FAQ-Frequently Asked Questions
Section 1- Technology
Section 2- Safety
Section 3– Gas Supply Options and Cost
Section 4– Hydrogen as a Tracer Gas
Section 1 Hydrogen Leak Detection Technology
What is the hydrogen sensing mechanism?
Our hydrogen leak detectors use a semiconductor type sensor that detects hydrogen in H2 form. The sensor does not detect hydrogen in forms such as H2O.
What effect does hydrogen background have on the leak test?
The natural background of hydrogen is 0.5 ppm. Compare that to helium which is 5 ppm and you see hydrogen is much less prevalent in atmosphere than helium. This low background allows the hydrogen leak detector to detect a 5% hydrogen concentration. Many are surprised at the low background of hydrogen but once again we are talking pure H2 in atmosphere.
Where does the sensing of hydrogen take place?
The sensor is located right on the tip of the probe. The cable to the base unit from the probe is electrical only. No sample (or other contaminants ) are being are being pulled into the probe. This is a major benefit as on major source of leak detector downtime and maintenance is clogged probes.
What is the minimum detectible leak rate?
Minimum leak rate that can be found is 1 x 10-07 atm cc/ sec with 5% hydrogen concentration. This is comparable to helium leak detectors.
How often must I change the sensor ?
The sensor usually will last 2-5 years. It´s like answering “How long will a light-bulb last?.” The sensor is not used up in the same sense as a light bulb but it ages and may become insensitive over time. Exposing the sensor to hydrogen actually has a cleaning aspect to the sensor. Oxidation over time is the failure mode. There is no sudden failure of the sensor.
Section 2 Safety
Hydrogen is a flammable gas, so how can I use that in my facility?
It is the nitrogen that does the trick. No combustion can take place without oxygen. When the 5% hydrogen/nitrogen mix is released into the air it dilutes the air. No matter how much you release, there will either be too little hydrogen or too little oxygen to allow the gas to ignite. Any mix of hydrogen and nitrogen containing less than 5.7% hydrogen is classified as a non-flammable gas. The safety margin is actually greater than that. Even a 10% hydrogen/nitrogen mix is extremely difficult (but not impossible) to ignite.
Is the 5% hydrogen/ 95% nitrogen a flammable or combustible gas requiring special handling?
The 5/95 mixture of hydrogen and nitrogen is a green label non-combustible gas, so no special handling is required.
If I mix the 5/95 on-site, do I have to be concerned about hydrogen accumulating if line a hydrogen line ruptured?
In that 95% of the mixture is nitrogen only a few (maybe only one) cylinders of hydrogen is needed. Those would be stored outside. A ½ inch line would run to the mixer. Hydrogen is a very high energy gas meaning it diffuses very quickly and is lighter than air. Thus hydrogen is extremely difficult to contain. It will diffuse quickly. Natural gas and propane are common flammable gases used in many facilities. These gases are low energy, are heavier than air and will pool up. Thus hydrogen is much safer than other gases already in use at most facilities.
Is hydrogen toxic or a threat to the environment?
Hydrogen is the most abundant material on earth. Hydrogen is neither toxic or environmentally unfriendly.
Section 3- Gas Supply Options and Cost
How can I supply the 5% hydrogen-95% nitrogen tracer gas to my facility?
The 5/95 Gas is common in welding applications, thus is a standard gas mixture. Most gas suppliers will supply 5/95 upon request.
Mixing on-site is also an option. Thermo Inc. manufactures a gas mixer that is now used in many industries to mix hydrogen and nitrogen. It has a proportioning valve and gas analyzer to insure the mixture stays at 5%. A bulk nitrogen tank and hydrogen cylinder would supply the mixer. In that only 5% hydrogen is needed, the hydrogen consumption is very low. Most gas companies will supply a total gas solution including equipment to you. You would contract them to maintain equipment and just pay for the gas you use.
What about the cost?
Hydrogen is much less expensive than 100% helium. When a gas company mixes the 5/95 there is an up charge to do that over the cost of the gases themselves. We have found in bulk that the 5/95 gas delivered to your facility will be between 20%-33% the cost of helium. That will go even lower if helium continues to accelerate in cost as expected.
Mixing on-site is a fraction the cost of helium. We have examples of this cost from less than 10% to 20% the cost of helium. In bulk mixed onsite, the cost of 5/95 mixed on-site is $0.01 or a penny per cu. ft.
What about availability?
Hydrogen is our most abundant resource on earth. Unlike helium which is mined with the extraction of natural gas, hydrogen can be produced from water.
Section 4- Hydrogen as a Tracer Gas
How does hydrogen different in use than what I have seen in using helium?
Hydrogen is a high energy gas. When escaping from a leak, it moves very fast. Thus you do need to be close to the leak. We recommend that since you do not have to worry about probe clogging that you have your operator touch the probe to the test joint. Because it is high energy gas, where the leak is detected is the exact location of the leak. So pinpointing is much more precise.
In testing with customers, we have found that the clean-up of 5/95 from an area is much faster than using 100% helium. This has been found to be a major factor in improving the leak checking environment. There are less false positives with the 5/95 than with helium which makes the job for the operator easier.
What about the helium background issues I face. How does 5/95 gas differ?
The natural background of hydrogen in air is 0.5 ppm versus 5 ppm for helium. This low background of hydrogen in air works in our favor to reduce background. Add that to the high energy of hydrogen moving away from the area and background is much less a factor with hydrogen.
Which is better as a tracer gas, helium or hydrogen?
Both technologies do a good job detecting leaks. Schoonover also sells helium leak detectors every day and supports helium as good tracer gas technology. In the sniffing applications where large amounts of gas are required as a tracer gas, the hydrogen leak detectors will do as good a job in detecting leaks as a helium leak detector. With the uncertain future of the helium availability, a hydrogen leak detector like the Vulkan Lokring is the less risky, more cost effective choice.