Published : 11/14/2017 05:08:10
If you are working in an industrial profession, there is a good chance you will eventually come into contact with a chemical metering pump. Not everyone who will work with a metering pump will be an expert when they first encounter it, and if you’re working alone or in a small group, you might find yourself with a shortage of much needed information. Reading this guide will help you have a basic understanding of what a chemical metering pump is, its function, and some important terms that might help you solve issues that could arise while working.
First off, let’s establish the definition of a metering pump. A metering pump is a device that allows for a designated volume of liquid to be moved at a very accurate rate. The term for the action of managing precise, but variable rates of flow is “metering.” As you can see, because of the rather broad definition of metering pump, many pumps could be constructed to be used as a metering pump. Certain configurations, however, are favorable due to their design and as a result industrial pumps tend to be designed according to a handful of archetypes, which we will explore below.
A piston pump is one of the most common forms of chemical metering pump, and its design is very simple and effective. The basic design of a piston pump involves a motor attached to a piston which slides in and out of a seal within a tightly designed pump head. The movement of the piston creates a vacuum which draws fluid in through a single-direction inlet valve. When the piston reverses, the fluid is pushed through another unidirectional valve out of the pump.
By carefully measuring and constructing the movement of the piston, the volume of the pump head, and the inlet/outlet valve functionality, a piston pump can end up delivering incredibly consistent flow rates. Readers can be attached and calibrated to the measurements of the pump in order to understand the rate of flow and the total amount of fluid passing through the pump.
Another type of pump that is frequently used (especially for particularly dangerous chemicals) is a diaphragm pump. Diaphragm pumps are completely sealed, unlike piston pumps which have a piston moving through the seal. The diaphragm is impermeable to the fluid within the pump and, when activated, pulls fluid in and pushes it back out via similar inlet and outlet valves to the piston pump.
The final common form of chemical metering pump is the peristaltic pump. These pumps are comprised of pliable tubing to which a rolling pressure is applied. You can imagine this something like squeezing toothpaste out of a tube. As rollers pass over the tube, they push fluid through and then new fluid rushes in to fill the new void. By understanding the speed of the rollers and the volume of the tube, chemicals passing through the tube can be metered.
It should be noted that no metering method is 100% accurate with each individual rotation of the pump. Metering is generally calculated based on averages over a specific space of time or rotations of the pump, so keep this fact in mind when considering your system. Also keep in mind that metering pumps can be very sensitive to changes in the internal pressure of a system. If you are modifying a metered system, make sure you pay close attention to your pump’s maximum pressure rating, and install relief valves if necessary to prevent damage to the metering pump.
Also keep in mind that metering pumps do not tend to work well in gas systems. This is because gas is much easier to compress than liquids are. The pumping action will, therefore, intake much less gas than can actually fit in the pump head, and may compress it with the return motion. This can create what is known as a “vapor lock,” in which a certain amount of gas is let into the pump and then remains in the pump, continually compressing and decompressing instead of pushing the gas out and bringing new gas in. Liquid systems are ideal for metering pumps.
With the basics of chemical metering pumps under your belt, you will know how to identify metering pumps in your workplace and understand the fundamentals of their function. Mastery of this component of an accurate pressurized system is much more than understanding the fundamentals, however, so don’t give up! With the information you’ve gained here, you should be able to have an idea of what you’d like to learn next, whether that means the engineering of such pumps or their safe installation.
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