Threaded pipe connections are essential components in systems that transport liquids, gases, and steam. These threads, which allow for a secure and tight seal, are commonly found on the ends of pipes and various fittings like couplings, elbows, and tees. The materials used for these threaded parts can vary, including steel, stainless steel, brass, bronze, cast iron, and various plastics such as nylon and PVC.
There are two main types of threaded connections: straight (or parallel) and tapered. In tapered connections, one end is narrower than the other, which helps to create a more secure fit. These types of connections are especially popular across numerous industries, including power plants, chemical sectors, oil and gas industries, manufacturing, and shipping.
When it comes to standards for threaded pipe connections, there are two main categories to consider: the National Pipe Tapered (NPT) and the National Pipe Straight (NPS) for American standards, and for British standards, the British Standard Pipe Tapered (BSPT) and the British Standard Pipe Parallel (BSPP). These standards guide the design and manufacturing of the threads to ensure compatibility and effectiveness in various applications.
What’s BSPT Thread?
A British Standard Pipe Taper(BSPT) is the standard design for most of the world’s tapered threads that meets ISO 7-1 standard. The diameter is widest at the shoulder of the connection and narrows toward the tip. Threads are pitched at a 55 degree angle with rounded peaks and valleys.
Unlike NPT tapered connections, both fittings in a BSPT connection do not have to be tapered. For example, a female fitting can be tapered while the male is straight. No matter the case, a thread sealant must be used in BSPT connections. An NPT tapered connection will sometimes fit into a BSPT fitting, or vice versa, but they will not create an effective seal.
What’s BSPP?
A British Standard Pipe Parallel(BSPP) is the straight equivalent of a BSPT thread that meets ISO 228-1 standard. BSPP connections require a bonded seal ring, which is sandwiched in between the shoulder of the male fitting and the face (opening) of the female fitting. Unlike other connections, a BSPP connection does not need thread sealant.
What’s The Main Difference Between BSP and NPT?
While the difference between straight and tapered threads is apparent to the naked eye, it is much more difficult (almost impossible) to tell the difference between an NPT or BSP fitting by sight.
If you’re unsure which kind of fitting you’re working with, you’ll need a pitch gauge to measure the angles of the threads. NPT fittings will have threads with a 60 degree spread while BSP threads will have a 55 degree spread.
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