A Complete Guide to Magnetic Drive Pumps
Contents
- Introduction & the basics - What is a magnetic drive pump? How does a mag drive pump work? What makes up a mag drive pump (Key components)
- Different types & variations of mag drive pumps
- Performance & capabilities - Plus the advantages to using plastic pumps & typical applications & industries.
- Operational considerations - Can they run dry? Common failures & how to prevent them
Introduction & the basics
What is a magnetic drive pump?
A magnetically driven (mag drive) pump uses a magnetic coupling to transmit power from the motor to the impeller. Unlike traditional pumps that use a direct drive shaft, a mag drive eliminates the need for a mechanical seal, which uses the method of a film of liquid covering the seal faces (which has a greater chance of liquid leakage). The magnetic coupling allows the pump to operate without any physical contact between the driving and driven components, resulting in a hermetically sealed & leak free design.
How does a mag drive pump work?
A magnetic drive pump works just like any other centrifugal pump with fluid entering the pump inlet and into the eye of the impeller, exiting at the outer diameter and directed through the volute to the pump outlet.
Where it differs is that the impeller is driven by two magnets rotating than being directly coupled to the motor. As the motor shaft turns the drive magnet, that in turn rotates the inner magnet and the impeller. This eliminates the need for a mechanical seal as the fluid is fully enclosed, allowing the pump to run without the risk of any leakage of potentially harmful liquids.
What makes up a mag drive pump (Key components)
- Outer (drive) magnet assembly – Connected to the motor shaft, transfers torque through the containment shell without physical contact.
- Inner magnet assembly – Mounted on the impeller inside the pump; rotates in sync with the drive magnet to move the fluid.
- Containment Shell – a non-magnetic barrier that fully seals the liquid chamber. We use materials like reinforced plastic (PP/ETFE) or metallic shells with PFA lining dependant on the range.
- Impeller – Hydraulically optimised to generate flow & pressure – our mag drive pump designs include high-efficiency geometries and optional reinforced or ETFE-lined versions built for aggressive chemicals.
- Pump casing / Volute – this houses the impeller and directs the flow. Crest offer solid plastic casings or metallic casings with corrosion-resistant linings.
- Bearings & shaft support system – Typically made from ceramic, carbon, silicon carbide, or combinations dependant on the chemical used and duty. Both the Crest Assoma AMXi & AME ranges include enhanced bearing protection and axial/radial load balancing features,
- Auxiliary cooling/lubrication channels - used to circulate process fluid to cool and lubricate internal bearings.
- Motor (or canned motor assembly)
Different types & variations of mag drive pumps
Magnetic drive pumps come in several configurations, each designed to handle specific industrial requirements, fluids, and installation environments. The most common types include:
- Horizontal centrifugal mag drive pumps – the most common type of mag drive and are ideal for general chemical transfer and recirculation as well as high corrosive, heavy duty applications. They feature a horizontal shaft and are available in both plastic and metallic-lined designs.
- Vertical sump / vertical in line mag drives – Designed for installations with limited floor space, or where the pump needs to sit above a tank. The motor remains outside the liquid, whilst the pump end is submerged. Ideal for corrosive sumps, etching baths & clean-in-place (CIP) systems.
- Canned motor mag drive pumps – Instead of a traditional motor & magnet coupling, canned motor pumps integrate the motor and pump into one hermetically sealed unit offering quiet, efficient and leak-free operation.
- Metallic & lined magnetic drive pumps – These pumps use metal casings (often stainless steel or ductile iron) lined with corrosion-resistant materials like PFA or ETFE. Ideal for high temperature or high-pressure applications where plastic pumps aren’t suitable.
- Plastic magnetic drive pumps – built entirely from corrosion resistant plastics such as Polypropylene or ETFE for maximum chemical compatibility. These are lightweight, cost-effective and widely used in both the chemical and wastewater treatment industries.
- ANSI Mag drive pumps – ANSI or ISO pump comply with international dimensional standards. Crest Pumps can now exclusively offer the USA made Truflo TNP ANSI mag drive. The TNP range incorporates a ductile iron casing that is lined with a fluoropolymer. This combination of materials allows for the mechanical strength of metal with the corrosion resistance of a non-metallic lining.
Performance & capabilities
Mag drive pumps are engineered to deliver reliable, leak-free performance across a wide range of industrial applications. Their hydraulics mirror standard centrifugal pumps, but with a sealless magnetic coupling which enable continuous operation with minimal maintenance and exception chemical resistance.
Depending on materials of construction (e.g. Polypropylene, ETFE, PFA-lined metals or high-grade ceramics) mag drives can safely handle highly corrosive acids, alkalis, plating solutions, solvents & ultra-pure process fluids. They perform best with clean, low viscosity liquids, however upgraded designs with reinforced bearings and internal cooling can tolerate high temperatures, solids traces and demanding duty cycles. Plastic mag drives usually operate comfortably up to 80-95°C, whilst the metallic or PFA-lined models can extend well above this range.
One of the main advantages is their leak-free operation. By eliminating mechanical seals (the most common failure point in conventional pumps) mag drives offer excellent containment for hazardous or environmentally sensitive fluids, making them suitable for industries where contamination control is essential.
With correct sizing & installation mag drive pumps offer long service life, low running costs & consistent, dependable performance.
Advantages of using plastic
Traditionally when faced with selecting pumps for handling corrosive liquids, engineers were faced with using pumps made from high nickel content alloys such as Hastelloy or using pumps lined with ceramic or glass. However, in the last 50 years plastics have come a long way and are now readily available in bar from up to 500mm in diameter for Polypropylene, PVC, PVDF & Polyethylene.
The advantages of using plastic pumps are many fold:
- They are less expensive to manufacture, meaning cheaper prices for the customer.
- Faster lead times!
- Better corrosion resistance giving the pump a longer life.
- Lighter in weight giving more manoeuvrability.
Typical applications & industries
- Chemical processing – Transfer of corrosive acids & alkalis, chemical dosing, solvent handling & circulation, reactor feed & recirculation.
- Water & wastewater treatment – Ph correction systems, chemical recirculation in scrubbers & neutralisation tanks, polymer transfer, Sodium hypochlorite, caustic & acid dosing.
- Metal finishing & surface treatment – Electroplating & anodising line circulation, pickling, stripping and cleaning baths, hot acid transfer, fume scrubber recirculation loops.
- Pharmaceutical & biotechnology – high purity chemical transfer, CIP chemical circulation, applications requiring hermetic sealing to protect clean environments.
- Semiconductor & electronics manufacturing – handling of aggressive fluoride-based or oxidising solutions, low contamination recirculation systems, ultra-pure chemical transfer (etchants, developers, rinses).
- Food & beverage – CIP acid & caustic circulation, chemical dosing
- Plastic, composites & resin production – solvent circulation, high temperature or viscous chemical duties, transfer of corrosive catalysts & additives.
- Environmental & air pollution control – wet scrubber circulation loops, odour control chemical systems, effluent treatment & neutralisation.
- Power generation & renewable energy – battery chemical handling, cooling circuit chemical dosing, fuel cell & hydrogen-related chemical transfer.
- General industrial manufacturing – safe transfer of hazardous chemicals, leak-free pumping in sensitive production areas.
Across all these sectors, magnetic drive pumps provide a cost-effective, low-maintenance solution that enhances safety, reduces downtime, and delivers consistent performance.
Operational considerations
Can they run dry?
Unfortunately, errors can occur in a process which causes a pump to run dry. For a mechanically sealed pump this can cause an almost immediate failure to the seal. Some mag drive pumps are now available with special material bearings to prevent the onset of damage from running dry, but our Crest Assoma mag drive pumps go another step further with the patented circulation path for additional cooling.
Under normal operating conditions, the pumped liquid acts as lubrication between the rotating and stationary parts, and the heat generated by the rotational action is gently taken away by the circulating liquid. But, when a pump is starved of liquid, these moving parts generate heat from friction and as the heat builds up, damage will occur.
However, with the Crest Assoma mag drive range, a patented auxiliary circulation channel runs between the bearing and the magnet capsule. The pressure difference has a convection effect for cooling both the interior and exterior of the bearing thereby preventing the high temperature build up caused from dry running. Crucially, whilst the design allows for increased cooling there is no reduction in pump efficiency.
We must point out that there are many ways to run a pump dry, and this design feature is in no way a failsafe method (you should question any pump manufacturer that does make this claim). It depends upon how (e.g. completely closed inlet valve, air lock, foot valve failure, etc) and for how long the pump is run dry, as to how long the Crest Assoma mag drive range will run without damage being causers.
*This run dry design only applies to carbon/ceramic internal parts and not SSiC.
Common failures & how to prevent them
Dry Running – this is where the pump has no liquid inside, so the internal bearings overheat & wear out quickly.
How to prevent it:
- Make sure the pump is primed before starting.
- Fit level switches, flow switches, or power monitors.
- Use pump designs with improved bearing cooling.
Cavitation – occurs when not enough suction pressure causes bubbles to form and collapse inside the pump damaging the impeller.
How to prevent it:
- Keep suction pipework short, straight, and oversized.
- Avoid clogged strainers or tight valves.
- Install the pump close to the liquid level when possible.
Magnet Decoupling (Magnet Slip) – The inner magnet stops turning because the pump is overloaded, while the outer magnet keeps spinning.
How to prevent it:
- Don’t run the pump with the discharge valve fully closed.
- Choose a pump with strong enough magnets for your duty.
- Use power monitors to catch overloads early.
Bearing Wear – Bearings wear our faster when the fluid contains solids, gets too hot or doesn’t flow properly.
How to prevent it:
- Use strainers if the fluid contains grit or solids.
- Keep liquid flowing through the pump at all times.
- Select the right bearing materials for your chemical and temperature.
Chemical Attack or Temperature Damage – This happens when the pump materials weaken or deform if the liquid is incompatible or too hot.
How to prevent it:
- Check chemical compatibility before choosing materials.
- Stay within the pump’s temperature limits.
- Avoid sudden temperature changes on plastic pumps.
Blocked Cooling Channels – the small internal passages that cool and lubricate the bearings become blocked which causes overheating.
How to prevent it:
- Filter out crystals or solids that may clog internal paths.
- Regularly inspect pumps used with crystallising chemicals.
- Choose pumps with self-flushing or wider cooling channels.
Containment Shell Damage – Excess pressure or heat can crack or deform the containment shell which keeps the pump leak-free.
How to prevent it:
- Stay within pressure and temperature ratings.
- Prevent dry-running and overloading.
- Use reinforced or metallic shells for high demands.
Installation Issues – This can include misalignment, vibration, or pipe strain which caused the pump to wear out prematurely.
How to prevent it:
- Support pipework properly.
- Ensure correct alignment during installation.
- Follow the manufacturer’s installation guidelines.
Magnetic drive pumps offer a powerful combination of safety, reliability, and long-term efficiency, making them an ideal choice for handling corrosive, hazardous, or high-purity liquids across a wide range of industries. By understanding how they work, the different types available, and the key factors that affect performance, users can select the right pump for their process and operate it with confidence.
If you need further assistance with selection or technical support, Crest’s team is always ready to help. Just talk to us today.