Metering pump parts include pump head, check valve, valve ball and sealing ball seat, diaphragm and hose joint. This article mainly answers what questions should be considered when selecting these parts.
It is important to consider its material, generally choose the general pump head material: PP,PVC,PTFE and SS316.
PP: easy to shape, low cost, acid and alkali resistance and certain high temperature resistance; But not suitable for organic solvents, strong acid base and liquid containing hypochlorite. Concentration is limited.
PVC: shaping easy, low cost, acid and alkali resistant, but not suitable for organic solvent, strong acid and alkali and 40 ℃ higher than the liquid measurement, not suitable for food and drinking water industry, toxic, food packaging bags will no longer use PVC bag.
PTFE: suitable for all kinds of media, high temperature resistant, but difficult to shape, high cost.
SS316: suitable for organic solvents and high-temperature liquids, but not resistant to strong acids
Metering pump diaphragm selection
Common diaphragm: composite diaphragm and pure PTFE diaphragm;
Compound diaphragm: the surface of NBR rubber diaphragm that sets a bolt inside affixed with a layer of PTFE film formed compound diaphragm, some in the rubber diaphragm also inlaid with wire mesh to increase its strength. This diaphragm is of low cost and large elastic deformation, which can generate a large flow rate from a small plane size, thus reducing the power of the electromagnet and reducing the power of the electromagnet and reducing the production cost. However, when running for a long time, the heat of the electromagnet will be accumulated on its rubber surface by radiation and the conduction of its mounting bolts. Coupled with deformation, the diaphragm will soon age and damage. Therefore, all the diaphragm metering pumps of this type have indication holes of diaphragm damage.
Pure PTFE diaphragm: it is processed by modified PTFE as a whole. The cost is relatively high and the diaphragm shape variable is relatively small, but it can never be damaged. Italy's metering pump on the market for pure PTFE diaphragm, other manufacturers for the composite diaphragm.
Flow and pressure selection
Overall consideration of the overall elements of the metering pump can be obtained, the selection should pay attention to two parameters: flow and pressure, the pressure on the label is the highest normal working pressure of the metering pump, the flow is the maximum flow under this pressure. Metering pump is a one-way volume pump, pump cavity pressure is greater than the external pressure when the metering pump can be out of the liquid. When the external is higher than the pressure on the label, the metering pump work in overload. If it is the electromagnetic diaphragm metering pump, its flow will drop a lot, or even hit the liquid; If it is motor driven metering pump, motor may be damaged by overheating.