Reference profile
- Designation
- API 674
- Title
- Positive Displacement Pumps — Reciprocating
- Issuing body
- American Petroleum Institute (API)
- Current edition
- 3rd Edition (Reaffirmed 2021 / ISO 13710 Equivalent)
- Status
- Active; international benchmark standard for heavy-duty reciprocating displacement pumps.
- Category
- Reciprocating Positive Displacement Pump Standard
Overview
API Standard 674 (ISO 13710) covers the minimum requirements for reciprocating positive displacement pumps and pump units for use in the petroleum, petrochemical, and natural gas process industries.
Both direct-acting pumps and power-driven pumps (simplex, duplex, triplex, quintuplex, multiplex) are covered. These units excel in high-pressure, fixed-volume services where discharge pressure is independent of flow rate.
Scope & Applicability
Covers
- Pump Types: Power pumps (motor/engine-driven via crankshaft and connecting rods: Simplex, Duplex, Triplex, Quintuplex) and Direct-acting pumps (steam/gas-driven).
- Liquid End (Fluid End) Mechanical Construction: Forged block cylinders, replaceable liners, plungers/pistons, suction/discharge valves (disc, wing, spherical), stuffing box packing, and lubrication/flush systems.
- Power End Mechanical Construction: Heavy-duty cast iron/steel frames, crankshafts, connecting rods, crossheads, and splash or forced lubrication systems.
- Pulsation Control: Suction and discharge pulsation suppression devices (dampeners/stabilizers) and acoustic/vibration design analysis.
- Testing Requirements: Hydrostatic testing (1.5x MAWP), mechanical running performance test, NPSH margin verification, and NDE of forged liquid ends.
Does NOT cover (exclusions)
- Controlled volume metering pumps—covered by API 675.
- Rotary positive displacement pumps (screw, gear, vane)—covered by API 676.
- Centrifugal process pumps—covered by API 610.
- In-service overhaul procedures and field packing replacement—refer to vendor maintenance manuals.
Key Requirements
Pulsation & Vibration Control (Design Approaches 1, 2, 3)
- Design Approach 1: Basic dampener sizing using standard empirical mathematical relationships.
- Design Approach 2: Acoustic simulation of the pump and piping system to eliminate acoustic resonance peaks.
- Design Approach 3: Combined acoustic simulation and mechanical piping dynamic stress analysis for high-energy or multi-pump installations.
Liquid End (Fluid End) High-Pressure Design
- Forged Block Construction: Forged carbon steel, stainless steel, duplex, or nickel alloy blocks are mandatory for severe high-pressure services to prevent fatigue cracking.
- Valves & Seats: Replaceable disc, wing-guided, or spherical check valves with hardened seats to resist erosion and high differential pressures.
Overpressure Protection & Safety Provisions
- Mandatory Safety Relief Valve (PSV): A liquid-certified safety relief valve must be installed on the discharge piping upstream of any isolation valve.
Inspection & Hydrostatic Testing
- Hydrostatic Test: Liquid end pressure-retaining components must be hydrostatically tested at a minimum of 1.5x MAWP for at least 30 minutes.
- Mechanical Running Test: Shop performance running test at rated speed, pressure, and capacity for at least 4 hours to verify volumetric efficiency, vibration, and bearing temperatures.
Technical Details
Pulsation Peak-to-Peak Limit: Peak-to-peak pressure pulsation in the line piping must be suppressed to less than 1.5% to 3.0% of average operating pressure.
NPSH Margin Requirement: NPSHA must exceed NPSHR by at least 1.0 m to 1.5 m (3 ft to 5 ft) to prevent fluid flashing in the suction stroke.
Volumetric Efficiency Benchmark: Typical API 674 plunger pumps achieve high volumetric efficiency (90% to 98%) depending on fluid compressibility and valve response.
Engineering Notes
- Never install a block valve between a positive displacement pump discharge and its safety relief valve (PSV); positive displacement pumps can generate infinite pressure until structural rupture if blocked.
- Mount pulsation dampeners as close as possible to the liquid end suction and discharge flanges (within 1 to 2 pipe diameters) for maximum dampening effectiveness.
- Specify a dedicated packing flush/lubrication system for toxic, corrosive, or abrasive services to extend plunger and stuffing box packing life.
Related Standards
Source, Edition & Status
- Publisher
- API
- Edition Year
- N/A
- Industries
- Refinery, Petrochemical, Oil & Gas
- Content Status
- reviewed
- Last Reviewed
- 2026-07-01
- Last Updated
- 2026-07-01
- Verified By
- Engineering Reviewer
- Official Link
- www.api.org
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