The importance of bump testing:
- Bump testing is one of those topics that crops up again and again, but still not everyone gets the point. A gas detector may not respond properly to gas for many reasons. Bump testing is a quick and easy way to ensure yours does because They may be exposed to rain, dust, oil, sealants, etc, and the sensor’s protective membrane may become blocked.
What a Bump Test Means:
- A bump test is the method of ensuring that the gas sensor and alarm functions of a gas detector are working properly. In this test the detector is exposed to a whiff of gas at a level higher than its alarm set points. It thus checks that the sensors can correctly pick up the high level and that the alarm goes off as expected. It is important to know that this test is not meant to certify accuracy, which is achieved by device calibration, a totally different thing to bump testing.
Example for case need to Pump Testing.
- Garry works at a local oil refinery and arrives in the morning to carry out his daily tasks. He wears all the safety equipment required for safe site entry. His job for that day is to carry out some heavy cleaning around the site using a jet washer.
- At the end of his shift, he returns to the changing room to clean up. He cleans his kit using common cleaning agents containing alcohols and silicones.
- The next day he arrives on site and collects his equipment before being briefed on his work for the day. Later he is working in a low-lying area when he smells something like rotten eggs, but the smell quickly passes and, as his gas monitor did not react, he continues working. Not long afterwards he suddenly collapses after being overcome by high levels of hydrogen sulphide.
What lessons can we learn?
- In this example, Garry has impaired his monitor by using the wrong cleaning products – an easy mistake to make if you don’t know, but one that would have been highlighted by a bump test.
- Sensors can become poisoned or inhibited with these cleaning agents. Alcohol can damage electro-chemical sensors and silicone-based products inactivate catalytic bead sensors intended for measuring hydrocarbons such as methane, pentane and propane.
- In both cases, the circuitry would still be complete, and so the unit would give a normal output. Without any additional tests, Garry would think it was working normally. However, the unit would not go into alarm if it encountered high gas levels.
What should Garry have done differently?
- Garry would have avoided this particular issue by checking what products were suitable for cleaning the detector – possibly warm water in this case. His gas detector’s manual would be a good place to start. The manufacturer would also provide additional guidance on how best to clean the unit, if required.
- Regardless, upon arriving on site he should have carried out a bump test. This would not only highlight poisoned or inhibited sensors, but also any blocked filters or faulty sensors. It would also check that the audible and visual alarms are working.
- In other words, it would confirm that the unit goes into alarm when it needed to.
- Garry would have then replaced his non-compliant unit with a functioning one, and so he would have avoided the H2S gas release that caused his injury. Fortunately for Garry, his colleague, John, saw him fall and raised the alarm. Garry wasn’t seriously injured but had to take two weeks off work to recover.
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