Pressure reducing valve
The VLR is a steam pressure reducing valve used in high and/or low pressure steam turbine systems. The most common application for the VLR is in venting to atmosphere. Here, the VLR is placed in a steam pipe branching from the pipe connecting the boiler and the turbine, providing a controllable conduit between the boiler and the atmosphere. During load rejection, the steam flow rate is too high for the system until the firing rate has been reduced, vent valves located at the main and reheat lines are used to handle the excess flow.
The large pressure differential between the boiler and the atmosphere can cause high noise levels that require attenuation. To reduce the noise potential in the steam pipe, the pressure drop is split between the valve and a downstream diffuser or silencer. The VLR itself is equipped with a pressure reducing stage at the spindle, and often a secondary stage at the valve outlet. The VLR is also used in general pressure control applications where desuperheating is required.
The VLR can be combined with a downstream desuperheater to emulate the functionality of a steam conditioning valve in situations where using a VLB proves difficult.
Steam passes through the extended drilled bonnet before being throttled though a cage type plug with multiple drilled holes which provides optimum characteristics for control of steam pressure.
- The extended bonnet prevents possible rotation forces caused by the steam flow, and acts as an extra pressure reducing stage.
- The extended bonnet also works as a strainer, protecting the valve seat and the bonnet from damage.
- The plug slides in a surface hardened bonnet, covering/uncovering throttling holes, regulating the flow through the valve. In the closed position, the plug sits on the hard-faced seat, isolating the inlet from the outlet. Pressure reduction continues in the outlet, through the pressure reducing pipes, engineered for each application.
- The pressure seal bonnet provides a tight seal in the valve neck while allowing easy access during maintenance.
- Homogenous forged body minimises thermal stress.
- Fully customisable inlet and outlet connections.
- Available in balanced tight design which reduces the required opening forces.