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Red Dragon Limited

Unit 15 Abergorki Industrial Estate

Ynyswen Road


South Wales

CF42 6DL

United Kingdom

T: +44 (0) 1443 772500

F: +44 (0) 1443 775426

E: sales@reddragonvalves.co.uk

Applications Valve Automation
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Valve Automation

Many of the products we supply are used as part of the instrumentation systems for the pneumatic actuators of process valves. The client may demand high speed operation, slow opening, emergency shutdown, one or more fail-safe actions or a combination of different functions which need to be incorporated into the pneumatic controls.

If the intention is to use natural gas, nitrogen etc, instead of compressed air, product selection needs to consider how the gas is exhausted and collected so that it can be re-used or vented in a safe area. Our volume boosters have an option for threaded exhaust ports as an example.

For more information and assistance with selection of an appropriate product for your applications or for us to specify a complete actuated valve assembly please contact us.

Products for On/Off Valves

Filter regulators provide pressure regulation as well as removal of water and particles from the air.

3/2 solenoid valves direct the operation of spring return actuators and 5/2 solenoid valves are used for double acting actuators.

Where no electricity is present, the solenoid valves can be replaced with either air operated 3/2 or 5/2 spool valves.

Manual control at the actuator can be achieved using 3/2 or 5/2 push button valves as part of an override or interlock function.

Actuator speed can be adjusted using unidirectional or bidirectional flow regulators.

Even with using high flowsilencers on the solenoid valves, the restriction as the air passes through the valve body can be a problem for ultimate closing speed. Quick exhaust valves divert the exhaust gas directly to atmosphere allowing faster actuator stroking.

Products for Modulating Valves

In addition to the above items that may also be employed, modulating valves will often use an electronic positioner to respond to a control signal and provide a variable pressure output to control the actuator stroke. The pilot valves in these units require the air to be very clean and additional filters may be necessary. An extra regulator may be employed where different pressures are controlled for the valve actuation.

For larger actuators or where faster stroking times are necessary, volume boosters or pilot operated regulators act as a slave regulator matching the pressure from the positioner through a larger valve to achieve greater flow capacity. This is particularly important for exhausting the actuator quickly during valve closure.

Fail-safe Operations

Can be achieved through single or dual circuit lock-up valves which sense a signal pressure and as it drops below a set threshold, the valve shuts to prevent the air in the actuator escaping and fixing it in position.

5/3 solenoid valves  default to a centre position in the event of electrical signal failure and configurations for feeding the supply to both outlet ports, releasing the air from both outlet ports or blocking all the ports to prevent actuator movement are all possible.

In the event of air supply loss, a pressure sensing relay (pneumatic pressure switch) can be used to automatically detect the fall in pressure and switch the actuator supply to a reserve system of air or nitrogen.

For operator intervention, manual reset or manual latching/electrical trip solenoid valves are available in 3/2 and 5/2 and air operated valves as manual reset in 3/2 or 5/2 functions. Manual reset requires the coil to be energised (or pilot air applied) and at the same time a button or lever is operated by hand in order for the valve to change state and remain changed. The valve will revert to the original position once the electrical or pressure supply is removed.

The opposite function requires the valve to be manually latched open and will only close again when the electrical signal is applied to the coil tripping the mechanism to close the valve.

Redundant dual 3/2 solenoid valves offer 1oo2 (1 out of 2) safety in that the valve operation will not be affected even if one of the 2 valves fails.

Pneumatic actuated ball valve, 3/2 solenoid valve, filter regulator, volume booster, lock-up valve, spool valve, quick exhaust valve, flow regulator, high flow silencer, bug scren, all ATEX certified for Zone 1 installation Filter regulators, volume boosters and lock-up valves in 316L stainless steel or epoxy coated copper free aluminium construction Sitecna 3/2 and 5/2 air and hand operated spool valves in 316L stainless steel Sitecna 316L stainless steel volume booster and version with threaded exhaust port for use with gases other than compressed air Single circuit lock-up valves in 316L stainless steel and epoxy coated copper free aluminium C90 dual 3/2 1oo2 redundant stainless steel solenoid valves, also available with ATEX Exd approval