Methods To Reduce Hydraulic Cylinder Failures

Manufacturers of hydraulic cylinders are proficient in all aspects of hydraulic cylinder technology, but may not know much about the sealing technology of cylinder seals. The general hydraulic cylinder manufacturer only knows the use, not necessarily the sealing principle of the cylinder seal, the dynamic change of the cylinder seal, and how the cylinder seal works in the cylinder. The manufacturer of the oil cylinder must understand the sealing technology of the oil cylinder seal, so that different oil cylinder seals can be selected according to different technical requirements. The seal manufacturer also understands the working principle of the hydraulic cylinder, and adopts different designs to meet the technical requirements of the cylinder. Therefore, the close cooperation between the cylinder manufacturer and the seal manufacturer is required to reduce the probability of the cylinder failure.

1. Several states of hydraulic cylinder seals (lip seal)

(1) When the hydraulic cylinder seal is installed, there are four sizes, which can be seen by everyone and measured by the measuring tool. The four dimensions are: the inner diameter of the root of the cylinder seal, the outer diameter of the root, the inner diameter of the lip, and the outer diameter of the lip.

(2) When the hydraulic cylinder seal is installed in the groove and has not yet worked, the size of the groove remains unchanged, but the size of the seal has all changed. The four dimensions are: the root outer diameter of the hydraulic cylinder seal, and the outer lip diameter at the same time. is the outer diameter of the groove, the diameter of the inner lip is the diameter of the piston rod, and the inner diameter of the root is the amount of clearance between the hydraulic cylinder seal and the piston rod plus the diameter of the piston rod.

(3) When the oil cylinder starts to work, the working state of the oil cylinder seal is as follows: the inner and outer lips are close to the inner and outer walls and move backward slightly. The root of the cylinder seal is squeezed backward. As the pressure increases, the force of the hydraulic oil on the seal also increases, and the overall deformation of the cylinder seal also increases. When the working cycle is completed and the cylinder is free of pressure, the cylinder seals return to their original state. Deformation repeatedly. Repeated recovery, the seal is not damaged until all the lip volume of the seal is lost.

2. The dimensional tolerance of the cylinder groove and the cooperation of the seal

(1) There are many types of reciprocating motion seals. The common ones are L-type, U-type, V-type, and Y-type, and most of them are lip seals.

(2) The reciprocating lip seal is widely used in the reciprocating oil cylinder of the hydraulic system. The pressure surface of this seal is lip-shaped, and there is a very small amount of interference during installation, so that the lip and the sealing surface are fully contacted to produce a sealing effect. When the cylinder is working, with the increase of pressure, its contact force and contact area increase, and the sealing performance increases with the increase of pressure. When the cylinder returns, the pressure decreases, the contact area and contact force decrease, and the sealing performance decreases. This lip operation process is similar to the human breathing process. In addition, this process also acts as a lubricating lip.

(3) Seal manufacturers all over the world have strict requirements on the tolerance and roughness of groove size. Therefore, the oil cylinder manufacturer needs to produce the oil cylinder strictly according to the tolerance and roughness requirements.

If the cylinder is not produced as required, there will be three situations

Case 1. If the groove is too deep, two situations will occur:

1. If the gap between the root of the cylinder seal and the groove becomes larger, the root of the cylinder seal will be unstable.

2. The smaller the interference between the sealing lip and the sealing surface, the smaller the seal, so the failure rate of low-pressure oil leakage when the piston rod is beating will increase.

Case 2. If the groove degree is not enough, two situations will occur:

1. The interference between the oil sealing lip and the sealing surface is increased, and the contact area is increased, which leads to the increase of frictional force. When the cylinder returns, the sealing lip of the seal cannot be lubricated enough, and the calorific value increases. This accelerates the damage to the sealing lip of the cylinder seal.

2. As a result, the clearance at the root of the cylinder seal becomes smaller, and as a result, the probability of the root of the seal being squeezed out increases when the cylinder is under high pressure.

Case 3. The finish of the oil cylinder

If the finish of the hydraulic cylinder does not meet the requirements, it will also lead to two situations:

1. The friction of the inner and outer lips of the hydraulic cylinder seal will increase, and the lip will be damaged quickly.

2. The amount of oil on the contact surface area between the hydraulic cylinder seal and the cylinder increases, which increases the possibility of oil leakage.