Below is a general checklist of inspection items and key methods for dimensional inspection of cast steel pump casings (pump bodies/pump shells). You may adjust or select according to your drawings or standards (such as JB/T, GB/T, or company standards).
1) Preparation and Reference Determination
Cleaning: Remove burrs, sand, and flash; inspect critical mating surfaces for surface defects (such as pitting or inclusions that may affect measurement).
Eliminate deformation effects: If necessary, perform stress relieving/straightening or confirm the current machined state (e.g., blank dimensions vs. finished machined dimensions).
Reference points (critical): Typically use
- Pump casing mounting base face/flange end face
- Shaft center reference hole/mounting hole
- Pump inlet and outlet sealing faces
as measurement references. Specifics follow drawing requirements.
2) Routine External Dimensions and Key Controlled Dimensions (Recommended for Mandatory Inspection)
For cast steel pump casings, focus primarily on dimensions that could affect sealing, assembly, concentricity, and hydraulic clearances:
A. End Face / Profile
Overall length, overall width, height (as per drawing when necessary)
Key end face flatness (e.g., flange end face, sealing end face)
End face runout (relative to assembly reference hole/axis datum)
Method: Straightedge + feeler gauge/dial indicator, gauge blocks, CMM, or height gauge.
B. Pump Inlet and Outlet Related Dimensions
Dimensions of inlet/outlet flange or end face sealing surfaces:
**Hole diameter (e.g., flange holes, bolt holes):**
- Hole diameter
- Hole spacing/center distance
- Distance from hole center to sealing surface/end face
- Sealing surface width/step height (affects sealing compression)
Method: Hole diameter gauge, internal micrometer, platform and gauge blocks, combination measuring tools; use of fixtures/templates for locating hole centers.
C. Internal cavity dimensions (pump hydraulic passages)
Internal diameter / internal diameter step dimensions
Key internal cavity length (from reference end face to a specific step or flow guide structure)
Fitting surfaces related to impeller and clearance (e.g., mating surfaces between pump casing and impeller, or clearance control surfaces)
Methods: Internal micrometer, internal diameter gauge, dedicated inspection fixtures; profile verification by CMM scanning when necessary.
D. Coaxiality/Perpendicularity (Core of Assembly Performance)
Coaxiality between the mounting hole axis and pump shaft axis
Perpendicularity of the sealing face relative to the shaft axis
Positional tolerance of the reference mounting surface relative to the hole/shaft axis
Method: V-blocks + dial indicator, ring gauge/axial gauge, coaxiality inspection fixture; positional tolerance evaluation using CMM if conditions permit.
E. Thickness and Wall Thickness (Indirectly Reflecting Casting Defects)
Wall thickness at critical areas (pump casing volute, ribs, reinforcement zones)
Local minimum thickness (to ensure strength and prevent collapse)
Method: Ultrasonic thickness gauge (commonly used) + measurement points based on drawings; spot checks when necessary.
3) Typical "Sampling Plan" (to facilitate your inspection planning)
It is recommended to follow the principles below for sampling, and assign fixed numbers in the inspection records:
Each sealing surface: at least 3–5 points along the end face/width direction
Each hole group: measure hole diameter (sample or full inspection per hole depending on tolerance), measure center distance (all adjacent holes must be measured)
Key internal cavity steps: measure 3 points on both sides and in the middle of each step
Wall thickness: place measurement points according to critical cross-sections of volute, stiffening ribs, and flow passages (commonly using a combination of circumferential and axial directions)
4) Inspection method selection (based on accuracy grade):
Roughing stage: focus on checking whether deviations are excessive enough to cause machining scrap; commonly use general measuring tools and templates.
After rough machining: verify key mating dimensions, focusing on concentricity and perpendicularity.
After finish machining: perform full or sample inspection (as per your quality requirements) on sealing surfaces, hole position tolerances, and surfaces related to critical clearances.
Common measuring equipment:
Vernier/ digital calipers, outside micrometers, inside diameter gauges / inside micrometers
Height gauge, dial indicator, level
CMM (coordinate measuring machine—better for position and profile measurements)
Ultrasonic thickness gauge (wall thickness)
5) Common causes of dimensional deviations (to help you identify the root cause):
Poor end face flatness: uneven casting shrinkage, lack of post-casting correction, or fixture indentation
Hole spacing deviation: misalignment due to casting hole positions and shrinkage differences, or change in datum reference
Sealing surface step height deviation: insufficient machining allowance or variation in blank wall thickness Coaxiality/perpendicularity deviation: inconsistent clamping datum, or mismatch between machining and assembly datums Local thinning of wall thickness: casting defects or process issues (especially at flow passages in volutes)