# How to calculate the leak rate based on pressure drop

• blinkz303
In summary, your project is looking at calculating the leak rate and amount of fluid lost from a pressurized vessel filled with water. You are using the Boyles Law which assumes that PV/T = constant. However, you have realized that this equation is not always accurate, and you are looking for a more accurate method. If you are working with pure water vapor, then head space above the liquid water may be an issue. The cracks may be found on the bottom of the vessel, and there may be cracks along the sides as well. The size of the crack openings may not be known.
blinkz303
TL;DR Summary
I am currently working on a project trying to calculate leak rates from pressurised vessels filled with water.
I am currently working on a project trying to calculate leak rate and fluid loss from pressurised vessels filled with water over a time period of 30 minutes. So far I have used the Boyles Law which assumes that PV/T = constant which gets us P1 * V1 = P2 * V2 and PdV+VdP = 0 I formed this over to PdV=VdP. and divided by the change in time to get dV/dt = - VdP/Pdt

Could anyone help me and tell me if I am on the right track here or have I overlooked something.

Is it liquid water or water vapor or are both present in the vessel. You need to establish the pressure drop vs flow rate relationship for the valve.

To clarify further: I am an intern at a company and I have been tasked with finding a method to calculate the leak rate and amount of fluid lost through possible cracks in a vessel. It can be assumed that the vessel is completely filled with water. I know the volume of the vessel and can figure out the hydrostatic pressure at the bottom of the vessel based on the volume. I have tried calculating the volume loss by calculating the change in the height of the water WH=P/rho*g
P being Pressure, rho being the density of water, g being the acceleration due to gravity.
I know the volume of water per meter of height and can therefore calculate the amount of water lost.
Would this be a viable method? I realized I am running into way to many problems using Boyle's law.

blinkz303 said:
To clarify further: I am an intern at a company and I have been tasked with finding a method to calculate the leak rate and amount of fluid lost through possible cracks in a vessel. It can be assumed that the vessel is completely filled with water. I know the volume of the vessel and can figure out the hydrostatic pressure at the bottom of the vessel based on the volume. I have tried calculating the volume loss by calculating the change in the height of the water WH=P/rho*g
P being Pressure, rho being the density of water, g being the acceleration due to gravity.
I know the volume of water per meter of height and can therefore calculate the amount of water lost.
Would this be a viable method? I realized I am running into way to many problems using Boyle's law.
Is there head space above the liquid water in the vessel? If so, what is in the head space, pure water vapor? Are the cracks exclusively on the bottom of the vessel, or are there cracks along the sides as well? how thick is the wall, and what are the approximate lengths of the cracks. Do you have any idea what the size of the crack openings are?

Lnewqban

## 1. What is the formula for calculating leak rate based on pressure drop?

The formula for calculating leak rate based on pressure drop is:
Leak Rate (mL/min) = (Pressure Drop (psi) x Flow Rate (mL/min)) / (Pressure Drop (psi) x Time (min))

## 2. How do I determine the flow rate and pressure drop for the calculation?

The flow rate can be measured using a flow meter, while the pressure drop can be measured using a pressure gauge. Both of these values should be taken at the same time in order to accurately calculate the leak rate.

## 3. Can I use different units for the pressure drop and flow rate?

Yes, as long as the units are consistent. For example, if the pressure drop is measured in psi, the flow rate should be measured in mL/min. If the units are not consistent, the calculation will not be accurate.

## 4. Is there a standard or recommended leak rate for certain applications?

Yes, there are industry standards for acceptable leak rates in different applications. For example, in the automotive industry, the standard leak rate for fuel systems is 3 mL/min. It is important to research and follow the appropriate standards for your specific application.

## 5. Can I use this calculation for any type of leak or only for pressure-based leaks?

This calculation is specifically for pressure-based leaks, where the leak rate is determined by the pressure drop over time. Other types of leaks, such as visual leaks or mass-based leaks, require different methods of calculation.

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