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Technical Updates, Tips, or Reviews
Water Essentials
How to Select the Right Metering for a Treatment Process By Laith Charles, Pulsafeeder SPO
Metering pumps are the conduit between good chemistry and a controlled process. There are limitless applications for chemical metering equipment, ranging from agriculture and car washes to water treatment for boilers, cooling towers, and wastewater. While the fundamentals of selecting the right metering pump are common throughout all applications, some application-specific considerations can be overlooked. This article is intended as a reference to pump fundamentals as well as some application-specific tips to serve as a useful refresher for some and an educational reference for others.
Diaphragm Pumps The rubber meets the road in the head of a diaphragm pump. The core components of a diaphragm pump are the suction valve, discharge valve, and reciprocating diaphragm. Other than the drive mechanism—solenoid or motor driven—the principals of diaphragm pumps are the same. Fundamentally, all diaphragm pumps have a suction and a discharge stroke, which is shown in Figure 1. Figure 1: Stroke styles of a diaphragm pump: suction (left) and discharge (right).
Before we begin, here is one important reminder for the expert or the beginner: always remember to take the appropriate safety precautions when working with metering equipment. Wear personal protective equipment (PPE) when handling chemicals, while in loud equipment rooms, and when working on electrical equipment. Now, let us look at the essentials for successfully using a chemical metering pump for water treatment applications.
Core Metering Technologies
A plethora of different technologies are available when it comes to choosing a chemical feed pump. Pump technologies include: diaphragm, peristaltic, piston, progressive cavity, gear, hose, and more. Alternatives to metering pumps are also worth mentioning, such as a venture and pot feeder, and solid feeders, such as a brominator.
The suction stroke is when the diaphragm retracts backwards from the forward position, increasing the distance between the surface of the diaphragm and the inner wall of the head. This increases the volume inside the pump head and causes a decrease in pressure, “The suction stroke is when the diaphragm which creates a vacuum retracts backwards from the forward because of the Ideal position.” Gas Law, as shown in Equation 1.
It is important to know all options and their respective strengths and weaknesses. With this knowledge, one can make sure to choose the right equipment the first time to balance cost, performance, and reliability. Nonetheless, the scope of this article will be limited to metering pumps, specifically diaphragm and peristaltic.
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Ideal Gas Law: P1V1 = P2V2
Equation 1
This vacuum, or negative pressure, creates suction, which the Analyst Volume 26 Number 1