In fluid handling processes which use positive displacement pumps, you will know that protection should be put in place to prevent over-pressuring equipment, by means of a pressure relief valve. If a blockage occurs within the pipework or if fluid properties change to cause an increase in pressure, this could cause damage to the pump as well as associated valves, instrumentation and pipework. An expensive and time consuming problem to fix!
To protect against over-pressurisation most customers will have a spring loaded pressure relief valve, either on a bypass or going to drain to relieve any excess pressure within the system. With this method additional pipework fabrication is required to create the bypass which comes at an additional cost, and the spring loaded pressure relief valve often needs recertifying to ensure it is relieving at the required pressure and still maintaining protection of the system.
So what can you do differently?
An alternative method of protection would be the use of an Alfa Laval Reverse Acting SSV with an Air/Air actuator.
With this valve no additional bypass pipework is required and the valve connects directly to the suction and discharge pipes, saving on installation costs.
Additionally the relieving pressure can be set on site and doesn’t require a fixed pressure to be set in the factory, giving more flexibility for you to protect your systems.
The valve, as standard, can also be forced open during cleaning to act as a CIP bypass and reduce pressure loss experienced when sending CIP fluids through the positive displacement pump.
Finally the SSV Reverse Acting Valve is available in many sizes and with a range of feedback options for Digital, AS-I and IO-Link systems, so you will find the option most suitable to your application and requirements.
How it works
The design of the Reverse Acting SSV has the plug drop into the lower body as opposed to the Standard SSV where the plug lifts into the top body. By having the plug drop into the lower body, the plug area can be much smaller so pressure drop through the valve is not a concern. The suction pipework runs through the bottom body of the SSV and the discharge pipework runs through the top body.
Air is applied to the actuator as holding air to keep the valve closed. The pressure of the air corresponds to a pressure at which the valve opens at. This is not a direct relationship, so for example, 2Bar holding does not equal 2Bar opening, the holding pressure should be calculated by the pressure relief curves of each valve. If the process pressure exceeds that of the holding pressure of the valve then the plug will drop and product will recirculate to the suction pipework continuously until the pressure reduces below the set threshold. During CIP the air can then be applied to the opposite side of the actuator to force it open during cleaning.
Would you like to know more about the Alfa Laval Unique SSV Reverse Acting Single Seat Valve?
Download the product leaflet here: Product Leaflet
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