Mini Bellows Metering Pump Operation

Featured Product from GRI Pumps (A Gorman-Rupp Company)

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Mini Bellows Metering Pump Operation
The Mini Bellows Metering Pumps operate on a positive displacement principle. The rotation of the motor shaft is transmitted into an up and down linear motion through an adjustable concentric crank mechanism. This motion provides a continuous compressing and relaxing force on the bellows module, forcing fluid between two check valves located in the module’s valve body. Up to two separate bellows modules can be operated by single motor for proportioning up to four separate fluid mediums. The flow rate of each module is independently adjustable. Multiple bellows modules operate out-of-phase with each other for most efficient power usage.

Optimum Operating Conditions
Optimum operating conditions consist of a 6” minimum suction life and a discharge head of not less than 6”. Pumps must be mounted vertically with the valve body at the top to obtain maximum metering accuracy. For conditions where a positive suction head condition exists, an anti-siphon spring or anti-siphon spring kit can be added to aid the poppet valve seal properly during operation. See Accessories section located in the Product Overview Sheet.

Mini Bellows Metering Pumps are ideal for low flow, low pressure metering applications. The pump is constructed entirely of plastic and uses GRI's time-proven bellows technology to provide an accurate chemically-resistant metering pump with a long life, at an economical price.


Mini Bellows Metering Pump Specifications:

  • Average Repeatability - From stroke-to-stroke ± 0.75%
  • Flow Rates - Range to 270 ml/min, Tandem models range to 432 ml/min
  • Max Fluid Temperatures - To 140°F (60°C)
  • Max Discharge Pressure - To 6 psi


Materials in Contact with Solution:

  • Connectors - Polypropylene
  • O-Rings (Elastomers) - EPT/EPDM or Viton®/Fluoroelastomer
  • Poppet/Duckbill Valves - EPT/EPDM or Viton®/Fluoroelastomer
  • Bellows - Standard Polypropylene Materials. Additional materials available.



  • Average repeatability from stroke-to-stroke, ±0.75%
  • Dry run capability
  • Self-priming
  • No dynamic seals
  • Superior corrosion resistance
  • Economical
  • Simple flow adjustment


Chemical Resistant Charts

GRI Certified to ISO 14001:2015 Environmental Standard

Frequently Asked Questions



Since 1953: Not Just Pumps, Pumping Solutions
There are many variables that must be considered when specifying a magnetic drive pump for an OEM application. At first glance you may not find a pump that meets your exact requirements. GRI recommends that you contact our Technical Sales Staff to discuss your project so that the right pump can be specified. Many times we will customize an existing pump to meet your needs or design a new pump according to your system’s exact specifications.

The Importance of Specifying a Pump Early in the OEM Design Process
Check out GRI’s “Emphasis On Pumps” article in the October 2013 issue of MDT magazine.  Knowing the specific fluid pumping requirements of an application upfront in the development process is important. Unfortunately many device and system designers neglect to consider the fluid pumping requirements until late in the design process.

Many times a designer will have to perform costly alterations to systems or devices to make their design compatible with a pump chosen late in the design process. Being that many times a pump is the “heart” of a system, it makes sense to begin the specification process early rather than later. Careful planning saves not only time and money, but also headaches. 

Fluid pumps for the Original Equipment Market
Serving the Original Equipment Manufacturer since 1953, Gorman-Rupp Industries’ reputation and success have been built on innovative fluid pump designs, customer service, and providing products to meet the exact specifications of our customers.

GRI’s fluid pumping knowledge and expertise comes from working with domestic and international partners in a variety of markets and OEM applications for over 60 years. Whether it is replacing an existing pump or working with you on a new OEM fluid pumping application, GRI’s proven concepts and engineered designs will provide a unique solution to your fluid pumping dilemma.

Custom Design and Manufacturing of fluid pumps for the OEM market, Bellows Metering Pumps, Magnetic Drive Pumps, Centrifugal Pumps, Oscillating Pumps, Gear Pumps, OEM Pumps