VALVESI------------------------------------------------
R3.51l1 high-pressurepinch valves order
Pinch valve manufacturerCorflex Engineering,which supplies pinch
valves for low- to high-pressureapplications, has received a R3.5-million order from a copper-min-ing project in Zambia for 500mmpinch valveswith a working pres-sure of 25 bar.The order was awarded on the
condition that the valvesbe testedand witnessed to be working at1.1 times the working pressureto ensure that they did not leakwhen closed.The force required to seal the
valves is over 120t at a pressureof 27.5 bar..Corflex previously performed
sealing tests on its valves; how-ever, this is the first time that asealing test was required for a500 mm pinch valve at thispressure.The most common method
used to construct pinch valvesuses rising actuators owing to itscost effectiveness. This is, how-ever, not suitable for pinch valvesoperating at high pressures asthe pincher mechanism is heldtogether using only two nuts.By using this construction
method, the actuators have thetendency to move about, caus-ing the valve to jam. The poten-tial danger with this method
is the high risk of bolts or nutsshearing.The valvesused in the test were
fitted with four hydraulic cylin-ders - two on either side - andcertified gauges were used.The sealing test is based on
the recognised API 598 testingstandard for valves.
The Test ProcedureThe open valve is first filled withpotable water and pressurised toa nominal 8bar to fully expel anyresidual air and to provide backpressure to the closing mecha-nism so that the sleeve can bepinched in an operating manneras normal as possible.Next, the hydraulic pressure
is applied and the valve is fullyclosed. The upstream side is thenpressurised to 27bar - 10%abovenominal operating pressure -and the down-stream side isexhausted to zero pressurethrough the stand pipe.The observations throughout
the test indicated that leakagewas a droplet of water formingon, and falling from, the standpipe. In this period, the up-stream pressure did not reduce.The test was repeated with
three valves and the same resultswere observed.MINING WEEKLY COUPON ON PAGE 64 E248583
PRESSURE TESTA representative from a Zambian copper mine had to bear witness to theCorflex pinch valve pressure test before a R3.5-million order was accepted
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MINING WEEKLY IMarch 9-15 2012 63
