Reference
Chemical Equipment Glossary
Terms used across pumps, tanks, valves, filtration, metering and scrubbers. Each definition links to the page that explains it in context.
A
- Acceleration head
- The demand a diaphragm metering pump creates because each pulsed stroke must accelerate the entire suction column of liquid almost instantly. Classical NPSH math, built for steady centrifugal flow, misses it. Read more
- Adsorption-desorption-recovery plant (ADR)
- The part of a heap-leach or CIL/CIP circuit where gold and silver dissolved in cyanide solution are adsorbed onto activated carbon, then stripped off in a hot elution circuit and recovered, usually by electrowinning. Read more
- Air-operated double-diaphragm pump (AODD)
- A reciprocating diaphragm pump that uses compressed air to cycle its diaphragms, in contrast to an EODD pump, which uses an electric drive. Read more
- ASTM D1998
- A standard covering single-piece, rotationally molded, flat-bottom, vertical, aboveground polyethylene tanks of 500 gallons and up. It does not apply to cone-bottom, horizontal or sub-500-gallon tanks. Read more
B
- Back-pressure valve
- A valve on a metering pump discharge that maintains a controlled minimum pressure, improving check-valve behavior and reducing siphoning or output variation when system pressure is too low or unstable. Read more
- Blinding
- A rapid rise in filter pressure drop caused by surface clogging, typically from a mismatch between filter media type and the particulate load. Read more
- Build America, Buy America Act (BABA)
- A 2021 federal law requiring iron, steel, manufactured products and construction materials used in federally funded infrastructure projects to be produced in the United States. Read more
C
- C-Veil corrosion barrier
- A resin-rich interior layer of an FRP tank, matched to the chemical and temperature, that forms the chemical-resistant barrier protecting the structural fiberglass from attack. Read more
- Chemical air scrubber
- Equipment that captures and neutralizes corrosive or hazardous fumes, such as hydrochloric acid vapor, before exhaust air leaves a process area, protecting equipment and reducing operator exposure. Read more
- Closed-loop wastewater pH control
- A system that uses real-time pH sensor feedback, automated dosing pumps and control logic to adjust chemical feed automatically instead of relying on manual corrections. Read more
- Continuous electrodeionization (CEDI)
- A process combining ion-exchange resin, ion-selective membranes and DC electrical potential to remove ions continuously, without the recurring acid/caustic regeneration cycle of a conventional regenerable DI bed. Read more
- CSI MasterFormat
- The numbering and title system the Construction Specifications Institute maintains for organizing construction specifications into standardized divisions and sections, using six-digit codes such as 46 33 44. Read more
D
- Destruction (wastewater treatment)
- Treatment that chemically breaks a compound down into different, typically simpler substances, as opposed to removal, which only moves the compound into another phase. Read more
- Differential pressure (ΔP)
- The pressure drop across a filter or strainer element. Rising ΔP signals debris accumulation and degrading flow performance. Read more
- Double open-end cartridge (DOE)
- A filter cartridge that seals against the housing end caps with flat gaskets, so seal integrity depends on correct fit and installation. Read more
- Dual containment tubing
- A tubing system with a secondary barrier around the primary line, designed for hazardous acid transport to prevent catastrophic leaks if the inner tube fails. Read more
E
- Electric-operated double-diaphragm pump (EODD)
- A reciprocating diaphragm pump driven by an electric motor and drive instead of compressed air. Read more
- Environmental stress cracking (ESCR)
- A test method and failure mode in which certain chemicals, even without directly attacking the polyethylene resin, accelerate cracking under mechanical stress. It is distinct from chemical dissolution. Read more
- EPDM
- An ethylene propylene elastomer with good general chemical resistance but poor resistance to strong oxidizers above 10 percent concentration; in bleach service it swells and loses sealing function. Read more
- Equalization tank (EQ tank)
- A tank that evens out flow and load before a downstream treatment step, such as dewatering, chemical dosing or a biological process, that performs better under steady conditions. Read more
- Extrusion-wound tank
- A polyethylene tank with a monolithic, solid wall and a ductile, detectable failure mode, with a service life of 20+ years. Read more
F
- Fail-safe (valve actuation)
- A valve actuator behavior in which the valve moves to a defined safe position when power or air is lost; pneumatics use spring return, while electric actuators need stored energy. Read more
- FKM
- A fluorocarbon elastomer, commercially known as Viton, with a fluorine-carbon backbone that is chemically inert to most oxidizing environments and does not swell in sodium hypochlorite service. Read more
- Flooded suction
- A pump installed below the liquid source so liquid flows into the casing by gravity and the pump never has to lift it. Read more
G
- Gas binding
- A pump losing prime because a gas bubble is trapped in the pump head, as with off-gassing sodium hypochlorite, even when suction hydraulics are acceptable. It is not the same as cavitation. Read more
I
- Integrally molded flanged outlet (IMFO)
- A drain flange manufactured as molecularly continuous with the tank wall, one piece rather than bolted, which removes a common leak point and enables zero-heel drainage. Read more
K
- Knife gate valve
- A gate valve that uses a sharpened blade designed to cut through slurry and solids to seat properly, unlike a regular wedge gate valve that can jam on solids. Read more
M
- Mag drive decoupling
- A failure in which the magnetic connection between the motor side and the impeller side breaks under excess load, such as from poor suction, deadhead pressure, viscosity or solids. Read more
- Mag-drive pump
- A sealless pump that eliminates the mechanical-seal leak path, the largest failure point of a sealed pump, but trades it for dry running, cavitation and magnet decoupling failure modes. Read more
- Metering pump
- A pump that delivers controlled volumes of chemical into a process, as distinct from a transfer pump that moves chemical between locations at higher flow rates. Read more
N
- Net positive suction head (NPSH)
- The pressure margin, in feet of the liquid being pumped, between the pressure at the pump inlet and the liquid's vapor pressure. If inlet pressure nears vapor pressure, the liquid flashes and the pump cavitates. Read more
- NPSH available (NPSHa)
- What the system delivers to the pump inlet: atmospheric pressure plus static suction head, minus friction losses and vapor pressure. It must exceed NPSHr with margin. Read more
- NPSH required (NPSHr)
- What the pump needs at a given flow, read from the manufacturer's curve. NPSH available must exceed it with margin. Read more
- NSF/ANSI 61
- A voluntary, third-party consensus standard that certifies wetted materials in drinking water system components. It is not a federal statute. Read more
P
- Peristaltic metering pump
- A tube-based, self-priming positive-displacement pump that feeds chemicals into a water or wastewater process at a controlled, adjustable rate. Read more
- PTFE diaphragm
- A valve diaphragm with a PTFE wetted face; the PTFE contacts the chemical while a backing material provides the elasticity needed for sealing and cycling. Read more
- Pulsation dampener
- A device that absorbs the flow and pressure pulses from a positive-displacement metering pump and releases the stored volume between strokes, so the system behaves more like steady flow. Read more
R
- Removal (wastewater treatment)
- Treatment that separates a compound from the water and concentrates it into another phase such as a sludge, spent medium or brine; the compound still exists and must be handled. Read more
S
- SEMI F57
- The industry specification for extractable-metals and ionic-purity testing on polymer materials and components used in ultrapure water and liquid chemical distribution systems. Read more
- Single open-end cartridge (SOE)
- A filter cartridge with 222 O-ring ends that creates a positive mechanical seal independent of end-cap clamping force; preferred where bypass is unacceptable. Read more
- Sintered silicon carbide (SSiC)
- A bearing material used in high-specification mag-drive pumps, chosen for chemical inertness and hardness. Without fluid it generates friction heat at the bearing within seconds. Read more
T
- True union ball valve
- A ball valve whose union design lets the ball, seats and seals be serviced or replaced without cutting the line or disturbing adjacent piping. Read more
- Tube failure detection (TFD)
- A safety feature that provides instant pump shutoff and alarm when dosing tubing ruptures, preventing a small failure from becoming a reportable spill. Read more
V
- Vapor lock
- In a metering pump on off-gassing sodium hypochlorite, gas collects in the pump head instead of escaping, displaces liquid and causes the pump to lose prime. Read more
- Vented ball
- A ball valve feature with a small relief path that lets pressure escape from the ball cavity rather than trapping it, which matters on off-gassing chlorine and hypochlorite service. Read more
X
- XLPE
- Crosslinked polyethylene: its covalent molecular bridges increase resistance to environmental stress cracking compared with standard HDPE tanks. Read more
Reviewed by James Riggins, 30+ years specifying water and chemical process equipment · Updated