Trims eliminate cavitation damage
April 2013
Valves, Actuators & Pump Control
To complement its range of control valves, PSV Mitech offers a range of trims, chokes, diffuser plates and other devices for cavitation and noise control. All devices are manufactured in materials selected for their resistance to cavitation, flashing, wear and corrosion.
To prevent cavitation, energy dissipating ZZ trims are used to gradually reduce the energy of the incoming liquid. Energy is dissipated through friction and abrupt direction changes when the fluid moves through the ZZ passages of the retainer. This trim is generally suitable for sizes up to 80 mm.
Disk stack trims also eliminate cavitation by causing the pressure to be dropped gradually over a large number of restrictions in conditions involving high pressure drops and high flow rates. The disk stacks are usually used in valves of 100 mm and over.
The low noise trims feature a low noise retainer in which pressure is dropped across one or more restrictions. They are fitted in standard valve bodies to produce low noise valves, where noise level can be reduced by between 5 to 15 dBA. The noise reducing retainers are available as one, two or three stage units and are fitted above the seat ring in the gallery of the valve.
Energy dissipating disk stack trims are also used to reduce noise levels in high pressure drop gas applications. By converting the high potential energy upstream directly into heat, high velocities are avoided, resulting in less noise being generated.
Diffuser plates are disks with many holes drilled through the centre portion and which can be fitted between adjacent flanges in a pipe line. They increase the back pressure to the control valve installed upstream, reducing the pressure drop across the control valve and increasing the back pressure. This decreases valve gas velocity and noise generated in the immediate vicinity of the valve and often enables a smaller valve to be selected.
For more information contact Greg Walker, PSV Mitech Control Valves, +27 (0)11 657 6000, [email protected], www.mitech.co.za
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