Still, this casing body is the pressure-retaining housing that carries the two intermeshing screw rotors, the timing gear chamber and the suction and discharge ports in twin-screw and multiphase pump ranges. Also, we cast it near net shape by silica sol lost wax. Additionally, we machine the rotor bores, bearing seats and port faces in house. That removes the leakage and alignment problems buyers see with welded fabrications and sand castings. Generally, the result is a dimensionally repeatable casing that assembles without shimming and passes hydrostatic testing first time.
Specifications
| Parameter | Specification |
|---|---|
| Casting process | Silica sol lost wax investment casting; water glass process for larger sections |
| Material options | ASTM A351 CF8M, CF8, CF3M, CF8C; ASTM A995 4A/5A duplex; ASTM A216 WCB; C95800 and C83600 bronze |
| Dimensional tolerance (ISO 8062-3 CT grade) | CT5 to CT7 as cast; ISO 2768-m or drawing tolerance after machining; rotor bore coaxiality within 0.05 mm |
| Machining | 4-axis and horizontal CNC machining of rotor bores, bearing housings, seal chambers and port flanges; single-setup boring where geometry allows |
| Surface finish (Ra) | As-cast Ra 6.3 um or better; machined sealing faces and bore Ra 1.6-3.2 um; Ra 0.8 um on lapped or polished flow passages on request |
| Pressure testing | Hydrostatic shell test to 1.5x design pressure per customer procedure; low-pressure seat and air-under-water test available; reports retained to heat lot |
| Weight range | 12 kg to 160 kg per casing |
| Typical lead time | 25 to 35 days for tooling and samples; 30 to 45 days for production after sample approval |
Scope and options
Key features
- Rotor bores and bearing seats machined in one clamping on a horizontal machining centre, holding bore-to-bore centre distance and coaxiality so the screw pair runs without contact.
- Investment cast internal flow passages give a smooth, turbulence-free suction path, cutting pressure drop and cavitation erosion versus sand cast or fabricated housings.
- Integral cast bosses for drain ports, pressure gauge taps, bearing lubrication lines and temperature sensor pockets, removing weld build-up and post-weld heat treatment.
- Duplex 2205 and super duplex options raise pitting resistance for chloride-bearing and multiphase service, with ferrite content verified on each heat.
- Thick-section junctions fed and simulated during tooling development to keep shrinkage porosity out of the pressure boundary before the first casting is poured.
- Machining stock held at 1.5 to 3 mm on all functional faces, so dimensional drift across batches stays inside the machining envelope.
Applications
- Twin-screw pumps for crude oil transfer, fuel oil forwarding and refinery charge service.
- Multiphase and wellhead boosting pumps handling gas, condensate and produced water together.
- Chemical and petrochemical transfer pumps for solvents, acids and polymer solutions.
- Marine cargo, ballast and lube oil pumps on vessels and offshore platforms.
- Hygienic twin-screw pumps for food, dairy, beverage and pharmaceutical product transfer.
- Bitumen, asphalt and heavy residuum pumps where heated jacketing is required.
Quality & compliance
Inspection and documentation
Generally, we build every casing body inside an IATF 16949 controlled process flow with documented control plans. In general, that flow includes a process capability study on critical rotor bore and bearing seat dimensions. Also, traceability runs from the finished part back to the melt record. Overall, we issue material certification to EN 10204 3.1 as standard, and 3.2 certification witnessed by a customer nominated or independent inspector can be arranged. We run hydrostatic shell testing and seat leakage testing to your written procedure. We also run radiography and ultrasonic survey. Magnetic particle inspection per ASTM E709 and liquid penetrant inspection per ASTM E165 complete the scope. In addition, signed reports are archived against the heat lot.
Overall, we perform positive material identification by handheld XRF on all alloy castings. In general, dimensional reports, PPAP documentation and first article inspection are supplied on request. Additionally, Ningbo Ruican does not claim API, CE or PED certification as a company certificate; all compliance is demonstrated to the customer’s specification with objective evidence.
FAQ
What pump sizes can you supply a casing body for?
Additionally, we routinely cast and machine casing bodies for twin-screw pumps from 40 mm to 300 mm rotor diameter, covering 12 kg to 160 kg castings. Send us your general arrangement drawing and duty conditions, and our engineering team confirms castability, machining envelope and an achievable tolerance scheme before tooling is cut.
How do you prevent porosity in the pressure boundary?
Tooling is developed with feeding simulation on every heavy junction before the first shot, and gating is tuned on the sample run. Every production heat is then checked by radiography or ultrasonic survey at the agreed critical areas, with repair only by customer-approved weld procedure when a discontinuity exceeds the acceptance level.
Can you machine the casing complete, including the port flanges?
Yes. Rotor bores, bearing housings, seal chambers, suction and discharge flanges, drain and gauge bosses are machined in house on horizontal and 4-axis CNC equipment, then verified on a CMM. In addition, we deliver the casing machined, deburred, pressure tested and cleaned ready for assembly.
Do you supply duplex and bronze casings as well as stainless?
We cast CF8M, CF8, CF3M and CF8C stainless, ASTM A995 4A and 5A duplex and super duplex, ASTM A216 WCB carbon steel, and C95800 or C83600 bronze. Overall, grade selection follows your fluid, temperature and chloride content, and we provide heat-by-heat chemical and mechanical certification.
What is your tooling and sample lead time?
Allow 25 to 35 days for tooling, sample casting, machining and first inspection, then 30 to 45 days for production release after sample approval. Generally, repeat orders from existing tooling typically ship in 30 to 40 days depending on quantity and heat treatment route.
Can you work from a sample part instead of a drawing?
Yes. Send a sample or a used casing and we do 3D scanning, produce a reverse-engineered model for your approval, and build tooling from the approved geometry, with material confirmed by spectrographic analysis of the sample before we quote.
CTA
Send your twin-screw pump casing drawings, annual volume and target grade to Ningbo Ruican for a detailed cast and machined quotation within two working days. Contact Wendy She at sales@cnsandcasting.com or WhatsApp +86-13777124360, or visit cnsandcasting.com to see more pump component case studies.
