Pinch valve manufacturer Corflex Engineering, which supplies pinch valves for low- to high-pressure applications, has received a R3.5-million order from a copper-mining project in Zambia for 500 mm pinch valves with a working pressure of 25 bar.
The order was awarded on the condition that the valves be tested and witnessed to be working at 1.1 times the working pressure to ensure that they did not leak when closed.
The force required to seal the valves is over 120 t at a pressure of 27.5 bar.
Corflex previously performed sealing tests on its valves; however, this is the first time that a sealing test was required for a 500 mm pinch valve at this pressure.
The most common method used to construct pinch valves uses rising actuators owing to its cost effectiveness. This is, however, not suitable for pinch valves operating at high pressures as the pincher mechanism is held together using only two nuts.
By using this construction method, the actuators have the tendency to move about, caus- ing the valve to jam. The poten- tial danger with this method is the high risk of bolts or nuts shearing.
The valves used in the test were fitted with four hydraulic cylinders – two on either side – and certified gauges were used.
The sealing test is based on the recognised API 598 testing standard for valves.
The Test Procedure
The open valve is first filled with potable water and pressurised to a nominal 8 bar to fully expel any residual air and to provide back pressure to the closing mechanism so that the sleeve can be pinched in an operating manner as normal as possible.
Next, the hydraulic pressure is applied and the valve is fully closed. The upstream side is then pressurised to 27 bar – 10% above nominal operating pressure – and the down-stream side is exhausted to zero pressure through the stand pipe.
The observations throughout the test indicated that leakage was a droplet of water forming on, and falling from, the stand pipe. In this period, the up-stream pressure did not reduce.
The test was repeated with three valves and the same results were observed. Corflex Engg is represented in India by Adroitt Flow Control. Please contact us for more details.
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