It’s 7 a.m. at a local wastewater treatment plant. You’re in the control room deciding which gas detector to use for a confined space evaluation that afternoon. You select an instrument that was just calibrated last week, pick it up and turn it on. Everything looks to be in good order and ready for use. Your decision is made…but is it the correct one?
Many people think that if a gas detector turns on and is not overdue for calibration, it can be relied upon to provide accurate readings and to alarm in unsafe conditions. Unfortunately, they have no idea what that gas detector may have been through. It may have been dropped, thrown around, overexposed to gas, etc. Simply turning it on will not help you determine if a serious sensor fault or blocked sensor screen exists.
So, as a user, how can you be sure your instrument will detect gas in harmful environments? The answer â€” dock the instrument before you roll.
Testing, calibration and data storage
Fortunately, most gas detection manufacturers offer some sort of docking system. These systems are invaluable in ensuring that an instrument functions properly, and they also provide permanent records of all scheduled events.
One of the automated processes a docking system can perform is a functional (“bump”) test. This is a brief exposure to calibration gases for the purposes of verifying sensor and alarm operations. Challenging the instrument to the gas ensures that the instrument will respond correctly and alarm in the presence of gas.
There is no way of knowing whether an instrument will detect gas properly unless it is tested prior to each day’s use. For many users without docking systems, this little task may go undone. When performed, it may be done incorrectly. Performing this procedure manually involves gathering the calibration gas, regulator, tubing and/ or calibration adaptor, allowing the gas to flow across the sensors for the appropriate time, viewing readings on the instrument’s display, matching the readings to the concentrations listed on the cylinder and making sure the readings are within tolerance. This is a lot to ask of a user who needs a gas detector in a hurry.
A docking system completely automates this process. In addition, it stores all bump test records electronically for safe-keeping. While some docking systems test automatically upon docking, others may require a push of a button. Whatever the process, testing shows that the instrument is ready to respond when called upon.
Another process that docking systems automate is calibration. While the frequency of calibration depends on the manufacturer’s recommendation, a monthly calibration is common. The docking system will perform calibration when the instrument is due, or it can be performed at any time by a simple push of a button. This provides assurance that the instrument is accurate. Just like a bump test, all records of the calibration can be stored for future reference or proof of calibration in an audit situation.
In addition to these two important scheduled events, most docking systems can also download the instrument’s datalogger and charge the instrument’s battery. Some docking systems can perform some or all of these processes automatically while the instrument sits in the station. This allows the user to set a scheduled time and date for these events to occur, ensuring that gas detectors are ready to use when removed from the docking system.
A more advanced type of program allows all instrument records to be stored on the customer’s server and duplicated to the manufacturer’s server. This allows the manufacturer to analyze the instrument data and replace the instrument when a fault has either occurred or is about to occur. By docking the instrument before use, any fault will be realized, not only by the gas detection user, but by the manufacturer as well, thus allowing for a quick response to the problem.
Regardless of the choice of docking system, docking the instrument before each day’s use will ensure that the gas detector is ready and able to provide reliable service. Just remember to dock before you roll!