Tapered Pipe Threads and Fittings: Making the Connection | ISM

30/5/2564 Tapered Pipe Threads and Fittings: Making the Connection | ISM

800.781.8487 ISM End your search, simplify your supply chain

Industrial Specialties Mfg. & IS MED Specialties ISO 9001:2015 Certifed Companies

TAPERED PIPE THREADS AND FITTINGS: MAKING THE CONNECTION

ENSURING A GAS OR LIQUID-TIGHT CONNECTION MEANS UNDERSTANDING TAPERED PIPE THREADS

NPT, National Pipe Taper (American) and BSPT (British standard Pipe Taper) are tapered pipe thread standards. Male and female tapered pipe threads wedge themselves together but need a sealant for a completely leak-free connection. Sealants fll any voids between the threads that could travel along the thread spiral.

Tube and pipe are not the same thing Tube and pipe are hollow structures designed to provide a path for the fow of fuids or gases. The main difference between tube and pipe is that pipe walls are thicker and stiffer. Tubing is never threaded because its walls are too thin. Pipe walls are strong enough to support cut or molded threads. Threaded pipe can provide gas or liquid-tight connections that are mechanically strong.

Pipe threads There are many national and international standards for pipe threads. They vary by intended use such as garden hose threads and fre hose threads among others. There are also historical developments behind “standard” pipe sizes and the shapes of threads. Examples of this are the differences between American and British threads. Units of measure play a part too.

How to Install The two basic categories of pipe thread Plastic Thread Fittings • Parallel or straight pipe thread • Tapered pipe thread Take a look at a selection of ISM's metal threaded fttings and plastic threaded fttings. These provide examples of the most common pipe thread types in use.

Tapered pipe threads Piping and fttings are primarily used to carry liquids and gases. Because of this, they need to have threaded connections that are gas or liquid tight. Tapered threads help make better seals. The male and female threads compress and wedge themselves together. As a result, these connections are stronger and leak resistant. The two most common standards for tapered pipe threads NPT American National Standard Taper Pipe Thread BSPT British Standard Pipe Taper Thread

NPT pipe thread is the most common tapered pipe thread used in the United States and Canada and is incompatible with BSPT pipe threads. https://www.industrialspec.com/about-us/blog/detail/tapered-pipe-threads-standards-intro 1/7 30/5/2564 Tapered Pipe Threads and Fittings: Making the Connection | ISM

Why NPT and BSPT pipe threads are incompatible

Thread angle or included angle NPT threads have a 60-degree angle BSPT threads have a 55-degree angle

Thread shape NPT threads have fattened peaks and valleys BSPT threads have rounded peaks and valleys

Thread pitch (TPI, threads per inch) Each NPT and BSPT pipe thread size has a specifc number of threads per inch

Some common acronyms for American tapered pipe thread types NPT National Pipe Thread Taper FPT, FNPT, NPT(F)* Female or internal tapered pipe threads MPT, MNPT, NPT(M) Male or external tapered pipe threads

*This is not NPTF. NPTF stands for National Pipe Taper Fuel. It is also called Dryseal American National Standard Taper Pipe Thread. The design of NPTF provides leak-free connections without using sealants. There are parallel and tapered pipe threads for all pipe standards. NPS, National Pipe Straight, is the American standard for parallel or straight pipe threads. NPS threaded connections need gaskets or O-rings to seal them.

Sealant and tapered pipe threads Tapered pipe threads need a sealant for leak-free connections. It flls any voids between the two threads that could cause a spiral leak. They also function as lubricants between the male and female threads. Assembling parts and pipe made of dissimilar materials need special care. This is because sealants make it easier to over tighten fttings. Over tightening fttings MODULAR CHECK VALVES can lead to damage and leaks. We've taken spring-loaded check Download the ISM Plastic Tapered Thread Fittings Installation Guide valves to a whole new level. Mix >> and match imperial and metric connections. Watch the video. Conclusion Understanding tapered pipe threads makes it easier to choose the best component, especially tapered pipe fttings. Parts with matching threads always perform better because matching threads are mechanically stronger and create better gas-tight and liquid-tight seals.

What kinds of problems have you had moving between different tapered pipe thread standards when sourcing components for your application? Help us by telling others what you learned. Have questions about tapered or straight pipe threads used on fow control components? If so, send me an email - [email protected]. You can also ask questions using the comments section below.

Some additional reading NPT National Standard Taper Pipe Threads Size Chart from Engineers Edge NPS Nominal Pipe Size (North America) from Wikipedia BSPT British Standard Pipe Taper Thread Sizes and Dimensions from AMES, Advanced Mechanical Engineering Solutions https://www.industrialspec.com/about-us/blog/detail/tapered-pipe-threads-standards-intro 2/7 30/5/2564 Tapered Pipe Threads and Fittings: Making the Connection | ISM p p f , g g BSP British Standard Pipe from Wikipedia

About the author

Steven C. Williams, BS, is the technical writer and an inbound marketing specialist at Industrial Specialties Manufacturing (ISM), an ISO 9001-2015 supplier of miniature pneumatic, vacuum and fuid circuitry components to OEM's and distributors all over the world. He writes on technical topics related to miniature pneumatic and fuidic components as well as topics of general interest at ISM.

« Go back to the blog homepage

ALSO ON ISM BLOG

Elastomers and What is Acetal Plastic? The Rubbers - Is There a … — POM Plastics for … Subscribe to our blog Stan

4 years ago • 2 comments 2 years ago • 2 comments 2 years ago • 2 comments 5 yea Rubber and elastomer are Acetal plastic is also called Industrial Specialties Mfg. Post words commonly used to polyacetal or and IS Med Specialties are at IS mean any material with … polyoxymethylene … ISO 9001:2015 … Inac

11 Comments ISM Blog  Disqus' Privacy Policy 1 Login

 Recommend 3 t Tweet f Share Sort by Best

Join the discussion…

Name

Garry • 6 months ago Hello, Thank you very much for this useful article. It seems that thread sealant is mandatory to use when sealing is achieved using contact between threads. Correct me i am wrong. Can we use NPT threads for an application having temperature = 350 deg C & pressure 150 bar? IMO, pressure is not the point of concern here. But temperature is certainly a point of concern. The reason is that there are no thread sealants which can operate upto 350 deg C. But thread lubricants are available upto 800 deg C. Could you please take a moment to express your advice. Thank you in advance. △ ▽ • Reply • Share ›

Steven Williams Mod > Garry • 6 months ago Garry https://www.industrialspec.com/about-us/blog/detail/tapered-pipe-threads-standards-intro 3/7 30/5/2564 Tapered Pipe Threads and Fittings: Making the Connection | ISM Garry,

Sealants are necessary for leakproof NPT threaded connections. I would recommend looking further for high temperature pipe thread sealant/lubricant compounds. There are definitely thread sealants available that are rated for temperatures over 350 degrees C (about 662 degrees F). You may have better luck if you search for sealant/lubricant pipe thread compounds.

NPT tapered pipe thread is suitable for high temperature/high pressure applications. Simply choose fittings and pipe rated for the operating temperatures and pressures.

You may want to consider using NPTF pipe threaded pipe and fittings instead of NPT. For leakproof seals, the mating threads of all the fittings and the pipe will need to be NPTF also. Unfortunately, NPTF threaded parts and pipe cost more than NPT threaded parts.

NPTF threaded connections do not require a thread sealant. This is because NPTF threads are designed so that the male thread crests interfere with the female thread roots. The thread is crushed in the installation process providing the mechanical seal. For this reason, NPTF fittings and pipe are also not reusable.

Here is a good reference resource that includes basic information about NPTF. It is at The Engineering Toolbox.

NSI B1.20.1 - NPT - American National Standard Taper Pipe Threads https://www.engineeringtool...

Steven Williams Technical Writer and Inbound Marketing Specialist △ ▽ • Reply • Share ›

βασίλης βελούδης • a year ago Hello, i wanted to ask i question that i have difficulty resolving. I have a ball valve of 3/4 in size and in the end, it has a 3/4 in NPT female thread. In order to connect this valve to a pipe or a fiting, do the pipe or the fiting need to have 3/4 in male NPT thread ? Thank you very much for your time. △ ▽ • Reply • Share ›

Steven Williams Mod > βασίλης βελούδης • 6 months ago In general, most thread pipe is used carrying liquids or gases. For these type of applications the connections need to be leak free and gas tight. To achieve this quality of a connection, thread standards need to match. You should also follow recommendations for the use of sealing compounds and/or sealing tape.

Tapered pipe threads like NPT require the use of pipe joint compounds or tape. This sealing material seals threaded pipe fittings by blocking the spiral leak paths that runs along the pipe threads. Keep in mind that improper sealing or improper use of a sealant can lead to serious problems, including leaks, pipe system damage, contamination and system downtime.

Proper installation includes using same material fittings or materials that are similar enough that there is no risk of stripping threads or splitting fittings. Over tightening is also a risk, especially with the use of Teflon tape. Be sure you know the proper installation procedure. For NPT, tightening should be finger tight plus about 2 turns for up to 1" inch sized fittings. Torque installation of pipe ttings is not a recom- mended practice.

Here are two reference resources I find particularly useful https://www.industrialspec.com/about-us/blog/detail/tapered-pipe-threads-standards-intro 4/7 30/5/2564 Tapered Pipe Threads and Fittings: Making the Connection | ISM Here are two reference resources I find particularly useful see more

1 △ ▽ • Reply • Share ›

βασίλης βελούδης > Steven Williams • 6 months ago Thank you for your answer, it helped me a lot !! △ ▽ • Reply • Share ›

ahl jay • a year ago Hello, I just have a question.

I'm working on a project where the General Specification it's saying that: "FOR INSTRUMENT IMPULSE TUBING ALL FITTING, UNION ECT. SHALL BE WITH TAPERED THREADS (ISO-METRIC)"

What I read down-side Mr. Williams is saying that "Metric tapered fitting threads use the ISO 7-1 standard but give the measurements in millimeters (mm) or centimeters (cm)", but why all the catalog for compression fittings does not mention the Metric Tapered Fitting Threads? All the tabe are in "inch" with NPT and BSPT/BSPP thread.

Why is not mentioned for example fittings as per ISO 7-1 with metric tapered threads like compression fitting M15x12O.D. or M10x10O.D.?

Thank you in advance for your answer, △ ▽ • Reply • Share ›

Steven Williams Mod > ahl jay • a year ago • edited Ahl Jay,

I am a little confused by the M15x1 reference. I understand M15x1 as referring a fastener and screw metric thread which would probably be based on the ISO 724 (DIN 13-2 to 11) standard.

I also believe that "ISO metric thread" might be referring to the German DIN 158 standard because the specification is related to instrumentation piping. If not, it is referring to the ISO 7 standard.

I have included some information and references below that I hope may be of some help to you. Thank you for posting your question on our blog.

Steven Steven Williams, Technical Writer ISM, Industrial Specialties Mfg.

===== Most countries in Europe and Asia use the metric system of measurement;

△ ▽ • Reply • Share ›

Kolli Nagaraju • 2 years ago Do we need to use tapered male part for using tapered female part and the vice-versa △ ▽ • Reply • Share ›

Steven Williams Mod > Kolli Nagaraju • 2 years ago Kolly,

For NPT (American) pipe threads, NPT male threaded and NPT female threaded parts need to be matched and used in combination with a thread sealant for an https://www.industrialspec.com/about-us/blog/detail/tapered-pipe-threads-standards-intro 5/7 30/5/2564 Tapered Pipe Threads and Fittings: Making the Connection | ISM parts need to be matched and used in combination with a thread sealant for an effective, pressure tight seal.

British BSPT and BSPP pipe thread standards have been superseded and replaced by R-Series (ISO-7) and G-Series (ISO-228) standards. BSPT, BSPP, R- Series and G-Series threads use the same British Standard Whitworth thread form and thread pitch. The tapered versions use the same thread taper or angle.

R pipe threads are external tapered pipe threads and will mate with Rc internal tapered pipe threads, Rp internal parallel pipe threads and G-Series internal parallel pipe threads. Effective seals are made through a combination of thread interference and the use of a thread sealant. R to Rp and R to G connections are appropriate only for moderate pressures because the threads have a sealing interference contact of only about one and one half turns.

Thanks for posting your question. I hope you find this information useful. Please

△ ▽ • Reply • Share ›

Muhammad Khalil • 2 years ago Hi, What is the taper angle of tapered metric threads △ ▽ • Reply • Share ›

Steven Williams Mod > Muhammad Khalil • 2 years ago Hi Muhammad. Thanks for posting your question in our blog.

ISO 7-1 or R-Series (formerly BSPT, BS 21 and DIN 2999) tapered pipe thread has a taper of 3/4" per foot or 1 in 16 on the diameter (1 degree 47 minutes or 1.78333 degrees). Metric tapered fitting threads use the ISO 7-1 standard but give the measurements in millimeters (mm) or centimeters (cm). The key differences between metric and both US and British standards measurements are the use of thread pitch and how the thread nominal diameter is measured.

Metric threads measurements use pitch instead of the US measurement of threads per inch. Pitch is the distance in millimeters from any one point on a thread to a corresponding point on the next thread, measuring parallel to the axis of the fitting.

The nominal diameter of straight and tapered metric pipe threads is the same as the major diameter (OD) of the thread. The US (NPT) as well British (BSPT or BS 21) d J (JIS PT) i l i th d di t th i t