Bump testing a gas detector is just one of those things that shouldn’t require much thinking. It is like buckling on your seat belt when you get into a car or donning a helmet on a bike. It is both simple and safe, a good habit which could save your life one day despite its simplicity. It is meant to ensure that the gas detector is sensitive and able to respond to gas threats and as such it is useful to know that the detector you are using is in a good working condition.
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.
Bump testing is to a gas detector what flicking the switch is to a flashlight – it shows if it works! Now if the flashlight fails to come on, the problem could be with the bulb, battery, or the whole flashlight, but the one you have in hand sure won’t help! In the same way, the gas detector must be bump tested to make sure it works when it is needed, so that if it doesn’t pass, maintenance is supplied or other troubleshooting measures are taken, before it is deployed in the environment in which it is meant to be used.
The Importance of Bump Testing
Gas detectors are designed for rugged and demanding conditions, since they may be dropped, or used in humid and hot environments, or exposed to dust, sludge, moisture, and mud, any of which may clog the filters, block it completely, and prevent gas detection.
Dropping an instrument may dislodge the sensors. For all these reasons, it is recommended that gas detectors are bump tested each time they are brought into use at the beginning of the day. Any of these could have a significantly negative impact on the way the detector performs in the moment of need.
How Bump Testing Works
When a sensor is used for toxic or combustible gases, the expected output in clean air is zero in parts per million (ppm), percent of lower explosive limit (LEL) or percent by volume. The exception is the oxygen sensor which reads about 20.9 percent by volume in ambient air during normal function. The use of bump testing on a four-gas monitor will therefore push up the gas readings for toxic and combustible sensors but reduce them in the case of the oxygen sensor.
However, most toxic, or combustible sensors generate a reading of zero in ambient air even if they are not working. Bump testing is done to test their response if gas levels go above zero.
How to do a Bump Test
Bump-N-Go cylinders are designed to simplify bump testing for mobile workers or those who do not have access to a docking station. The miniature cylinders are only 3.8 inches (97 mm) tall and provide up to 250 bump tests when using the corresponding pushbutton regulator. The cylinders have a one-year shelf life and are available for single-gas CO and H2S instruments as well as standard 4-gas (CO, H2S, O2, LEL) instruments.
Given the large range of gas detectors, there are many manufacturer-recommended ways to do a bump test, but the simplest and most efficient method is the use of a docking station, often in connection with software that manages gas detection networks through the Web.
The software enables the individual user to schedule bump tests each day, and in case of any failure, it notifies the person in charge for further action. These docking stations carry in gas from a cylinder connected to them to test the docked detector and simulate a manual bump test.
A manual bump test is a simple setup, consisting of a gas bottle and tubing, a regulator, and a calibration cup in case a diffusion detector is used, with the gas detector itself. The gas detector is set to bump test mode and the gas is applied to it. According to the settings, the gas either reaches the sensors all together or one at a time.
After completion of the test, the results will be shown as pass or fail. Otherwise, the test can be done simply by exposing the instrument to gas while the main screen for gas reading is on and checking that each sensor shows appropriate readings in response, and the alarm is activated, which shows the instrument is in working order.
Difficulties in Bump Testing
Bump testing may be difficult if a company has numerous instruments or uses them in certain applications or locations. For this reason, there is an array of gas cylinder sizes and shapes, larger ones for docking stations since these come into play every day, and portable ones for testing instruments being carried out by workers. In addition, there are customized and readymade gas blends to fit all user applications.
A second challenge has to do with training people to do the bump testing. Safety managers as well as workers are often too busy to impart training to others. This difficulty may be overcome by taking advantage of the large range of training facilities and materials offered by gas detector manufacturers, including videos, information articles, and best of all, hands-on training by trainers who can come to the client’s plant site.
Bump testing is a crucial part of gas detection safety measures, and no gas detector should ever be deployed before making sure that the instrument is working. Training users is just as important, and this must be followed up to make sure the workforce understands the importance of the procedure and by regular repetition of the training until bump testing becomes a habit of the workplace.
This information has been sourced, reviewed and adapted from materials provided by Industrial Scientific.
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