Diaphragm Valves, Larox pinch valves, Stubbe diaphragm valves for Industrial, Mining and chemical applications Australia.
Do you use a Diaphragm valve or a Pinch valve? Which is best a diaphragm valve or a pinch valve? These are 2 common questions that are often asked. Firstly, diaphragm valves are to 16 bar maximum, some types and sizes can be limited to 5 bar. Pinch valves can go to 25 bar and beyond in our “specialty versions”. Size is another consideration diaphragm valves are from 3/8″ to 3″ screwed and 1/2″ to 14″ flanged. Pinch valves can be 1″ through to 48″ flanged.
Saunders were the first to produce the diaphragm valve around 1928, when the patient expired others copied the design. “Our” factory has been meticulously manufacturing both styles of valves for 20 years offering interchangeability of spares that give customers economical alternatives.
Commercially diaphragm valves are more economical in the WT type as well as in some ST sizes. WT diaphragm valves reduced flows give control benefits while the ST is more a full flow but does not compete with pinch valve flows. Pinch valves give far superior flows. Which lasts longer? Generally the pinch valve however the sleeve is the wear item if it wears it gets replaced economically. With a diaphragm valve the diaphragm can be replaced but if there is wear on the linings or unlined bore the valve has to be replaced. We think above 4″ the pinch wins in every aspect but if its on heavy slurries consider the pinch valve every-time. If the pressures or temperatures are high another option we can offer from our range is the severe service slurry ball valves.
Diaphragm Valves
Diaphragm valves are an enclosed body valve in two main styles straight through (ST) and weir type (WT).
Straight through type are semi full bore with a convex shaped rubber diaphragm that pushes down to throttle or stop the flow. Therefore straight through types are popular in mining applications.
Weir type are an up and over a hump flow path, having a flatter rubber diaphragm. This allows a short stroke to regulate or give on / off operation. With ease of operation they are ideal as a general process valve in the likes of Chemical Plants, Water treatment facilities and Marine service.
Bodies can be plastic, iron or stainless in threaded and flanged connections although some special pharmaceutical varieties can be clamp-ended. They can also be lined eg glass, ETFE or rubber along with PTFE backed diaphragms for aggressive chemical services The majority are manual valves however they do lend themselves to Actuation which is also part of our package.
Size range is 8nb to 350nb.They are not a high pressure valve and limited to the temperatures of their construction/elastomers. Depending on the selection pressure rating PN 10/16 and up to 175C. For higher pressures or higher flows consider the PINCH valve.
Actuated Diaphragm Valves
Diaphragm valves in the last 20 years have been common place due to advances in both the casting and actuator technology. Some can be direct mounted while others still require an intermediate bracket. The most common actuation is pneumatic however with smaller electric actuators becoming more reliable and some sites not wishing to use compressed air, electrics is gaining popularity.
The majority of actuated diaphragms are WEIR type (WT). The short travel which is similar to a globe making it simple and reliable. The straight through (ST) have a longer travel distance to open and close. This can stress the diaphragm giving it a shorter life-span. Whilst this can be said in general with the ST type if a lot of repetitive cycles which is why many valves are actuated it can be an issue. Whether they are pneumatic or electric we can assist.
NEWS! As of July 2024 our Pinch Valve range now covers valves up to 2300PSI!
Pinch Valves
Pinch valves can be open or enclosed body valves and are a full flow design. The sleeve (which is sacrificial) is mechanically ” pinched” to regulate or / open close the valve. Some pinch valves can also be pneumatically or hydraulically operated instead of a using a mechanical force.
Pinch valves are a flanged valve from 25nb to 1200nb and limited by their sleeve materials in pressure and temperature. The limiting temperature is around 120 C. Some designs can sustain over 1000psi however most services are low pressures below 150 psi.
Bodies can be iron, steel, stainless or polyamide, most are manually operated and easily actuated if required. As the sleeves are the wear component they are usually carried in stock.
Food Grade Pinch valves
Compact inline stainless steel body pinch valves with food grade liners from DN 40 to DN 200 flanged connections and DN 15 to DN 50 in screwed connects are now available. These valves are air actuated only, or water with consultation / verification to suit the service.
Australian stocks up to 8″ DN200 Diaphragm Valves and pneumatic actuated PVE style Pinch Valves