5 things you should know before using the A/C POM check valve

Table of Contents

What is the POM check valve?

The performance of the POM material

The raw material of the POM check valve comes from Polyoxymethylene, POM for short.

POM is a hard and dense material with a smooth, shiny surface, it’s color yellow or white, and can be used for a long time in the temperature range of -40-100°c.

POM is also superior to most engineering plastics and it has good oil resistance and peroxide resistance, but it is intolerant to acids, strong alkalis, and ultraviolet radiation.

What the POM check valve look like?

The POM valve is a process part used in the manufacturing and installation process of the air conditioner internal unit, especially for the inflation and pressure maintenance of the air conditioner internal unit test.

POM check valve has two parts, one is called warning nuts, another is called inflatable nuts, they must work together closing. their combination name is the check valve in the air conditioner internal detection.

Detection valve structure model

The detection valve is composed of 7 parts of the four-leaf valve, the spring, sealing ring-1 valve’s core, sealing ring-2, the compressing red ring, the valve body. It has the advantages of easy use and repeated inflation and pressure retention.

Products Diagram

  • Four-leaf valve
  • The spring 
  • Sealing ring-1
  • Valve’s core
  • Sealing ring-2
  • Thread
  • Compressing red ring
  • valve body
  • commutator
  • Lap groove
  • Air inlet
  • Lap ridge

How to work of POM Check valve in theory

There is an annular sealing groove inside the valve body. The red ring is compressed to fix the sealing ring in the valve body groove. 

One end of the spring is fixed on the valve body limit ring, and the other end is fixed with a four-leaf valve. 

The upper end of the valve core is connected to the four-leaf valve. The leaf valve is well inlaid and assembled, and the spring is compressed to form an elastic force opposite to the compression direction. 

Under the action of the spring force, the sealing cone of the valve core is in close contact with the sealing ring, thereby achieving a sealing effect. 

When inflating, the quick connector valve core is pressed down The four-leaf valve displaces the valve core in the direction of the thread, and the sealing cone of the valve core is separated from the sealing ring to come out a gas path to achieve the purpose of inflation.

Here’s how you can see the whole production process.

To avoid failing to performance of inflatable nuts caused by the inconsistent tightening torque of the warning nut in the production process, which will cause unnecessary quality impact. 

We should clarify relevant process operation specification as follows:

Production Process-1

  • Fixed on inflatable nuts and warning nuts 
  • Filling in nitrogen with pipes 
  • well welding 
  • Leak detection 
  • Vacuum pumping 
  • Filing in nitrogen gas
  • Helium detection 
  • Nitrogen recovery
  • Nitrogen filling and pressure maintenance

Production Process-2

  • Conventional assembly 
  • Warning nuts 
  • Mounting plate
  • Regulation assembly 

5 ways to work out the procedure of POM check valve 

  1.  Inflatable nuts and warning nuts assembly

Firstly, Tighten at least one thread manually before fixing on inflatable nuts and waring nuts that make sure the thread alignment. and then use fixed torque to lock in batches.

Here’s you can see correspond torque specification:

Code No.Material nameModelTorque 
1806748inflatable nuts7/16”-20UNF1.0-1.5 N.m
1806753warning nuts5/8”-18UNF1.5-2.0 N.m
1806756warning nuts3/4”-16UNF1.5-2.5 N.m
1806798inflatable nuts5/8”-18UNF1.5-2.0 N.m
1806796warning nuts7/8”-14UNF2.5-3.5 N.m
1813279warning nuts7/16”-12UNF3.5-4.5 N.m
1815593inflatable nuts3/4”-16UNF1.5-2.5 N.m

In mixed-line production, the torque can be unified to 2.0±0.1 N.m but in the model of  1806796, 1813279 mixed-line productions, the torque should be unified to3.5±0.2N.m

Pay attention please, When locking, fix the pipe joints with tooling to ensure that the input and output pipes are free of force and distortion.

  1. Filling in nitrogen with pipes 

Plugin the nitrogen-filling pipe before inserting pipe and while the nitrogen-filling tube is allowed to be removed when the last tube inserting finished 

  1. Leak detection 

Mare sure the detection pressure is 3.0MPA to 3.5MPA when leaking detection

  1.  Nitrogen filling and pressure maintenance

Make sure the nitrogen filling pressure is 0.6 to 0.7MPA

  1.  Mounting plate process

Make a full inspection when the happen of the ejection of the tube nut thimble.

Quality warranty and storage requirements.

  • The service life of the inflatable nuts and warning nuts is half a year from the date of delivery. If more than half a year, the refrigerant oil applied to the internal sealing structure will be invalid.
  • Incoming goods inspection, for materials with a delivery date of more than half a year, will be treated as unqualified returns
  • The production line shall do a good job of marking management, and materials of different dates shall not be mixed in one package, 
  • and at the same time, priority shall be given to consume incoming materials from earlier production dates.
  • Incoming materials should be kept clean and dry and sealed and packaged to prevent dust.


Hi, I’m jenny cheng, the funder of Chinahvacparts.com, I’ve been running a manufacturing sourcing company in China for many years. and the purpose of this article is to share with you the knowledge related to "how to manage your supply china in China.

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