered external threads and Rp parallel or Rc tapered internal threads. A label saying only BSP can therefore be ambiguous.
Why should BSP and NPT not be forced together?
Pitch, profile and diameters can differ. A connection that begins to screw together can still fail to seal or damage the parts. Use the specified mating thread or a correctly rated adapter rather than treating the systems as interchangeable.
How do I identify an existing fitting?
Record whether the thread is male or female, its measured outside diameter where accessible, threads per inch or pitch, and whether it is parallel or tapered. Include clear photographs and any equipment markings. Confirm with suitable thread gauges when identification is uncertain.
What details should I send for a quote?
Specify BSP or NPT, the exact thread designation if known, nominal size, male/female arrangement, fitting shape, material grade, required pressure class and quantity. State the operating fluid, pressure and temperature when requesting selection assistance.
Technical reference: Swagelok thread identification guide · Outokumpu corrosion guidance.
General purchasing guidance. Confirm selection against your project specification and qualified engineering advice. Product suitability and supplied documentation are confirmed during quotation.