Hydraluic ratchet issue

H

Thread Starter

Haseeb123

The normal sequence of ratchet assembly is as follows:
1. 88HR motor starts and 20CS-1 SOV energizes. As a result, hydraulic pressure reaches Sequencing valve. At this point, limit switch on sequencing valve which indicates start of forward stroke (ZSL-300) = 0
2. Reverse stroke starts (pressure in R appears)
3. When feedback pressure Rs appears, sequence valve action changes and forward stroke starts. ZSL-300 = 1. Pressure in F appears.
4. When feedback pressure Fs appears, sequence valve action changes and ZSL-300 = 0. Due to the falling edge of ZSL-300, motor 88HR stops and 20CS-1 de-energizes.
5. Timer of 3 minutes starts. After completion of timer, go to step-1

Our observation is that the ratchet becomes problematic after step # 3. When sequence valve operates, pressure on F is 800 psig ~ 1000 psig. ZSL-300 becomes ‘1’. Ratchet assembly moves slowly and then becomes stuck. Pressure on Fs does not appear.

To overcome this, we do frequent start-up/stop of the ratchet motor to repeat the process till the time Fs appears and normal sequence is resumed. This manual intervention takes around 40 minutes. After few strokes, ratchet assembly starts to behave normally. In forward stroke, reading on F gauge normalizes to 600 psig.

 
Have you checked VR-5, the relief valve just after the pump, also check the filters before and after the pump. Looks to me like you have marginal low pressure and may just not have enough pressure to get the forward stroke started.
 
Top