Dear All

Is it possible to calculate value of internal leakage in valves (e.g. lit/min) by ultrasonic evaluation?

Regards,
Farahani

Hello Farahani,
you ask a difficult question.
I would suggest that you look at ultrasonic flow meters as a possible answer.

Best Regards,
Tom Murphy

Dear Tom

Let me ask in another way. Some of ultrasonic leak detector (e.g. Vpac) claim that are able to calculate the amount of internal leakage (passing) in valves. I think they do this experimentally based on measured dB. Does SDT 170 do this? [I seek a way except using ultrasonic flow meters].

Regards,
Farahani

Farahani,
I would think you are wright as far as they are doing it by experiment.

The things to consider when trying to determine how much leakage is present are as follows:
Size of hole
Shape of the hole
Pressure
Temperature of fluid or gas
Viscosity

The position of the reading you collect and what type of method you are using (touch probe or magnet probe)

All are things that are variables that can change the result you get.

I believe this is why it can be extremely difficult to measure how much loss is in the system without doing any maintenance/ mechanical work.

On an underground longwall mining system I tested before maintenance and compared the results after at the pump station. We have had mixed results depending on what was changed out through this time. Most of the time we are able to reduce the leakage in thease systems to be able to put one of the 4 pumps from continual service back to standby.

The best thing about this service is that the maintenance planner can get the results before the shutdown, order the parts required and plan the job properly. This is where you can save alot of time and money.


These are just my thoughts on your little problem, I hope this helps!

Regards,

Hooch

Farahani,

The only product that I have seen make a claim to correlating ultrasound to leak flow rate is the VPAC 5131 that uses Physical Acoustics sensor technology.

This info from http://www.russelltech.com/UT/VPAC%205131.html

"The Model 5131/VPAC is an intrinsically safe digital AE leak detector. Widely used in refineries, chemical plants and offshore platforms, the 5131 estimates through-valve gas leakage.

Features
• Loss control for refineries, chemical plants and offshore platforms
• Identifies through-valve gas losses
• Field proven
• Fully digital
• Usability
• Battery operated

Database
The basis of VPAC is a database built up by British Petroleum over the past decade that estimates leak rate from the acoustic signal level, taking into account valve type, size, and pressure. The database was built up by removing valves from service that had been identified as leaking by the use of the portable monitor, and testing them under controlled conditions in the laboratory. Several hundred measurements were made. This data is included in the package in both numeric and graphical form, together with procedures for making site measurements and calculating losses.

Benefits
B.P. uses this technology in its operations and loss-control, resulting in a very fast payback. Site experience has shown that 5-10% of valves leak, and 1-2% of valves cause 70% of total loss. Savings in excess of $100,000 per site are easily achieved. Where gas recovery systems are in use, monitoring product valve leakage helps to identify and estimate the extent of the downgrading of valuable products to fuel gas due to valve leakage. This is something previously identified by the flare, but goes unseen with gas recovery in use. Cost savings are achieved in maintenance planning, troubleshooting plant operations and monitoring of losses for environmental purposes."

The key info here is that it is based on empirical data for a specific instrument for GAS leaks. It does not mention liquid leak detection. If this instrument is what you want, then check it out carefully so that you know it will work for your applications and desired results. I doubt that SDT or UE Systems has an equivalent product.

Walt

Dear Hooch
Dear Walt
I appreciate your good explanations. They were very useful for me.
Regards,
Farahani