API 610 is the internationally recognized standard for centrifugal pumps in petroleum, petrochemical, and power generation industries, specifying design, materials, testing, and documentation requirements for high temperature and high pressure service. This article covers API 610 pump types (OH, BB, VS), material classifications, design requirements, testing and inspection, and how to specify API 610 compliant pumps for boiler feed, thermal oil, and high temperature applications.
API 610 is the global standard for centrifugal pumps in petroleum, petrochemical, and gas industry services. For high-temperature applications, API 610 specifies design, materials, testing, and documentation requirements that ensure reliability and safety. This guide covers API 610 specifications relevant to high-temperature pumps and compliance verification.
API 610 Overview
- Standard: API Standard 610, Centrifugal Pumps for Petroleum, Petrochemical and Natural Gas Industries
- Current edition: 12th Edition (2020), ISO 13709 equivalent
- Covers: horizontal (OH, BB), vertical (VS), and canned motor pumps
- Applicable temp: -50°C to +450°C (some designs higher with special materials)
- Applicable pressure: up to 400 bar (depending on type)
- For high-temp: API 610 is the most common specification for process pumps
API 610 Pump Types
| Type | Description | Temp Range | Pressure | High-Temp Use |
|---|
| OH1 | Overhung, foot-mounted | -50 to 300°C | Up to 50 bar | General, low temp |
| OH2 | Overhung, centerline-mounted | -50 to 450°C | Up to 100 bar | Most common high-temp |
| OH3 | Overhung, vertical in-line, separate bearing bracket | -50 to 250°C | Up to 50 bar | Limited high-temp |
| BB1 | Between bearings, axial split, double suction | -50 to 300°C | Up to 100 bar | Large flow, moderate temp |
| BB2 | Between bearings, radial split, single stage | -50 to 450°C | Up to 200 bar | High temp, high pressure |
| BB3 | Between bearings, axial split, multistage | -50 to 300°C | Up to 200 bar | High pressure, moderate temp |
| BB4 | Between bearings, radial split, multistage (barrel) | -50 to 450°C | Up to 400 bar | Very high pressure/temp |
| BB5 | Between bearings, radial split, multistage (double casing) | -50 to 450°C | Up to 400 bar | Critical high-pressure |
| VS4 | Vertical, wet pit, single stage | -50 to 300°C | Up to 50 bar | Sump, moderate temp |
| VS6 | Vertical suspended, double casing | -50 to 450°C | Up to 200 bar | High pressure, toxic service |
High-Temperature Design Requirements
Centerline Support (OH2, BB2, BB4, BB5)
- Pump casing supported at centerline (not at feet)
- Allows vertical thermal growth without misalignment
- Mandatory for pumps operating >150°C (API 610)
- For API 610 OH2 pumps: centerline support is standard
- Foot-mounted (OH1) limited to <150°C or non-critical service
Thermal Growth Compensation
- Shaft: allow axial growth (floating bearing)
- Casing: centerline support, flexible piping
- Coupling: flexible (disc, gear, diaphragm) to accommodate misalignment
- Alignment: cold alignment with target offset (compensate for thermal growth)
- API 610 requires: pump shall be designed for thermal growth without binding or misalignment
Casing Design
- Pressure rating: at least 1.5x design pressure at design temp (hydrotest)
- Radial split (BB2, BB4, BB5): preferred for high pressure/temp (no split line leakage)
- Axial split (BB1, BB3): limited to <300°C or non-hazardous (split line gasket risk)
- Casing thickness: per pressure/temp rating (ASME Section VIII, API 610)
- Nozzles: integral or welded (not threaded for high pressure/temp)
- Nozzle loads: API 610 specifies maximum allowable forces and moments
Shaft Design
- Minimize deflection: L3/D4 ratio, large shaft diameter
- Shaft sleeve: protect shaft from wear/corrosion (replaceable)
- Mechanical seal: per API 682 (not packing for hazardous/high-temp)
- Keyways: rounded corners (stress concentration reduction)
- Runout: <0.025 mm (0.001 in) at seal journal
Material Requirements
API 610 Material Classes
| Class | Casing | Impeller | Shaft | Temp Limit | Application |
|---|
| S-1 | WCB | WCB/316 | 4140 | 350°C | Non-corrosive, water/oil |
| S-2 | CF8M (316) | CF8M | 316 | 400°C | General corrosive |
| S-3 | CF8M | CF8M | 316 + Ni-resist rings | 400°C | Abrasive/corrosive |
| S-4 | CD4MCu (duplex) | CD4MCu | CD4MCu | 250°C | Chloride, high strength |
| S-5 | CF8C (347) | 310 | 310 | 550°C | High temp, thermal cycling |
| S-6 | CN7M (Alloy 20) | CN7M | Alloy 20 | 300°C | Severe corrosive (acid) |
| S-7 | CW-12MW (Hast C) | Hast C | Hast C | 400°C | Very severe corrosive |
| S-8 | WCB + 316 trim | 316 | 4140 | 350°C | Water, mild corrosive |
High-Temp Material Selection
- <150°C: any class (S-1, S-2, etc.)
- 150-350°C: S-1 (non-corrosive), S-2 (corrosive), verify material temp rating
- 350-450°C: S-5 (347/310), 2.25Cr-1Mo (F22), Incoloy 800
- >450°C: special alloys (HK40, HP, Inconel, Hastelloy X) — beyond standard API 610
- For high-temp chemical pumps: verify material compatibility with specific chemical
- Carbon steel (WCB): limited to <425°C (graphitization risk above)
- 316 stainless: limited to <450°C (sensitization, carbide precipitation)
- 347/321 (stabilized): better for 400-800°C (resists intergranular corrosion)
Mechanical Seal Requirements (API 682)
Seal Types
- Type A: single, cartridge, spring outside (general)
- Type B: double, cartridge, high pressure
- Type C: double, cartridge, rotating metal bellows (high temp)
- For high-temp (>200°C): Type C (metal bellows, no elastomer) or Plan 32 injection
- For hazardous: Type B/C double seal (Arrangement 3, pressurized barrier)
Seal Plans for High-Temp
- Plan 11: Recirculation from discharge — general, not for high temp (no cooling)
- Plan 21: Recirculation + cooler — cools seal, common for 150-300°C
- Plan 32: External flush (clean, cool fluid) — best for >300°C or dirty fluid
- Plan 53A/B/C: Double seal barrier system — for hazardous/high-temp
- Plan 62: Quench (steam/water) on atmospheric side — for high-temp, prevents coking
- For API 610 OH2: Plan 21 or 32 common for high-temp
Seal Materials
- Seal faces: SiC vs SiC (high temp, general), SiC vs carbon (general), tungsten carbide
- Springs: Inconel 718 (high temp/corrosion)
- Elastomers: limited to <200°C — use metal bellows or PTFE wedge above
- Metal bellows: Inconel 718, Hastelloy C (for >200°C)
- Gaskets: spiral wound (316/graphite), camprofile, RTJ (high pressure)
Testing Requirements
Hydrostatic Test
- Casing: 1.5x design pressure at design temp, held 10 minutes
- No leakage, no permanent deformation
- For high-temp: test at ambient (material strength higher at ambient — conservative)
- API 610 requires: hydrotest before performance test
Mechanical Running Test
- Run at no load (water) for minimum 1 hour
- Vibration: <4.5 mm/s RMS (unfiltered), <3.0 mm/s (filtered) per API 610
- Bearing temp: stabilize, no sudden rise
- Seal leakage: within acceptable limits (drip rate)
- No unusual noise, rubbing, or leakage
Performance Test
- Measure head, flow, power, efficiency at: shutoff, min, normal, rated, max (at least 4 points)
- Compare to approved curve: head ±3% at rated, efficiency ±2% (API 610)
- NPSHr test: if specified, verify at rated flow (3% head drop)
- For high-temp: test with water (corrections for viscosity/density if needed)
- Standard: ASME PTC 8.2, ISO 9906 Grade 1 or 2
Hot Running Test (Optional)
- Test at operating temperature (if specified or critical service)
- Verify: thermal growth, seal performance, bearing temp, vibration at temp
- For high-temp critical pumps: recommended (catches thermal issues before installation)
- API 610: optional, but common for >300°C or hazardous service
NDT (Non-Destructive Testing)
- Castings: visual, radiography (RT), ultrasonic (UT) per API 610
- Welds: RT, UT, dye penetrant (PT), magnetic particle (MT)
- Shaft: UT for inclusions, surface hardness
- Pressure boundary: 100% RT/UT for high-pressure/hazardous
- Material verification: PMI (positive material identification) for alloys
Documentation Requirements
| Document | API 610 Requirement | High-Temp Notes |
|---|
| Data sheet | Completed API 610 data sheet | Include max temp, material class |
| Performance curve | Head-flow-efficiency-NPSHr | Note temp/fluid corrections |
| GA drawing | Dimensions, weights, connections | Show centerline support |
| Cross-section | Internal construction, materials | Show seal plan, cooling |
| MTR | EN 10204 3.1 for pressure parts | Verify material temp rating |
| Test report | Hydro, mechanical, performance | Include hot test if done |
| Seal data sheet | API 682 seal specification | Show plan, materials |
| O&M manual | Installation, operation, maintenance | Include warm-up procedure |
| Spare parts list | Recommended spares | Include seal, bearings, rings |
| Rotor dynamics | If specified (critical speed) | High-speed/multistage |
Compliance Verification
Pre-Award
- Verify supplier API 610 certification (or proven track record)
- Review data sheet: all fields completed, temp/pressure consistent
- Review material class: appropriate for temp and fluid
- Review pump type: OH2/BB2/BB4/BB5 for high-temp (not OH1/BB1)
- Review seal plan: Plan 21/32 for high-temp, double seal for hazardous
- Review testing: performance test, NDT, hot test (if needed)
During Manufacturing
- Material inspection: MTR review, PMI verification
- Casting inspection: NDT (RT/UT) per API 610
- Dimensional inspection: GA drawing verification
- Witness testing: hydro, mechanical, performance (FAT)
- Seal inspection: verify type, plan, materials
- Documentation review: all required documents complete
Post-Delivery
- Verify nameplate: API 610, type, material class, temp/pressure
- Verify documentation: all required documents received
- Verify spare parts: per spare parts list
- Installation: per O&M manual, centerline support, alignment with thermal growth
- Commissioning: warm-up procedure, performance verification
Common Non-Compliance Issues
- OH1 instead of OH2: Foot-mounted for >150°C — thermal growth misalignment. Specify OH2.
- BB1 instead of BB2: Axial split for high pressure/temp — gasket leakage. Specify BB2/BB4.
- Wrong material class: S-1 for corrosive or >350°C. Verify compatibility, use S-2/S-5.
- Packing instead of mechanical seal: Not for hazardous/high-temp. Specify API 682 seal.
- No seal cooling: Plan 11 for >200°C — seal overheating. Specify Plan 21/32.
- No centerline support: Foot-mounted for high-temp. Verify centerline.
- No performance test: Only hydro test. Specify performance test per ASME PTC 8.2.
- No MTR: Material not certified. Require EN 10204 3.1 for pressure parts.
- Wrong bearing cooling: Grease for high-temp — bearing failure. Specify oil/cooling.
- No thermal growth compensation: Rigid coupling, no target offset. Specify flexible coupling, alignment procedure.
Procurement Recommendations
- Specify API 610 (12th Edition) / ISO 13709 for all high-temp process pumps
- For general high-temp: specify OH2 centerline-mounted, material class S-1 or S-2
- For high pressure/temp: specify BB2 (single stage) or BB4/BB5 (multistage), material S-5 or alloy
- For zero leakage: specify a magnetic drive pump (sealless, zero-leakage) or a canned motor pump
- For >350°C: specify S-5 material (347/310) or 2.25Cr-1Mo, verify temp rating
- Specify API 682 mechanical seal with Plan 21 or 32 for >150°C
- For hazardous: specify double seal (Arrangement 3, Plan 53)
- Require performance test per ASME PTC 8.2 Grade 1 or 2
- Require MTR (EN 10204 3.1) for all pressure-containing parts
- Require NDT per API 610 (RT, UT, PT as applicable)
- For >300°C critical: specify hot running test
- Specify centerline support, finned/water-cooled bearing housing
- Include spare parts: seal cartridge, bearings, wear rings, shaft sleeve, gaskets
- Require O&M manual with warm-up procedure and alignment target offsets
- Verify supplier has API 610 high-temp pump references
Related Industries
API 610 high-temperature pump principles apply to oil and gas (refinery, upstream, pipeline), petrochemical, power generation (fossil, nuclear), chemical processing (high-temp, corrosive), and LNG (cryogenic, but similar standard approach). The core principle — standardized design, materials, testing, and documentation for reliable high-temperature service — is consistent across API 610 applications.
L
Linda
Process Engineering Specialist
12+ years in chemical process pump selection and fluid handling. Expertise in corrosive fluid applications, magnetic drive pump technology, and pharmaceutical/hygienic pump systems. Holds a M.S. in Chemical Engineering and has authored pump selection guidelines for multiple industry journals.