Home | News | About Us | Contact | Links | Product Search | My Account

Plunger pumps are positive displacement, reciprocating pumps. With each revolution of the crankshaft there is a direct motion in the plunger rods plunger resulting in a positive output of flow from the pump. This output of the pump flow is in direct relation with the RPM of the pump. The bore and stroke determine the amount of liquid handled with each revolution. Positve displacement pumps move a known quantity of liquid with each revolution of the pumping elements. In a reciprocating pump, a volume of liquid is drawn into the cylinder through the suction valve on the intake stroke and is discharged under positive pressure through the outlet valves on the discharge stroke. The discharge from a reciprocating pump is pulsating and changes only when the speed of the pump is changed. For this reason a properly designed pressure relief or safety valve must be installed in the discharge plumbing.

How it works
The spring-reinforced, preset packing design of the plunger pumps permits significantly greater pressures than piston pumps. The plunger pumps also offer tremendous versatility with optional direct coupling drives and wet-end material options.
Like the piston pumps, the design of the plunger pump also allows for forward liquid flow, however, both the inlet and discharge valves are spring-loaded closed and hydraulically opened. 
At the beginning of the stroke, the plunger displaces the liquid in the manifold chamber and forces the discharge valve open. There is a split second at the end of the stroke when both inlet and discharge valves are closed.
As the plunger rod begins its backward stroke, the inlet valve opens to allow more liquid into the manifold chamber, thereby keeping a smooth forward flow of liquid.

For more information:
 pdf documents • Handy Pump Formulas • Trouble-Shooting Guide •

Diaphragm pumps are very common and come in many sizes. Modern diaphragm materials are flexible and long lasting making this an ideal low-maintenance pump for many applications.

Double Diaphragm pumps offer smooth flow, reliable operation, and the ability to pump a wide variety of viscous and impure liquids.

This pump uses a very simple valve system to move the DIAPHRAGM ROD. The flexible diaphragms are round disks attached at each end of the Diaphragm Rod.
The PILOT SPOOL is pushed back and forth whenever the Diaphragm Rod reaches the end of its throw. The Pilot Spool allows air to move the Air Distribution Valve back and forth.
The AIR DISTRIBUTION ROD controls air flow to the left or right air chamber, reversing on each stroke. 
The four BALL VALVES are free-floating and operated by pressure differences in the pumped liquid. Flapper valves are also commonly used.

Sanitary diaphragm pumps, often made of plastic and/or stainless steel, are used in the food industry to pump everything from sliced fruit, to sausage, to chocolate.
Diaphragm pumps can be air or electric driven and are typically considered low pressure pumps although some have high outlet pressures.  They can be run dry without damage.

Include vane pumps, impeller pumps and centrifugal pumps and are used for countless applications such as reverse osmosis repressurization, sump and liquid transfer.

Vane Pumps
The vanes are in slots in a rotor. When the rotor spins, centrifugal force pushes the vanes out to touch the casing, where they trap and propel fluid. Sometimes springs also push the vanes outward. When the vanes reach the return side they are pushed back into the rotor by the casing. Fluid escapes through a channel or groove cut into the casing.

Centrifugal and impeller pumps
Also known as rotary pumps, centrifugal pumps have a rotating impeller, also known as a blade, that is immersed in the liquid. Liquid enters the pump near the axis of the impeller, and the rotating impeller sweeps the liquid out toward the ends of the impeller blades at high pressure. The impeller also gives the liquid a relatively high velocity that can be converted into pressure in a stationary part of the pump, known as the diffuser. In high-pressure pumps, a number of impellers may be used in series, and the diffusers following each impeller may contain guide vanes to gradually reduce the liquid velocity. For lower-pressure pumps, the diffuser is generally a spiral passage, known as a volute, with its cross-sectional area increasing gradually to reduce the velocity efficiently. The impeller must be primed before it can begin operation—that is, the impeller must be surrounded by liquid when the pump is started. This can be done by placing a check valve in the suction line, which holds the liquid in the pump when the impeller is not rotating. If this valve leaks, the pump may need to be primed by the introduction of liquid from an outside source such as the discharge reservoir. A centrifugal pump generally has a valve in the discharge line to control the flow and pressure.

'Centrifugal and impeller pumps' From "Pump (mechanics)," Microsoft® Encarta® Online Encyclopedia 2001
http://encarta.msn.com © 1997-2001 Microsoft Corporation. All rights reserved.

 <PREVIOUS | Pumps | NEXT>