Pump Valve
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The Pump Valve Is Frozen In Winter, Which Is Not Necessarily Caused By The Dryer

The air dryer is basically an original standard on the air braking truck. Its function is to remove the moisture from the compressed air and make it dry air, so as to ensure the dryness of the truck braking air. At low temperature in winter, the moisture in the air will not condense in the pump valve, resulting in braking failure and braking drag failure.

The dryer is like a sponge, which will lose its function after absorbing enough water. So what is the way to remove the moisture on the dry particles like wring the sponge, so as to prolong the service life of the dryer?

What is dryer regeneration? It's like screwing a sponge

Card friends who have seen the truck home disassemble the drying tank know that the main component in the drying tank is many absorbent particles. These particles can be understood as common sponges in life. You can imagine that after the sponge is filled with water, you have to wring it dry before it can absorb water again. The same is true for the particles in the drying tank. If the absorbed water is not removed in time, it will soon be full of water and lose its function. So how to achieve the purpose of removing water?

After the compressed air reaches the specified air pressure and the unloading valve is unloaded, the dried air is used to blow the drying tank in turn to remove moisture, which is the back blowing regeneration device on the drying tank.

There Are Two Types Of Back Blowing, Both For The Purpose Of Prolonging Service Life

There are two forms of back blowing on the market. One is the back blowing of independent gas cylinder, that is, there is an independent small gas cylinder with a capacity of 5 liters, which is connected in parallel on the air outlet of the dryer. When pressurizing the gas cylinder, the small gas cylinder is also inflated at the same time. After reaching the specified air pressure, the dryer releases the pressure, and the dry air in this small cylinder in turn blows out the water in it through the dryer. This form of back blowing regeneration is easy to identify. It can be identified only by finding the small gas bottle along the gas path.

The other is to use the vehicle’s own gas cylinder to return part of the dried air to blow back the dryer after the dryer is unloaded. For the dryer with this back blowing form, there will be a return valve on the dryer valve body, and after unloading, it can be seen that the pressure of one of the barometers will drop by about 50kPa, This is the process of back blowing the drying tank with its own gas cylinder pressure.

The purpose of the two back blowing methods is the same, which can prolong the service life of the dryer and make the dryer work more efficiently. However, many kayou cars have this device, and the drying tank is also replaced regularly. Why is there still water in the gas circuit?

The Dryer Works Efficiently, And The Inlet Air Temperature Is The Key Point

The Auman LNG tractor of forum card friend “dssn. 01” always has the phenomenon that the trailer relay valve is frozen recently. His car was originally a reflux blowback dryer. It is suspected that the blowback effect of this form is not good. At present, it has been changed to an independent blowback tank dryer. However, from his fault performance and the temperature measurement sticker at the air inlet, the fault of the freezing trailer valve has little to do with the form of the dryer.


The 70 degree window of his temperature measurement stick has been dark, which shows that the air inlet of his dryer often exceeds 70 degrees, and the upper limit of the temperature of the air inlet of the dryer is 65 degrees. Only when the air inlet is within this temperature can we ensure the efficient operation of the dryer. Therefore, the root cause of the failure of the card friend is not entirely in the back blowing form of the dryer. The high inlet temperature is the core cause of the freezing valve failure of the card friend. Here, we suggest that the card friend reduce the temperature of the air inlet of the dryer by adding a spiral pipe to cure the freeze valve failure.


In winter, the brake pump valve is frozen, either there is no brake, or the brake drag does not return. These two faults seriously affect the driving safety. Many repair shops and card friends do not seriously analyze the root cause of the fault and blindly replace the dryer, resulting in their own economic waste, and it is useless to eliminate the fault. Here, we call on the repair shop to correctly and seriously analyze the cause of the fault and not to blindly replace and refit. (text / picture: Jiang DAI)

Related Reading:

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What’s the use of the spiral pipe of the air circuit of the car (25)?

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