Excess Closing Pressure with Pinch Valves

A food manufacturing company in the UK have been using numerous PInch Valves from the VF range within their different sites across the country for 12 years.

An engineer on site was kind enough to talk to us and send through some images of the VF Pinch Valves in situ. Unfortunately, he had been experiencing some frustrating problems with one of the Pinch Valve internal rubber sleeves failing rather quickly, after just a few weeks whereas they were previously lasting months, if not years. Customer satisfaction is AKO’s top priority, so when the engineer told us the details of the application and how the company were operating the pinch valve, we were able to help.

pinch valve for sugars and salts

The ambient media passing through the pinch valve are dry powders, fats, gums, starches, pectin’s, sugars and very occasionally, salt. These products are not passing through the valve constantly. There are periods when the pinch valve is operational as it is part of the system but not necessarily with product flowing through. The pinch valves operate 5 days a week, and for roughly 7 hours per day.

The pinch valve is normally open, and performs two cycles per day under normal operation – on start up and on finish. The valve is also designed to close in an explosive situation.

Pinch Valve used within this application – VF080.02X.35.30LA

VF model, air operated, aluminium body, aluminium PN10/16 flanges with stainless steel bushings, natural rubber white food quality sleeve (FDA approved).

Pinch Valve Problems Solved

PROBLEM: The engineer on site was using vacuum pressure to keep the valve open/cylindrical. The media described above would be flowing through the pinch valve at 0.3 BAR, and the engineer was shutting the valve off using 5.8 BAR. The degree of vacuum was sucking the rubber sleeve from the inside, pulling it into a partially closed position. With the sleeve partially closed and the fairly abrasive media (sugars and salts)  flowing through at 5.8 BAR, this was wearing the sleeve at the partially closed points, adding too much stress and causing it to split.

SOLUTION: To achieve an optimum control pressure, AKO Pinch Valves only need 2 BAR above the line pressure to shut the valve off fully. We advised the engineer that far too much pressure was being used to close the rubber sleeve, and only 2 BAR maximum should be ideal to close the valve. On top of this, we recommended piping the same vacuum pressure back to the inlet of the pinch  valve so that the vacuum would suck from both sides (inside and outside), to equalise the pressure.

pinch valve for sugars, salts, fat
valve for dry powders

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