​What are the methods for checking the quality of jacks?

What are the methods for checking the quality of jacks?
 Hydraulic Jack refers to the jack which uses plunger or hydraulic cylinder as rigid jacking parts. It has the characteristics of compact structure, stable operation, large supporting force and self-locking. Hydraulic Jack has strong supporting capacity, and the supporting force of heavy hydraulic jack exceeds 100 t.           
 In order to reduce the frequency of hydraulic jack failure, we should pay attention to a few points in use. Hydraulic Jack in the work, should first try to lift a part of the weight, carefully check the hydraulic jack no abnormality, then continue to lift the weight. If it is found that the cushion plate is uneven, unstable or the hydraulic jack is inclined, the hydraulic jack will be released and returned to the journey, and can be operated again after timely handling.
 What causes the jack not to work?           
 A jack is a light lifting device that uses a rigid lifter as a working device to lift heavy objects in a small stroke through a top bracket or a bottom bracket claw. The jack is mainly used in the factory, mining, transportation and other departments as vehicle repair and other lifting, support and other work. Its structure is light, firm, flexible and reliable, one person can carry and operate.           
 The Jack doesn't work anymore. So what causes this?           
 1.  The internal parts of the jack are damaged, which prevents the jack from lifting.
 2.  Overload operation of jack, the lifted weight exceeds the load-bearing range of jack, which makes Jack unable to lift operation.           
 3.  The ground where the jack is placed collapses, which makes the jack unable to work normally.           
 4.  The Jack enters the air inside, which makes it impossible to lift normally.
 In the process of Jack placement, the action line of load center of gravity should be consistent with the axis of jack. In the process of jacking up, the danger of Jack deviation and inclination due to the settlement of Jack foundation or the horizontal displacement of load should be strictly avoided. To prevent the jack from sliding in contact with the metal or smooth surface of concrete, the jack should be padded with hard wood blocks.                     
 Dynamic Load Test           
 The hydraulic jack should meet the requirements of 5.1.2.1 in JB2104-91 Hydraulic Jack and 5.1.2.1 in JB2592-91 QL Spiral Jack.           
 Appearance quality           
 The outer surface of the product should be sprayed with paint according to the regulations. The paint should adhere firmly, the surface of the coating should be uniform and the color should be the same. No obvious defects such as spots, wrinkles and bubbles should be observed. The exposed surface should be rust-proof.           
 Handle force           
 Under the test load of rated lifting weight, the operating force should be measured at 50mm from the end of the handle. Its action force should be perpendicular to the axis of the handle, and the measured results should conform to the standard.
 Static Load Test           
 At  room temperature, according to the standard method, the hydraulic jack should meet the requirements of 5.1.1.3 in JB2104-91 Hydraulic Jack and 5.2.1 in  JB2592-91 QL Spiral Jack.           
 No-load test           
 In the no-load condition, the operation mechanism of the jack should be flexible  and reliable. There is no tightening phenomenon in the whole travel range. The rise should be stable and the limit reliable.           
 Above are the related matters of jack. I hope it will be helpful to you.