Conical threaded hydraulic fittings
Conical threaded hydraulic fittings are used in various industries,
including the oil, gas, petrochemical, shipbuilding and aerospace industries.
(NPT Hydraulic Fittings is one of the most commonly conical thread fittings)
One of the most commonly fittings is the NPT Hydraulic Fittings.
The following items apply to ( tapered or conical thread ).
These fittings are designed to be sealed by its thread. In fact, in this method, threads are responsible for sealing.
For some pipe fittings that have used this method, it is best to use teflon tape to seal.
In cases where the quality of the threads is not very suitable, it is better to use lubrication to close them.
The use of lubrication will reduce the risk of fracture of the threads.
The following is an example of the fracture of the threads.
Fig. 3.1. Threading fracture
After sealing with Teflon tape or other similar materials, as well as thread lubrication, the torque closing these fittings;
Unless the designer suggests, it is optional and there is no specific standard for it.
Now we present these types of threads, their specifications, as well as their hydraulic fittings and their standards.
3-1 Types of Conical threads
Two types of tapered threads are the most well known of these types of threads.
These threads include NPT threads and threads ISO 7/1.
These threads are included in the piping standards.
These threads are used in a variety of fittings and, as noted, its sealing mechanism is by using of threads.
Below is the introduction of these threads.
3-1-1 NPT Hydraulic Fittings Thread
These fittings are also known as ASME B1.20.1 connections [1].
(Standard of the Mechanical Engineering Community of America)
in this standard is devoted to these threads.
In the standards section, we will become more familiar with this standard.
The NPT thread and its general characteristics are shown in the following figure.
Figure 3-2 NPT thread specifications
NPT threads specification:
The conical angle of these threads is 1 degree 47 minutes, as shown in the figure.
Note: To measure angles of less than 1 degree, are not used a ten and a hundredth degree.
The unit that is used is minutes and seconds.
Each minute in this system is equivalent to 1.60 degrees, and each second equals 1.60 minutes.
In the following figure, the degrees are displayed in minutes and seconds.
Show the minutes with the mark (‘) and seconds with the mark (“).
So
- The degree is 60 minutes or 3600 seconds.
- The surface on the tip and root of the thread is flat.
- According to the shape, the angle between the threads is 60 degrees.
- In NPT threads, the thread screw is specified in terms of the number of conical thread per inch.
2-1-3 ISO 7/1 conical fitting thread
ISO 7/1 threads, also known as EN 1026-1 and JIS B0203 threads,
are another common conical threaded or tapered thread.
The specifications of these threads are given in EN 1026-1 and JIS B0203 standards,
which are introduced in the standards section.
In the below figure, have been shown these kinds of threads.
ISO 7/1 tapered fitting thread
ISO 7/1 thread specifications
-As shown in the figure, the conical angle of these threads is 1 degree and 47 minutes.
-The surface on the tip and roots of the thread is round.
-According to the shape, the angle between the threads is 55 degrees.
-In threads NPT, the thread screw is determined by the number of conical threaded per inch.
3-2 Conical Threaded Hydraulic Fittings
Hydraulic fittings with cone angles are:
NPT Hydraulic Fittings
NPT Hydraulic Fittings with O-ring
BSPT fittings
The thread screws NPT, NPT and OING and BSPT fittings are shown in the following table.
Table 3-1 Thread screws [8] NPT, NPT, Orange and BSPT connections
Note: It is difficult to distinguish between BSPT and NPT threads in the sizes of 1/2
and 4/4 inches due to the similarity of the screws.
The difference between these two is at the angles of the threads
(for the NPT this angle is 60 ° and for the BSPT this angle is 55 °)
and the tip surface and the root of the threads.
Note: As mentioned, the thread screw here means the number of threads per inch.
3-2-1 NPT Hydraulic Fittings
These connections, as presented in previous articles, are fully covered here.
Below is a sample of these connections.
The following table describes the standard for conical threaded fitting.
Figure 3-5 is an example of the NPT hydraulic connections
Table 2-3 NPT Hydraulic Fittings Standards
3-2-2 NPT hydraulic fittings with O-ring (NPT with O-Seal)
Along with this type of fittings, uses an O-ring for sealing.
The sealing is done by squeezing this o- ring into the female button.
Below is a sample of these connections.
NPT Hydraulic Fittings with O-ring (NPT with O-seal)
Fig. 3-6 NPT Hydraulic Fittings with O-ring (NPT with O-seal)
The table below describes the thread type and standard for conical threaded fittings.
Table 3-3 NPT Hydraulic fittings standard with O- ring (NPT with O-seal)
3-2-3 Hydraulic fittings BSPT, JIS R and JIS Rc, DIN 3852 part 2, type C
These hydraulic fittings, which are made from cone-shaped fittings, have been used of ISO 7/1 threads.
These fittings are very similar to NPT fittings.
Below is a sample of these connections.
Fig. 3-7. Example of hydraulic fittings BSPT, JIS R and JIS Rc, DIN 3852 part 2, type C
In the table below, the sealing mechanism, type of fittings and thread standard of these kinds of fittings are given.
Table 4-4 Types of fittings and the standard introduction of hydraulic fittings BSPT, JIS R and JIS Rc, DIN 3852 part 2, type C
In the future articles, we will look at Straight thread’s fittings and introduce them in a variety of ways.
[1] The American Society of Mechanical Engineers