The volute casing body is the pressure containing shell of a ballast, seawater cooling or bilge pump, converting impeller velocity into discharge pressure while carrying suction and discharge flange loads. It sits in the engine room pump bay or ballast pump room and handles cold seawater, occasionally with sand and debris ingress. Buyers come to us because thin wall leakage, erosion at the cutwater and poor flange alignment are the recurring failures in service, and because pump OEMs need a casing that machines cleanly on the seal faces without porosity opening up after the first cut. We design the feed to keep the cutwater and the flange fillets sound.
Specifications
| Item | Specification |
|---|---|
| Casting process | Silica sol investment casting, with ceramic core for internal volute passage on enclosed designs |
| Material options | Nickel aluminium bronze C95800, gunmetal CC491K, duplex 2205, super duplex 2507, CF8M / 316L stainless |
| Dimensional tolerance (ISO 8062-3 CT grade) | CT7 to CT9 as cast; CT6 on seal housing bore and flange faces |
| Machining | Horizontal CNC boring and milling of split line, seal housing bore, suction and discharge flange faces and drain ports |
| Surface finish (Ra) | Ra 3.2 um on wetted flow surfaces, Ra 1.6 um on seal faces and flange gasket faces |
| Corrosion / wear protection | Internal flow surfaces shot blast and passivated, epoxy coating for seawater service, sacrificial anode bosses cast in |
| Weight range | 15 kg to 320 kg per casing body |
| Typical lead time | 4 to 7 weeks including tooling, 3 weeks for repeat orders |
Scope and options
Key features
- Cutwater and volute throat cast to near net shape, so flow geometry is retained rather than ground away during fettling.
- Hydrostatic test of the pressure boundary performed before shipment at your specified test pressure.
- Moreover, Seal housing bore and stuffing box machined concentric to the impeller axis within 0.05 mm.
- Sacrificial anode bosses cast into the casing to protect the wetted surface in seawater service.
- Erosion resistant material and optional hardfacing at the cutwater for pumps handling sandy water.
- Interchangeable with OEM casing dimensions for overhaul replacement without piping modification.
Applications
- Ballast water pumps on bulk carriers, tankers and general cargo vessels
- Main seawater cooling pumps and auxiliary cooling water pumps in engine rooms
- Bilge and ballast stripping pump systems
- Dredger jet water and slurry service pumps
- Offshore platform seawater lift and firewater pumps
- Desalination and reverse osmosis feed pumps on vessels and rigs
Images
Quality & compliance
Every casing body is supplied with EN 10204 3.1 certification and heat number traceability, and hydrostatic testing of the pressure boundary is performed with the result recorded against the serial number. Dye penetrant testing of the cutwater and all fillet radii, plus radiographic examination of critical sections, are available on request. Moreover, we issue a dimensional report covering seal bore concentricity, flange face flatness and bolt hole position. Ningbo Ruican supplies components to shipyards and marine OEMs; classification-society type approval of the finished part remains the customer’s responsibility, and we supply the material, pressure test and NDT records needed for that submission.
FAQ
Can you cast the volute passage with a ceramic core?
Yes. For enclosed designs we use a ceramic core to form the internal volute, which gives a smoother as-cast flow surface than a fabricated or cored-and-welded alternative. Core prints and washout are controlled, and the passage is inspected before machining.
What test pressure do you use for the hydrostatic test?
Also, we test to the pressure on your drawing, typically 1.5 times design pressure, and hold for the specified dwell. The certificate records test pressure, dwell time, medium and result, and witnessed testing by your inspector or a third party can be arranged.
How do you prevent leakage at thin wall sections?
We run solidification simulation before tooling is released and position feeders to keep the cutwater, flange fillets and bolt bosses sound. Every production casting is ultrasonically surveyed in the thin wall zones, and any indication is evaluated against the acceptance level before machining.
Which material do you recommend for sandy seawater?
Super duplex 2507 gives the best combination of pitting resistance and erosion resistance for sandy seawater at higher velocity. Nickel aluminium bronze C95800 remains the standard choice for general seawater cooling where velocities are moderate.
Do you supply matched casing and impeller sets?
Generally, we can supply the volute casing, suction cover and impeller as a matched set, machined and balanced together. This avoids the clearance and concentricity problems that arise when casing and rotating element are sourced separately.
Can you replace a casing without changing the pipework?
In most cases yes. We machine the suction and discharge flanges to the existing drilling pattern and rating, so the replacement bolts straight into the existing pipework. Send the flange dimensions and rating and we will confirm before tooling.
CTA
Send your pump casing drawing, pressure rating, media and annual quantity for a quotation within 48 hours. Contact window: Wendy She — sales@cnsandcasting.com — WhatsApp +86-13777124360. Ningbo Ruican supplies newbuild and replacement pump castings in bronze, duplex and stainless with hydrostatic test records for every part.
