The nuclear power plants watch carefully the thickness of the carbon steel pipes where the fluid is flashing water or wet steam.
Look for a document of EPRI (Electrical Power Research Institute) that has by title: "Recommendations for controlling cavitation, flashing, liquid droplet impingement...
I agree with the previous answers. It is not a good idea to drain a liquid and a gas through the same pipe, even if done separately.
In any case, the orifice design should be of multi-stage type, each stage consisting of a multi-hole plate.
This design will prevent cavitation in the case of the...
Shvet, I´ll try to clarify your doubts.
My previous comments assume that the topicstarter has a single C. V. that wants to know what is the best option to install it.
From the data of the Option A, assume to simplify that the pressure drop in the pipe from the H. P. Separator to the HX outlet is...
Shvet, I agree that there are not enough data to fully analyze the question. The fluid vapor pressure, the height between both separators, the C. V. pressure drop ,etc. are unknown. But in relation with the possible flashing of the oil stream, other aspect to take into account, is the influence...
In the case that the fluid flashes passing through the valve, the Option B is the best.
The scenario is similar to the cascade heater drain system of the power plants, where saturated water passes from a condensate heater to other with less pressure through a drain pipe with a level control...
From your post, it appears that the actual flow control is acceptable and the problem is the valve cavitation when it operates at openings less than 30%.
It is possible to eliminate the cavitation in the valve, by symmetrically drilling several holes in the valve disc, making it a multi-hole...
Probably the cause of the damage is the cavitation. If the water temperature is 180ºC, its vapor pressure is approximately 10 bara and the cavitation index is (265 - 10)/(250 - 8) = 1.05
You need a valve with a cavitation coefficient equal or less than 1.05
The damaged valve surely has a...
As the pipe is only 4m long, practically the flashing occurs at the pipe exit and you can consider that the critical pressure at the end of the pipe is the saturation pressure of the water with 146 ºC. Therefore, calculate simply the flow rate of water through a pipe 4m long and 100 mm diameter...
Snickster,
A throttled valve has a significative frictional pressure drop, therefore the expanansion is closer to isenthalpic than isentropic.
For example, in a nozzle, as in the case of a steam safety valve, the friction is very low and the expansion is close to isentropic.
In any case, the...
The steam passing through the valve has an expansion close to the isenthalpic. With an inlet pressure of 270 psi and the valve discharging to a zone at 10 psi, the valve has choking conditions in its throat and the pressure here will be approximately 135 psi. Therefore, to calculate the velocity...
Usually, you can consider that the condensate is saturated at the steam trap outlet. It can get subcooled in the draining piping if it has not thermal isolation.
There are not data about the design of the blowdown line to depressurize the tank. If it is a short pipe with a valve that has a inner pass section little than the pipe, consider only the valve where the flow of air chokes. To calculate the air flow rate through the valve, use the equations and...
Dear pradeep4u,
I only want to say that the steam and whichever other compressible fluid, has a pressure drop (expansion) flowing along the pipe, that cools it. This expansion along the pipe is close to an intermediate value between the isentropic and the isenthalpic expansions.
If the expansion...
If the expansion of the air in the pressure reducing valve were close to the isentropic, the air has an additional cooling passing through the valve.
Usually the expansion through the valves is more close to isenthalpic, but for example, if the valve has a nozzle at the valve inlet, the...
Probably the problem is due that in the heavy rains, the pipe is wet and with much water in the external surface. In this case the heat loss transmission from the pipe to the water is higher than in the case of the transmission to the air when the pipe is dry. The thermal conductivity of the...
I think also that the reason to avoid choking at the discharge pipe exit, is to make sure that the pipe doesn´t decrease the discharge capacity of the valve.
The choking pressure in the valve, calculated with the equation (1) of the first paper attached by pierreick, considers that the expansion...
I think that the rule of 30% control valve pressure drop, is applicable to liquids, but in this case, as you say, there is flashing in the valve and in the downstream line 200m long.
If the line and the valve completely open, has capacity to discharge the peak flow, the design is correct.
Keep...
See the attached paper. I hope help you to solve the problem.
In any case, you can contact a valve supplier to select the appropriated valve.https://files.engineering.com/getfile.aspx?folder=3ab58b66-5495-4fe0-aa4a-e35adb3f4816&file=Válvulas_de_Alivio_Térmico_(1).pdf
