Metering pumps move precise volumes of liquid in a specified time period to provide accurate flow rates. This class of pumps moves liquids in two stages: the suction stroke and the discharge stroke. During the suction stroke, liquid is pulled into the pump cavity past the inlet check valve. During the discharge stroke, the inlet valve closes; the outlet valve opens, and the liquid is pushed out. Vary the flow either by changing the stroke length or by adjusting the cycle frequency. Described below are a few types of metering pumps listed in this catalogbellows, diaphragm, and piston.
- Bellows Pumps move a bellows back and forth to displace liquid. These pumps do not require seals. Special nonclogging valves are available for abrasive or particulate applications. Bellows pumps produce a maximum pressure of 50 psi.
- Diaphragm Pumps pulse a flexible membrane to displace liquid with each stroke. These pumps require no seals, so you can pump abrasives and slurries if the valves are kept clean. Diaphragm pumps produce pressures to 1100 psi.
- Piston Pumps use a reciprocating plunger to move liquid through the pump. These pumps require a seal to prevent leaks and are not recommended for use with abrasive fluids. Piston pumps produce pressures to 5000 psi.
- Travelling Cylinder Pumps use four out-of-phase cavities and patented cylinders to give high accuracy and low pulsation.
- Polymer Feed Systems combine a high-viscosity diaphragm pump and proprietary mixing technology to give a fully diluted and activated polymer without a batch feed system.
Guide to Metering Pumps
Use the following guide to help you select the best type of metering pump for your application. The information given is intended as a general guideline and will not hold true for all pumps within a classification; check individual pump specifications for complete details. Pumps that have all PTFE/PFA wetted parts are recommended for applications involving aggressive liquids.
| Pump type | Flow rates | Maximum
pressure | Self-
priming | Pulseless
flow | Viscous
fluids | Particulate
matter | Run
dry | Advantages |
| Bellows | 6 mL/min
to 2475 mL/min | To
50 psi | Good | Poor | Fair | Yes | No | Can pump liquids
or gases. |
| Diaphragm | 10 mL/min
to 19.558 L/min | To
250 psi | Poor to
Good | Poor | Good to
Excellent | No | Yes | Ideal for
high-accuracy
applications,
such as
pH/ORP control. |
Peristaltic
(tubing) | 170 mL/min
to 9.4 L/min | To
125 psi | Excellent | Good at
high rpm | Good | Yes | Yes | Noncontaminating;
available in
a wide variety
of pump materials. |
Polymer feed
systems | Diluted polymer
to 6.2 L/min | To
100 psi | Poor | Poor | Excellent | No | N/A | Used for
polymer make down. |
| Piston | 0.016 mL/min
to 404.6 L/min | To
5000 psi | Good | Poor | Fair | No | No | Highest pressure
and accuracy;
ideal for
HPLC applications. |
| Syringe | 0.001 µL/min
to 147 mL/min | To
40 psi | N/A | Excellent | Poor | No | Yes | Handle very low
flow rates. |
Travelling
cylinder | 192 mL/min
to 1536 mL/min | To
100 psi | Good | Excellent | Excellent | No | Yes | Extremely high accuracy
and pulseless
flow rates. |
