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How to Identify Size and Type of Tube Fittings ?

Many of our clients, especially Power Plants have a dilemma of choosing the right product. During installation of machinery and building the plant they appoint foreign companies for installation, erection purpose or buy the part or machinery directly. Over time these Plants need to change their Tube Fittings due to wear and tear. Unfortunately  many of them do not make the necessary replacement or order the surplus in time. Due to this, there is a temporary fear of stalling of processes and plant. 

Considering this issue, we are trying to make it easy for our readers to identify the types of Tube Fittings. 

TUBE FITTINGS : Tube Fittings are Fittings used to Connect Tube to Tube or Tube to Male Threads or Female Threads.

IDENTIFICATION : The photos in mentioned link ( clearly indicate the types of fittings (Union, Union Elbow, Union Tee, Union Cross, Male Connector, Female Connector, Connector Elbow, Run Tee, Branch Tee etc.,)


  1. With a vernier Measure the size of the OD (Outer Diameter) of the Tube

or the ID (Inner Diameter) of Nut to find the accurate dimensions of the Tube connection side.

2. Measure the diameter of the threads (do not measure the pitch diameter) for the End Connection side and refer the details below:

1/8” NPT or BSP : 9mm to 10mm Appx.

1/4” NPT or BSP : 12.5mm to 13.5mm Appx.

3/8” NPT or BSP : 16mm to 17mm Appx.

1/2” NPT or BSP : 20mm to 21mm Appx.

3/4” NPT or BSP : 25.5mm to 26.5mm Appx.

1” NPT or BSP : 32mm to 33mm Appx.

The above method is raw, yet effective. Considering the urgency or emergency it can be very helpful. Most of the techno commercial / User departments do not have easy access to the Purchase transaction history. They are helpless when it comes to easily identifying and checking the Size, Type, MOC of the material installed. 

In case if the purchase history is available, you may identify the parts by their billed names , for instance : 

SS 304L Union Tee,  SS 304L Union Elbow, SS 304L Connector, SS 304L Union, SS 304L Run Tee, SS 304L Male Tee, SS 304L Male Elbow, SS 304L Cross, SS 304L Nuts, SS 304L Ferrule, SS 304L Double Ferrule Tube Fittings, SS 316L Union Tee,  SS 316L Union Elbow, SS 316L Connector, SS 316L Union, SS 316L Run Tee, SS 316L Male Tee, SS 316L Male Elbow, SS 316L Cross, SS 316L Nuts, SS 316L Ferrule, SS 316L Double Ferrule Tube Fittings etc., 

The Sizes like 8mm, 10mm, 12mm, 25mm, 1/4", 1/2", 3/8", 3/4",  1" etc., along with their connection size: 1/4"BSP/NPT, 1/8"BSP/NPT, 1/2"BSP/NPT, 3/4"BSP/NPT, 1"BSP/NPT  etc., are mentioned. 


For More Details on How to Identify Size and Type of Tube Fittings  contact us on

***Monel, Hastelloy, Inconel, Incoloy, SMO254, Nitronic, AL6XN, Stellite, Sanicro, Tantalum, Nimonic , Alloy A286, Invar, Cupronickel etc., are the trademarks of their respective companies.

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