Magnetic Drive Pumps: Sealless Chemical Process Pump Selection
Iwaki magnetic drive centrifugal pump series, flow rate and head ranges, casing materials, dry-running and self-priming capabilities, and ISO 2858 drop-in replacement options.
Three Questions That Determine Selection
- Which casing material and temperature? GFRPP, CFRPVDF, CFRETFE, PFA or SUS316; liquid temperature varies by series, such as 0–80 °C (MD, MX), -20/105 °C (MDM CFRETFE), -20/150 °C (MDM PFA) and -30/150 °C (MP). Consult the manufacturer's chemical resistance chart for the specific fluid.
- Which flow rate and head? Ranges extend from 135 L/min and 14.3 m on the MD series up to 5,000 L/min and 98 m on the MDW series; table values are maximums and the operating duty point is selected from the pump curve.
- Which operating conditions? Dry-running risk, suction elevation (whether self-priming is required), ISO 2858 replacement and solid particle content determine the series.
How a Magnetic Coupling Works
In a magnetic drive centrifugal pump, the outer drive magnet rotated by the motor shaft attracts and turns the inner impeller magnet across the sealed wall of the rear casing. Because no shaft penetrates between the impeller and the motor, there is no mechanical seal, no seal wear and no seal leakage. Iwaki implements this construction with GFRPP in the MD series, GFRPP and CFRETFE in the MX series, ETFE and PFA casings in the MDM, MDE and MDW series, and SUS316 casings in the MP, MTFO and MEK series.
A magnetic coupling also introduces specific operating boundaries. The MD series manual notes that the pump contains a powerful magnet, must not be used with liquids containing magnetic metals such as iron or nickel, and that slurries will wear the bearings. Rapidly opening or closing valves can cause the coupling to decouple. For this reason, selection evaluates not only flow rate and head, but also fluid content and operating sequence. If metered chemical injection is needed, see chemical dosing and transfer pumps.
Plastic and Fluoroplastic Magnetic Drive Pumps
| Series | Casing | Max flow | Max head | Liquid temperature | Key feature |
|---|---|---|---|---|---|
| MD | GFRPP | 135 L/min | 14.3 m | 0–80 °C | Compact; 50 models; viscosity limit 30 mPa·s |
| MD-V | CFRPVDF | 86 L/min | 14.3 m | 0–80 °C | Built-in OEM equipment applications |
| MD-F | CFRETFE | 125 L/min | 10.5 m | 0–80 °C | Transfer of strong acids, alkalis and organic solvents |
| MX | GFRPP | 800 L/min | 35 m | 0–80 °C | Self-radiating structure; 0.15–4 kW |
| MX-F | CFRETFE | 510 L/min | 28 m | 0–80 °C | Same dry-running resistance as MX; 0.26–2.2 kW |
| MXM | CFRETFE, ductile iron armor | 600 L/min | 29 m | -10/90 °C; high-temperature version 105 °C | Heavy duty; dual containment |
| SMX | GFRPP | 440 L/min | 25.5 m | 0–80 °C | Self-priming: 4 m in 90 seconds on clean water |
| SMX-F | CFRETFE | 440 L/min | 25.5 m | 0–80 °C | Self-priming; high corrosion resistance |
| MDM | CFRETFE / PFA | Series max 1,400 L/min | 74 m | -20/105 °C (CFRETFE); -20/150 °C (PFA) | Patented non-contact system (CF type); ISO 2858; 1.5–15 kW |
| MDM NP | PFA / CFRETFE | 1,400 L/min | 70 m | -20/150 °C (PFA) | ISO 2858 long-coupled; 4–15 kW |
| MDE | ETFE / PFA | 4,000 L/min | Above 50 m (MDE50-200: 53.0 m) | 0–100 °C | Metal-free wetted end; casing pressure 1.6 MPa |
| MDW | ETFE / PFA | 5,000 L/min | 98 m | -10/120 °C (MDW50); -10/105 °C (MDW80/100) | 11–75 kW; flanged motor option (MDW-F) |
| NRD / RD | GFRPP(E) | 5.1–140 L/min | 15 m | 0–80 °C | Brushless DC canned motor; 24 VDC; 1-5 VDC flow control |
| MDT | GFRPPS, CFRPEEK | 20 L/min | 0.35 MPa pressure | -20/65 °C (L); -20/95 °C (H) | Metal-free; viscosity limit 2 mPa·s |
Metallic Magnetic Drive Pumps
| Series | Casing | Max flow | Max head | Liquid temperature | Key feature |
|---|---|---|---|---|---|
| MP | SUS316 | 1,100 L/min (50 Hz); 1,300 L/min (60 Hz) | 80 m (50 Hz); 120 m (60 Hz) | -30/+150 °C; MH version +280 °C; ML version -80 °C | Fast maintenance via PB block replacement; viscosity 300 mPa·s |
| MMP | SUS316 | 80 L/min | 20 m (50 Hz); 28 m (60 Hz) | -30/+150 °C | Compact; ATEX-compliant version; viscosity 100 mPa·s |
| MDK | SCS14 casing, SUS316 impeller | Up to 60 L/min | Pressure 0.6–0.8 MPa | 0–80 °C | Regenerative turbine type; specific gravity limit 1.3 |
| MEK | SS316 | Up to 60 L/min | Up to 45 m | -20/+120 °C | SiC-D bearing; design pressure 1.0 MPa |
| MTFO | SUS316 (SCS14) | 1,600 L/min (50 Hz); 1,200 L/min (60 Hz) | 80 m (50 Hz); 85 m (60 Hz) | Standard -20/+120 °C; special -80/+280 °C | ISO 2858 compliant open impeller; ATEX; 2.2–22 kW |
Values are taken from Iwaki catalogs and datasheets. For magnetic drive gear pumps (GM-V and MDG) and all process pump series, see pumps and Iwaki.
Dry Running, Cavitation and Closed-Valve Operation
MX and MX-F
The patented self-radiating structure circulates liquid around the spindle and bearing through holes in the impeller and magnet capsule. Resistance to short-term dry running, cavitation and closed-discharge operation is improved. On the MX-F, to avoid continuous operation against a closed discharge, a minimum flow of 10 L/min (20 L/min for MX-F402/403) is specified. The optional Iwaki DR-20 current-sensing protector detects dry running, air ingress on suction and overload, stopping the pump.
MDM
The patented non-contact system prevents high-strength magnets from rubbing against the rear casing thrust ring and melting the fluororesin through frictional heat. This protection applies only to the CF type (high-density carbon bearing); dry running is not permitted on the KK type.
MD
The MD manual requires that the pump never be run dry, never be operated with the suction or discharge valve closed, and that the discharge valve not remain closed for longer than one minute. For the metallic MP and MTFO series, the optional DRN series current-sensing protector provides dry-running and overload protection.
Installation and Operating Rules (MD Manual)
- Suction: The MD series is not self-priming; install the pump at least 30 cm below the suction liquid level and prime it with liquid before initial startup. Route the suction line with a 1/100 upward slope toward the pump, avoid loops that can trap vapor pockets, and keep the tank liquid level at least 30 cm above the tank outlet.
- Piping: Install a ball valve close to the pump for flow adjustment and maintenance, a pressure gauge for discharge pressure, a drain valve between the suction valve and pump inlet, an air vent line on long horizontal discharge runs, and a check valve on long vertical discharge runs. Water hammer on long discharge lines can damage the pump; a check valve is recommended.
- Startup: Start the primed pump with the suction valve fully open and the discharge valve fully closed, then open the discharge valve gradually. To degas an unvented chamber, run the pump with an open discharge line for one second and repeat the procedure three to five times.
- Shutdown and storage: Close the discharge valve slowly before stopping the pump; for long-term storage, drain the liquid from the pump and run it with clean water for 5 minutes every three months to prevent the motor bearing from seizing.
- Safety: The pump contains a strong magnet; keep away from magnetically sensitive devices such as watches. Ambient temperature range is 0–40 °C; do not operate the pump in direct sunlight, rain, or dusty or humid environments.
Information Required for Pump Selection
Liquid
Chemical name, concentration, specific gravity and viscosity. The MX documentation recommends leaving a 5–10 percent margin on motor power as specific gravity increases; the viscosity limit is 30 mPa·s on the MD series and the specific gravity limit is 1.3 on the MDK series.
Flow and head
Required flow rate (L/min or m³/h) and total dynamic head. Values shown in tables are maximums; the duty point is read from the pump curve.
Temperature and environment
Liquid temperature, ambient temperature, hazardous area classification (ATEX-compliant versions available for MMP and MTFO) and installation location.
Suction condition
Whether suction is flooded or lift; if suction lift is required, select a self-priming series such as SMX or SMX-F.
Electrical supply
220–240 V single-phase on the MD series; 400/440 V three-phase on larger frames. The NRD/RD series operates on 24 VDC.
Maintenance approach
Back pullout construction on MDM, MDE, MDW and MTFO allows servicing without disturbing the piping; PB block replacement on MP shortens downtime.
See dosing pumps and dosing pump maintenance for metering pumps and maintenance, and polymer dosing pumps for viscous fluids.
Frequently Asked Questions on Magnetic Drive Pumps
Operating principle, dry running, self-priming, casing materials, ISO 2858 replacement and solids handling.
What is a magnetic drive pump and how does it differ from a mechanically sealed pump?
In a magnetic drive (magnetically coupled) pump, the drive magnet on the motor shaft rotates the impeller magnet inside the pump chamber through a hermetically sealed rear casing. Because the pump chamber remains completely enclosed by the casing and covers, there is no conventional mechanical shaft seal, eliminating shaft seal wear and associated chemical leakage. Where metered chemical feed is required, dosing pumps are selected instead.
Can a magnetic drive pump run dry?
It depends on the series. The Iwaki MD series manual requires that the pump never be run dry. In the MX and MX-F series, a patented self-radiating structure improves resistance to short-term dry running, cavitation and closed-discharge operation; the carbon-bearing CV/CE type is the most tolerant option for brief dry running. In the MDM series, the patented non-contact system resists dry running only in the CF type; dry running is not permitted in the KK type. Current-sensing protectors such as the DR-20 are available as options.
Are there self-priming magnetic drive pumps?
Yes. The SMX and SMX-F series self-prime up to 4 m in 90 seconds on clean water; the suction line diameter must match the suction port and suction pipe length must not exceed 4.7 m. The GM-V magnetic gear pump is self-priming up to 1 m when wetted. The MD series is not self-priming; the manual recommends flooded suction, installing the pump 30 cm or more below the suction liquid level.
Should a plastic casing or a metal casing be selected?
Selection depends on the chemical, temperature and pressure. On the plastic side, casings include GFRPP (MD, MX, SMX), CFRPVDF (MD-V), CFRETFE (MD-F, MX-F, MXM, SMX-F) and PFA/ETFE (MDM, MDE, MDW); the MD-F documentation notes that CFRETFE offers a wider chemical resistance range than CFRPVDF. On the metal side, SUS316 (MP, MMP, MEK, MTFO) and SCS14 (MDK) are available; the MP series operates from -30 to +150 °C. For a specific chemical, always consult the manufacturer's chemical resistance table; this page does not assign chemical-material pairings.
Can a magnetic drive pump replace an ISO 2858 pump directly?
Yes, without modifying the piping. The MDM NP series is an ISO 2858 long-coupled design built for one-to-one replacement of other ISO standard pumps; MDE conforms to ISO 2858/3661/5199, MDW to ISO 2858/3661 and MTFO to ISO 2858. MDM, MDE, MDW and MTFO feature a back pullout design that allows access to internal parts without disturbing the piping.
Can solids-laden liquids or slurries be pumped?
It depends on the series. The Iwaki MD series manual prohibits slurries because they abrade the pump bearings, and also prohibits liquids containing metals such as iron and nickel. In the MX series, the AV/AE type with full alumina ceramic bearings is specified for liquids containing abrasive particles. In the MTFO series, slurries containing up to 30 percent solids are possible with factory approval. In applications involving solids, the series and bearing type are confirmed with the manufacturer.
Why does the magnetic coupling decouple and how is it prevented?
The MD series manual states that sudden opening or closing of the suction or discharge valve can cause the magnetic coupling to decouple; if this occurs, power must be shut off immediately. Valves should be opened and closed gradually, the pump must not be operated with the suction or discharge valve closed, and the discharge valve must not be left closed for longer than one minute. During shutdown, the discharge valve is closed slowly; solenoid valves are not used.
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