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satendrakumart
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Join Date: May 2011
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How to Detect Leakage in Impulse Line of Vaccum Transmitter

03/22/2013 11:51 PM

Vacuum transmitter of steam turbine is showing less reading than actual. Cross checked the transmitter at other point, it is ok. I think, there is minute leakage in impulse line. We detect leakage in pressure line by applying soap foam. Is there any method to detect the leakage in vacuum line?
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porky2009
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Join Date: Sep 2009
Posts: 72
#1

Re: How to detect leakage in Impulse line of Vaccum transmitter

03/23/2013 5:56 AM

ultrasonic leak detector

http://www.ctrlsys.com/products/leak_detection.php
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bigg
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#2

Re: How to Detect Leakage in Impulse Line of Vaccum Transmitter

03/23/2013 7:21 PM

2. If you can block it off temporarily, pressurize it with air and use your soap solution.

3. Assuming it is dry, put a little water around potential leak points and see where the water disappears. Another variation of this is to smear some thick grease around potential leak points while watching the transmitter output. When the vacuum reading goes up, there's your leak point.
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KeepItSimpleStupid
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#3

Re: How to Detect Leakage in Impulse Line of Vaccum Transmitter

03/23/2013 10:50 PM

Helium Leak detection is the GOLD STANDARD. see: http://www.pfeiffer-vacuum.com/products/leak-detectors/container.action

The system usually includes a vacuum pump and is basically equipped with a RGA (Residual Gas Analyzer) sensitive to Helium.

Once the system is pumped out, Helium is sprayed in the vicinity of the leak and you wait for the helium to get pumped into the detector. If you saturate with Helium then you may have to wait for Helium to dissipate. You don't use a Helium leak detector for big leaks.

Using a Vacuum system with a gage. Pressure around 100 milllitorr, it may be water having to be pumped out. That's what is know in the industry as a "virtual leak". Not really a leak, but it acts like one. If it's around 50 millitor, you can sometimes use methanol externally. When it gets sucked in, the pressure rises. This regime generally uses a Thermocouple vacuum gauge.

You might also employ your local HVAC technicians to pressurize the system with a little bit of Freon and then look for a leak with an electronic leak detector.

The "leak up" rate is a standard way of proving the system. In an HVAC system, you can use a vacuum pump and pump out the system and then close off the vacuum pump. Then wait.

So, yea it kinda depends on what regime your at and what you can use. Commercial soap bubble solution will let you find fine leaks in say a gas line, but a detector sensitive to the gas might be a better option.

You can buy detectors sensitive to particular gasses or ones that basically sense the difference in thermal conductivity.

Some of the electronic Freon leak detectors, initially do a sample of the surrounding air for the initial thermal conductivity and then when you get close to the leak the tones change. Thus it can be used in the presence of the gas.
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Stuart21
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#4

Re: How to Detect Leakage in Impulse Line of Vaccum Transmitter

03/24/2013 4:02 AM

Download "fourier" or 'fourier lite' to your iPhone, or similar to other smart phone. Open app, resize visible output to display, put near suspected leak, turn vac on and off. Leak should show up as a high level of high freq noise.

Did this with my compressed air line, found 5 leaks in half an hour, compressor now running half previous time.

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roy hammy
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#5

Re: How to Detect Leakage in Impulse Line of Vaccum Transmitter

03/24/2013 7:34 AM

Porky 2009 has the answer. As air rushes in it creates turbulence this creates noise in ultra sound range and is easily detected. Leak can be tiny but can be located.

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Stuart21
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#6
In reply to #5

Re: How to Detect Leakage in Impulse Line of Vaccum Transmitter

03/24/2013 8:03 AM

Stuart21 same.

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DKT
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Join Date: Dec 2012
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#7

Re: How to Detect Leakage in Impulse Line of Vaccum Transmitter

03/24/2013 11:58 AM

Hi dude,

Use joss stick arround vaccum line, smoke of joss stick start to inter in leak area of vaccum line with atmospheric air, due to this vaccum leak can be detect.

R u agree with this idea.
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PWSlack
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#8

Re: How to Detect Leakage in Impulse Line of Vaccum Transmitter

03/25/2013 4:57 AM

There's a fundamental error here: if the transmitter is OK on the test bench and there is an inward leak when it is attached to the pipework, then the transmitter is telling the truth!

The only way to eliminate the leak is to chase through every joint in the pipe and re-make it to the highest standard. It is important to do so, as air in the condenser will affect the turbine performance and efficiency. So do it today.

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jsmclaren
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#9

Re: How to Detect Leakage in Impulse Line of Vaccum Transmitter

03/25/2013 11:44 AM

KeepItSimpleStupid has the right idea. May I also suggest www.agilent.com/chem/leakdetection

Happy to help you arrange a test/demonstration of an instrument on your application.
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tonykuphaldt
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Location: Bellingham, WA
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Good Answers: 46
#10

Re: How to Detect Leakage in Impulse Line of Vaccum Transmitter

04/11/2013 10:28 AM

If there is an isolation valve where the impulse line connects to the turbine, you can shut that valve and see if the vacuum reading from the transmitter changes. If the vacuum reading decreases (i.e. goes toward atmospheric pressure), then you do indeed have a leak. If the vacuum holds constant, then you don't. It's a simple test that will at least confirm whether or not a leak exists at all, before you spend a lot of time searching for the location of a leak that might not be there.

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Users who posted comments:

bigg (1); DKT (1); jsmclaren (1); KeepItSimpleStupid (1); porky2009 (1); PWSlack (1); roy hammy (1); Stuart21 (2); tonykuphaldt (1)

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