Threaded Pipe Fitting
Threaded pipe fittings are mechanical components that use the principle of threaded connection to change the direction of the fluid, adjust the pipe size, or connect different components. Disassembly and assembly are very convenient and are used in pipe systems with a nominal diameter of NPS 2 or smaller.
American Threaded Cap
American Threaded Couplet
Threaded Pipe Fitting Specifications
Pipe Size Range: NPS 1/8″~NPS 2”
Pressure Rating: Class 2000/3000/6000/9000
Material: stainless steel, carbon steel, cast iron
Thread type: NPT/BSP
Connection form:Female/Male/Nipple
Standard:ASME B1.20.1,ISO 7-1
Certification:UL/FM
Threaded fittings have significant advantages in small-diameter pipelines, but need to be based on the characteristics of the medium, pressure level and environmental conditions of the comprehensive selection of type
Threaded Pipe Fitting Process
Raw material preparation and materialization
Raw material selection: carbon steel (ASTM A105), stainless steel or ductile iron, etc. Spectral testing is required to ensure that its chemical composition meets the standard. After the material is tested and qualified, laser cutting or water cutting is used to perform preliminary processing on the metal sheet or tube blank, and the cross-section flatness error is ≤0.5 mm.
Forming process
Cold rolling: The cold rolling process is suitable for finishing small diameter pipes. It uses a four-roll reversible rolling mill to roll in stages (0.5-1.2 mm per stage) to improve the dimensional accuracy (ovality ≤ 0.3 mm) and surface finish (Ra ≤ 1.6 microns) of the pipes.
Hot rolling: Large diameter pipes with NPS of 2 inches and above are formed by hot rolling, first heated to 1200°C, and then pierced and rolled.
Threading:
Use CNC lathe or thread rolling machine to cut the threads, the accuracy needs to be in accordance with ASME B1.20.1 (NPT) or ISO 7-1 (BSP) standards, tooth angle tolerance ±1°.
Heat treatment and surface treatment
Eliminate cold rolling/welding stresses, heat to 800-950°C and then slow cooling to improve material toughness. Galvanized (carbon steel parts) or pickled passivated (stainless steel parts) to improve corrosion resistance.
Assembly and sealing treatment
Combine the fittings by welding or threaded connection (e.g. double threaded nipple), welding needs to use TIG process to ensure the strength of the weld. Apply sealant (e.g. silicone-based adhesive) on the inner threads and wrap PTFE raw material tape around the outer threads ≥ 3 times to ensure low-pressure sealing.
Threaded Pipe Fitting Advantages
Easy installation
Threaded connection does not require welding and can be installed only by thread engagement. In situations where open flames are prohibited or welding is restricted, this connection method is undoubtedly the best choice. The threaded structure can be quickly disassembled and reused, which is convenient for subsequent pipeline maintenance and other operations.
Economical and maintenance cost
Compared with welding or crimping, this connection method does not require professional workers, reduces labor costs, and does not require the purchase of additional sealing equipment.
Because of its flexibility and high compatibility, it is widely used in instrument air, cooling water, fire protection pipe network and other non-critical fluid transportation. It is especially common in small diameter pipe systems with a nominal diameter of NPS 2 or smaller (≤50mm), and can be made of stainless steel, carbon steel, ductile iron and other materials to adapt to different media and corrosive environments.
Reliability and Flexibility
Self-tight sealing by tapered thread (NPT/BSPT) or parallel thread (BSPP) with gasket/O-ring can realize stable sealing of low to medium pressure system. Threaded fittings can be flexibly connected to different equipment or piping branches to meet the needs of complex piping layouts.
Thread classification
American Standard Thread (NPT)
Tooth type and taper: 60° tooth angle, taper 1:16, self-tight sealing by conical structure. Mainly used in petroleum, chemical, water treatment and other high-pressure and high-temperature systems, North America dominant use.
The sealing method needs to be matched with PTFE raw material tape or sealant to fill the thread gap.
British Standard Thread (BSP)
BSPT (conical thread): 55 ° tooth angle, taper 1:16, sealing depends on the thread bite and gasket assistance.
BSPP (parallel thread): 55° angle, cylindrical thread, sealing with O-rings or flat gaskets. Mainly used in Europe, Asia and Commonwealth countries for water supply and drainage, fire protection systems.
Japanese Standard Thread (PT)
55° angle tapered thread, old JIS standard, equivalent to ISO standard Rc. Mainly used in Japan and Southeast Asia for low pressure piping systems.