Packing: Packing is a method used to gradually reduce the fluid pressure within a pump, allowing for acceptable leakage by the time the fluid reaches the final step. Typically, a set of rings is employed to create a pressure gradient and prevent excessive leakage into the atmosphere.

Packing ring: A packing ring is a sealing mechanism consisting of multiple rings that effectively prevent fluid from leaking into the surrounding environment.

Parallel operation: In contrast to series operation, parallel operation involves connecting two pumps to the same head, resulting in a flow rate that is twice that of a single pump. This configuration enhances capacity and provides redundancy in fluid handling systems.

Partial emission pump: Also known as a vane pump, a partial emission pump is specifically designed for handling corrosive chemicals at low flow rates. These pumps were initially developed during World War II to pump fuel into German Ram jet engines.

Pascal: The Pascal is the SI derived unit of pressure, equivalent to one Newton per square meter. One atmosphere of pressure is approximately equal to a little over 100 kilopascals (kPa).

Passivated: When a metal surface develops a protective oxide layer, it is said to be passivated. This oxide layer provides a barrier against corrosion and helps maintain the integrity of the metal.

Pattern: A pattern, often made of wood, is used in the casting process to create molds for shaping metal. It serves as a template for forming the mold cavity, ensuring accuracy and consistency in the final castings.

PD pump: PD pump stands for Positive Displacement pump. These pumps are designed to deliver high pressure but at relatively low flow rates. They operate by trapping and displacing a fixed amount of fluid, enabling precise flow control.

Performance curve: A performance curve is a graphical representation that illustrates the relationship between total head and flow rate for a specific pump with its unique impeller and characteristics. The performance curve provides valuable information about a pump’s operating range and efficiency.

Peripheral (regenerative) pump: Also known as a regenerative or regenerative turbine pump, a peripheral pump is an alternative design to centrifugal pumps. In these pumps, fluid passes through the vanes multiple times, enhancing energy transfer. The impeller features short vanes at the periphery, which pass through a ring-shaped channel. The fluid enters between two impeller vanes and is set into a circular motion, adding energy to the fluid particles. These particles follow a spiral-like path from the inlet to the outlet, continuously gaining energy from each set of vanes.

Peripheral speed: Peripheral speed refers to the velocity or speed at the periphery of a particular diameter, as applied to rotating objects such as impellers or rotors.

pH: pH is a logarithmic measure of the acidity or alkalinity of a solution, indicating the concentration of hydrogen ions (H+) or hydroxide ions (OH-) present. The pH scale ranges from 0 (highly acidic) to 14 (highly basic).

Pickling: Pickling is a metal cleaning process that involves immersing the metal in a bath of nitric and hydrofluoric acids. These acids effectively remove impurities and oxides from the metal surface, preparing it for further processing or applications.

Pipe friction loss: Pipe friction loss refers to the reduction in head pressure caused by the friction between the process fluid and the inner walls of pipes and joints. It is an important consideration in fluid flow systems, impacting overall system performance.

Pipe roughness: Pipe roughness refers to the measurement of the roughness or irregularity of the inner surface of a pipe system. Multiple measurements are taken and averaged to determine the average size of peaks present on the internal surface of the pipes, which contribute to friction during fluid flow.

Pipe strain: Pipe strain is the strain or stress exerted on the volute of a pump due to the piping connected to it. Excessive pipe strain can lead to mechanical seal failure and other operational issues.

Piping pressure (maximum): Pipe systems are designed with a maximum pressure rating to ensure they can safely withstand the pressure exerted on them. If subjected to pressure beyond their maximum rating, pipes may burst or experience failure. This includes connections, joints, and flanges. The ASME pressure piping code B31.3 provides guidelines for determining the maximum stress allowed for pipes made of different materials.

Pitot pump: A pitot pump is a type of pump that incorporates a rotating casing to induce fluid rotation. Within the rotating cylinder of fluid, there is a pitot tube or pickup tube that captures a small amount of the rotating fluid and delivers it under high pressure to the discharge.

Pitting: Pitting refers to the erosion or formation of pits on the surface of a material due to corrosion, erosion, or cavitation. Pitting can weaken the material and compromise its integrity.

Pitting resistance equivalent number (PREN): The pitting resistance equivalent number is a characteristic assigned to a material that indicates its resistance to pitting corrosion. Higher PREN values indicate greater resistance to pitting corrosion, which is beneficial for materials used in corrosive environments.

Plan 11: Plan 11 is a single seal piping plan for mechanical seals referenced by standards such as API 682, ISO 21049, and ASME B73.1&B73.2. It involves using the pump liquid as a medium for the seal arrangement. The Plan 11 flush line originates at the pump discharge or a point on the pump casing with higher pressure than the seal chamber. The liquid is piped through a flow control orifice to the flush port on the seal flange or seal chamber tap. It flushes the seal face, circulates around the seal, passes through a pressure-reducing throttle bushing, and flows back into the impeller suction area.

Plastic range: Metals have an elastic range where they can return to their original shape after deformation, and a plastic range where they retain their new shape even after the applied force is removed.

Positive displacement pump: A positive displacement pump is a type of pump that moves fluid by trapping a fixed amount of the fluid and transferring it into the discharge pipe. These pumps provide a consistent flow rate and are suitable for a wide range of applications.

Pour point: The pour point of a liquid is the lowest temperature at which it ceases to flow or becomes too viscous to pour. It is an important property to consider for fluids that operate in low-temperature environments.

Power end: The power end of a pump is the section that connects to the power source, such as an electric motor or engine. It often houses the bearings and other components necessary for power transmission.

Power factor: Power factor refers to the ratio between the real power (power that is doing useful work) and the apparent power (total power supplied) in an alternating current (AC) circuit. It indicates the efficiency of power usage in the circuit.

Precision bearing: Precision bearings, such as ball bearings and roller bearings, are designed to provide high accuracy, stability, and smooth operation. They are commonly used in applications where precise rotational motion and low friction are required. In contrast, sleeve bearings do not offer the same level of precision.

Press fit: Press fit is a method of joining components where one component, often graphite due to its softness, is pressed into an irregularly shaped holder. The graphite material conforms to the shape of the holder through shearing, creating a secure fit.

Pressure: Pressure is the force applied per unit area. It is a fundamental concept in fluid dynamics and is expressed in units such as pascals (Pa), pounds per square inch (psi), or bar.

Pressure drop: Pressure drop refers to the decrease in pressure between two points within a pump or across a system, such as a pipe or container. It is influenced by factors such as fluid flow rate, pipe resistance, and friction losses.

Pressure gradient: The pressure gradient, in the context of mechanical seals, refers to the pressure drop across the faces of the seal. It plays a critical role in ensuring effective sealing and minimizing leakage.

Pressure head: Pressure head refers to the pressure exerted by a fluid within a pump, typically resulting from atmospheric pressure and other additional pressures present in the system. It is an important factor in determining the pump’s performance and the fluid’s flow characteristics.

Prime: In a centrifugal pump, priming refers to the process of infusing a small amount of process fluid into the pump to initiate the suction process when the source of the fluid is located below the pump’s level.

Progressive cavity pump: A progressive cavity pump, also known as an eccentric screw pump, is a type of positive displacement pump. It is particularly suitable for pumping fluids with high viscosity, such as grease and pastes. These pumps utilize a rotating eccentric screw within a rubber stator to create a progressing cavity that displaces the fluid.

Propeller pump: A propeller pump, also known as an axial flow pump, is a type of pump in which the impeller imparts lift to the fluid, propelling it along the axial direction. The impeller’s shape creates a lifting force that moves the fluid in a manner similar to the operation of a propeller.

Pseudoplastic: Pseudoplastic refers to the behavior of a fluid that exhibits a decrease in viscosity as the shear rate or stress applied to it increases. In other words, the fluid’s viscosity decreases slowly as the rate of shear or stress increases.

PT factor: The PT factor is a characteristic given to gaskets, representing the product of the operating pressure and temperature at which the gasket can be safely used. It helps determine the suitability and performance limits of gasket materials under specific operating conditions.

Pump curve: The pump curve is a graphical representation provided by the pump manufacturer that illustrates the relationship between the pump’s head (pressure) and its capacity (flow rate). Typically, different curves are included for various impeller sizes, allowing users to select the optimal operating point for their specific requirements.

Pumping ring: A pumping ring is an element within a mechanical seal system that facilitates the circulation of fluid between two mechanical seals. It is necessary when using oil as the barrier fluid due to the oil’s low specific heat, ensuring effective cooling and lubrication of the seal faces.

Pump out vane: The pump out vane is a feature found in certain impeller designs that helps reduce the pressure within the stuffing box of a pump. By directing a portion of the fluid flow back to the suction side, the pump out vane alleviates pressure build-up and enhances the overall efficiency and reliability of the pump.

Pumps as turbines (PAT): Pumps as turbines refers to the operation of a pump in reverse, where the fluid that enters the pump causes it to rotate and generate power. This concept is utilized in certain applications to harness energy from flowing fluids, converting them into useful mechanical or electrical energy.

Pure oil mist lubrication: Pure oil mist lubrication is a method of lubricating bearings that involves the use of an oil mist rather than a liquid lubricant in a sump. The oil is atomized and delivered as a fine mist, ensuring efficient and controlled lubrication of the bearing surfaces while minimizing oil consumption and contamination.

Purge oil mist lubrication: Purge oil mist lubrication is a lubrication system in which an oil mist is directed specifically to the bearing housing to provide lubrication and cooling. Unlike pure oil mist lubrication, it focuses solely on supplying the necessary lubricant to the bearings, ensuring their smooth operation and longevity.

Pusher seal: A pusher seal is a type of mechanical seal design that employs a spring-loaded dynamic elastomer to create a seal between rotating and stationary components. While pusher seals may be considered lower quality compared to other designs, they still provide effective sealing in certain applications and operating conditions.

PV factor: The PV factor is a correlation often used to estimate the performance and durability of mechanical seal faces by considering the product of the pressure (P) and velocity (V) at the seal faces. However, it is important to note that the PV factor’s correlation does not always hold true universally and should be used with caution, considering other factors and specific application requirements.

Related Links

• Pump Glossary
• Pump info