ANSI MARK III STANDARD PUMP

Decrease overall cost of possession from opposite vane impeller, which eases protection and presents renewable, high-efficiency performance over the pumps' life.

Increased reliability and mechanical seal existence because of the correct seal environment created through the sealsentry seal chamber.

Ease of preservation as a result of most appropriate, predictable seal chamber pressures which are re-installed after each impeller putting.

START-UP CONSIDERATIONS

ENSURING PROPER NPSHA

Net Positive Suction Head – Available (NPSHA) is the measure of the energy in a liquid above the vapor pressure. It is used to determine the likelihood that a fluid will vaporize in the pump. It is critical because a centrifugal pump is designed to pump a liquid, not a vapor. Vaporization in a pump will result in damage to the pump, deterioration of theTotal Differential Head (TDH),and possibly a complete stopping of pumping.

Net Positive Suction Head – Required (NPSHR) is the decrease of fluid energy between the inlet of the pump, and the point of lowest pressure in the pump. This decrease occurs because of friction losses and fluid accelerations in the inlet region of the pump, and particularly accelerations as the fluid enters the impeller vanes. The value for NPSHR for the specific pump purchased is given in the pump data sheet, and on the pump performance curve.

For a pump to operate properly the NPSHA must be greater than the NPSHR. Good practice dictates that this margin should be at least 5 ft (1.5 m) or 20%, whichever is greater.