16th Mar.2026
API 610 (current 12th edition, 2021) specifies that the pump body (casing) is a critical pressure bearing component and must be made of weldable cast steel (grey iron/ductile iron is prohibited for high-pressure/high-temperature process conditions) to meet the requirements of high-pressure, high-temperature, long-period, safe and reliable petrochemical/oil and gas processes.
1）ASTM A216 WCB (most commonly used): Weldable carbon cast steel, corresponding to domestic ZG280-520
Applicable: -29 ℃~427 ℃, water, light oil, general process medium
Strength: σ b ≥ 485MPa, σ s ≥ 240MPa
WCC: Higher strength, used for higher pressure/temperature
2. Chromium molybdenum heat-resistant cast steel (S4 grade, high temperature and high pressure)
ASTM A217 WC6（1Cr0.5Mo）：-29℃~540℃
ASTM A217 WC9（2.25Cr1Mo）：-29℃~565℃
Applicable: High temperature hot oil, boiler feedwater, steam, hydrogenation equipment
Features: creep resistance, high temperature resistance, good weldability
3. Stainless steel/duplex steel cast steel (S2/S3 grade, corrosion condition)
ASTM A351 CF8/CF8M (304/316 cast steel)
ASTM A890 CD4MCu (duplex steel)
Applicable: acid, alkali, seawater, chlorine containing media
3）、 API 610 Mandatory Requirements for Cast Steel Pump Body Design
1. Pressure bearing and strength design
MAWP (Maximum Allowable Working Pressure): ≥ 2.0MPa at room temperature; Flange grade ≥ Class 300 (Class 150 usually does not meet API 610)
Stress control: Design tensile stress ≤ 0.25 × σ b or 0.67 × σ s (whichever is smaller); The casting needs to be multiplied by the casting coefficient (conservative design)
Pipe mouth load: withstand 2 times the force/torque of the pipe mouth in Table 5, without leakage or contact between moving and stationary parts
2. Structural and process requirements
Whole casting, smooth flow channel, uniform wall thickness, avoiding stress concentration
Prohibit the use of core supports (impeller components are strictly prohibited); Pressure bearing parts shall not be blocked/immersed for repair, only welding repair and re inspection are allowed
Surface treatment: sandblasting/shot blasting, meeting the appearance requirements of MSS SP-55
4）、 API 610 Manufacturing and Inspection Requirements for Cast Steel Pump Bodies
1. Material verification
Material certification (MTR) must be provided: chemical composition, mechanical properties, heat treatment status
Key components: 100% UT/MT/PT non-destructive testing; RT radiographic testing in important areas
Sulfur printing, intergranular corrosion (stainless steel), impact testing (low/high temperature)
2. Welding and repair
Welding process requires WPS/PQR approval; Re NDT the repaired area according to the original standard Post weld heat treatment (stress relief): Carbon steel ≥ 620 ℃, chromium molybdenum
steel ≥ 690 ℃
3. Hydrostatic Test
Test pressure: 1.5 × MAWP, holding pressure ≥ 30 minutes, no leakage or deformation
Stainless steel pump body: Test water Cl ⁻ ≤ 50ppm (mandatory in 12th edition)
5）、 Typical application pump types of API 610 cast steel pump body
OH2 (cantilever single-stage): chemical process pump, light hydrocarbon pump
BB2 (two end support open): circulation pump, oil transfer pump
BB3 (multi-stage): boiler feedwater pump, water injection pump, hydrogenation feed pump
VS4/VS6 (vertical drum bag): tower bottom pump, high temperature and high pressure submersible pump
The API 610 cast steel pump body is made of WCB, WC6, and WC9 as the core materials. Through strict strength design, non-destructive testing, pressure testing, and welding control, it ensures long-term safe operation under high-pressure, high-temperature, and corrosive conditions in petrochemical/oil and gas industries. It is the most mainstream and reliable shell solution for process pumps.
