Metering Pumps
Metering pumps are used to pump a variety of liquids at different flow rates,
sometimes slow and sometimes fast, so that a specific amount of fluid is moved from one location to another within
a certain time. Even though metering pumps can be used to pump water they are mainly used to pump other
types of liquids, such as fuel, chemicals, and other types of solutions. The pumps are designed to flow at a steady rate no matter how high or low the outlet
pressure is.
Piston Pumps
Majority of the metering pumps are considered piston pumps, which is good because piston pumps
can pump water at a constant flow rate even with high discharge pressure. How piston pumps work is the motor pulls
the piston out of the piston chamber, which sucks water in through the inlet value. To pump the water out the motor
forces the piston back into the piston chamber, this forces it out through the outlet valve.
Diaphragm Pumps
This style of metering pumps is used when you want to avoid any kind of leaks at the seal of the
pump because of how dangerous the chemicals are. How a diaphragm pump works is the liquid is transported through
the diaphragm of the pump so that it doesn’t come into contact with the outside. The liquid enters through an inlet
check value when the diaphragm is decompressed and exits through the outlet check value when the diaphragm is being
compressed.
Peristaltic Pumps
These metering pumps use rollers to force liquid from flexible tubing. The rollers are driven by
motors that causes the rollers to compress the tubes so that the liquid inside is forced out the open end of the
tube. These metering pumps are designed to be used under low pressure, unlike other pumps, because the tubing is
only rated for certain levels of pressure. When pressure level is too much, the tubing can burst apart.
Things To Look Out For In Metering Pumps
One of the biggest issues that you face with metering pumps is, if a gas bubble happens to gets
into the pump. Metering pumps are great at pumping liquids, but are not very well suited for pumping gases because
of how compressible gases are. Water is not very compressible so it is easily forced out of the pump head. If a
gas bubble gets into the piston chamber, the pump is still going to go through the motions of pumping the fluid,
but none of the fluid will come out. With pumps that have to be primed, this problem can occur while priming the
pump or after the pump has been working for awhile. Which means you will have to reprime the pump once you get
rid of the gas bubbles. To prevent this from occurring degassing the fluid before pumping is recommended.
Another thing that you may face with metering pumps is pressure problems; the outlet pressure is lower than the inlet
pressure even when pumping fluids. The pressure problems can cause fluids to flow freely from the inlet value to
the outlet value, even if the pump is turned off. To prevent this, all you have to do is place a positive
pressure differential check value on the pump, but make sure that it is correctly rated.
- Diaphragm Metering Pumps
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- Fluid Metering Pumps
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