Packing ring - a ring, or series of rings, made of pliable lubricated material provided at the stuffing box of a pump to prevent the leakage of liquid into the atmosphere.
Parallel operation - a set-up whereby two or more pumps operate in a manner where all pumps discharge into a common header . The discharge head of each pump is the same for all pumps, but their total capacity is the sum total of the capacities of the individual pumps which could be different from one another. (see series operation.)
Pattern - a model, usually made of wood, for making a mold into which molten metal is poured to obtain a casting such as casing, impeller, cover, bracket, nozzle head, etc. Strictly speaking, a term pattern refers to the outside shape of a casting, and the term core refers to its inside shape, or the so-called wetted surface of a pump. Read more..
Peripheral speed - speed at the periphery of a given diameter resulting from its rotation.
Peripheral velocity - same as peripheral speed.
Pickling - acid cleaning of a surface in a nitric and HF acid bath. The acids remove the oxide and iron particles embedded on a surface, usually that of stainless steel.
Pitting Resistance Equivalent Number (PREN) - an index used to determine the susceptibility of an alloy material to pitting corrosion. The higher number indicates a greater resistance to pitting corrosion. It is based in the percentage content of Cr, Mo and N in the alloy.
Plan 11 - a mechanical seal flush plan referenced by API 682, ISO 21049, and ASME B73.1& B73.2, for single seal arrangement using the pump liquid as medium. Plan 11 flush line originates at the pump discharge, or at a point on the pump casing where the pressure is higher than that at the seal chamber, and is piped through a flow control orifice to the flush port on the seal flange or seal chamber tap. The liquid flushes the seal face, flows around the seal, exists through a pressure reducing throttle bushing, and flows back into the impeller suction area.
Pour point - The temperature below which a liquid, such as oil, will cease to flow. The pour point of lubricating oil must be compatible with the bearing temperature, or the oil will not feed into the bearing causing it to fail from lubricant starvation.
Pressure - the force exerted per unit area, usually expressed in pounds per square inch (PSIG).
Propeller pump - pump in which the head is developed by the propelling or lifting action of the vane on the liquid ; the liquid enters and exits the impeller axially. Also known as axial flow pump.
Pure oil mist lubrication - a lubrication system in which oil mist lubricates the bearing, or bearings, and also purges the bearing housing without an oil level in the sump (dry sump.) See oil mist lubrication and purge oil mist lubrication.
Purge oil mist lubrication - a lubrication system in which oil mist only purges the bearing housing (wet sump.) See oil mist lubrication and pure oil mist lubrication.