DC Motors in Chemical Injection Pump Applications

Chemical injection pumps1 (also called dosing pumps2 or metering pumps3) are used to insert or pump chemicals in measured portions in pipes, liquid streams, tanks 4 or other systems used in industries such as, agriculture5, oil/gas6, water/wastewater7 treatment, among other industries. They serve many functions that include antifreezing, corrosion inhibition, friction reduction, pipeline scale inhibition, product reaction catalyst, chemigation (applying “fertilizer, herbicides, insecticides, fungicides, nematicides, and growth regulators via irrigation systems” 8). Typically, chemical injection pumps are electrically driven by AC or DC electric motors. 9 In DC motor applications, chemical injection pumps generally use DC permanent magnet motors10 ; however, DC brushless motors11 are also used in applications that require high power efficiency and advanced functionality such as “digital dosing.” 12

Chemical Injection Pump Systems

Chemical injection pump systems typically consist of a pump, gate valves, check valves, prime mover (electric motor), storage tank, filter, directional valves and interlocks. 13 They utilize reciprocating, positive displacement pumps14 to accurately pump controlled volumes of liquid from a storage tank into the system receiving the chemical additive. These positive displacement pumps are “driven by a variable speed DC motor drive, which ensures the proper speed based on travel speed.” 15

The types of positive displacement pumps used in chemical injection pump systems are diaphragm and plunger pumps. Diaphragm pumps16 pump chemicals by way of an electromagnetic solenoid which is connected to the pump’s diaphragm. When the solenoid is energized by the control circuit, it moves the diaphragm which, in turn, moves chemical additive fluid out of the pump discharge under pressure. When the solenoid is de-energized it returns the diaphragm back to its home position and pulls more chemical fluid into the pump’s inlet. The cycle repeats itself as the solenoid is energized and de-energized. Plunger pumps17 use reciprocating, single- or double-acting cylinders to pull chemical fluids into the pump and force it out of the discharge end of the pump. 18

They are used in metering applications to deliver a pre-determined flow of liquid with extreme accuracy +/- 1%. 19.

Uses of DC Motors in Chemical Injection Pumps

DC motors function as the prime mover20 of the chemical injection pump. Electric motors are considered by industry experts as more cost-effective than engine-driven prime movers. They are less costly to install and maintain. In addition, electric motors pose no external costs relates to fuel or emissions compliance. Some chemical injection pump systems are solar-electric powered which extends another cost saving advantage. Solar-electric powered systems utilize solar cells to create electrical current via the photovoltaic effect. This electrical current is connected to a battery bank, which, in turn, powers the DC electric motor to drive the pump.

There are two types of DC motors commonly used in chemical injection pump motors: DC permanent magnet and Brushless DC motors. DC permanent magnet motors21 offer the advantages of low current/power consumption, high reliability and low maintenance with sealed bearings and heavy duty brushes. Brushless DC motors22 are used in applications that require continuous duty, variable speed, and high torque response to maintain a constant pump speed even when pressure varies. Brushless DC motors usings digital controllers provide chemical injection pumps the added benefits of improved precision and accuracy of injection rates. These valuable benefits can prevent over-injection and the “corresponding waste rates [can be] dramatically lowered.” 23

  1. ANSI/HI Pump Standards. Controlled-volume Metering Pumps. Hydraulic Institute, 2012.
  2. Brian Nesbitt. Handbook of Pumps and Pumping. Elsevier, 2006. Page 46.
  3. Lev Nelik. Centrifugal & Rotary Pumps: Fundamentals With Applications. CRC Press, 1999. Page 75.
  4. Brian Nesbitt. Handbook of Pumps and Pumping. Elsevier, 2006. Page 46.
  5. Dennis R. Heldman, Ed. Encyclopedia of Agricultural, Food, and Biological Engineering. CRC Press, 2003. Page 133.
  6. James F. Lea, Henry V. Nickens, and Michael R. Wells. Gas Well Deliquification. Gulf Professional Publishing, 2008. Page 499.
  7. David L. Russell. Practical Wastewater Treatment. John Wiley & Sons, 2006. Page 170.
  8. Bobby Alton Stewart, Terry A. Howell. Encyclopedia of Water Science. CRC Press, 2003. Page 67.
  9. Francis S. Manning, Richard E. Thompson, Richard E. Thompson (Ph.D.). Oilfield Processing of Petroleum: Crude oil. Pennwell Books, 1995. Page 184.
  10. Ohio Electric Motors. Permanent Magnet DC Motors. Ohio Electric Motors, 2012.
  11. Ohio Electric Motors. Brushless Dc Motors: Low Maintenance and High Efficiency. Ohio Electric Motors, 2012.
  12. Mike Riley. The Case for Digital Dosing. Pumps & Systems, 2012.
  13. S. Cohen, T. Martin, and M. L. Flint. Field Fumigation. ANR Publications, 2009. Page 54.
  14. Engineer’s Toolbox. Positive Displacement Pumps. The Engineer’s Toolbox, 2012.
  15. K. A. Sudduth, S. C. Borgelt, and J. Hou. Performance of a Chemicial Injection Sprayer System. USDA and the Applied Engineering in Agriculture, Vol. 11 (3): 343-348.
  16. Dennis R. Heldman, Ed. Encyclopedia of Agricultural, Food, and Biological Engineering. CRC Press, 2003. Page 133.
  17. Garr M. Jones, Robert L. Sanks, Bayard E. Bosserman, and George Tchobanoglous. Pumping Station Design. Butterworth-Heinemann, 2008. Page 11-33.
  18. “Engineer’s Edge. Plunger Pumps.
  19. Francis S. Manning, Richard E. Thompson, Richard E. Thompson (Ph.D.). Oilfield Processing of Petroleum: Crude oil. PennWell Books, 1995. Page 184.
  20. M. H. Ali. Practices of Irrigation & On-farm Water Management. Springer, 2011. Page 441.
  21. Ohio Electric Motors. Permanent Magnet DC Motors. Ohio Electric Motors, 2012.
  22. Ohio Electric Motors. Brushless Dc Motors: Low Maintenance and High Efficiency. Ohio Electric Motors, 2012.
  23. Duncan McFarland, Ferguson Beauregard, and Sudip Sarker. Diaphragm Pumps Enhance Chemical Injection Systems During EOR. Ohio Upstream Pumping Solutions, 2012.
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