How do you prevent cavitation in restriction orifice?
This phenomena is well known as cavitation. One way to avoid cavitation in restriction orifice is to reduce pressure drop across RO so that the pressure dip is maintained as high as possible. This results multiple restriction orifices to break the pressure drop in several steps.
What is cavitation index?
The cavitation index is the ratio of the pressure differential between the equipment inlet pressure and the fluid vapour pressure to the pressure differential pressure across the equipment.
How do I know what size orifice to get?
Divide the flow of the liquid by the velocity of the liquid to determine the area of the orifice in square feet. In the above example, you would divide 8 by 2. The total area of the orifice would be 4 square feet.
What is a restriction orifice?
Restriction orifice unions are flow control devices used in fluid piping systems to limit the process fluid’s flow rate. They feature a one-piece metal orifice metering plate that fits snugly within the union seat.
How do you calculate cavitation?
The value of the cavitation number, i.e. CN = (p1 − pv)/(p1 − p2), determines the extent of the region that is filled with vapour inside the nozzle.
Can valves Cavitate?
Cavitation can occur in valves when used in throttling or modulating service. When flow passes through a throttled valve, a localized low pressure zone forms immediately downstream of the valve. If the localized pressure falls below the vapor pressure of the fluid, the liquid vaporizes (boils) and forms a vapor pocket.
What size is a propane orifice?
Propane (LP) orifice sizes typically vary from 0.010 to 0.016′′ diameter, but 0.010′′ appears common, for which energy con- sumption is 548 Btu/hr at a typical 11′′ pressure.
Is propane orifice bigger than natural gas?
Because of gas service pressure, natural gas orifices are larger than propane ones. Attempting to use a propane appliance with natural gas will likely result in a very small flame or no burner flame because of the lower pressure gas and the smaller orifice.
How is the cavitation index used in valves?
The cavitation index is a heuristic method for analysis of restriction orifice plates and valves, and the acceptable C i will depend on the several factors including, flow stability, piping geometry near the orifice and the particulars of the orifice design.
How are restriction orifices used to prevent cavitation?
A typical set up may include a control valve with a restriction orifice downstream. The restriction orifice then provides the back pressure on the control valve to prevent cavitation through the valve. However the restriction orifice itself must also be correctly sized to prevent cavitation.
What should the C I be for cavitation?
For example in the case of a typical square-edged concentric orifice plate a C i of 2 or above would be unlikely to cause cavitation, whereas values below 2 would indicate cavitation or incipient cavitation are likely.
When does cavitation occur in a pressure reduction system?
Cavitation may occur in a pressure reduction system even if the final system pressure is the above vapour pressure of the liquid. This is because the intermediate pressures may fall below the final pressure.