Frequently Asked Questions

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 their quality goal, We have put together a list of frequently asked questions about FMI pumps . We hope you will find these answers beneficial.
Frequently Asked Questions  
Q. What is the accuracy of the FMI Pump ?

A. Accuracy of ± 1%. Can be expected for low to medium viscosity (1 - 500 cps) fluids providing, consistent precise output from microlitres to full flow range.   

Q. How do I Identify which FMI pump I have ?

A.  Find the serial numbers on your unit and contact FMI customer service. From the serial numbers, FMI can tell you all about your unit.   

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Why is my pump making a hammering sound  ?

A.  The hammering sound is usually an indication of CAVITATION. Cavitation is caused when the suction side tubing ID is too small to allow adequate flow of fluid to the pump. CAVITATION can cause problems such as hammering, flow variation, bubble formation, loss of prime and eventually pump damage.

Q. Is the FMI Pump self priming ?

A.  Yes, FMI pumps will self prime to 15 feet vertical dry or 26 feet wet

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Q. Can the sanitary pump heads be autoclaved or sterilised ?

A.  YES, FMI Sanitary Pump heads are designed for autoclaving, clean in place, or complete disassembly for brush cleaning. Cleaning procedures can be followed without loss of system operating efficiency.

Q. What is dead volume ?

A.  Dead volume is the amount of fluid which remains in the pump when the fluid discharge is completed. For low volume dispenses or low flow rates, FMI has special low dead volume pump heads signified by the suffix "LF", which utilise low flow fittings that facilitate bubble clearing in the pump.

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Q. How do I adjust my FMI pump for a specific rate ?

A.  On all FMI pumps, flow rates may be altered when operating or at rest. On the “Q” line this is done by turning the Flow Control Knob which moves the flow rate indicator along a fixed 20 unit scale linearly calibrated “10-0-10”. The “10” equals 100% flow rate in that direction, “0” equals zero flow. To improve the fine adjustment of the flow rates on the “Q” line, there is an optional Dial Indicator Kit Q485 which provides for 1000 discrete settings. The “RH” line flow adjustment is accomplished by turning an easy-grip Flow Control Ring graduated in 450 divisions from 0 to 100% flow.

Q. What are the pressure limitations of PVDF Pump Heads ?

A.  PVDF pump heads have an operating temperature rating of 212 deg. F (100 C). However, these pump heads can be autoclaved (non-operating) at temperatures up to 240 deg F (116 C).

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Q. How can I increase the flow adjustment accuracy on the "Q" pump head ?

A.  The Q485 Dial Indicator accessory is available for "Q" pump heads which provides direct reading of pump head position in 0.1% increments for ultra-fine flow rate adjustment. It can be ordered with the pump or separately.

Q. How can I monitor the speed (RPM) of my FMI pump ?

A.  A variety of rotational sensors are available which will provide a signal for monitoring RPM. For pumps which utilise the standard Q style base, hall effect and proximity rotational sensors are available. For stepper motor driven pumps, Opto-sensors can be provided.

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Q. Can I mount an RH style pump head on my Q style base ?

A.  Yes. The RH/Q adaptor adds versatility to your Q pump. It is a quick, easy, low cost solution for mounting RH pump heads to a Q style base.

Q. When should I select a low flow pump head and fittings ?

A.  In general, when the flow rate is 50 ml/min or below, a low flow pump head, designated by the suffix "LF" should be used. These pump heads have very low dead volume and accept 1/4-28 fittings used with small bore tubing for zero dead volume connections. FMI offers the Small Bore Tubing Kit Q661 combinations for 1/8" and 1/16" small bore tubing which include tubing and fittings. These fittings connect directly to PVDF and Tefzel® "LF" pump heads. For use with 316SS pump heads (except SAN), the R479 adaptor is also required.

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Q. How does viscosity affect the accuracy of the FMI pump ?

A.  The FMI pump is positive displacement and, in general, viscosity independent. However, viscous fluids should use lower RPM drives (400 RPM or less) with pump heads adjusted to longer piston strokes. There is no absolute value for the maximum viscosity an FMI pump can handle. For extremely viscous fluids, pressure feeding on the inlet side of the pump and/or heating of fluid are commonly used to aid in feeding fluid to the pump. FMI also manufactures temperature controlled pump heads "WT" to help maintain fluid temperatures up to 360 F as it flows through the pump.


FMI pumps are considered viscosity independent indication 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 Pump Heads.
In most cases no additional steps are required to achieve good performance.

Viscous fluids above 500 centipoise may require the following steps to achieve better results -

  1. The slower the RPM the better. Try to keep RPM below 400.
  2. Use stainless cylinder case material (CSC, CSY, SSY).
  3. Set Pump Head closest to 100% of Pump Head Module flow rate. A longer piston stroke is better than a short piston stroke.
  4. Use the largest ID suction line possible.
  5. Increasing tubing size on discharge side can help reduce back-pressure build-up.
  6. Reduce viscosity if possible - try....
    Heating - check temperature limits of Pump Head Module in catalogue.
    Dilute using suitable thinner.
  7. 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.
  8. 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 “touching off”. This will help prevent the drop from remaining on the dispenser tip.
  9. High viscosity fluids may require modified ceramic Piston-Liner sets. Consult factory.

Q. How do I know what pump head materials are compatible with my fluid ?

A.  FMI can search through our reference material as well as our comprehensive application database to make recommendations. However, a quick and easy way to determine compatibility is to consider what materials of construction are currently used in your piping, fittings, vessels, and containers to handle your product. There are also reference compatibility charts available in print and online. The chemical manufacturer's MSDS data sheets may contain compatibility information as well.

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Q. What is the maximum dispense volume of the FMI pump ?

A.  The FMI pump can dispense up to 1.28 ml per piston stroke. However, larger volumes can be dispensed using stepper driven pumps which can dispense up to 7 strokes (8.96 ml) with a single dispense signal. For larger volumes, FMI continuous metering pumps can be used in conjunction with a 3-way diverter valve and a timer. Contact FMI customer service for more information.

Q. How do I prevent fluid splashing when dispensing into a small vial, cuvette or micro plate well ?

A.  Fluid splashing when dispensing is caused by the fluid being dispensed at a high velocity. The fluid velocity can be decreased by either reducing the drive RPM or by changing the dispense tip to one with a larger orifice. Dispense tip design can have an influence on the velocity and pattern of dispensing to reduce splashing as well.

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Q. Do I require two separate pumps to proportionally meter two different fluids at different flow rates ?

A.  No. FMI's Ratio:Matic® pumps can meter two different fluids proportionally up to 100:1 ratio. The two pump heads are driven by a single variable speed drive motor and can maintain the fluid ratio while infinitely varying the overall flow rate. Ratio:Matic® pumps include the QB2 12/24 VDC drive, QV2 with V200 Controller, and a variety of stepper driven duplex pumps.

Q. Can I use FMI's CeramPump® pumping technology with my existing drive motor ?

A.  Yes. FMI's can be easily driven by belt, chain, or shaft coupling, or connected directly to special motor drives. FMI can also provide adaptors to connect QP and RH motorless pumps to Masterflex® LS drives.

Do you have a 56C face motor ? FMI's P56C Adapter Kit will provide an easy connection of FMI's QP motorless pump to your NEMA 56C face foot mount motor.

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