On my latest helium leak detection journey, I put down the spray gun and picked up a sniffer probe to enter the world of sniff testing. I teamed up with our specialist leak detector engineer to find out more.
Standard or Smart?
One thing to consider before starting a sniff test is what type of sniffer probe you require. Essentially, there are two different types, standard and smart.
Smart sniffer probes can measure lower leak rates of around
2.5×10-6 whereas a standard sniffer can detect 5×10-6. These leak rates are measuring the natural helium in the air. Although there isn’t a huge difference between the measurements, if the test part requires a greater sensitivity for a leak then it can make a difference.
The smart sniffer has a useful feature for detecting leaks. As previously mentioned, the lowest leak rate that a smart sniffer can detect in the atmosphere is 2.5×10-6 . The smart sniffer can be set to this leak rate as a base for the test and a LED light on the side of the sniffer will show a green light. During the test, the LED light will flash red if there is a higher leak rate than what is set on the smart sniffer (indicating a leak is present).
A standard sniffer is also accurate when detecting leaks. However, there is no visual aids on the sniffer to indicate there is a leak. Instead, it requires you to follow the graph on the leak detector’s LED display and the leak detector will bleep if there is a leak present. This means that a standard sniffer probe is easier to use if you have some previous leak detector experience.
The Set Up
In comparison to spray testing, sniff testing is easier to set up and execute. Sniff testing does not require a hard vacuum to carry out the test. Firstly, you will need to insert the sniffer probe connector into the correct port.
Once the sniffer probe is plugged into the helium leak detector, it needs to be set to sniffer mode. This can be done by pressing the home button and cycling the menu until you get to the test screen. Change the method to Sniffer and make sure the probe type is standard (unless using a smart probe). A smart probe will instantly change to smart on test settings once plugged in. The helium leak detector is now set up for a sniff test.
Tip: Make sure there is no added helium in the room at time of testing. This will confuse the leak detector and lead to inaccurate readings.
Press start on the leak detector LED screen to begin the sniff test. This will switch on the filaments inside. The start up is generally quicker when using a smart sniffer. Unlike spray testing, sniff testing requires you to start testing from the bottom of the test part. For example, If you had a leak halfway up a pipe, starting at the bottom means that you wouldn’t find a leak (helium) until that halfway point. If you started at the top then you might detect more helium than there actually would be at that the leak source. This is due to the fact that helium rises and would give you an inaccurate reading.
Working from the bottom, move the sniffer probe slowly up the test part. The nozzle should be 2-3mm from the point that you want to test. Make sure to cover any leak points (O-rings, welding spots etc). It is advisable to move the sniffer probe around test part at 20mm/sec.
If a leak is present then the LED display will flash. It is advisable to switch to graph mode on the display screen during the test. This shows any peaks with the leak rate at and is visually easier to interpret.
I completed the test with a standard and smart sniffer probe. Being a complete leak testing novice, I found it easier to use the smart probe due to the LED light indicator. When I was using the standard probe, I found it slightly harder to interpret the graph when a leak was present. The LED light on the smart probe would flash red when a leak was present which made it easier for me to identify where the leak was.
Similar to the spray test, I found carrying out the test a lot easier than interpreting the data. Even though I could see when a leak was present, I lacked the wealth of knowledge needed to interpret how big it was and exactly where it was. Our lead helium leak testing engineer could pick this up instantly. Therefore, it would save a lot more time and effort getting one of our engineers to find leaks than carrying it out myself. I enjoyed my training and it has left me with a deeper understanding of leak testing and a deeper respect for the process and intricacies of the work involved.