API 610 is the global standard for centrifugal pumps in the petroleum, petrochemical, and natural gas industries. When a refinery engineer says "we need an API pump," they mean a pump built to API 610 specification — not just any pump that happens to handle hydrocarbons.
This selection example walks through a typical API 610 OH2 pump application in a refinery. Operating parameters are representative, not a real customer project.
What API 610 Actually Means
API 610 (American Petroleum Institute Standard 610) specifies the minimum requirements for centrifugal pumps in petroleum, petrochemical, and gas industry services. It is not just a pump size chart — it covers materials, seals, testing, inspection, and documentation.
Key API 610 requirements that differ from standard industrial pumps:
- Materials: Castings must meet ASTM A487 or A890 grades. Standard cast iron is not acceptable.
- Mechanical seals: Dual mechanical seals with API Plan 53B barrier system for hazardous service. Single seal only for non-hazardous, clean service.
- Testing: Hydrotest at 1.5x design pressure. Performance test on water. Optional NPSH test and noise test.
- Documentation: Material mill certificates, test reports, dimension drawings. All traceable.
- Design life: Minimum 20 years continuous operation, with 3 years between overhauls.
Example Application: Refinery Hydrocarbon Transfer
The example is a crude oil transfer pump between tank farm and distillation unit feed. The pump runs 24/7 at base load, with flow turndown during maintenance.
| Parameter | Value | Notes |
|---|---|---|
| Fluid | Crude oil, desalted | Hydrocarbon mixture, varying gravity |
| Flow rate | 120 m³/h | Refinery feed rate |
| Head | 65 m | Lift to distillation tower feed + piping loss |
| Temperature | 40°C (suction) to 60°C (discharge) | Warmed crude — not cryogenic, not hot |
| Specific gravity | 0.86 (typical Arabian light) | Varies with crude slate |
| Viscosity | 5–15 cP at operating temp | Light crude — close to water behavior |
| NPSH available | 8 m (from tank at 4 m static head + 1.5 bar) | Good — no cavitation risk at design flow |
| Hazardous classification | Zone 1 (flammable hydrocarbon vapors) | Requires explosion-proof motor |
Why OH2? Not OH1 or BB1?
API 610 pumps come in different configurations. OH2 is the most common for refinery process service.
| Type | Description | Typical Application |
|---|---|---|
| OH1 | Overhung, single stage, end suction | General service, smaller flows |
| OH2 | Overhung, single stage, centerline mounted | Refinery process, medium flow & head |
| BB1 | Between bearings, axially split casing | Large flow, low head (cooling water) |
| BB2 | Between bearings, radially split casing | Medium flow, medium-high head |
| BB3 | Between bearings, axially split multistage | High head, boiler feed or pipeline |
Selection conclusion: For 120 m³/h at 65 m in refinery service, an OH2 pump is the right choice. The centerline mounting design handles thermal expansion — the pump stays aligned as it heats up during operation. See our API 610 OH2 process pump range for refinery and petrochemical applications.
OH1 would be cheaper but lacks centerline mounting — it will misalign as temperature rises. BB2 would be overkill for this flow/head combination.
Material Selection for Crude Oil Service
Crude oil is not corrosive in the traditional sense, but it contains sulfur compounds, water, and salts. API 610 material class for this service:
Casing: Cast carbon steel (ASTM A216 WCB). Standard for hydrocarbon service. Not enough sulfur to require duplex.
Impeller: Cast carbon steel (ASTM A216 WCB) or 13% Cr stainless (CA15). The 13% Cr upgrade costs 10% more but provides better erosion resistance if crude contains fine solids.
Shaft: 4140 alloy steel, heat-treated. API 610 requires minimum yield strength of 550 MPa. Standard carbon steel does not meet this.
Wear rings: Renewable, made from 13% Cr stainless. Replaceable without replacing the entire casing or impeller.
Gaskets: Spiral-wound stainless with graphite filler. Resists hydrocarbon and high temperature. Avoid asbestos-based gaskets — banned in most refineries.
Mechanical Seal Arrangement
Refinery service with flammable hydrocarbons requires dual mechanical seals per API 610:
Seal type: Dual mechanical seal, with pressurized barrier fluid (API Plan 53B). Barrier fluid is a clean, compatible oil (typically ISO VG 32 turbine oil). Barrier pressure is 1–2 bar above pump discharge pressure.
Seal faces: Silicon carbide / silicon carbide. Hard faces handle hydrocarbon service with minimal lubrication. Carbon / silicon carbide would work, but SiC/SiC lasts longer in continuous refinery service.
Barrier fluid system: Accumulator tank with sight glass. Operator checks barrier level weekly. If level drops, it means the inner seal is leaking — schedule maintenance before the outer seal fails.
Single mechanical seals are acceptable only for non-hazardous services like cooling water or boiler feed. For hydrocarbon service, dual seals are mandatory.
Testing and Inspection Requirements
API 610 requires formal testing before shipment. Verify the supplier includes these in the quote:
Hydrostatic shell test: 1.5x design pressure for 30 minutes. No weeping at joints or gaskets. Test report signed by inspector.
Performance test: Run on water at rated speed. Record flow, head, power, efficiency, vibration. Acceptance: flow within ±5%, head within ±3%, efficiency within ±2% of curve.
NPSH test (optional but recommended): Vary suction pressure and measure NPSHr at 3% head drop. Confirms the pump will not cavitate in actual operation.
Raw data sheet: All test data delivered as a raw data sheet, not just a summary. The refinery engineer verifies the data matches the curve.
Final Configuration Summary
| Selection Item | Recommendation |
|---|---|
| Pump type | API 610 OH2, centerline mounted, single stage |
| Flow / head | 120 m³/h at 65 m |
| Speed | 2,950 rpm (2-pole motor) |
| Casing material | Cast carbon steel (ASTM A216 WCB) |
| Impeller material | 13% Cr stainless (CA15) |
| Shaft seal | Dual mechanical seal, API Plan 53B, SiC/SiC faces |
| Motor | 37 kW, 3-phase, 50 Hz, TEFC, EX d IIB T4 |
| Baseplate | Steel baseplate with drip rim, grouted |
| Testing | Hydrotest + performance test + raw data sheet |
Common API 610 Pump Selection Mistakes
Mistake 1: "API 610" on the PO but no documentation requirement. The supplier ships a pump that looks like an API pump but has no test report and no material certificates. When the refinery inspector rejects it, you wait 6 weeks for re-testing. Specify the exact documentation set on the purchase order.
Mistake 2: Wrong material class. Engineers write "cast steel" on the PO. The supplier quotes cast iron to save money. Cast iron is not acceptable per API 610. Always specify the ASTM grade: "ASTM A216 WCB" for casing, "CA15" for impeller.
Mistake 3: Forgetting spares. API 610 pumps are expensive and have long lead times (12–16 weeks). Order the recommended spares with the pump: mechanical seal kit, wear ring set, gasket kit. Lead time for these spares is another 8 weeks — do not order them after the pump fails.
Mistake 4: No alignment check on site. API 610 pumps are precision machines. The pump and motor are aligned at the factory, but after shipping and site installation, alignment shifts. Do a laser alignment check after grouting the baseplate, before starting the pump for the first time.
For API 610 pump selection and quotation, our OH2 process pump range meets API 610 latest edition requirements. For performance verification, the pump power calculator confirms motor sizing. For refinery pump requirements, request a quote with your operating conditions and API specification.