Grease pumping

[FilipLund]

We have a problem with pumping high viscous NLGI 3 grease. We need to feed a cartridge filling line with constant flow and constant pressure. This first problem is solved by using an air operated double diaphragm pump that feeds an progressive cavity pump.

Now we have another problem. We get air in the system. I assume that the grease is full of air becuase airpockets. We have a bleeding valve between the two pumps. However, even if we open the valve we still cant get the diaphragm pump to get any product. It pumps out air and sucks it back in thorugh the outlet.

We solve the problem if we open up the pump and fill it with grease. Then it runs for a while untill it starts suckin air again. I am thinking it might be that the balls are stuck because of the viscous product and it both blows and sucks air from the outlet. Nitrile balls and membranes.

Filip

 

[ccfowler]

Are you sure that there is no internal leakage of compressed air into the grease stream within the diaphragm pump?

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[ccfowler]

Oops! I touched the wrong key too soon!

With the grease, I would want to use spring loaded check valves and be sure to use a very low cycling rate on the diaphragm pump. Am I correct in assuming some significant cost or space constraints dictate the use of the diaphragm pump rather than another type?

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[LittleInch]

Figure out where the air is potentially coming from first. Is is sucking past the intake nozzle? Is it coming from the pump?

How are the two pumps in series being matched, i.e. if the PC pump is trying to pump even a little bit faster than the diaphragm pump can deleiver then it will pull a vacuum and allow air in from somewhere?

With viscous material a little bit of heat never went astray - is it possible to heat the raw material up, even to 30 or 40 degrees?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Pumpsonly]

To put 2 PD pumps in series is already against the rule. What more with the pulsation flow of AOD pump feeding the PC pump.
The PC pump is continuously "puling" the grease but there is pulsation flow from the AOD pump. There will be a pressure drop between the 2 pumps in between the strokes of the AOD pump. The discharge check valve of the AOD will not see back pressure to close it unless you spring load it.

 

[ccfowler]

To compensate for the pulsations of the diaphragm pump, it would be a good idea to install a relatively VERY large diaphragm-type pulsation damper as close as practical to the discharge of the diaphragm pump. It won't eliminate pulsations entirely, but it will attenuate the pressure fluctuations enough that the PC pump will remain happy.

Depending on the piping and arrangement details of your system, it may make sense to install a diaphragm-type pulsation damper near the suction of the diaphragm pump, too. As with the pulsation damper for the discharge side, it, too, should be relatively very large.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[FilipLund]

Thanks for all the advice. However, we solved the problem. It was very simple. We are pumping out of 1000L flexible grease bags. The top cap was leaking and the pump was creating air channels through the grease. It is very viscous so when a channel was created it did not close up even if you left the bag standing. We sucked all the air out of the bag, closed the top cap, and bled the pump for air. Problem solved.

Next thing:
Some of you touched the point I am wondering about. If we will have pulsation after the PC pump because of the setup. We are running the AOD Pump at 3 bar. The PC pump have to push at a constant pressure of 5 bar into a dosage pump on the cartridge filling machine. We have an adjustable bypass that takes care of the constant pressure.

You think we need a pulsation damper between the AOD pump and the PC Pump?

We have this setup with two pumps because the PC pump was not able to do the job by itself.

 

[ccfowler]

A simple sketch of your system would be helpful in understanding the situation. As is often the case, insufficient information can lead to less useful or less appropriate advice being provided due to missing vital information. This latest posting describes a system with significantly different characteristics than those described in the original posting.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.