Technical Support

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Technical Tips


Technical Tips  
Q. What is the recommended FMI "Q" Pump Mounting for maximum performance ?

A. Please see drawing below.


Q. What is the recommended FMI "Q" Pump Mounting for maximum performance ?

A.  The recommended FMI "STH, RH or STQ PUMP DRIVE MODULES".  Pump Mounting for maximum pump performance, mount the pump with motor at 12 o'clock and pump head at 6 O'clock position. This orientation will allow air bubbles that enter the pumping chamber to directly exit thru buoyant assist.  Discharge lines should be inclined upward from pump head.


Q. What is the general guideline for pumping high viscosity fluids ?

A.  FMI pumps are considered viscosity independent indicating that most high viscosity fluids can be dispensed or pumped at low flow rates and low speeds. Free flowing fluids are easier to pump than non-flowing fluids.

Viscous fluids up to 500 centipoise can usually be pumped by most FMI Drives and Pumps Heads. In most cases no additional steps are required to achieve good performance.

Viscous fluids above 500 centipoise may require one or more of the following steps to achieve better results -

  1. The slower the RPM the better. Try to keep RPM below 400. Use stainless cylinder case material (CSC, CSC-WT, CSC-TC, CSY, SSY)

  2. Set Pump Head closest to 100% of Pump Head Module flow rate. A longer piston stroke is better than a short piston stroke.

  3. Use the largest ID suction line possible.

  4. Increasing tubing ID size on discharge line can help reduce backpressure build-up.

  5. Reduce viscosity if possible - try Heating the fluid (use CSC-WT pump head) or if applicable dilute the fluid using suitable thinner. Check temperature limits of Pump Head Module in catalogue.

  6. Improve flow to pump -Free flowing fluids should be gravity fed.  Non-flowing fluids may require the use of a pressure pot to get fluid into pump head. Do not over pressure the suction line, use minimum pressure necessary to help deliver the fluid into the pump head.

  7. Dispensing small drops of high viscosity fluids may require physically moving the dispenser head to the point of delivery and making contact at that point. This will help prevent the drop from remaining on the dispenser tip.

  8. High viscosity fluids may require modified ceramic Piston-Liner sets. Consult factory.

Note – The molecular chemical composition of certain fluids may pose a pumping challenge even though a similar viscous fluid can be easily pumped. Typically polymers in the Cationic family may pose such difficulties.

Q. What is the isolation gland "W" option setup ?

A.  In a special modification of certain FMI Pump Head Modules (designated by suffix “W” or “WT”), a pair of extra ports provide a barrier gland of liquid, gas, steam or whatever fluid required to isolate the pumped fluid from the seal area and atmosphere. Slurries, particulates, crystal formers, and anaerobics are easily handled at temperatures and pressures unattainable before. The Isolation gland option is available for Q1, Q2,Q3, CKC, CKC-LF, & CSC Pump Head Modules.

Gland Feed Rate 2 - 5 ml/min is recommended
Pressure Feed Gland inlet pressure must be less than or equal to the fluid being pumped
Gravity Feed For continuous operation, we suggest installing a level device so the gland does not run dry

FMI Metering Pumps & Dispensers Application Tips

FMI are dedicated to providing all of their customers with the highest quality valveless metering pumps, the very best service, and technical support. To further our quality goal, We have put together these application recommendations. We hope you will find these tips beneficial. For assistance with a specific application or for custom design support, use our secure Application Request Form to provide us with details of your project. One of our specialists will contact you to target a solution.


In most FMI pump models, motor starting torque is the limiting factor in the stated pressure rating. Fluids such as oils, creams and gels that are good lubricants are more easily pumped than aqueous or "dry" fluids and therefore require less motor torque and may be pumped against pressures considerably greater than those given in the rating charts.

All pump head components are designed to withstand backpressures up to 100 psig at room temperatures, though pump heads with fluorocarbon cylinder cases may exhibit some loss of pumping capacity at pressures over 60 psig.


FMI pump accuracy is based on a simplified positive displacement mechanism. The valveless design provides a precision of better than 0.5% when handling medium viscosity fluids (50 to 500 centipoise). Aqueous solutions and light solvents work well but may exhibit some sensitivity (fluid slip) to variations in discharge head pressure. Gums, gels and non-abrasive semi-solids are handled with a high degree of accuracy... a direct result of the valveless design.

Viscous, tacky solutions, semi-solids and heavy slurries which tend to resist (cavitate) suction flow into a pump head can be handled with ease by selecting an FMI pump employing a relatively slow reciprocation rate.

The principal flow rate deviations of an FMI pump are fluid slip and stroke repetition rate. These two factors in turn are related to load factors such as viscosity, differential pressure, and drive motor voltage. When these two factors are controlled, the FMI pump will handle most fluids with reproducibility of better than 0.5%


Due to the valveless design of the FMI pump "CKY" and "CSY" pump heads are able to perform accurate gas transfers. With no valves to introduce random compression errors, gas sample flow in bagging, scrubbing and transit operation can be accurately preset based on actual piston displacement.


While a certain amount of caution must be exercised in the use of abrasive fluids in any metering pump, the "CKC" and "CSC" tend to be more tolerant of suspended solids than other metering pumps. To assure fluid compatibility, consult the Materials of Construction information above.


Select an FMI PUMP having a maximum flow rating as near to the desired flow rate as possible.

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