Halogen: Halogen is a group of chemically related elements in the periodic table consisting of fluorine, bromine, chlorine, astatine, and iodine.

Hard Face: The hard face refers to the surface of a mechanical seal, whether rotating or stationary. Typically made from hard materials such as silicon carbide or tungsten carbide, the hard face provides enhanced durability and resistance to wear.

Harmonic Vibration: Harmonic vibration refers to oscillations that occur in a periodic sinusoidal pattern.

Hastelloy “C”: Hastelloy “C” is an alloy primarily composed of nickel, molybdenum, and chromium. It is commonly used in mechanical seals due to its excellent corrosion resistance and resistance to halide stress corrosion.

Hazen-Williams Equation: The Hazen-Williams equation is an equation used to relate the flow of water in a pipe to the properties of the pipe and the pressure differential caused by friction. Although widely used in the past, it has been superseded by the more accurate Darcy-Weisbach and Colebrook equations.

Head: In fluid mechanics, head refers to the energy stored in a fluid due to the pressure exerted on its container. It is typically measured as a length of fluid, where a standard of 10 meters is equivalent to one atmosphere or 14.7 pounds per square inch (psi).

Helium Light Band: The helium light band is a unit of measurement used in interferometric methods to assess the flatness of seal faces. It represents a length of 0.0000116 inches or 0.3 micrometers. Seals are typically manufactured to a flatness tolerance of three helium light bands.

Horizontal Pump: A horizontal pump is a type of pump in which the rotating shaft is positioned horizontally, as opposed to vertically.

Horsepower: Horsepower is a unit of power used to measure the rate at which work is done. One horsepower is equivalent to 746 watts. Originally, it was employed to compare the power output of steam engines to the power of draft horses.

Hot Oil Pump: A hot oil pump is designed specifically for pumping high-temperature oil, typically ranging from 350 to 800 degrees Fahrenheit.

Hot Work: Hot work refers to any type of work that generates an arc, spark, or open flame, such as cutting, grinding, or welding of metal. Such activities require proper permits and trained personnel due to the associated fire and safety hazards.

Hydraulic Balance: Hydraulic balance refers to a method of reducing heat generation in the stuffing box by minimizing the seal face area exposed to the closing force.

Hydraulic Drawings: Hydraulic drawings pertain to the hydraulic systems of an instrument or device rather than its mechanical components. In the case of a centrifugal pump, hydraulic drawings would include the impeller, volute, liquid passageways, suction valves, and more.

Hydraulic Force: Hydraulic force relies on Pascal’s principle, which states that the pressure in a closed system remains constant. It enables the amplification of force in one area by applying a smaller force to another area within the system.

Hydraulic Gradient: The hydraulic gradient involves converting all the energy terms of a system, such as velocity head and friction loss in piping and fittings, into head and graphing them above an elevation drawing of the installation. This helps visualize the distribution of energy terms and ensure nothing is overlooked.

Hydraulic Power Recovery Turbine (HPRT): An HPRT is a turbine that recovers energy from a flowing liquid by reducing higher pressure to a lower pressure.

Hydraulic re-rate: Hydraulic re-rating refers to modifying the hydraulic parts of a pump to alter its operating capacity, speed, differential head, liquid type, temperature, pressure, suction, or other conditions.

Hydrocarbon: A hydrocarbon is an organic compound consisting solely of hydrogen and carbon atoms.

Hydrodynamic Bearings: Hydrodynamic bearings, such as sleeve bearings and tilting-pad bearings, rely on the principle of hydrodynamic lubrication to support and guide rotating components.

Hydrodynamic Force: Hydrodynamic force refers to the force exerted on an object by a fluid flowing over or around it.

Hydrodynamic seal: A hydrodynamic seal utilizes a rotor with grooves to act as a pump, creating an air cushion upon which the opposing sealing face rides. Hydrodynamic seals offer superior performance compared to hydrostatic seals.

Hydrogen embrittlement: Hydrogen embrittlement is the process by which metals become brittle and susceptible to cracking or failure after exposure to hydrogen.

Hydrogen sulfide (H2S): Hydrogen sulfide is a highly toxic component found in hydrocarbons. It is released during combustion. Pumps handling hydrocarbons containing hydrogen sulfide require special construction considerations.

Hydronium ion: A hydronium ion (H3O+) is a water molecule with an additional proton, formed by the transfer of an H+ from one water molecule to another in extremely acidic conditions.

Hydrostatic seal: A hydrostatic seal is a type of mechanical seal that balances the opening and closing forces to maintain a controlled gap between the seal faces.

Hysteresis: Hysteresis refers to the dependence of a system not only on its current conditions but also on its past conditions. For example, the magnetic field response of a ferroelectric material may exhibit hysteresis when an increasing electric current is applied and subsequently decreased.

Related Links

• Pump Glossary
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