Durco Mark III Group 3 Replacement Casing — 100% Bolt-On Interchangeable
When highly corrosive media — mixed acids, wet chlorine, hot sulfuric acid — eats through the volute wall of a Durco Mark III Group 3 large frame pump, plant maintenance teams face a brutal reality: 16 to 20 weeks for an OEM Flowserve replacement casing. For a chemical plant running 24/7, that timeline means thousands of hours of lost production. Many operators scramble to retrofit a different pump, only to discover the discharge piping, suction spools, and baseplate anchor bolts don’t line up.
Our Group 3 large frame replacement casing solves this at the root. Every casting is dimensionally verified against OEM prints — same flange faces, same nozzle centerlines, same volute geometry. You unbolt the failed OEM casing, drop ours in place, and torque the fasteners. No pipe fitting. No grinding. No welding. And because we stock raw castings in Hastelloy C-276, Alloy 20, and CD4MCuN specifically for the Group 3 large frame, typical lead times are 6–10 weeks — a 60% reduction compared to OEM on exotic alloys.
Technical Specifications
| Specification | Detail |
|---|---|
| Pump Compatibility | Flowserve Durco Mark III Group 3 (Large Frame) |
| OEM Part # | Item 100 (Casing / Volute) |
| Max Flow Rate (Group 3) | Up to 7,500 GPM (1,700 m³/h) |
| Casting Method | Sand casting and V-process — up to 2,000 kg (4,400 lbs) pour weight |
| Wall Thickness | Exceeds OEM minimum wall thickness at all critical sections — including volute cutwater and discharge nozzle — for maximum corrosion allowance |
| Hydrostatic Test | 1.5× working pressure per HI 14.6 |
| Quality Documentation | Full EN 10204 3.1 MTR + PMI verification standard; CMM dimensional inspection reports available on request |
Material & Alloy Coverage
Our large-frame foundry pours a complete range of metallurgies — from standard stainless to exotic alloys. Every heat is certified with full traceability to EN 10204 3.1.
Why material selection matters for Group 3 interchangeability: The Group 3 large frame handles flow rates up to 7,500 GPM — the highest in the Durco Mark III lineup. At these flow volumes, even minor corrosion pitting at the volute cutwater can progress to wall breach within months. The wrong alloy choice — or a casting with undocumented chemistry — is a production risk no plant can afford.
Unlike catalog suppliers who impose minimum order quantities on exotic alloys, we stock raw pours in Hastelloy C-276, Alloy 20, CD4MCuN, and 316SS specifically for the Group 3 large frame pattern. That means no MOQ penalty on single-unit exotic casings — you order exactly what your process demands, poured to the alloy and wall thickness you specify.
| Material | ASTM Spec | PREN | Best For |
|---|---|---|---|
| CF8M (316SS) | ASTM A743 | ≥ 24 | General chemical processing, moderate temperatures |
| CD4MCuN (Duplex SS) | ASTM A890 Gr. 1B | ≥ 35 | Seawater, brine, high-chloride environments |
| Hastelloy C-276 | ASTM A494 CW12MW | ≥ 64 | Mixed acids, wet chlorine, severe corrosive media |
| Titanium Grade 2 | ASTM B367 Gr. C-3 | ≥ 30 | Nitric acid, oxidizing chlorides |
| Alloy 20 (CN7M) | ASTM A743 | ≥ 28 | Sulfuric acid — all concentrations to 40% at 150°F |
| Zirconium 702 | ASTM B752 | N/A | Hydrochloric acid, extreme corrosive service |
Volute Wall Integrity — Built for Extreme Service
All Group 3 large frame casings feature thicker wall dimensions for maximum corrosion allowance — exceeding OEM minimum wall thickness specifications at all critical sections. Key quality checkpoints include:
- Volute cutwater: The highest-velocity zone in the casing. Our castings maintain full wall thickness through the cutwater profile with radiography-verified integrity.
- Discharge nozzle: Reinforced flange transition with generous fillet radii — eliminates the stress risers that cause fatigue cracking in thin-walled OEM casings.
- Hydrostatic proof test: Every casing is hydrostatically tested at 1.5× maximum working pressure per HI 14.6, with a minimum 30-minute hold time.
- PMI verification: Positive Material Identification via XRF on every casting before machining — ensuring the alloy you ordered is the alloy you get.
Related Durco Mark III Products
Lead Time & Rush Order Availability
📦 Standard Lead Time: 6–10 weeks for large frame exotic alloy castings — manufactured to order with full EN 10204 3.1 MTR, PMI, and hydrostatic test reports
✅ Stock Availability: Select Group 3 CF8M and CD4MCuN casings may be in stock — contact us for current inventory
🔥 Emergency Rush Orders: 3–4 weeks — Request expedited pattern allocation and priority scheduling
📥 Need a Group 3 Large Frame Casing with Shorter Lead Time? Request a Quote for Item 100 Now →
Disclaimer: ANSI Pumps Pro is an independent aftermarket manufacturer. Durco and Mark III are registered trademarks of Flowserve Corporation. All OEM part numbers are used for compatibility reference only. We are not affiliated with or endorsed by Flowserve.
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