Guide for selection of pipe fittings

Pipe fittings are available in various shapes, sizes and materials. Used to connect pipes of different lengths 

and sizes, these pipe fittings and flanges should make the right connections. Pipe and pipe-fittings are 

produced from a various materials for the transport of wide variety of solids and fluids. The wrong pipe 

fitting can lead to many problems like:

1. leaks

2. unwanted flow restrictions and

3. extra cost



The proper pipe fittings and flanges let your equipment do the work that you intend it to do. The various 

types of pipe fittings include  plugs,  90 degree elbows, 45 degree elbows,  flanges, nipples, concentric 

reducers, eccentric reducers,  straight tees, reducing tees, unions, pipe caps, full coupling, half coupling 

and many more. You should select the right fittings for your application among the wide range of fitting 

types and sizes offered.



• Common points to consider

The integrity of any fitting for proper functioning depends upon the following: 

1. Selection of correct components or fittings appropriate for the application

2. Careful preparation and cleaning

3. Careful installation and assembly

4. Correct tightening and loading



• Selecting Your Pipe Fittings

The points to consider are as follows: 

1. Determine Material Compatibility: Material selection plays a vital role in the proper working of fittings. 

There are certain fluids which are not compatible with fitting material and these fittings cause leakage or 

system damage. It is very essential to check the material compatibility of your fluid with any chemicals.

2. Check Temperature and Pressure Conditions: Appropriate temperature and pressure ratings are 

needed for proper operating conditions. It is necessary to know whether the fittings are capable of 

performing at their maximum temperature and maximum pressure ratings because most fittings cannot 

perform both the task simultaneously.

• Some popular fitting types

1. Threaded Pipe Fittings:

These are the most commonly used fittings based on certain standards. For instance, there are threaded fittings of pipes in BSP (British Standard Pipe), NPT (National Pipe Taper), UNF (Unified Fine Thread) sizes 

for permanent, high-pressure pipe connections.

2. Socket Weld Fittings:                                                                                                                                                                   

 A socket weld fitting is unthreaded, but has large sockets at both ends to accept a pipe end. The fitting is 

then permanently welded to the pipe.         

3. Butt Weld Fittings:

Buttweld (BW) fittings whose dimensions, dimensional tolerances et cetera are defined in the ASME B16.9 standards. Light-weight corrosion resistant fittings are made to MSS SP43.

4. Flanges:

A flange is a method of connecting pipes, valves, pumps and other equipment to form a piping system. It 

also provides easy access for cleaning, inspection or modification. 



• Pipe Thread Sizes

This is a very important consideration for any pipe fitting. All pipes were manufactured with specification of a standardized outside diameter (OD) and wall thickness which in turn implies that the nominal pipe size is approximately equal to the inside diameter (ID). Nowadays, various thread configurations are used. We give below an example of British Standard Pipe (BSP) fittings for connecting systems that use both NPT and BSP thread configurations. The table shows a comparison of these two thread styles.

Size	Threads per inch
	NPT	BSP
1/8″	27	28
1/4″	18	19
3/8″	18	19
1/2″	14	14
3/4″	14	14

• To sum up: Selection criteria for buyers 

1. Material

2. Pressure Ratings

3. Design and operation

4. Safety information

5. Temperaturepipe fittings and flanges, certain questions need to be answered for that particular pipe fitting and the manufacturer who is manufacturing that particular fitting. Some of these questions are as follows: 

• Buyer’s assistance

Before purchasing 

1. Can it handle pressure?

2. Can it handle high temperature?

3. Does it have proven long-term performance?

4. Are the joints or seals reliable?

5. Can it be fitted properly?

6. Does it have confidence of manufacturers?

7. Can it withstand outdoor storage and ultraviolet rays?

8. Can it resist punctures and abrasion?

9. Does it have widespread approval and acceptance from inspectors and engineers?

10. Does it have quality and value?The more the number of “YES”, the better is your product.



The more the number of “YES”, the better is your product.

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