36 essential technical terms for anyone specifying, operating or maintaining industrial pumps — short, citable definitions verified by FB Bombas engineering.
Technical Glossary
Hydraulics
(12)
NPSH
Net Positive Suction Head · Net Positive Suction Head
Hydraulics
NPSH is the absolute pressure available at a pump suction flange above the liquid's vapor pressure, expressed in meters of liquid column. It is the parameter that determines whether a pump will cavitate in a given application.
There are two NPSH values: NPSH available (NPSHa), calculated by the installation designer from suction height, friction losses and fluid vapor pressure; and NPSH required (NPSHr), provided by the pump manufacturer on the characteristic curve. The rule of thumb is NPSHa > NPSHr + safety margin (typically 0.5 to 1.5 m), otherwise cavitation occurs and damages the impeller. Hot, volatile or near-vaporization fluids require special attention in sizing.
Cavitation is the formation of vapor bubbles inside a pump when local pressure drops below the liquid's vapor pressure, followed by bubble collapse in higher-pressure regions — generating microjets that erode the impeller and volute.
Classic cavitation symptoms are characteristic noise ("gravel inside the pump"), excessive vibration, flow and efficiency drop, and premature erosive wear on the impeller suction side. Prevention is achieved by correct NPSHa sizing, keeping the pump near the suction level, avoiding restrictions on the suction line, and selecting resistant materials for critical applications. External gear pumps (FBE) are less sensitive to cavitation than standardized centrifugals (FBCN) due to the positive displacement principle.
Volumetric flow rate (Q) is the volume of fluid a pump moves per unit of time, expressed in L/min, m³/h or GPM depending on context and magnitude.
In centrifugal pumps (like the FBCN), flow depends directly on the installation head — the higher the head, the lower the flow. In positive displacement pumps (like FBE and FBEI), flow is nearly constant and proportional to speed, regardless of discharge pressure, making them ideal for precise dosing. The FBCN covers flow up to 2,200 m³/h; the FBE, from 0.5 to 6,500 L/min; and FB Bombas fire systems go up to 10,000 L/min.
Total head (H) is the energy per unit weight a pump delivers to the fluid, expressed in meters of liquid column. It represents the sum of static elevation height, friction losses and pressure differences between suction and discharge.
Total head is the sum of: geometric head (level difference between suction and discharge), piping friction losses (friction in pipes, valves and fittings) and required residual pressure at delivery point. Unlike gauge pressure in bar or kgf/cm², head in meters is independent of fluid density — conversion is direct: H(m) = P(bar) × 10.2 / specific gravity. The FBCN line delivers up to 138 m of head, with Q×H curves available for each of the 53 models (43 standard + 10 large capacity); for greater heights, series or multistage pumps are used. Correct selection requires the pump curve to intersect the system curve at the desired operating point, preferably near BEP.
BEP is the point on the characteristic curve where the pump operates at maximum hydraulic efficiency for a given speed — corresponding to the ideal combination of flow and head for that specific impeller.
Operating far from the BEP (for example, with the discharge valve partially closed) causes internal recirculation, vibration, accelerated bearing and seal wear, and unnecessary energy consumption. Best practice is to select a pump whose BEP falls between 80% and 110% of the expected operating flow. FBCN technical manuals include characteristic curves with the BEP clearly marked for each of the 53 models in the series (43 standard + 10 large capacity).
The characteristic curve of a centrifugal pump is the chart relating flow (Q) to total head (H), efficiency, absorbed power and required NPSH, for a given speed and impeller.
The curve is the central technical document for pump selection: the operating point is determined by the intersection of the pump curve and the installation friction curve. For correct selection, the designer must overlay both curves and verify that the crossing point is near the BEP of the chosen pump. FBE (12 sizes) and FBCN (53 models) technical manuals include curves for 1750 and 3500 rpm at 60 Hz.
Discharge pressure is the gauge pressure measured at the pump discharge flange (outlet) in operation, usually expressed in bar, kgf/cm² or psi. It is the parameter used to specify a pump's capacity to reach the pressure required by the application.
The maximum allowable pressure depends on casing material and fluid temperature — the FBCN manual includes charts (Figures 1-4) showing how maximum pressure drops with temperature for cast iron, A216 WCB carbon steel and A743 CF8M stainless steel. For cast iron, the typical limit is 20 bar at -50 to 120°C, dropping to 10 bar at 260°C. Operating above these limits compromises the pump's mechanical integrity.
Viscosity is a fluid's resistance to flow. The most used units in industrial pumps are Saybolt Universal Second (SSU) and centistoke (cSt). The higher the viscosity, the more the fluid needs positive displacement pumps instead of centrifugals.
Reference values: water (1 cSt ≈ 31 SSU), diesel oil (3 cSt ≈ 37 SSU), SAE 30 oil at 40°C (150 cSt ≈ 700 SSU), honey (10,000 cSt ≈ 46,500 SSU), hot asphalt (50,000 cSt ≈ 230,000 SSU). The FBE line supports up to 100,000 SSU — above this, FB Bombas engineering recommends the FBEI with specific configuration. Standardized centrifugals (FBCN) lose efficiency dramatically above 500 SSU.
Discharge (recalque) is the piping that conducts pumped fluid from the pump outlet to the point of use or elevated reservoir, in contrast to suction (the line preceding the pump).
The discharge head (Hr) is the geometric difference between discharge level and pump shaft. Together with suction head (Ha), it forms the total geometric head (Hg = Ha + Hr). Total dynamic head (TDH) further includes distributed and localized friction losses. In the hydraulic design phase, discharge pipe diameter is sized for velocities of 1.5 to 3.0 m/s in low-viscosity liquids, avoiding water hammer and noise. In fire systems, NFPA 20 requires a check valve and isolation valve on the discharge line.
Suction is the piping and section upstream of the pump, from reservoir to suction flange. This is where atmospheric pressure pushes liquid into the pump — limited by the fluid's vapor pressure (NPSH).
Two scenarios exist: flooded suction (pump below reservoir level, safer for NPSH) and negative suction or suction lift (pump above reservoir, theoretical maximum 10.33 m in water at 20 °C at sea level — practically 6 to 8 m considering losses and NPSH margin). Best practices: suction piping diameter larger than discharge, minimum bends and valves, eccentric reducer before the flange (flat face up) to avoid air pockets and hydraulic eccentricity.
The affinity laws describe how flow rate (Q ∝ N), head (H ∝ N²) and power (P ∝ N³) vary with rotational speed or impeller diameter of a centrifugal pump, geometry being constant.
Essential for sizing with variable frequency drives (VFD): reducing speed by 20% reduces flow by 20%, head by 36% and power by 49%, yielding energy savings. Valid for speeds close to nominal (±20%); outside this range, efficiency drops and the models lose accuracy. For impeller diameter variation, valid within the hydraulic family (same casing) and up to ±10% of nominal diameter. In FBCN pumps, impeller trimming is a common field practice to fit the curve to the operating point.
Shut-off pressure is the pressure developed by a centrifugal pump with the discharge valve fully closed (zero flow), corresponding to the leftmost endpoint of the characteristic curve.
A critical parameter for mechanical sizing of casing and downstream piping: maximum system pressure must account for shut-off + suction pressure, not just the operating point. In acceptance testing (FAT), shut-off is measured as the curve reference. Prolonged shut-off operation is prohibited in centrifugals — generates heating from internal recirculation, potentially vaporizing the liquid in seconds. In fire systems, NFPA 20 limits shut-off to 140% of rated pressure to avoid pipe overpressure.
A centrifugal pump is a device that transfers energy to a liquid through the rotation of an impeller inside a volute — the liquid enters at the center, is radially accelerated by the impeller blades, and exits through the discharge nozzle with increased pressure.
It is the most common type of industrial pump for low-viscosity liquids at medium to high flow. Ideal for water, aqueous solutions, light solvents, thin fuels and process fluids. FB Bombas' FBCN line follows the ASME B73.1 (mechanical) standard, with back pull-out construction allowing impeller maintenance without disconnecting piping. Variations exist: end-suction (FBCN), double suction, multistage and vertical.
An external gear pump is a type of positive displacement pump in which two parallel gears rotate in opposite directions inside a casing, transporting fluid in the volume formed between the teeth and the outer wall.
It is the ideal type for viscous fluids — lubricating oils, heavy fuels, asphalt, resins, biodiesel, molasses, chocolate and viscous chemicals. FB Bombas is the original Brazilian manufacturer of this type of pump at industrial scale, continuously operating since 1944. The FBE line has 12 standard sizes from 1/8" to 6", covering flow from 0.5 to 6,500 L/min, pressure up to 22 kgf/cm² and viscosity up to 100,000 SSU with heat-treated alloy steel helical gears.
An internal gear pump is a positive displacement pump in which a smaller inner rotor rotates eccentrically inside a larger outer rotor, creating crescent-shaped chambers that transport fluid with very low pulsation.
The main advantage over external gear is practically continuous pulseless flow, making this type ideal for precise dosing, hot-melt applications, polymers, latex and very viscous fluids. FB Bombas' FBEI has 10 catalogued models from 1" to 4" (technical manual MAN001-10) in three construction configurations — with integrated relief valve, compact and heavy-duty 3" — plus the FBEI-LS engineered-to-order version for large capacities in asphalt, bitumen and heavy oils. Standard integrated relief valve and optional heating jacket (steam up to 185°C, thermal fluid up to 232°C, both at 10 bar).
A positive displacement pump moves fluid in discrete, constant volumes per cycle, independent of discharge pressure. Gear pumps (FBE, FBEI), diaphragm, piston and screw pumps are all positive displacement.
The most important characteristic is that flow depends almost exclusively on rotation — allowing precise dosing. In contrast, centrifugal pumps deliver variable flow with system pressure. Positive displacement pumps must never be operated with closed discharge without a relief valve, under penalty of reaching destructive pressure. The FBE and FBEI lines include an integrated relief valve as optional (FBE) or standard (FBEI).
Standardized centrifugal · ANSI/ISO 2858 pump · Back pull-out pump
Pump Types
A standardized centrifugal pump is a pump whose mounting dimensions (flanges, shaft span, footprint) follow international standards like ANSI B73.1 or ISO 2858, allowing interchange between manufacturers without altering piping or baseplate.
Dimensional standardization emerged to reduce spare-parts cost and changeover time in industrial plants. FB Bombas' FBCN line is dimensionally compliant with ASME B73.1 / ISO 2858, with back pull-out construction (removing the rotating assembly without disconnecting piping) and covers flows up to 2,200 m³/h and head up to 138 m, with 53 models (43 standard + 10 large capacity DN150-300). Serves petrochemical, sugar-ethanol, pulp-paper, mining and industrial water treatment. Materials available: cast iron, carbon steel, stainless 304/316, duplex and super duplex, with single or tandem mechanical seal per API 682.
A thermal oil pump is a centrifugal pump designed to move heat-transfer fluids at high temperature (up to 350°C), with materials resistant to thermal expansion, cooled mechanical seal and construction that avoids fluid vaporization point.
FB Bombas' FBOT line covers applications with synthetic thermal fluids (Therminol, Marlotherm, Dowtherm) and mineral oils, in closed industrial heating systems — sugar-ethanol mills, textile, chemical, food (chocolate), asphalt and oil processing. Critical construction: seal chamber with convection or internal coil cooling, double bearing with oil bath or mist lubrication, alloy steel 4140 shaft, materials per API 610 BB1/OH1/OH2 depending on model. Cautions: thermal oil pumps require gradual heating startup (1-2°C/min) to avoid thermal shock in seal and bearings, and operation in systems with expansion tank to accommodate fluid volumetric expansion (~30% between ambient and 300°C).
Back pull-out is a centrifugal pump construction configuration in which the rotating assembly (impeller, shaft, bearings and seal cover) can be removed from the back of the pump without disassembling the main casing or disconnecting suction and discharge piping.
The big advantage is maintenance time: impeller replacement, mechanical seal inspection and sleeve adjustment are done in hours, not days. It is a requirement of the ASME B73.1 standard for process standardized centrifugals. The FB Bombas FBCN line meets this standard and maintains coupling alignment even after rotating assembly intervention.
A mechanical seal is a pump shaft sealing device composed of two flat faces — one fixed to the housing and one rotating on the shaft — pressed against each other with a very thin lubricating film between them.
It is the preferred option over packing when zero visible leakage, operation with toxic/flammable/high-value fluids, and extended maintenance intervals are required. Configurations include single, double (with barrier fluid), cartridge, balanced and unbalanced. Typical face materials: silicon carbide, tungsten carbide, ceramic. The FBCN line includes 6 sealing chamber configurations (ST, S1, S2, S3, S4 and S) described in the technical manual to serve different fluid/temperature/solids-in-suspension combinations.
Packing is a pump shaft sealing element composed of braided rings (typically synthetic fiber, graphite, PTFE or carbon) axially compressed by a gland against the shaft sleeve to reduce leakage.
Unlike a mechanical seal, packing operates with intentional controlled drip — this small flow is needed to lubricate and cool the rings. It is the economical choice for water, non-aggressive fluids and applications where small leakage is acceptable. FB Bombas technical manuals include the required sealing liquid flow table for each pump size, typically 1 to 5 L/min. Packing requires periodic retightening and replacement every 6-12 months depending on service.
A radial impeller is the rotating component of a centrifugal pump in which the blades direct fluid from the center to the periphery at 90° to the shaft — transferring kinetic energy to the liquid which is then converted to pressure by the volute.
There are three basic centrifugal impeller types by exit angle: radial (blade perpendicular to shaft, high pressure, low flow), mixed-flow (intermediate) and axial (blade parallel to shaft, high flow, low pressure). The FBCN line uses a radial impeller with single suction — suitable for most industrial process applications. For wear resistance in fluids with light solids, there is a pressure-side wear ring (except in smaller models 25-150, 32-125 and 32-125.1).
The volute is the outer spiral-shaped casing of a centrifugal pump, whose function is to collect fluid discharged by the impeller and gradually decelerate it — converting kinetic energy into pressure energy before exiting through the discharge nozzle.
The volute spiral profile is designed so that fluid velocity drops continuously as the cross-section increases toward discharge — minimizing turbulence losses. The FBCN has a single-piece cast volute in cast iron, A216 WCB carbon steel or A743 CF8M stainless steel, with a suction-side wear ring to maintain ideal clearance even after hours of operation.
A bearing is the component that supports the pump's rotating shaft, absorbs radial and axial loads, and maintains precise alignment between impeller and volute. It can be the rolling element type (rigid ball, angular contact) or sliding type (bushings).
The FBCN line uses pairs of 6306 C3, 6308 C3, 6310 C3, 6314 C3 or 6315 C3 bearings by size range, with oil lubrication via sight gauge or optional automatic refill cup. The FBE line uses self-lubricating TM23 bronze sliding bushings — robust, silent and requiring no external lubrication in normal conditions. Bearing MTBF is one of the main reliability indicators of an industrial pump.
A motor-pump assembly is an integrated unit consisting of pump, electric motor, common metal baseplate and flexible coupling, factory-assembled and aligned for direct field installation.
FB Bombas delivers complete motor-pump assemblies for all series (FBCN, FBE, FBEI, FBOT) with WEG motor or equivalent, sized flexible coupling, coupling guard (NR-12) and carbon steel or stainless baseplate. Alignment is done at factory with precision instruments, eliminating the main cause of field-installed pump failure. Motor power reserve follows FBCN manual: 20% up to 2 hp, 15% up to 20 hp, 10% above 20 hp.
A self-priming pump can draw fluid and expel air from the suction line without a foot valve or auxiliary priming device, provided the pumping chamber has been previously filled with fluid.
Gear pumps (FB Bombas FBE and FBEI) are naturally self-priming — the gear meshing creates sufficient vacuum to draw fluid. Conventional centrifugal pumps (like the FBCN) are not self-priming and require prior priming or a foot valve at suction. The self-priming capability of gear pumps is an important advantage in installations where the pump is above fluid level.
The impeller (rotor) is the rotating component of a centrifugal pump, with curved vanes that transfer kinetic energy to the fluid through centrifugal force, defining the pump flow and head.
In the FB Bombas FBCN series, the impeller is radial single-suction type with wear ring on the pressure side (except models 25-150, 32-125 and 32-125.1). Impeller diameter defines the head — larger impellers generate more pressure. Available materials: gray cast iron, ductile iron, AISI 316 and AISI 304 stainless steel, Duplex and special alloys upon consultation. The impeller is dynamically balanced at factory to minimize vibrations.
Duplex stainless steel is a family of stainless steels with austenitic-ferritic microstructure (50/50), offering twice the yield strength of common austenitic grades (AISI 316) and superior resistance to pitting and chloride corrosion.
The PRE index (Pitting Resistance Equivalent = %Cr + 3.3·%Mo + 16·%N) classifies the family: Lean Duplex (PRE 25-30), standard Duplex UNS S31803/S32205 (PRE 35) S32750/S32760 (PRE 40+) and Hyper Duplex (PRE 48+). Typical applications: seawater handling, fertilizers (urea, phosphates), paper pulp and chlorinated fluids in refineries. FB Bombas offers Duplex impellers and casings upon consultation for FBCN pumps handling fluids with chlorides > 200 ppm or pH < 4.
A heating jacket is an external envelope around the pump body, designed for circulation of steam, thermal oil or hot water, keeping the process fluid at ideal viscosity temperature throughout operation.
Typical application in asphalt pumping, CAP (petroleum asphalt cement), bitumen, animal fats, honey sugar, glycerin, resins and any fluid that solidifies or increases viscosity below a critical temperature. Without jacketing, cold product inside the pump can clog the gears or prevent startup on the next cycle. FB Bombas offers jacketed variants of the FBE line (external gear) — FBE-J — with saturated steam heating at 6-10 bar or thermal oil, sized according to the minimum pumping temperature required by the fluid. In critical assemblies (CAP, bitumen), jacketing extends also to casing, covers and short discharge piping up to the first valve.
ASME B73.1 is the North American standard that specifies mechanical and construction requirements for horizontal end-suction centrifugal pumps used in chemical processes — including back pull-out, hydrostatic test pressure, alignment and materials.
ASME B73.1 focuses on the internal mechanics of normalized horizontal centrifugals: mandatory back pull-out construction, minimum 3 mm corrosion allowance, hydrostatic test at 1.5× maximum operating pressure, and minimum clearance between impeller and volute. The FBCN fully meets this standard and all models undergo hydrostatic testing per ANSI B73.1 before shipping.
API 610 is the American Petroleum Institute standard for centrifugal pumps used in petroleum, petrochemical and natural gas industries. It is considered one of the world's most stringent specifications for process pumps.
The standard requires robust construction for continuous 24/7 operation in severe conditions, corrosion and high-temperature resistant materials, redundant sealing for hazardous fluids, and detailed acceptance tests. API 610 pumps are classified by types (OH, BB, VS) according to shaft orientation and construction configuration. FB Bombas has pumps meeting API 610 requirements and is a registered supplier in the CRCC (Supplier Registry) of Petrobras.
Standard for the Installation of Stationary Pumps for Fire Protection
Standards
NFPA 20 is the National Fire Protection Association international standard that establishes requirements for design, installation, maintenance and testing of stationary fire protection pumps — including centrifugal pumps, diesel and electric motors, control panels and accessories.
The standard requires redundant configuration (main pump + reserve pump + jockey pump for pressurization), independent power source (diesel motor in addition to electric to ensure operation during power loss), certified automatic control panel, and performance curve testing per NFPA. In Brazil, it is complemented by ABNT standards NBR 10897 (sprinklers), NBR 13714 (hydrants) and NBR 16704 (fire pumps). FB Bombas fire-fighting systems fully meet this standard.
NBR 16704 is the Brazilian ABNT standard establishing requirements for fixed fire fighting pump systems — analogous to NFPA 20 but adapted to Brazil's regulatory and construction context.
NBR 16704 covers sizing of main, jockey and auxiliary pumps, control panels, diesel controllers, hydraulic installation and acceptance testing. Coexists with NFPA 20 in Brazilian projects: state fire departments usually accept both, but large insurer-backed projects require explicit NFPA 20. FB Bombas designs its FBFS skids meeting both NBR 16704 and NFPA 20 requirements, ensuring approval under any regulatory scenario.
API 682 is the American Petroleum Institute standard for shaft sealing systems (mechanical seals) on centrifugal and rotary pumps, defining categories 1/2/3 and flush plans (Plan 11, 13, 52, 53A/B/C, 62, etc.).
The 4th edition (2014) is consolidated as the worldwide reference in refineries and chemical plants. Category 1 covers non-critical services (Type A); Category 2 adds qualification testing (Type A/B/C); Category 3 covers hazardous fluids with severe testing. Flush plans control the seal interface: Plan 11 (simple recirculation), Plan 53 (pressurized barrier-fluid system) and Plan 62 (external quench) are the most common. FB Bombas offers API 610 pumps with sealing sized per API 682, meeting Petrobras CRCC.
FAT is the acceptance test performed at the manufacturer's factory, with or without client witness, to verify that the pump meets the contracted technical specifications before shipping — including hydrostatic test, performance curve, vibration, noise and dimensional inspection.
The FAT generates a formal signed report documenting results and serving as basis for equipment acceptance. It is mandatory in large projects, Petrobras contracts (CRCC) and critical applications in refineries and petrochemical plants. FB Bombas has its own test bench in Cabreúva-SP with capacity to test all standard models of the FBE, FBEI, FBCN and FBOT lines with calibrated instrumentation and complete documentation.
MTBF is the expected mean operating time of a pump between two consecutive failures — typically expressed in hours. It is the main reliability indicator of rotating equipment in an industrial environment.
The main components limiting MTBF in industrial pumps are: mechanical seal (3,000 to 25,000 h), bearings (8,000 to 40,000 h), impeller (depending on erosion and cavitation) and coupling. Best practices to maximize MTBF include operating near BEP, avoiding cavitation, maintaining correct alignment, using adequate lubrication and following the preventive maintenance plan. Robust construction and FB Bombas' design tradition contribute to high MTBF even in severe environments.
Corrosion allowance is the extra amount of material (in millimeters) added to the minimum structural thickness of a pump part to compensate for expected corrosion loss over the equipment's service life.
The ASME B73.1 standard requires a minimum corrosion allowance of 3 mm for chemical process pumps. FB Bombas' FBCN comes with 3.3 mm corrosion allowance, providing margin above the normative minimum. This margin is critical in moderately corrosive fluids and high-temperature environments that accelerate corrosion rate. For highly corrosive service, more noble materials (316 stainless, duplex) should be used instead of increasing the allowance.
A booster pump is used to increase (boost) the pressure of a system that already has partial but insufficient pressure for the desired application.
Typical booster pump applications include: public network pressure boosting for tall buildings, boiler feed, fire fighting systems (jockey pump is a type of booster), and industrial process lines where available pressure does not reach the most remote point. FBCN centrifugal pumps are frequently used as boosters in industrial water and sanitation systems.
A jockey pump is the pressurization pump of a fire fighting system, sized at ~1% of main pump flow, which maintains network static pressure by compensating for small leaks.
NFPA 20 (section A.4.26) recommends the jockey pump have flow of approximately 1% of the main pump. Its function is to prevent repeated main pump starts that would cause premature wear. Operates with automatic setpoints: starts when pressure drops (e.g., 6.5 bar) and stops upon reaching the upper setpoint (e.g., 7.0 bar). Continuous operation indicates significant system leak. FB Bombas supplies jockeys as integrated part of fire skids.
Shaft alignment · Angular and parallel misalignment
Operation & Maintenance
Pump-motor alignment is the geometric precision between motor and pump shafts through the coupling, measured in angular and parallel tolerances. Deviations beyond tolerance reduce bearing and mechanical seal MTBF by more than 50%.
Typical tolerances (ANSI/ASA): parallel misalignment ≤ 0.05 mm and angular ≤ 0.1 mm/100 mm coupling diameter for speeds up to 1,800 rpm; half those values for 3,500 rpm. Measurement methods in order of precision: straightedge + feeler (rough), dial indicator (industrial standard), laser alignment (precise, recommended by FB Bombas for FBCN and FBOT). Alignment must be verified in two stages: cold (installation) and hot (after thermal stabilization in 30-60 min of operation) — thermal expansion can introduce 0.1-0.3 mm deviations that need pre-compensation.
If the term you are looking for is not here, it means our engineering has not yet consolidated a public definition for it. Send your question to our team in Cabreúva-SP — we reply with the calculation, the normative reference and the selection criterion applicable to your case.
