Metering with Gear Pumps - Liquiflo - #1

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L I Q U I F L O C H E M I C A L P R O C E S S I N G P U M P S TM 443 North Avenue Garwood New Jersey 07027 USA tel. 908.518.0777 fax. 908.518.1847 www.liquiflo.com for Metering, Transfer, Circulation & Injection Applications Liquiflo™ Rotogear® External Gear Pumps APRIL 2003 VOLUME 11 NUMBER 4 Gear Pumps: A Simple Solution for Metering Applications Metering or dosing refers to the delivery of an accurately measured amount of liquid. Metering, in one form or another, is used throughout all industries — from paper making to film processing, to chemical manufacturing, to plating, cleaning, etc. Until recently, many users have considered only diaphragm pumps or piston pumps for their metering applications. Advances in electronics over the last 15 years, however, have closed the gap between rotary and diaphragm pumps, making metering with gear pumps a very simple and extremely accurate solution. These days, the traditional reasons for selecting a diaphragm pump over a gear pump are no longer valid. Typically, gear pumps can compete directly with diaphragm metering pumps up thru 10-15 bar. by Greg Miller, Liquiflo Metering Situations There are three basic metering situations: (a) Metering at a constant flow rate over a range of differential pressure; (b) Delivering a metered flow in a set proportion to a process variable for the purpose of controlling the process variable (e.g., keeping a pH level constant); (c) Delivering a given volume of fluid irrespective of flow rate – Batch processes (e.g., filling a tank to a specified level or volume). Diaphragm and piston pumps historically have been associated with the first of the above metering situations, because of the following characteristics they possess: • Precise volumetric displacement • “Infinitely” adjustable range • Pressure “stiffness” (i.e., the ability of a pump to maintain consistent flow rate over a wide pressure range) No longer are diaphragm and piston pumps the only players in the game. Liquiflo Rotogear® 3-Series & H-Series (Sealed Gear Pumps shown) 1