Canned Motor Pump & Sealless Centrifugal Pump — hermetic, leak-free by design

A canned motor pump is a sealless centrifugal pump in which the hydraulic end and the electric motor form one hermetically sealed unit: the impeller is mounted directly on the motor rotor, and both are enclosed inside thin, non-magnetic cans so that no shaft ever penetrates the pressure boundary. With zero dynamic seals there is nothing to leak — the reason canned motor technology is the default choice for liquid chlorine, heat-transfer oil, refrigerants, petrochemical feedstocks and nuclear cooling circuits. ZGPV builds the H-series in 25+ construction types handling 600+ fluids, from −200 °C cryogenics to 450 °C heat-transfer service.

Also known as sealless pump seal-less centrifugal pump glandless / hermetic pump zero-leakage pump no-seal / canned rotor pump API 685 sealless pump liquid chlorine transfer pump hot oil circulation pump refrigerant / LNG cryogenic pump
Horizontal sealless canned motor pump, single-stage end-suction, with integrated motor barrel and baseplate Standard type · single-stage, closed coupled
Explosion-proof canned motor pump with Ex d terminal box and reverse circulation piping Ex-proof · Exd II C T1–4
High temperature canned motor pump with external cooling coil and air vent valve HT type · up to 450 °C

H-series sealless canned motor pumps built by Sichuan Zigong Pump & Valve Co., Ltd. (ZGPV) — West China’s largest chemical pump manufacturer, est. 1967, ISO 9001 / ISO 14001 certified.

0 sealsDynamic seals — zero leakage
600+Fluids handled
−200–450 °CFluid temperature range
25+Construction types

Canned motor pump class at a glance

TypeSealless rotodynamic
Capacity2–1,200 m³/h
Total head2–800 m
Motor output0.4–220 kW
Design pressureup to 40 MPa

Per-series limits vary: see the construction table below. Performance tested per ISO 9906 / GB/T 3216; API 685 format available.

Why sealless

The mechanical seal is the weakest link — canned motor pumps simply delete it

Industry data is consistent: roughly 75% of conventional centrifugal pump failures trace back to the shaft seal and its support systems — flushing plans, quench lines, seal pots, alignment and gland maintenance. A canned motor pump removes the seal, the coupling and every auxiliary line that comes with them.

01

Fugitive emissions & product loss

Chlorine, phosgene, benzene, refrigerants, monomers — even a “ acceptable” seal leak on these fluids is an incident. Sealless construction confines the liquid inside a fully welded pressure envelope, so VOC and toxic-emission audits stop being a pump problem.

Fix: hermetic one-piece pump-motor unit, static seals only
02

Seal-support plumbing that never ends

Flush plans, cooling circuits, quench and barrier-fluid systems add cost, footprint and failure modes of their own. On a canned motor pump the process liquid itself cools the motor and lubricates the bearings — no external auxiliary systems are required.

Fix: self-circulation through the rotor chamber
03

Vacuum, high pressure & extreme temperature

A seal needs a positive differential to hold. Canned motor pumps hold vacuum tightness for systems that suck in air if leaked, survive 40 MPa design pressures (HTM type) and span −200 °C to 450 °C with the right construction.

Fix: one platform, 25+ construction variants

Why engineers specify canned motor pumps

  • Zero leakage — no dynamic seal; only static gaskets on the casing
  • Double containment — even if the stator can fails, the shroud keeps fluid inside (API 685 secondary containment)
  • Best-in-class MTBF — no seals to swap, no coupling to align
  • Compact one-piece design — smallest installed footprint for the duty
  • Low noise & vibration — no fan, no rolling bearings
  • Vacuum-tight — suitable for systems that must not ingest air
  • Safe in explosive areas — Ex d II C T1–4 / Ex d II B T1–4 terminal boxes, IP54–68

Where a canned motor pump is not the answer

  • Never run dry — the liquid lubricates the bearings and cools the windings; dry running destroys them in seconds (fit a dry-run / liquid-presence protection)
  • Can losses — eddy-current losses in the shield sleeves cost a few efficiency points versus a sealed pump
  • Abrasives — plain product-lubricated bearings prefer clean or softly-particulate fluids; specify slurry types with back-flushing for particle-laden duties
  • Very high viscosity — circulation flow degrades above roughly several hundred cP; consult the factory
Working principle

How a canned motor pump works — the motor swims in the process liquid

The impeller and the motor rotor share one shaft inside a single pressurized chamber. Thin-walled, non-magnetic stator and rotor cans (Hastelloy C or SS) isolate the windings from the fluid, while a small circulation flow runs through the rotor chamber to cool the motor and lubricate the fluid-film bearings.

1

One shaft, one chamber

Suction liquid enters the impeller and discharges into the volute. The rotor is immersed in the same liquid — there is no shaft penetration, therefore no dynamic seal anywhere in the machine.

2

Cans isolate the windings

The stator winding is sealed inside its can; the rotor spins inside a second can. The magnetic field crosses both sleeves with no electrical contact — even a ruptured can does not leak to atmosphere (double containment).

3

Circulation flow cools & lubricates

Discharge liquid is routed through holes in the front bearing housing, across the rotor-can gap and rear bearing, back to the impeller eye (hollow-shaft types) or to the suction tank (reverse-circulation HN types, ideal for easy-vaporizing fluids).

Cross-section of a hollow-shaft canned motor pump showing circulation flow through the rotor chamber
Hollow-shaft basic type: circulation flow runs from the discharge side through the rotor chamber back to the impeller inlet. Yellow = liquid path.
Cross-section of a canned motor pump with external circulation tubing
External-circulation type (HP): a circulation pipe routes cooling flow from the casing to the rear bearing housing — used where internal routing does not suit the fluid.
Engineering note — reverse circulation for easy-vaporized liquids. For fluids close to their vapor pressure (LPG, LNG, liquid ammonia, refrigerants), HN reverse-circulation types return the warmed motor flow to the suction tank instead of the impeller eye, protecting NPSH and preventing flashing inside the pump. Keep the reverse-circulation flow rate at or above the figure on the pump datasheet at all times while operating.

Canned motor pump terminology (glossary)

Stator can / rotor canThin non-magnetic sleeves (SS, Hastelloy C) separating windings from fluid
Sealless / glandlessNo shaft seal; only static gaskets on the pressure boundary
Double containmentSecondary shroud keeps fluid in even if a can ruptures (API 685)
Circulation flowInternal slipstream that cools the motor and lubricates the bearings
TRG meterBearing-wear / rotor-position monitor; red zone = stop and investigate
HPB monitorHardware protection board: bearing wear, rotation, phase-failure detection
Fluid-film bearingsSiC / graphite / steatite journal bearings lubricated by the pumped liquid
Reverse circulationHN construction returning motor flow to the suction tank
Ex d terminal boxFlameproof winding compartment, Exd II C T1–4 / II B T1–4, IP54–68
Types & construction

25+ canned motor pump construction types — one hermetic platform

Every type shares the same sealless architecture; the differences are circulation routing, thermal isolation, vertical orientation, self-priming ability and multi-staging. Limits below are the maximum of each type’s series.

Five canned motor pump constructions: reverse circulation, external circulation, high temperature isolation, self-priming and multi-stage
Circulation routing is what defines the type: HN reverse, HP external, HT thermal isolation, HZ self-priming, HP-M/HN-M multi-stage.
TypeCapacityHeadOutputKey feature
HV hollow shaft basic600 m³/h160 m132 kWWorkhorse; internal circulation
HP external circulation750 m³/h160 m315 kWCirculation pipe outside casing
HNP pressurized circulation800 m³/h220 m315 kWAuxiliary-impeller internal recirculation
HN reverse circulation600 m³/h160 m315 kWEasy-vaporized fluids, LPG/LNG
HW vertical reverse circ.2,000 m³/h260 m400 kWVertical, easy venting, low NPSHr
HT high-temp isolation800 m³/h160 m315 kW450 °C, thermally isolated motor
HP-M multi-stage200 m³/h800 m400 kWBack-to-back staged impellers, 400 °C
Self-priming canned motor pump cross-section

HZ — Self-priming type

Primes from underground tanks and empty suction lines. Q 50 m³/h, H 50 m, 45 kW. The suction chamber evacuates air on start-up, then switches to normal pumping.

self-priming canned pumpempty-tank duty
Back-flushing slurry canned motor pump

HS — Slurry handling type

Few moving parts, mechanical-seal-free, with back-flushing for particle-laden media. Q 750 m³/h, H 130 m, 220 kW — fluids with slurry content below 30% by weight.

slurry canned pumpback-flushing
Vertical high pressure high temperature canned motor pump

HTM — High pressure & temperature

Vertical barrel construction with external heat-exchanger cooling circuit. Q 600 m³/h, H 160 m, design pressure to 40 MPa, 400 °C, 220 kW — supercritical and nuclear service.

high pressure canned pumpsupercritical
Multi-stage sealless canned motor pump

HP-M / HN-M — Multi-stage type

Staged impellers for high-head sealless duty: Q 280 m³/h, H to 800 m, 400 °C, 315 kW. Reverse-circulation multi-stage builds available.

multi-stage canned pumphigh head sealless
Reverse circulation canned motor pump cross-section with flow to suction tank

HN — Reverse circulation

Motor flow returns to the suction tank — the standard answer for LPG, LNG, liquid ammonia and refrigerants with low NPSH margin.

LPG pumprefrigerant pump
Self-priming canned motor pump with vertical discharge

HR / HV-X — Extreme temperature

Full-jacketed high-melting-point builds (300 m³/h, 300 °C) and super-high-temperature types with no cooling required (350 m³/h, 400 °C, 110 kW) for bitumen, salts and waxes.

molten / jacketed pump400 °C sealless

Extended sealless range — engineered canned motor pump types

Beyond the core constructions: pressurized and vertical circulation, jacketed high-melting builds, gas-sealed slurry, in-tank submersibles, refrigerant and glycol packages, agitators, transformer oil pumps and low-flow regenerative turbines — all with the same zero-leakage canned motor driveline.

Pressurized circulation canned motor pump cross-section with auxiliary impeller

HNP — Pressurized circulation type

Internal recirculation from high pressure through the rotor chamber via an auxiliary impeller back to discharge — no reverse-circulation pipe needed. Q 800 m³/h, H 220 m, 315 kW for high-vapor-pressure fluids.

pressurized circulation pumpauxiliary impeller
Vertical reverse circulation canned motor pump cross-section

HW — Vertical reverse circulation

Vertical configuration for volatile hydrocarbons: easier venting and lower NPSHr, motor flow returned to the suction tank. Q 2,000 m³/h, H 260 m, 400 kW — the large-capacity sealless workhorse.

vertical canned pumpvolatile hydrocarbons
High melting point canned motor pump with full heating jacket cross-section

HR-S — High melting point type

Full heating jacket (steam or thermal oil) keeps waxes, bitumen, caprolactam and naphthalene liquid from casing to discharge. Q 600 m³/h, H 220 m, 200 kW.

jacketed sealless pumpmolten media
Super high temperature canned motor pump cross-section

HR-Y — Super high temperature

Super-high-temperature canned motor with full heating jacket for the most demanding melting-point fluids — no external cooling required. Q 260 m³/h, H 120 m, 90 kW.

super high temperature pumpno cooling water
Gas sealed slurry canned motor pump cross-section

HJ — Gas-sealed slurry type

Inner mechanical seal plus gas seal chamber isolates bearings from solids — handles crystallizer circulation and slurries up to 30% wt. Q 300 m³/h, H 160 m, 110 kW.

slurry sealless pumpcrystallizer duty
Submersible in-tank canned motor pump cross-section

HE — Submersible in-tank type

Mounts directly through the tank roof: minimum NPSH requirement, maximum safety, no suction piping. Q 200 m³/h, H 360 m, 280 kW, to 300 °C.

submersible canned pumptank mounting
Ammonia freon CO2 refrigerant canned motor pump

Refrigerant pumps — NH₃ / Freon / CO₂

Dedicated sealless refrigerant packages in horizontal HN, vertical HW and multistage HN-M builds: −50 to +40 °C, 1.6–5.0 MPa, Q 0.2–100 m³/h, H 5–100 m. Hermetic by nature — refrigerant charge never escapes.

ammonia pumpCO2 transfer pumpfreon pump
Glycol circulating canned motor pump for wind turbine and locomotive cooling

Glycol circulating pumps — HVE / HV

Closed-loop glycol cooling for wind-turbine converters and railway power electronics: −40 to +70 °C, 2.0 MPa, Q 5–80 m³/h, H 15–80 m. Maintenance-free, silent, leak-free.

glycol circulation pumpwind turbine cooling
NP series canned motor pump for lithium bromide absorption chillers

NP series — Absorption chiller pumps

For central air-conditioning absorption chillers: circulates lithium bromide solution and water with NPSHr as low as 0.3–0.5 m, fully welded sections, CE certified. Q 0.6–160 m³/h, H 2–50 m, 0.2–26 kW.

LiBr solution pumpHVAC sealless
Canned motor agitator for tanks and reactors

HA — Canned motor agitator

Sealless agitator driveline, bottom- or side-mounted: mixing, homogenizing, emulsifying and solids suspension from vacuum to high pressure, 200–960 rpm, to 300 °C, 30 kW — chemical, food and pharma reactors.

sealless agitatorreactor drive
Transformer oil circulation canned motor pump type TR TA TAL

TR / TA / TAL — Transformer oil pumps

Insulation-oil circulation for static and mobile transformers and converters: lightweight, any-position mounting, direct into pipework. −40 to +90 °C, Q to 150 m³/h, H to 20 m, 37 kW — TAL for locomotive transformers.

transformer oil pumplocomotive cooling
HX regenerative turbine sealless canned motor pump

HX — Regenerative turbine type

Sealless regenerative turbine pump for low flow at high head: Q 0.5–3 m³/h, H to 90 m, 15 kW. Zero-leakage handling of volatile, expensive fluids — cleaning agents and thermal-control fluids; Ex-proof builds for petrochemical OEM skids.

low flow high headregenerative turbine
Structure & monitoring

Inside the can: construction details and protective instrumentation

Annotated cutaway of a canned motor pump: embedded RTD, explosion-proof terminal box, HPB monitor, API 610 changeable seal rings, API 685 secondary containment, bearing materials
Annotated H-series cutaway: embedded winding thermistors/RTD, Ex d terminal box, HPB condition monitor, axial-thrust auto-balance, API 685 secondary containment and changeable wear parts.
ComponentFunctionTypical options
Casing & impellerHydraulic end, static-sealed onlyCS / SS304 / SS316 / SS316L; closed, semi-open or multi-stage impellers
Stator canHermetic barrier over the windingSS304 / SS316 / Hastelloy C; H, C, Super-C insulation classes
Rotor canSeals the rotor assemblySS316 / Hastelloy C; eddy-loss-optimized thickness
Journal bearingsFluid-film support, product-lubricatedSiC, SSC, CFTE (carbon graphite), steatite
Thrust collar / bearing shaftAxial thrust balanceSiC / tungsten carbide / Stellite hard chrome
Suction strainer / filterProtects bearings & clearancesRemovable, cleanable insert
Terminal boxWinding connection, Ex-ratedExd II C T1–4 / Exd II B T1–4, IP54–68
TRG / HPB monitorBearing wear, rotation, phase-failure detectionLocal meter, remote-mount converter, 4–20 mA to PLC/DCS
Winding protectionOverheat protectionEmbedded bimetal thermostats or RTD (Pt100) at hot spot
Built-in protections. Embedded bimetal strips or RTDs trip the pump before windings overheat; the HPB system detects bearing wear, wrong rotation and phase failure and can output 4–20 mA or a digital signal to the plant PLC/DCS; anti-condensation space heaters keep the winding dry on standby.
Performance

Hydraulic and motor range of the H-series

2–1,200 m³/hCapacity Q
2–800 mTotal head H
0.4–220 kWMotor output
2/4/6 pole2,900 / 1,450 / 960 rpm · 50/60 Hz
Motor frame seriesRated outputPoles / speed (50 Hz)Typical duty
112–313 (2-pole)0.4–15 kW2 / ≈2,900 rpmSmall transfer, sampling, refrigerant duty
212–913 (2-pole)18.5–315 kW2 / ≈2,900 rpmChemical & petrochemical process
321–922 (4-pole)2.2–160 kW4 / ≈1,450 rpmCirculation, heat-transfer, slurries
Super heat-resistant (312–714)3.7–90 kW2–4 poleHT / HV-X builds to 450 °C
Back-to-back multi-stage sealless canned motor pump cross-section for 800 m head
HP-M back-to-back multi-stage sealless pump: staged impellers reach 800 m head with zero leakage — the canned-motor answer to high-head chemical transfer.
Multi-stage canned motor pump unit on baseplate with motor barrel
HP-M multi-stage canned motor pump unit on its baseplate — barrel motor, staged hydraulics, no coupling, no seal. Max 200 m³/h, 800 m, 400 kW, 400 °C.
Selection from the motor datasheet. Frames carry matched insulation classes (F / H / C / Super-C), winding thermostats or RTDs, and anti-condensation heaters. Non-standard voltages (200–690 V) and 60 Hz ratings are available — the pump and canned motor combination charts match every frame to its hydraulic series.
Materials

Material of construction — matched to 600+ fluids

Wetted parts and cans are selected against corrosivity, temperature and contamination. Standard series plus exotic metallurgy on request (titanium, Monel, nickel, Alloy 20, 904L, duplex CD4MCu / 2205 / 2507).

PartCarbon steel (CS)Stainless SS304Stainless SS316
CasingZG230-450SCS13SCS14
Impeller / adapter / bearing housingsZG230-450SCS13SCS14
Motor flange / stator flangeSS304SS304SS304
Stator can (standard)SS304 (H/HT variants: Hastelloy C)SS304SS304
Rotor canHastelloy CHastelloy CHastelloy C
Shaft / shaft sleeve / thrust collarSS316 / SS316L (+W.C.)SS316 / SS316LSS316 / SS316L
BearingsSS304 + SiC, or CFTE carbon graphite / SSC / steatite, PTFE composites
GasketsPTFE, metal spiral wound, aromatic & cryogenic grades
Insulation materialsClass H, C, Super-C heat-resistant systems
Corrosion margin matters twice. The can wall is only fractions of a millimeter — select metallurgy for the full design life, not just year one. For chloride, acid and alkali services specify SS316L minimum; Hastelloy C cans and SiC bearings for hot concentrated acids and caustic.
Selection

Specifying a sealless canned motor pump in five steps

The more of this you can tell us, the closer the first quotation lands to the pump you actually need.

1

Define process parameters

Capacity Q, differential head H, liquid name, density, temperature, system & vapor pressure, viscosity, NPSH available — plus normal / min / max values.

2

Choose the hydraulic model & check NPSH

Select pump size from single-stage performance curves; pick the highest-efficiency area with comparable flat NPSHr; add NPSHa ≥ NPSHr + 0.5 m margin.

3

Calculate shaft power

P = ρ·g·Q·H / (η × 3.6×10⁶) with η from the curve; add margin for viscosity or slurry before sizing the motor frame.

4

Match the canned motor frame

Pick frame No., poles (2/4/6), voltage and Ex class; motor protection (thermostats, RTD, HPB) is specified at the same time.

5

Fix the construction type

Temperature → HT/HV-X; easy-vaporized → HN/HNP; solids → HS/HJ back-flushing or gas-sealed; high melting point → HR-S/HR-Y jacketed; high head → HP-M multi-stage; in-tank → HE submersible.

ApplicationFluidTemp.Recommended typeMaterial route
Chlorine / chlor-alkaliLiquid Cl₂, NaOH, HCl, brineamb.–120 °CHN / HVSS316L, Hastelloy C can, SiC bearings
Heat-transfer systemsThermal oil, Dowtherm, KYKto 450 °CHT / HV-XCS / SS304, Super-C insulation
Refrigeration & gasLPG, LNG, NH₃, freons, CO₂−200–40 °CHN / HN-M reverse circulationSS304/316, cryogenic gaskets
High-melting mediaBitumen, wax, caprolactamto 300 °CHR-S / HR-Y full jacketCS + steam/oil jacket
Particle-laden fluidsCrystallizer circulation, slurriesamb.–150 °CHS back-flushing / HJ gas-sealedHardened sleeves, SiC
Nuclear / supercriticalHigh-P hot waterto 400 °CHTM verticalSS, 40 MPa design
High-head transferVarious chemicalsto 400 °CMulti-stage HP-MPer fluid
Low-flow high-head dosingVolatile & expensive fluidsamb.–350 °CHX regenerative turbineSS316 / Ex-proof motor
Protection is part of the selection. Specify minimum-flow orifice or auto-recirculation, liquid-presence / dry-run protection, TRG or HPB monitoring to the control room, and (for HT builds) confirm heating & cooling procedures before start-up and shutdown to avoid thermal shock to gaskets and cans.
Applications

Where sealless canned motor pumps earn their keep

Chemical, petrochemical, petroleum refining, textile, central air conditioning, nuclear power, locomotive cooling, aerospace and hydrogen production — wherever a leak is not an option: liquid chlorine transfer pumps for chlor-alkali plants, hot oil circulation pumps on polyester lines, ammonia and LNG loading pumps at tank farms, refrigerant recirculation in refrigeration systems, and hermetic agitator drives on reactors.

Chlor-alkali & chlorine

Liquid chlorine transfer, caustic soda circulation, hydrochloric acid and brine — the reference application for API 685 sealless pumps, where a single seal leak is a reportable incident.

Heat transfer & thermal oil

HT / HV-X canned motor pumps circulate Dowtherm, KYK and other thermal fluids to 450 °C with no seal to coke or fail — standard on polyester, CAP and synthetic fiber plants.

Refrigerants, LPG & cryogenics

HN reverse-circulation builds pump ammonia, propane, propylene, freons and LNG at −200 °C without flashing or leaks — tank farms, loading bays and gas processing.

Nuclear & supercritical power

Vertical HTM canned motor pumps serve nuclear and supercritical loops — hermetic containment is the entire point; shielded motor designs trace back to reactor coolant duty.

Locomotive, rail & aerospace

Central AC and high-speed train cooling circuits, aerospace fuel and hydrogen-peroxide systems — compact, silent, zero-maintenance units approved for national defense supply.

Pharma, food & fine chemicals

Hermetic pumping keeps product uncontaminated by air, lubricant or seal wear — TDI, acrylates, solvents and monomers stay pure and stay inside the pipe.

Sealless units across industries — built examples

Vertical reverse circulation canned motor pump for volatile hydrocarbons
HW vertical unit — large-capacity volatile hydrocarbon transfer, 2,000 m³/h
Submersible in-tank canned motor pump
HE in-tank build — tank-roof mounting, minimum NPSH, 360 m head
Jacketed high melting point canned motor pump
HR-S jacketed pump — waxes and high-melting media kept liquid
Super high temperature canned motor pump with heating jacket
HR-Y super-HT pump — hottest melting-point duties, no cooling water

Typical fluids handled by canned motor pumps

CategoryRepresentative fluids
AcidsSulfuric, hydrazinic, nitric, mixed acids, phosphoric, hydrofluoric, hydrocyanic, acetic, chromic, formic, propionic, boric, succinic
Alkalis & saltsCaustic soda/potash, sodium & calcium hydroxide, ammonia water, sodium & ammonium bicarbonate, lithium bromide, ammonium sulfate, alum, brines
Aromatics & hydrocarbonsBenzene, toluene, xylene, phenol, TDI, naphthalene, butane, nonane, cyclohexane, hexane, aniline, PVC, PVA, PIA, acrylic acid
Halogens & refrigerantsLiquid chlorine, bromine, silicon tetrachloride, phosphorus trichloride, Freon R-11/R-12/R-22, DEC, propane, LNG, ethylene, butadiene
Heat transfer & cryogenicDowtherm, molten salts, KYK, SK oil, liquid nitrogen, liquid oxygen, liquid CO₂
Water & coolantsBoiler water, pure water, sea water, locomotive cooling water, ethylene glycol coolants, cutting fluids
Inside the factory

Where sealless pumps are built and proven

Every canned motor pump leaves the plant only after stator can winding, rotor balancing and a full hydraulic run test at duty point. Click any photo to enlarge.

PMI spectrometer material verification on a pump flange
Material verification — PMI spectrometer confirms alloy grade on every flange and wetted part before assembly
Finished stainless steel rotor assemblies with impellers
Rotor assemblies — machined shafts with balanced impellers, ready to enter the motor barrel
Workers joining the motor barrel and pump end on the baseplate
Final assembly — pump end and motor barrel joined and aligned on the steel baseplate
Stainless steel volute casings finished on pallets
Stainless casings — machined and passivated volutes awaiting pairing with their motor units
Comprehensive performance test centre with pumps on test stands
Performance test centre — every unit run at rated head and flow; TRG readings logged before release
Finished painted pump sets on skids in the warehouse
Finished sets — Ex-proof canned motor pump units painted, on skids, awaiting dispatch
Packed pumps in VCI wrap loaded into export wooden crates
Packing line — VCI-wrapped units crated for export shipment worldwide
Operation & maintenance

Running rules and preventive checks for sealless pumps

Golden rules of operation

  • Never run dry — prime completely and vent the motor housing before start; open all reverse-circulation lines first
  • Never keep the discharge valve closed for more than 1 minute; never run with the TRG meter in the red zone
  • If the motor trips, find the cause before restarting — blocked circulation overheats bearings and windings fast
  • Avoid rapid temperature changes; follow published heating / cooling procedures on hot services
  • Keep the suction strainer clean — foreign matter is the No.1 bearing killer
  • Assume residual liquid is present before opening any bolt; loosen drain plugs slowly

First-response troubleshooting

  • TRG / current rising → bearing wear, rotor rubbing or low circulation flow: check strainer, vent, clearance
  • Capacity drop / pressure not developed → air not fully vented, suction loss, impeller clearance — re-prime and re-check NPSH
  • Noise & vibration → cavitation, misaligned rotor unit or worn bearings — verify suction conditions first
  • Winding fault → measure stator insulation resistance regularly; it is the earliest warning of can perforation
  • Rain water / moisture in terminal box → repair gaskets and conduit sealing immediately

Bearing wear limits (per motor frame)

Motor frame No.Diameter wear limit (φA−φB)Length LAction
1100.3 mm44.2 mmReplace bearing and set screw when measured wear exceeds the limit; check thrust collar and shaft sleeve at the same time
2100.4 mm49.2 mm
310/2200.4 mm59.2 mm
410/3200.4 mm69.2 mm
510/420–610/5200.5 mm78–113 mm
710/620–7200.5–0.6 mm119–128.5 mm
Instrumentation and protection system components for canned motor pumps
Instrumentation & protection system hardware — sensors, monitors and converters wired to the plant DCS.
CodeSensor / function
ZE1Shaft-position sensor — bearing radial wear monitor (HPB)
ZE2Shaft-position sensor — bearing axial wear monitor (HPA)
TE1Thermal cutout — stator winding overheat protection
TE2Thermowell temperature sensor — circulation-flow thermal protection
PEPressure sensor — stator can leakage indication
RERotation monitor — motor rotation indication
JEOutput sensor — motor over/under-load protection
LE1Level sensor — dry-running protection
FAQ

Frequently asked questions about canned motor pumps

What is a canned motor pump?
A sealless centrifugal pump whose impeller is mounted directly on the rotor of a special motor inside one hermetically sealed housing. Thin non-magnetic cans isolate the stator and rotor windings from the pumped liquid; static gaskets on the casing are the only joints, so the pump is inherently leak-free.
Canned motor pump vs magnetic drive pump — which should I choose?
Both are sealless and zero-leakage. Canned motor pumps integrate motor and hydraulics in one unit: shorter shaft, no coupling alignment, better pressure capability and double containment even if a can fails. Mag-drive pumps use a standard motor and suit simpler duties but risk immediate external leakage if the containment shell fails. For toxic, high-pressure or high-temperature services (API 685), canned motor construction is generally the stronger choice; for smaller clean duties mag-drive can be more economical.
Can a canned motor pump run dry?
No. The pumped liquid cools the motor and lubricates the fluid-film bearings — dry running destroys bearings and windings within seconds. Always fit liquid-presence or dry-run protection and minimum-flow recirculation, and vent the motor housing completely before start-up.
What efficiency should I expect?
Hydraulic efficiency is comparable to an equivalent sealed centrifugal pump, minus a few points of eddy-current loss in the shield sleeves. In real projects the elimination of seal flushing, cooling and standby seal maintenance usually more than repays those points over the lifecycle.
Which fluids cannot be handled?
Very abrasive slurries (use the back-flushing HS type below ~30% solids), fluids above several hundred cP viscosity, and liquids that polymerize or solidify inside the rotor chamber without jacketing. Otherwise the catalog covers 600+ fluids from −200 °C to 450 °C, including liquid chlorine, LNG, ammonia, thermal oils and high-pressure hot water.
Do you build to API 685?
Yes — sealless formats with secondary containment, changeable wear parts per API 610 practice, Ex d II C T1–4 / Ex d II B T1–4 terminal boxes, HPB/TRG bearing-wear monitoring and 2× API nozzle-load flanges. Flange standards: ANSI, ASME, HG, DIN, JIS, GB, SH.
How is bearing wear monitored?
A TRG meter indicates rotor axial position (bearing wear) with a red zone that mandates a stop; the HPB system adds bearing-wear detection, wrong-rotation and phase-failure alarms, outputting 4–20 mA or digital signals to PLC/DCS. Periodic stator insulation-resistance measurement is the earliest warning of can perforation.
How does it handle high temperature media like heat-transfer oil?
HT isolation types thermally separate pump and motor housings with an air gap and restrict heat transfer via the adapter; HV-X super-high-temperature builds use insulation materials needing no cooling to 400 °C; HR full-jacketed builds keep high-melting fluids liquid in the casing. Follow the specified heating and cooling ramps to protect gaskets and cans.
Are explosion-proof canned motor pumps available?
Yes. Standard Ex-proof terminal boxes are rated Exd II C T1–4 / Exd II B T1–4 with ingress protection IP54–68, and anti-condensation space heaters are available for outdoor and humid installation.
What data do you need for a quotation?
Liquid name & density, normal/min/max capacity, required differential head, temperature, vapor pressure at pumping temperature, NPSH available, viscosity, solids content, Ex requirements and driver voltage/frequency. Then we select type, materials and motor frame from the combination charts.
Request a quote

Send us your duty — we’ll return a selection

ZGPV engineers size the hydraulic, the canned motor frame and the construction type together, then quote with performance curve, materials and Ex certification. Company: Sichuan Zigong Pump & Valve Co., Ltd. — Add: No.56, Golden Hill Rd., Hi-Tech Industrial Zone, Yantan District, Zigong, Sichuan, China · Tel: +86 28 8518 1162 · E-mail: sales@zgpumpvalve.com · www.zgpumpvalve.com

Include in your enquiry

  • Liquid name, density, viscosity, solids & corrosivity
  • Q (min/nom/max), H, NPSH available, vapor pressure
  • Temperature profile incl. heating / cooling ramps
  • Ex area classification & terminal-box grade
  • Voltage / frequency / poles; monitoring outputs to DCS

What you receive

  • Construction type + dimensioned general arrangement
  • Performance curve tested per ISO 9906 / GB/T 3216
  • Material certificate line-up (cans, bearings, gaskets)
  • Motor datasheet with protection & monitoring list
  • Operation & maintenance manual (English available)