ANSI B73.3 (also cited as ASME B73.3-2003 for the sealless variant) defines the dimensional envelope of horizontal chemical-process centrifugal pumps, including the magnetic-drive configuration where the process casing and bearing frame are dimensioned for drop-in interchangeability [S4][S5].
Conforming models span the full flow range typical of chemical service: the Magnatex MAXP alloy series reaches 2,000 GPM at 470 ft of head with a -150°F to +800°F process envelope, while the close-coupled SLM-AVB covers 50–800 GPM at up to 250 ft between -185°F (-120°C) and +248°F (+120°C) [S2][S4].
Dimensional Footprint and Hydraulic Coverage
The standard's core value is interchangeability: any ANSI B73.3 magnetic-drive pump, regardless of vendor, can replace another on the same baseplate without pipework rework, because shaft height, foot-to-suction centerline, and mounting face are fixed [S1][S2].
Coverage splits into two practical windows. Heavy-duty frames such as MAXP and the Goulds 3298/3298 V family sit at the top of the hydraulic map, with MAXP listed at 2,000 GPM / 470 ft and Goulds 3298 / SP 3298 lined magnetic-drive models covering the same chemical-process envelope under ASME B73.3 [S2][S5]. Close-coupled frames including SLM-AVB and the Magnatex MPL/MP sub-ANSI/ANSI line trade maximum flow for compactness, landing at 50–800 GPM and 150 GPM / 190 ft respectively [S3][S4][S6].
Flange interfaces are drilled to ANSI B16.5 Class 150 and Class 300, matching the same end-suction top-discharge pattern used on mechanically sealed ANSI pumps, which is what enables the drop-in replacement model [S4].
Inner and Outer Magnet Architecture
Conforming mag-drive pumps replace the mechanical seal with a synchronous permanent-magnet coupling: the inner magnet sits on the pump shaft inside a closed isolation shell, the outer magnet rides on the motor shaft, and torque crosses the shell as a magnetic field rather than a mechanical connection [S4].
This shell is the second containment barrier. On the SLM-AVB it is listed as 316 SS / Hastelloy C4, and dual-wall containment (CDS) plus a TPS isolation-shell temperature probe are offered as standard options for toxic or hot-oil services [S4]. The MAXP process-side standard of construction covers 304 SS, 316 SS, duplex stainless, Alloy 20, and Alloys B & C, with optional ETFE, Kynar (PVDF), PFA, and PTFE linings for the lined Goulds 3298 family [S3][S5].
A common process-side failure point in sealless pumps is the inner-bearing system, because the bearings run in the pumped fluid and see any upset in lubrication. SLM-AVB uses liquid-lubricated alpha-grade sintered silicon carbide bearings as standard, with carbon/SSIC and carbon/Stellite as engineered alternatives, while MAXP and MPL are offered with optional SiC-X bearings to extend dry-running survivability [S3][S4].
Materials of Construction Across the Datasheets
Alloy B, Alloy C, Alloy 20, and titanium are listed as the high-nickel / corrosion-resistant options on SLM-AVB; duplex stainless appears on MAXP for chloride-containing streams; and rare-earth samarium-cobalt magnets are the standard outer-rotor material on the SLM-AVB because they hold magnetic strength at the upper process temperature without demagnetising [S2][S3][S4].
Magnatex explicitly quotes ISO 9001 quality registration on the alloy MAXP datasheet, and 50 Hz performance curves at 1450/2900 rpm and 60 Hz curves at 1750/3500 rpm are published for SLM-AVB, which is what process engineers need to overlay onto a system curve during selection [S2][S4]. A practical reference for how ANSI-dimensioned sealless pumps fit into a broader chemical-service spec map is the magnetic drive pump primer, which covers coupling geometry, eddy-current losses, and containment-shell design at a level complementary to the dimensional data here.
Comparison: Where Each Conforming Frame Fits
Frame selection under ANSI B73.3 is driven by flow, head, temperature, and required alloy, not by a single "best" model. The four reference lines stack as follows: [S2]
Magnatex MAXP (alloy): up to 2,000 GPM, 470 ft, -150°F to +800°F, full alloy coverage 304 SS through Alloy B/C, ISO 9001-registered build. Specified for hot-oil, chemical-feed, and high-temperature chemical service where the full ANSI envelope is needed [S2][S3].
Klaus Union SLM-AVB (close-coupled): up to 800 GPM, 250 ft, -185°F to +248°F, standard 316 SS, isolation shell 316 SS or Hastelloy C4, SiC bearings, SamCo magnets. Specified for refineries, liquid-gas plants, and pharmaceutical/galvanic plants where a small footprint and dual containment (CDS option) matter more than top-end flow [S4].
Magnatex MPL/MP (sub-ANSI/ANSI): up to 150 GPM, 190 ft, -112°F to +660°F, close-coupled, optional SiC-X bearings. Specified for medium-flow, medium-to-high-head chemical skid applications where a full MAXP frame is oversized [S2][S3][S6].
Goulds 3298 family (lined and metallic): 3298 lined magnetically driven chemical process pump, SP 3298 lined self-priming variant, 3298 V chemical process pump, 3299 heavy-duty lined chemical pump, plus the ICM metallic magnetic-drive process pump. Specified when the buyer wants a lined (PTFE/PFA) wetted path for aggressive acids alongside the ANSI dimensional envelope [S5].
Selection rule of thumb from the published envelopes: if the duty point is above 800 GPM or above 250 ft of head, the heavy-duty frame (MAXP, 3298, 3298 V) is the only ANSI B73.3 option. If it sits below that and the plant needs a small baseplate, the close-coupled SLM-AVB or MPL/MP frame is the cost-effective answer [S2][S3][S4][S5].
Limits, Failure Modes, and Spec Pitfalls
Magnetic-drive pumps under ANSI B73.3 still inherit the process-side limits of any sealless design. The MAXP and MPL datasheets both list a 1% solids @ 500 µm / 5% solids @ 100 µm baseline, with optional baffle rear casings and self-cleaning strainers for higher solids, which sets the practical upper bound on slurry duty [S3].
Dry running is the most common cause of inner-bearing failure in this architecture, because the bearings rely on the process fluid for lubrication. Both MAXP and MPL offer an SiC-X bearing upgrade for extended dry-run capability, and SLM-AVB offers carbon/SSIC and carbon/Stellite alternatives in the same role [S3][S4].
Containment is dual: the isolation shell is the first static barrier and the outer magnet housing is the second. SLM-AVB publishes a CDS double-wall shell as a documented option for EPA Risk Management Plan (RMP) and similar regulated services, while TPS probes flag shell overheating before a magnet degausses [S4]. Magnetic-circuit behaviour, degauss curves, and the rationale for SamCo over neodymium in high-temperature service are covered in the magnetic material reference and the related magnetic sensor page for shaft-position / overspeed instrumentation on these frames. In parallel, leak detection at the containment shell uses either conductivity or capacitance probes whose calibration logic overlaps with the magnetic level gauge family.
A spec pitfall to flag: the 800 GPM / 250 ft envelope on SLM-AVB is the published ceiling, not a parallel-rated duty point. Real selection should derate by 10-15% on flow and head when the process fluid is above 200°F, when specific gravity is below 0.7, or when viscosity is above 50 cP, because magnetic-coupling torque transfer and NPSHr both shift in that range (qualitative guidance from the published temperature and head envelopes [S2][S4]).
Standards Anchoring the Footprint
ANSI B73.3 is the chemical-process pump dimensional standard, and the sealless variant is published as ASME B73.3-2003 ("sealless pump standard for general emission-free services"), which is the citation SLM-AVB uses to declare compliance [S4]. The flange standard is ANSI B16.5 Class 150 / 300 for both the suction and discharge connections [S4]. Quality management is registered to ISO 9001 on the alloy MAXP datasheet [S2].
Heavy-duty sealless pumps for refinery and severe-service duty step up to API 685 (the Klaus Union SLM-AVP is the API 685 heavy-duty member of the same magnetic-drive family), not ANSI B73.3, so engineers should be careful not to substitute an ANSI B73.3 frame on a duty that requires API 685 [S4]. Within ANSI B73.3 itself, the difference between a "lined" frame (Goulds 3298 / 3299 with PTFE or PFA liners) and a "metallic" frame (MAXP, ICM) is dictated by chemistry, not dimensional envelope, so both are footprint-compatible [S2][S5].
Two trackable signals to watch on the 6-month horizon: (1) whether any major OEM publishes a refreshed ASME B73.3 revision beyond the 2003 sealless edition cited today, and (2) whether more chemical-plant EPCs standardise on the CDS double-wall containment option for new RMP-listed services, given that SLM-AVB is the only frame in this comparison that lists it as a catalog option [S4]. Related reading on how ANSI-standard chemical pumps are paired with continuous-duty motors in modern skids is summarised in the AC vs DC motor selection guide.