Pros and Cons of the Diaphragm Metering Pump: Part 2 of the Best Metering Pump

Known as the workhorse of the chemical metering industry, diaphragm metering pumps are the most common type of metering pump. These pumps have a reciprocating diaphragm that compresses and decompresses the liquid chamber, while check valves create suction that forces the liquid to move in a certain direction. The metered flow rate is proportional to the displacement of the liquid chamber multiplied by the number of strokes per minute: precise flow is proportional to the stroke speed of the diaphragm.

With low maintenance costs and extended pump longevity, diaphragm metering pumps are used by the chemical, water, wastewater, oil & gas, pulp & paper, agricultural and mining industries. While they are a strong contender in our selection of the best metering pump, they do have some limitations worth considering. Let’s dive in!

Pros of the Diaphragm Metering Pump

• These are relatively low-cost metering pumps, especially at low feed rates
  • -Up to 500 LPH boasts the lowest cost compared to other metering pump alternatives
  • -Costs rise dramatically for over 1000 LPH
• They are constructed from a wide range of plastics and metals, which makes them compatible with most chemical applications
• Maintenance isn’t very complex and can be relatively infrequent (depending on the application)
• They have a lifespan of many years (for most applications) and are often more energy efficient than other types of metering pumps
• They can handle liquids that contain solids (slurries)… however, in some applications, this may slow down the pump
• They are able to handle viscosity / shear sensitivity
• 3000-5000 cps standard construction
• 10 000 cps special construction

Cons of the Diaphragm Metering Pump:

• Both solenoid and motor diaphragm pumps have a metering range/turndown of 10:1, 100:1 (depending on the application) due to pulse lag.

(Note: this is not a disadvantage for stepper motor pumps with metering range/turndown of 600: 1 to 1000:1)

• They don’t handle off-gassing chemicals well; gas-locking of head can occur
• Large pumps can experience high pulsation which can cause piping/system damage without pulsation dampeners.

(Note: this is not an issue for stepper motor pumps with low pulsation).

• • -Pulsing flow is more difficult to measure with flow meters
  • -Slug dosing can occur
• They suffer from moderate wet and dry suction lift
• In most designs, chemical containment can be an issue if diaphragm failure occurs. This means diaphragm metering pumps require regular and proper maintenance to ensure optimal performance and leakage prevention
• Diaphragm pumps feature more valves, which increases complexity and necessitates a tech-savvy operator

When it comes to metering pumps, choosing the one that meets your specific needs and makes the most sense for your operation is critical. You need a reliable system that will last for years to come. Fortunately, the diaphragm metering pump is just one of four types of metering pumps in the running for the best metering pump. Look out for the next part of the series to discover the range of metering pump options we recommend.

Are you considering a metering pump, but not sure which way to turn? Give us a call on 1-800-367-4180 (toll-free). As your metering pumps supplier, we’re here to help you choose, install, maintain, and monitor a variety of equipment. And to answer questions about things you’ve previously tried gone wrong.