Tailored to plastic pipes Butterfly Valves Avoid Diameter Mismatch with PE and PP Pipework

When concentric wafer-type or lug-type butterfly valves are installed between stub flanges in polyethylene (PE) or polypropylene (PP) pipework, mismatches in diameter often require users to accept compromises. Is that really necessary?

Related Vendors

DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

CAC ENGINEERING GMBH

Maag Pump Systems AG

EBRO ARMATUREN Gebr.Bröer GmbH

The problem is that PE and PP pressure piping has a narrower bore than the equivalent steel pipe, so the edge of the valve disc fouls the inside rim of the pipe. Users often chamfer the inside diameter of the stub flange to create clearance and allow the disc to turn, but this reduces the wall thickness, weakens the pipe and reduces the surface area over which the gasket seals the joint. Modifications to the stub flange also mean that it no longer complies with the original piping standard. Another compromise is to add spacer blocks to provide the necessary dimensional adjustment. In technical terms, however, this is an even worse solution than chamfering the pipe rim. Both of these unsatisfactory approaches requires extra effort during planning and installation, and add direct as well as indirect costs.

Instead of chamfers or spacers, the answer is to use a butterfly valve purpose-designed for installation in PE/PP piping systems, such as one chosen from the Ebro Armaturen series Z 411-A or Z 414-A. With their slightly reduced disc diameters, these valves ensure that the rim of the stub flange will never interfere with the movement of the disc. The valves are available in a full range of sizes from da 50 (DN 40) up to da 630 (DN 600).

Both series comprise standardized industrial valves which can be supplied with through borings (wafer series Z 411-A) or threaded holes (lug type series Z 414-A), suitable for installation between standard short stub flanges conforming to DIN 16962/3 Part 4 (Item 1,3), SDR 11/17/17,6/33) and loose flanges (EN 1092–1 PN 10). The face-to-face diameter complies with EN 558 Series 20.

To ensure quick and error-free installation, the valves are clearly marked with details of their special application in PE/PP pipework.

The actuator interface conforms to EN ISO 5211, so the valves can be used in automation applications — including retrofits — without problems. They are also approved for use in potentially explosive atmospheres (Ex zone II categories 1, 2 and 3).

The series Z 411-A and Z 414-A butterfly valves feature a one-piece, compact and inherently stable body which is completely soft-seated. The one-piece liner prevents the process medium from contacting the valve body, and also provides sealing for the spindle and flanges, so separate flange gaskets are not required. The liner incorporates beads which hold it firmly in place, so it cannot work loose in operation.

According to the manufacturer, the profile of the valve disc is optimized for smooth fluid flow, giving the valves excellent flow characteristics compared to other types commonly used with plastic piping, which have considerably smaller cross sections.

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