Feb 19, 2010

Neptune Chemical Pump Co. Offers Tips on Selecting Metering Pumps

Company creates technical bulletin

Neptune Chemical Pump Co. has a full line of metering pumps. To assist its customers and clients, Neptune has created a technical bulletin titled, “Sizing and Selecting Metering Pumps—Planning a Metering Pump Installation.” The technical bulletin, which is available free via the Internet at http://www.neptune1.com/pumps/sizing-select-guide.htm is meant to be a guide to help the user define the variables that need to be evaluated for proper selection and installation of a chemical metering pump or a complete chemical feed system.

The first step in effective metering pump sizing is determining the size needed in terms of both the pump’s flow rate and discharge pressure. Metering pumps should not be over-sized but rather the maximum expected flow should be 85% to 90% of the pump’s capacity; the minimum capacity should never be less than 10% of capacity.

The best type of metering pump for an application cannot be determined until the proper flow rates, discharge pressures and types of fluids to be handled at identified, Neptune said. Drive end choices are hydraulic diaphragm, mechanically actuated diaphragm or solenoid. Choice of liquid end designs are available for corrosive, viscous or slurry applications.

Liquid end options include double diaphragm heads with leak detection and alarm capabilities for applications where diaphragm failures must be sensed immediately. Drivers must be matched to the available utilities, including electric, air, gas or other means of driving the pump. Knowing the atmosphere in which the pump will operate also plays a role when selecting the driver, as hazardous area requirements must be identified.

Method of control is also a crucial choice, with manual continuous operation, on/off operation and automatic proportional control in response to a process signal the usual choices. Micrometer dials can be manually adjusted to control flow rates, allowing the pump to be operated between 10% and 100% of capacity depending on the stroke length. Flow rates can also be controlled automatically by electric positioners that change the pump’s stroke length in response to a process signal, or by variable speed drives that alter stroking speed.