Air operated diaphragm pumps
The use of air operated diaphragm pump has increased over the last few years. The reason for this increase in use, is because the pump has a relative simple construction and it doesn't need a start-up motor. This type of pump is suitable for aggressive, abrasive and viscous liquids. The pump however has to meet up to certain construction and material requirements.
The air operated diaphragm pump is often constucted with two diaphragms. This means the pump has two pump chambers. In both chambers there is a vertical placed diaphragm. The center of both diaphragms are connected with each other by a shaft. The diaphragms both move simultaneously from each other. The space behind a diaphragms, is called the diaphragm chamber. These diaphragm chambers have a pressure and a suction valve. The air valve is controlling the oscillating movement of the diaphragms, by controlling the air flow in both diaphragm chambers. Because of pressure balancing the stress on a diaphragm is much lower when comparing it with other types of pumps.
(1) The air pressure valve regulates the air-pressure flow into diaphragm chamber A. Because the air pushes diaphragm A, both diaphragms move to the left creating a decrease in volume inside pump chamber A, while pump chamber B has an increase in volume. The liquid inside pump chamber A is pushed out towards the outlet side. The empty pump chamber B is sucking liquid into the empty space.
(2) All the liquid inside pump chamber A has been pushed out, by the diaphragm. Pump chamber B has filled itself with liquid.
(3) Between picture 2 and 3, the air valve regulates the air flow into diaphragm chamber B and the diaphragms start moving to the right. The volume inside pump chamber B is decreasing, creating pressure on the outlet valve. The liquid inside the chamber is now pushed towards the outlet side. At the same time, pump chamber A has an increase in volume, thus sucking the liquid from the inlet into it's empty space.
(4) The liquid has been pushed out of pump chamber B and pump chamber A has been filled with liquid. The pump is about to regulate the air flow into the other chamber to let the diaphragms move to the left.
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The plunger and diaphragm pump both have their advantages. The plunger pump can achieve relative higher pressure rates than a diaphragm pump, but has a mechanic sealed shaft. The plunger diaphragm pump combines both advantages from the different pumps.
Three plungers, which are placed in an angle of 120°. The allocated drillings, make sure the diaphragm chambers are filled with oil. The plungers push the hydraulic liquid, over the entire surface of the diaphragm. The hydraulic liquid used for these pumps is motoroil with a viscosity of SAE 30 suitable with a temperature of 90°C or a viscosity of SAE 40, with a temperature of 90°C.
When the axe is rotating, the plunger will oscillate, which will cause the diaphragm to create an impuls with every cycle. The inlet and outlet side if the pump are interior connected with eachother, one suction side and one pressure side. The diaphragms have an angle of 120° and because of the overlapping impuls, an almost continous flow will be created.
The hydraulic liquid remains separated from the pump liquid. Because the pump is driven by hydraulics, it functions without vibration, having a minimum of noise when operating. Because of this, the pump won't wear of quickly. Other than mechanical driven diaphragm pumps, the hydraulic driven diaphrams are exposed to less pressure difference. This makes it possible for the diaphragms to withstand plunger pressures up to 70 bar. The pump is also suitable for hazardous chemicals.