Positive Displacement Pumping Principles

Do you know the basic pumping principles when applying a positive displacement pump?

A few months ago I was in south Georgia with our salesman Chris Carlisle and we were visiting a bio fuel transfer facility.

Essentially, this facility unloads bio fuels from tankers and stores the fuel until it is loaded into another tanker for distribution.

This facility was having some challenges with a Viking Q4124A, which is a 4” Universal Series pump, which they had purchased from another distributor out west thru their home office. Basically, they were not seeing the flow they expected thru the pump, so it was taking longer to unload the tankers.

Upon our visit we looked over their system and they informed us it was exactly like their facility on the west coast, which was running with no problems and getting the exact flow they needed. However, we soon discovered that this was not the case.

For this facility they tried to save some money and instead of using 4” piping they went with 3” pipe. For those of you unfamiliar with basic pumping principles this means they were starving their pump.

When a Viking Internal Gear pump is sized for an application it expects to see a certain volume of liquid entering the pump at any given time. The principle of positive displacement pumps, in laymen’s terms if you will, is if you get it to one side the pump will move it to the other side.

For this application the Viking Q4124A pump was looking for a volume of liquid that would flow thru the 4” pipe and that volume wasn’t there. Subsequently, the output flow would not be the 300 GPM that the customer was looking for.

Now in the interest of full disclosure, there were also some issues with the length of pipe between the tanker and the pump, the number of 90 degree elbows, various other changes in elevation but the main issue was their system starving the pump.

We then made three recommendations. First they could come back and replace all their piping with the proper 4” size pipe. Or they could purchase a 3” Viking pump which would still provide less flow (200gpm vs 300gpm) than what their west coast facility was getting but would eliminate starving their pump as a system issue. Or they could accept what they have and continue to operate as they were doing.

This specific issue of starvation is why it is important to have efficient communication between everyone in designing any pumping system. The Viking Q4124A pump was perfect for the application on the West Coast but due to some simple design changes the desired flow rate was effected and the facility was not able to meet their transfer time requirements.

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