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Fluid Air


Home / Tech Tips / Pumps
I have a Graco pump, but it doesn’t seem to be keeping up, is there a way to troubleshoot/test it?

Yes, close your valve or gun and the pump should stop completely, do this on both the up and down stroke. If the pump doesn’t stall on eh up stroke, this means you have a fluid leak by the upper ball and seat, or through the gasket at the top of the cylinder. If the pump doesn’t stall on the down stroke, this means you have a fluid leak by the bottom or intake ball and seat. Balls are usually included in the repair kits, if your pump still leaks on one or both strokes after putting in a kit, then you need to look at replacing the seats.

How do I get the pump to prime, especially first thing in the morning after it’s been sitting all night?

The most common cause of this situation is an intake ball that is not seated properly. Tap on the pump lower with a rubber mallet to dislodge the ball so it rests tightly on its seat. Other possible causes may be a worn inlet hose o-ring (which you should replace). You may need to tighten a loose suction hose fitting or clogged inlet strainer. To alleviate the problem, flush your sprayer with mineral spirits at the end of the day.

How do you solve the problem of fracturing diaphragm pumps while they are being used as a feed supply pump?

It is not recommended to use a low-pressure pump to feed a high-pressure pump without the addition of a high pressure check valve installed directly before the intake of the high-pressure pump. The reason for the high-pressure check valve is prevent any high-pressure material from backing up into the low-pressure supply hose and pump. One of the reasons this happens is when the intake valve or lower ball and seat on the main pump do not seat properly on the down stroke. This is the main reason for installing the check valve prior to the high-pressure pump inlet

I have a new diaphragm pump and it leaks almost immediately after installation. This leak usually occurs around the diaphragms, or at the manifolds. What can be done?

Polypropylene is a very soft almost waxy material that when it is compressed, instead of pushing back against the compression, like a Buna material, it moves out of the way or “cold flows.” Pumps that have Teflon parts (o-rings, diaphragms, etc.) also “cold flow”. So, when a pump is first assembled the material will cold flow resulting in the original torque actually relaxing causing leakage. This is why all diaphragm pumps are shipped with a tag attached recommending all fasteners be re-torqued prior to installation. That is not to say that all pumps if not re-torqued will leak, but the likelihood would be greater. It is important to torque the fasteners before leakage occurs as any amount of tightening may not be able to overcome the leak path that has been established. Also, if the manifolds are being removed and reoriented, I would recommend the o-rings be replaced.

There is oil leaking out of a small hole underneath the air motor of my pump. Can this hole be plugged?

No! If oil is coming out of the small hole underneath the air motor of your pump, the throat packing should be replaced. It may also be advised to ensure there are no imperfections on the rod.

What is the air consumption of a diaphragm pump in cubic feet per minute?

As a general rule PUMP RATIO X FLOW RATE (GPM) @ 100 PSI = CFM. All diaphragm pumps are a 1:1 ratio, therefore the flow rate in GPM will equal the cubic feet per minute.

The pump on my lube truck seems to operate fine, but material volume has dropped. What might be the problem?

If the pump is being used outdoors and the temperature has dropped, the material has thickened resulting in lower pump performance. Pump performance can be improved by . . .

  1. Using a larger diameter hose.
  2. Using a shorter hose length.

Warming the grease to room temperature (with a barrel heater or heater blanket.

Should a lubricator be used on a diaphragm pump?

No. Lubricators are not recommended on diaphragm pumps. An air filter is recommended to maintain good clean dry air.

What causes premature throat seal leakage and is there a way to prevent it?

Premature throat seal leakage and packing wear can occur when Throat Seal Liquid (TSL) is not used in the pump wet cup. A thin film of paint can accumulate on the pump displacement rod while the pump is running. When the pump is not being used and the displacement rod is exposed to air the film of paint on the rod can dry and harden. When paint has dried on the displacement rod and the pump is run, the throat packings are damaged and will begin to leak.

To prevent premature throat packing wear, fill the pump wet cup 1/3 full with Graco Throat Seal Liquid (TSL). This will keep a wet film on the displacement rod and prevent paint from drying on the displacement rod. Keeping the displacement rod wet with a film of TSL will prevent paint from drying on the rod extending the life of the throat seal packings.