A company manufacturing and delivering machines to production sites all around the world are using AKO Pinch Valves on their systems. This company distributes materials and solutions which are key ingredients in the wellbeing of each of us and the future of all. They can be found everywhere in our living places and our daily life: in buildings, transportation, infrastructure and in many industrial applications.

One system manufactured by this company that we have looked at in further detail is on a gypsum slurry application, used within a company within the plasterboard manufacturing industry.

Application Details

Gypsum slurry at approximately 28-30°C passes through the pneumatically operated Pinch Valve at 0.5 Bar line pressure. The valve is positioned horizontally, on the body of a mixing unit. The air operated Pinch Valve assists the application by being used as an open and close function for gypsum slurry flow or no flow.

VMP015.xx.50R.71
Pinch Valve used within this application:

VMP model, air operated, POM white FDA approved body, stainless steel weld-on ends, natural rubber sleeve.

Depending on the site that this machine is installed at, the valve is normally closed. The valve is opened by applying air to the inlet on the body casing anywhere between 1-4 times per day, so the number of cycles is low. 6 Bar air pressure is used to shut off the valve, collapsing the rubber sleeve into a tight seal.

A volume restrictor is associated with creating back pressure between the volume restrictor and the outlet for keeping the mixer full, and a pressure reducer associated with the discharge spout and configured for reducing the pressure of the slurry dispensed from the discharge spout is fitted to the machine. The machine is configured for maintaining a generally laminar flow from the mixer outlet to the discharge spout. This means the fluid particles follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing.

gypsum slurry mixer unit controlled by pinch valve
gypsum slurry mixer unit controlled by pinch valve with adapted ends

The end connections shown in the photographs for the small white AKO Pinch Valve have been modified by the end user to fulfil the company’s process requirements.

gypsum slurry mixer with hand operated pinch valve

There is also an AKO manually operated Pinch Valve installed onto part of the same machine which is for a foam system to create back pressure by partial closing of the valve.

gypsum slurry mixer with hand operated pinch valve
OV050.03.30M
Pinch Valve used within this application:

OV model, manually operated via hand wheel, aluminium body, aluminium flanges PN10/16, natural rubber sleeve.

AKO Advisories

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.

 

Customer Satisfaction

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.

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