A magnetic drive pump is the default sealless centrifugal choice when the process fluid is toxic, hot, expensive, or flammable and a mechanical seal is the weakest link in the loop. Selection turns on four numbers — flow, head, temperature, and specific gravity — and one chemistry table.
Across the OEM catalogs surveyed on 2026-08-06, mag-drive flows span roughly 3 GPM in miniature polypropylene units [S8] to 225 GPM / 128 ft head in the Iwaki MX(F) series [S7]; wetted materials range from GFRPP and PVDF through 316 SS with optional tungsten-carbide-coated shafts and Sm-Co magnet cups [S1][S2].
Flooded Suction and the Permanent-Magnet Coupling
Every mag-drive pump surveyed is a close-coupled centrifugal in which the motor torque crosses an air gap to an encapsulated driven magnet; there is no dynamic seal on the process side, which is why flooded suction is mandatory [S3][S6].
The stationary containment shell (often called the "magnet cup") sits between the drive and driven magnets and becomes the primary pressure boundary. In 316SS HP-series pumps that cup is 316 stainless; the magnets themselves are Samarium Cobalt (Sm-Co), which keeps magnetic strength and corrosion resistance stable up to roughly 350°F (177°C) when paired with Viton O-rings [S1]. GRI specifies NSF-certified versions, sealed ball-bearing motors, and class B insulation as standard on its 14110/14520/15651 lines at 75 PSI system pressure and 203°F (95°C) fluid temperature [S3].
Wetted-Material Selection by Service
Resin-bodied mag-drives dominate below 80°C and modest pressures: Iwaki's MX-70/100 use PP bodies, MX-250 to 401 use GFRPP, and the MX-402H through 505H step up to CFRPPS or CFRPEEK with high-purity alumina ceramic bearings and EPDM or FKM O-rings [S2].
For aggressive chemistry at higher temperatures, metallic bodies are the safer pick. The HP75MDSS and HP100MDSS are all-316SS with a 6.00" max impeller, carbon-graphite bushings, ceramic thrust washers, and 300 PSI (21 bar) working pressure, with optional tungsten-carbide-coated shafts and SiC bearings for slurries [S1]. Iwaki's MX(F) reaches 225 GPM and 128 ft (39 m) head in metallic wetted ends for chemical-process duty [S7], while March Pump's Series MDX (10 GPM, 17 ft, PP/Kynar/Delrin options) covers lab and plating flows [S8]. When the magnet material itself is the question, the magnetic material page catalogs the Sm-Co vs Nd-Fe-B trade-offs that drive this 177°C ceiling.
Performance Envelope: Flow, Head, and Temperature
Pick the smallest pump that meets the design point with at least 10% head margin; oversizing kills mag-drive efficiency because the bearings tolerate dry-running and closed-valve conditions only briefly. [S3]
Real envelopes from the surveyed catalogs: GRI's largest stock mag-drive (14520) hits 26 GPM at 35 ft head and 75 PSI; HP series reaches 65 GPM (15 m³/hr) at 165 ft (50 m) head with 0.5 GPM minimum flow [S1][S3]. Iwaki's MD/WMD line stops at 35.6 GPM and 66.6 ft (20.3 m) head — typical of small-process sealless pumps [S7]. Temperature windows are stricter than on sealed pumps because the O-ring and magnet adhesive set the ceiling: 80°C for resin MX, 95°C (203°F) for GRI, 177°C (350°F) for the HP metal series with Viton [S1][S2][S3]. March Pump's entry units operate at lower heads (4.6 ft to 17 ft) but accept 12V/24V brushless DC for OEM integration [S8].
Comparison: Main Mag-Drive Variants on Four Criteria
Four variants are in production and stocked across the surveyed catalogs: PP, GFRPP/CFRPPS, all-316SS, and miniature OEM. The table below lines them up on the criteria a buyer should score first. [S3]
Resin PP/GFRPP (Iwaki MX-70 to 401): max 80°C, low-to-mid flow (≤ 100 GPM class), best chemical resistance to acids/alkalis, lowest cost, lowest pressure rating [S2]. Reinforced CFRPPS/CFRPEEK (MX-402H to 505H): same 80°C cap but higher pressure tolerance, alumina bearings, lock-pin construction against uncoupling [S2]. All-316SS (HP series): up to 177°C, 300 PSI, 65 GPM / 165 ft, Sm-Co magnets, SiC or tungsten-carbide options for abrasives [S1]. Miniature OEM (GRI 14110/15651, March Series 1/2): 3 to 11 GPM, sub-50 ft head, 115/230V AC or DC brushless, NSF options for potable/medical [S3][S8]. For an overview of how these sealless designs fit in a plant's broader pumping fleet, the magnetic drive pump reference lays out the full mechanical architecture.
Failure Modes and Operating Constraints
The dominant failure mode on a mag-drive is bearing wear, followed by magnet decouple during overload — both accelerate sharply if the pump runs dry, against a closed discharge, or with insufficient NPSHa. [S1]
Iwaki explicitly rates the MX-250 to 505 for "brief periods of dry running" using its self-radiating structure and non-contact rear-thrust geometry, but stresses that continuous dead-head operation is not a design point [S2]. Price Pump notes that "motors 5 HP and above require VFD or soft starter" and that temperature limits depend on both the O-ring compound and the specific liquid [S1]. Magnet-cup pressure is the real safety boundary on metal units — 300 PSI for the HP series [S1] — and 75 PSI on most resin OEM units [S3]. Suction piping must keep the pump flooded; a mag-drive cannot clear air like a self-priming sealed pump. Process liquids with ferromagnetic particles will bind to the magnet cup and are a hard exclusion unless an isolation screen is fitted upstream.
Standards, Certification, and Sourcing Signals
For flammable or explosive service, the magnet-drive pump must be specified as a unit, not as a bare pump, and the assembly should carry ATEX (2014/34/EU) or IECEx certification appropriate to the zone; many chemical-plant builds now require dual ATEX + IECEx marking on the nameplate. [S1]
Wetted-material certifications to verify: NSF/ANSI 61 for potable water (offered on GRI models) [S3]; FDA-conformant elastomers (Viton, EPDM, Kalrez) where the line contacts pharmaceuticals [S1]. Motor compliance typically follows UL 1004 / NEMA MG-1 frame and insulation class B; March Pump offers 12V/24V brushless DC for battery and OEM embedded use [S8]. At the specification step, an electromagnetic flowmeter downstream of the mag-drive gives a leak-proof, sealless flow reading that matches the pump's no-leak philosophy. Installation manuals such as the T-Mag AMX series and Price Pump HP-MD manual are the authoritative sources for torque, fastener, and VFD wiring values [S1][S4][S5].
Who Should NOT Pick the Mainstream (All-316SS) Mag-Drive
An all-316SS HP-class unit is the wrong default for low-flow, low-head OEM loops where a GRI 14110/15651 or March Series 1/2 will deliver 3 to 11 GPM at a fraction of the cost and with 12/24V DC options the metal pump cannot match [S3][S8].
It is also the wrong pick for hot concentrated acids — HCl, H₂SO₄ above 90%, hot NaOH — where a resin GFRPP or CFRPEEK wet end (Iwaki MX-402H to 505H) outperforms 316SS at the cost of the 80°C temperature ceiling and lower maximum head [S2]. Slurries above ~3% solids by mass are also outside the sealless envelope: the internal clearance between driven magnet, spindle, and bearing is small, and even SiC bushings wear rapidly. Buyers sourcing mag-drives alongside the broader electric motor manufacturing equipment line should treat motor frame, insulation class, and VFD compatibility as a single matched spec, not three independent ones.
Track the next selection cycle against two signals: (1) published performance curves for the specific liquid being pumped, at the actual specific gravity and viscosity, not the water curve; (2) confirmation that the magnet-cup pressure rating and ATEX/IECEx zone marking both match the P&ID and the area classification drawing. For chemical-resistance cross-checks beyond the OEM guides, the Iwaki MX and T-Mag AMX chemical-resistance tables are the most commonly updated documents in the surveyed set [S2][S4].