T-U-V

The seals are facing in the same direction with a low-pressure barrier fluid circulating between them.

Total discharge head. A combination of the suction head and the head being produced by the pump.

The strength measured when the part is being pulled axially.

A measure of the material’s ability to conduct heat. This is a very important factor in the selection of mechanical seal faces.

The viscosity of the fluid decreases with agitation. Non drip paint is an example of such a fluid.

Locates the rotor or shaft axially. Normally located close to the coupling.

The amount of head produced by the pump. Discharge head minus suction head. If suction head is a negative number it is added to the discharge head.

In a centrifugal pump it refers to the axial movement of the shaft. The thrust can be towards the wet or power end of the pump and at start up it thrusts in both directions.

Designed to take the axial thrust in pump applications. It is usually located next to the coupling and is often supplied in a “double row” configuration.

A common hard face seal material available in several grades depending upon hardness and corrosion resistance. Cobalt and nickel are the two most common types.

Disturbed fluid. Can cause cavitation problems in a centrifugal pump. Often caused by an elbow located too close to the pump suction inlet.

A method of balancing a mechanical seal in two directions. A very important consideration in dual seal applications.

Not hydraulically balanced to generate low heat at the seal faces. Typical of original equipment designs.

Containing carbon/ graphite and nothing else. Filled carbons contain inorganics that will be sensitive to some chemicals and temperature extremes. Unfilled carbons are the preferred seal faces.

Used to control flow in a system by varying the frequency of the motor. Recommended for circulating systems and any other system where the main head is friction losses in the piping system.

Any pressure less than atmospheric. Can present a problem for the elastomer in many seal applications.

A type of cavitation caused by the impeller/ cutwater clearance being too small.

Below this pressure, the liquid at this temperature will vaporize.

The fluid passes from a liquid to a gaseous state. If this happens at the seal faces the seal faces will be blown open.

A measurement of the speed of the liquid in the system. Measured in feet or meters per second. The pump is a constant velocity device.

Part of the total head calculation. Derived from the formula h = V2/2g

To remove air or gas from the system. It is important to vent the stuffing box in vertical pumps to prevent the seal faces from running dry.

Important in metal bellows seal designs. The elastomer acts as a vibration damper in the other seals. The vibration can chip carbon faces, destroy anti-rotation drive lugs, and open the lapped seal faces.

Resistance to pouring. Higher viscosity can restrict seal movement. Centrifugal pumps can handle a maximum viscosity similar to 30-weight oil at room temperature. Above this viscosity a positive displacement pump should be used.

An E.I. Dupont Dow manufactured elastomer widely used in the sealing industry. The generic name is fluorocarbon. Water and steam attack many of these compounds.

Derives is name from a spiral shaped casing surrounding the pump impeller. It converts velocity energy to pressure energy.

A type of pump used for excessive solids. The impeller is recessed into the volute. A very low efficiency design, but practical in many applications.

Creating a “whirlpool affect” that can draw air into the suction of the pump.