Face Combination: The selection of appropriate materials for the seal faces of mechanical seals is crucial to avoid premature seal failure.

Face Flatness: Face flatness refers to the degree of flatness exhibited by a seal face. To ensure a proper seal and prevent leakage, seal faces must be flat, with variations across the face of less than 300 mm. This measurement is typically determined using an optical technique involving an optical flat, a monochromatic light source, and interference.

Face Lubrication: Face lubrication refers to the lubricant used between lapped seal faces in mechanical seals. This lubricant helps reduce friction and ensure smooth operation.

Face Pressure: Face pressure refers to the pressure exerted on the mechanical seal face. It is calculated by summing all the loads acting on the seal face, including spring load, hydraulic load, and shaft axial thrust, and dividing it by the area of the seal face.

Face-to-Face Seals: Face-to-face seals involve the configuration of two seals with a common seal face. In this type of seal, the pressure of the barrier fluid is always lower than the pressure in the stuffing box.

False Brinelling: False brinelling refers to the gradual removal of material from a ball bearing. Unlike brinelling, which occurs in a single load event, false brinelling happens over time due to corrosion or fretting.

Filled Carbon: Filled carbon refers to a type of carbon that is combined with organic or inorganic materials. These additional components may not possess the same strength as carbon itself, resulting in a lower-grade carbon. Filled carbon is often chosen for its lower manufacturing and purchasing costs.

Filter: A filter is a device used to separate solid particles from a liquid. Its effectiveness is determined by the size of particles it can remove from the liquid.

Finite Element Analysis: Finite element analysis is a mathematical technique used to approximate solutions to boundary value problems. It is commonly employed in hydraulics to calculate seal face distortion.

Fire Pump: A fire pump is a specialized pump designed to provide protection against fires. These pumps must meet specific requirements outlined by fire regulatory agencies and undergo testing and approval by third-party agencies. Fire pumps can also refer to the main pump in a fire sprinkler system.

First Critical Speed: The first critical speed is the velocity at which the rotor bearing support system reaches a state of resonance when accelerated. It is the lowest speed at which this resonance occurs, while subsequent speeds at which resonance occurs are referred to as the second, third, and so on, critical speeds.

Flashing: Flashing is the rapid transformation of a substance from a liquid state to a gaseous state.

Flatness: In applications where two metal surfaces must form a seal, the flatness of the surfaces is essential. It is measured by placing an optical flat on the surface, directing a Helium Neon laser through the flat, reflecting it off the surface, and observing the resulting interference patterns to determine the flatness of the surface.

Flexible-Coupled Pump: In contrast to a close-coupled pump, a flexible-coupled pump features separate shafts for the pump and the driver, which are connected through a flexible coupling.

Flexible Member: The flexible member of a mechanical seal contains the spring or bellows and plays a crucial role in accommodating shaft movement and maintaining the seal integrity.

Flexible Rotor: A rotor is considered flexible when it operates at or near its critical speed. Typically, a rotor is deemed flexible if it operates above 70% of its critical speed.

Flexible Shaft: A flexible shaft is designed to operate at speeds higher than its first critical speed without significant issues.

Flexibility Factor: The flexibility factor is a ratio calculated by dividing the length of a shaft cubed by the diameter to the fourth power. This factor is used to predict whether a shaft will experience bending problems.

Floating Throat Bushing: A floating throat bushing is a bushing that possesses radial movement to compensate for non-uniform shafts. Typically made of carbon, this circular ring bushing can have less clearance than a fixed throat bushing due to its radial mobility.

Floating Throttle Bushing: The term “floating throttle bushing” is synonymous with “floating throat bushing.” Generally, “throat” bushing is used in low-pressure stuffing boxes, while “throttle” bushing refers to the bushing in a high-pressure stuffing box.

Flooded Suction: Flooded suction occurs when the pump is positioned below the liquid source and the suction is supplied by gravity. This method is preferred for centrifugal pumps.

Fluid: A fluid is a substance that continuously deforms under an applied shear stress. Examples of fluids include gases, liquids, and plasmas.

Fluorocarbon: Fluorocarbon refers to a compound consisting only of carbon and fluorine atoms bonded together with carbon-fluorine bonds.

Flush: Flushing refers to the introduction of an external fluid source at a higher pressure than the operating pressure of the stuffing box in a pump. This additional fluid mixes with and dilutes the process fluid, serving various purposes such as cooling and lubrication.

Fluting: Fluting refers to the degeneration of bearings caused by electrolysis resulting from the passage of small amounts of current through the bearing. Over time, coupled with lubricant breakdown, this can lead to noisy bearings.

Foot Valve: A foot valve is a valve designed to prevent the loss of priming in centrifugal pumps when the fluid source is located below the pump.

Formed Metal Bellows: Formed metal bellows are manufactured by compressing and stretching the metal bellows material, providing flexibility and accommodation for axial and angular movements. This differs from welded bellows, which are created through welding processes.

FPM (fpm): FPM stands for “feet per minute” and is used as a measure of speed or velocity in various applications.

Francis Vane Impeller: The Francis vane impeller is a popular impeller design used in fans and pumps that operate within the range of 1500 to 4000 rpm.

Free Length: Free length refers to the axial length of a mechanical seal before it undergoes compression or installation.

Fret or Fretting: Fretting refers to damage caused to the interior of a pump or fitting due to the removal of the protective oxide layer from corrosion-resistant materials. This phenomenon occurs when a softer material rubs against a harder shaft or sleeve, and it is more likely to happen with lower-cost seals.

Friction Head: Friction head refers to the pressure required to overcome the friction solely attributable to the internal surfaces of pipes, fittings, and pumps in a system.

Friction Factor f (Pipe): The friction factor of piping measures the amount of frictional force generated per unit length of the pipe. The friction factor varies for different types of pipes and depends on whether the flow is laminar or turbulent. This factor is crucial in calculating friction losses within a pipe.

Friction Loss (Pump): Friction loss in a pump refers to the pressure loss resulting from friction between the pump components and the process fluid. Different parts of the pump may experience varying levels of friction.

Friction (Pipe): Friction in a pipe occurs when the process fluid moves internally, causing fluid layers to rub against each other and the pipe walls. The roughness of the pipe surface can impact the level of friction, with rougher pipes leading to higher friction.

Fugitive Emission: Fugitive emission refers to the escape of certain chemicals into the atmosphere. Regulatory agencies have deemed these chemicals harmful to human health

Related Links

• Pump Glossary
• Pump info