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1 Products availableOur product range contains a wide range of Digital Control Valves, Diaphragm Digital Control Valves and PV Breather Valves
Diaphragm Digital Control Valve is an electrically actuated, hydraulically operated multi-function control valve. It can be used for local as well as remote controlled batching operations with electronic batch controller. The valve also offers an in-built flow governing function
The Diaphragm Digital Control Valve basically consists of a diaphragm operated main valve and two solenoid valves. Normally open (NO) solenoid connects the valve cover chamber to the upstream pressure, whereas normally closed (NC) solenoid connects the valve cover chamber to the downstream pressure.
When the Diaphragm Digital Control Valve is used with an electronic batch controller, it can be digitally controlled by operating the solenoid valves through any of these three stages :
The operation of the valve is simple and is explained below. The total batch quantity delivered and controlled through the valve is divided into 7 stages (Refer graph) for the purpose of convenience.
Initially both NO and NC solenoid valves are in de-energized condition. The NO valve applies high upstream pressure on the diaphragm, whereas the NC valve prevents this pressure from getting drained to the downstream side. The valve remains close as a result of this.
Stage 1Both NO and NC solenoids are energized. NO valve now restricts the high upstream pressure from entering into the cover chamber. NC valve permits the pressure above the diaphragm to vent to the low downstream pressure. This creates a differential pressure across the diaphragm, the high upstream pressure acting from below the diaphragm opens the main valve and allows the flow to start through the valve.
Stage 2As the flow rate reaches predefined value (set in the batch controller as Low Flow Start) the NC valve is de-energized. This prevents further draining of the chamber and locks the valve at this flow rate. Initial delivery at slow speed avoids splashing of product and also avoids the generation of static charge.
Stage 3When sufficient quantity is delivered at the slow speed, the NC valve is energized again. This allows further draining of the chamber and hence increases the flow.
Stage 4When the flow reaches to the maximum level (set in the batch controller), the NC solenoid is de-energized. This maintains the constant high flow rate for the remaining batch. During this stage, the flow rate control is done by the batch controller. When a number of flow meters are connected to the same pump, stopping (or starting) one or more meters increases (or decreases) the flow rate at the remaining meters. When the flow rate increases, the NO solenoid is energized momentarily. This injects some high pressure in the cover chamber and makes the valve to throttle in order to maintain the set flow rate. If the flow rate decreases, the NC solenoid is energized momentarily. This allows slight draining of the chamber and allows the valve to open further in order to maintain the set flow rate.
Stage 5At the end of the batch, the NO solenoid is de-energized. This injects high upstream pressure into the cover chamber and throttles the valve.
Stage 6When the valve throttles sufficiently to achieve the predefined slow closing flow rate (set in the batch controller), the NO solenoid is energized. This maintains the uniform flow rate.
Stage 7When the batch quantity is delivered, the NO solenoid is de-energized. (NC solenoid is already de-energized.) This applies high upstream pressure into the cover chamber, which makes the main valve to close completely to achieve bubble-tight shut-off.
Note:The number of stages during opening and closing are programmed in the batch controller and can be as many as desired. One stage during opening and two during closing are recommended.
Caution:Sufficient pumping flow rate should be available to achieve the flow parameters set in the electronic batch controller. In the absence of this, there are chances of delayed response in closure, resulting in valve over-run.
The Series 8300 range of Breather Valves minimise vapour losses from storage tanks during operations whilst preventing internal pressure & vacuum conditions from exceeding the tank design limits. Hence both product & vessels are protected as well as tank environmental conditions.
COMBINED UNITSSeries 8300 Pressure & Vacuum Breather Valves can be fitted in combination with Series 8350 Flame Arresters.Note This type of installation reduces valve flow capacities and thus special sizing calculations are applicable.
CHEMICAL SERVICESeries 8300 Pressure & Vacuum Breather Valves can be supplied in a range of alternative materials for chemical and/or cryogenic services and can be used with air dryers fitted at the vacuum inlet port, to protect those products which could be adversely affected by normal atmospheric air.
It is suitable for wide range of services in the petroleum, chemical and related industries for land tankages only.
LOW BLOW-DOWNBlow-down is the difference between opening and closing pressures.
The floating diaphragm operation ensures that blow-down is minimised to 10% for pressure relief and 10-15% for vacuum relief.
LOW LEAKAGECapability of the resilient diaphragm to wrap around the edge of the pallet seat. The high ratio of seating force to seating area provides a tight seal.
As the pressure or vacuum rises, the relevant pallet begins to lift, but the diaphragm wrap around at the edge of the seat maintains a good seal.
As the pressure or vacuum continues to rise, the pallet lifts further, but the diaphragm naturally assumes a good seal.
When pressure or vacuum reaches the set conditions, the pallet opens fully.