Liquid Pump not cycling but still builds pressure and holds it?

[Amar Ljubovic]

Hello. I am using a Haskel 4B-14 air driven liquid pump that uses one single air head inside. Instead of using a manual air regulator for controlling the pumps pressure, I used a electronic version (IP current to pneumatic Transducer) so I could automate this process. Basically, when I try and run the pump and reach a certain pressure setpoint the pump never cycles. I first send 3psig to the pneumatic transducer to start the pump. After that the program starts increasing the pressure to the inlet of the pump by 1psi every second. Once the pressure is 75% to setpoint the program changes to 0.1 psi a second, and once the pressure on the other side reaches the setpoint the program keeps the pressure constant. Not sure why but the pump never cycles during this process not even once, it's so quiet as the pressure slowly rises to setpoint. Once holding at setpoint, after 15 to 30 seconds the pump randomly cycles and a pressure spike goes through the outlet side of the system. For example, once the pressure gets to 250psi the transducer holds constant the psi it is outputting, then as the pressure is being held at 250psi the pump cycles and causes a pressure wave in the outlet side for 1 second before dropping back down to 250psi again, it goes up about 100psi for a second.

I have been researching for weeks and cannot find the right solution. I dont understand why the pump does not want to cycle, when I give the pump an initial pressure of 3 psig it should start cycling from the start. I am confused to why the pump cycles once the pressure is trying to be held, and then causes the pressure wave.

My theory is that the pump is not exhausting/venting the initial stroke from the air pushing the piston head down, once the pressure is constant and not increasing the cycling valve opens and causes the air head to switch and causes a pressure spike? but I dont even know 100% how my pump works.
I have no clue but it would be great if other people chimed into what the problem might be. I have been struggling with this for weeks.

EDIT: Also, it does this multiple times when holding at setpoint, it all depends for how long I am holding it. Once at setpoint it sounds like the pump does one cycle, the pressure wave happens then falls back down to setpoint, then after 30 seconds to a minute it does it again, and again, and again. It only stops once I shut off the fluid supply, and relief the pressure.

 

[Valveman]

The stalled condition can last indefinitely unless something disrupts equilibrium (for example: turning off the power).

The pump will automatically start to cycle once the pressure is released or if the drive air pressure is increased.

https://www.haskel.com/en-us/produc...4_sHyG3GSOuG4fzq4FFhn_AxlMob25ZEaApZ2EALw_wcB

 

[Amar Ljubovic]

The stalled condition can last indefinitely unless something disrupts equilibrium (for example: turning off the power).

The pump will automatically start to cycle once the pressure is released or if the drive air pressure is increased.

https://www.haskel.com/en-us/produc...4_sHyG3GSOuG4fzq4FFhn_AxlMob25ZEaApZ2EALw_wcB

The problem is when it is at stall there can be a random pressure spike in the liquid outlet of the pump. The air pressure stays constant during this process and randomly a pressure spike happens. here is a video. Also, there is no cycling sound when I am pumping up to pressure setpoint, not sure if I am doing it too slow but there is also no ventilation through the exhaust port at all. I am certain that the pump is supposed to exhaust the air out of the piston each cycle, but it is not doing it at all. Can the pump even cycle at less than 10psi air pressure? Is that why the pressure spike is happening?

 

[Valveman]

I think you may need to contact the factory that makes those things to get help on how they work. It is a new one to me.