From a vacuum perspective the design rests on the sizing to allow a maximum of 35 kPa drop of internal pressure in the pipeline . The sizing is done by performance curves in each individual valve specification sheets ( PDF format ) . Where the design is significantly different is in the venting . Essentailly only antishock orifices are used for venting . Continuous research shows that the small orifices are more efficient at controlling the velocities of water entering the valve and the subsequent induced pressure . Even more beneficial though , is the ability to control pipeline surges and spikes in pressure by controlling the volume of the release of air . Most of this is set out in the technical paper that was first published in 2001 ( see ” Air Release Valves – understanding the myth ” in the technical section )
Release under pressure
There are few if any valves that can open the antishock orifices once the pipeline is pressurised ( including any closing caused by general spashing) . Conventional air release valves have large orifices for vacuum relief and then only very small orifices ( sub 2.0 mm dia ) that open at full working pressure . Some have antishock orifices but they can only operate when the pipeline is filling and once pressurised they remain closed , eliminating any further benefit . The Vacuvent design allows the antishock orifices to open and close as required up to full working pessure of the valve !
Induced pressure from high discharge of air
This is one of the most misunderstood areas of air release application . Controlling the volume and speed which air is released during filling and operation is critical and that is one of the design strengths of the Vacuvent range .
Where possible most parts are made in the country of origin . This supports the local economy , and has echological benefits too . Only critical assemblies are made at one location to ensure quality and reliability .
The basic tube and flange system has been proven over many years of manufacturing . One major change we have made is internal tie rods . We played around with internal tie rods in the early 90’s but never got around to implementing them in our valve range . Using the tie rods as the float guides has substantial benefits : –
* It reduces the flange area so we can now substantiate the use of full stainless steel upper flanges ( and lower ones on special order – see below ) .
* Stainless steel in the critical o-ring sealing area ( upper flange ) eliminates corrosion and extends the usefulness of the valve over many years .
* Internal pressure pivots on the tie rods increasing the seal as the pressure rises .
* Reduces the part count , simplfies the assembly and increases relability .