Because this is a normally open Pinch Valve (white valve pictured) that is being kept normally closed, when the rubber sleeve inside the valve is opened again, it may not open fully with a 100% true bore because the memory of the rubber has been held pinched down for long periods of time, causing the sleeve to deform. If the sleeve is only partially opening, this can create surface areas for wear points, meaning that when the gypsum slurry flows through the valve it can not only cause wear on the partially closed sleeve over time, but it also creates a restricted flow.
To correct this issue, the optimum control pressure should be no more than 2.5 BAR. Since the line pressure is 0.5 Bar in this instance, then a control pressure of no more than 3 Bar should be used to close the sleeve.
6 Bar pressure is holding these Pinch Valves shut all day, apart from the 1-4 times they are open, and the line pressure of the product is not strong enough to push the sleeve back to the fully open position.
In this scenario we would advise to reduce the control pressure to prevent the sleeve from deforming into the closed position. This will lengthen the lifetime of the sleeve. Also, if the Pinch Valve is not in use such as when the site is closed, the sleeve should be left open if possible.
This company have been using AKO Pinch Valves for 10 years, and to date do not have any issues with the valves used within their applications. The AKO Pinch Valves meet their process requirements, and they are satisfied with the products.
With the rubber sleeve being the only wearable part of the Pinch Valves, the production plant replaces the sleeves as and when needed and there is no need to replace the complete unit.