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Volute Casing

The spiral scroll, cast to the original profile.

Volute Casing

The spiral scroll, cast to the original profile.

The volute is not a decorative shape. Its cross-section grows along the spiral so that velocity stays roughly constant as flow is collected off the impeller. Change that taper and the pump still runs, but the duty point moves and efficiency drops — usually several points, and always in the wrong direction.

On aftermarket work we reconstruct the profile rather than tracing the worn one. An eroded volute is wider than it left the factory; copying it would build the wear into the new part. Where a dimension came off the sample rather than a drawing, we say so on the quotation.

Casting process	Vertical-line sand moulding on two lines (national patent)
Materials	Grey iron · ductile iron · WCB carbon steel · CF8M stainless
Machined features	Joint face and bolt circle · suction and discharge flanges · register bore
Minimum order	100 pieces
Certification	EN 10204 3.1 per heat, spectrometer results
Source of geometry	Your drawing, 3D file or a worn sample

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Casting Notes

What Is Difficult About This One

Every casting has one or two features that decide whether the batch repeats. On this part they are these.

The profile is the part

Everything else on a volute is ordinary casting work. The spiral is where the value is, and it lives entirely in the core box.

Section grows along the spiral

Feeding has to follow that growth, so the thick end near the discharge solidifies last. Feed it the other way round and the shrinkage lands in the throat.

The cutwater is the thin bit

Where the spiral meets the discharge, the wall is at its thinnest and the metal has already travelled furthest. It is the first place to check on a first article.

Materials

Alloy Options

The same geometry is a different part in three different plants. Chloride content, abrasion and temperature drive the choice — not the name of the fluid.

Alloy	Grade	When it is the right choice
Grey iron	HT200 / HT250	Default for water duty. Damps vibration, machines easily, lowest cost.
Ductile iron	QT450 / QT500	When the duty is cyclic or the part takes shock. Tougher than grey.
WCB carbon steel	ASTM A216 WCB	Higher strength, weldable. For pressure-bearing bodies.
CF8M stainless	ASTM A743 CF8M	Chloride and corrosion duty — the cast equivalent of 316.

Enquiry

What to Send Us

These are the ones specific to this part. A drawing, a 3D file or the worn original covers all of them at once.

Item	Why it matters
Pump make and model	Or the worn casing itself — either lets us reconstruct the profile
Impeller diameter	Sets the volute throat and the register that holds it central
Flange standard	PN/ANSI rating, or a drawing of what it bolts to