Category: Gas Detectors
Handheld Gas Detectors-which ones are best?
Handheld gas detectors are those portable gas detectors that can be held in your hand. These gas detectors include toxic gas detectors, oxygen meters , explosive gas meters (also known as lel meters, lel being the acronym for lower explosive limit) or PID meters used for workplace monitoring of VOCs and other compounds. This post is to get reader feedback about such instruments, which ones are best? Best technologies? Makes? User friendliness?
I must say that we have come a long way since the early 70s and even 80s, when many of these technologies were not developed and not as reliable as they are today. Workers and professionals working in process plants used to rely more on chemical tubes (also referred to as Drager tubes) and other methods to check for presence of toxic gases, or for workplace monitoring. Now the monitoring has become simpler for the end user with lost of competing technologies, sophisticated instruments and powerful data storage and handling capacities. Today’s handheld gas detectors can sense the gas/ vapor, store the readings over a 8 hour period and record & calculate values such as the Time Weighted Average. This was not possible with the earlier technologies. However these newer gas detection instruments require the users as well as the Instrumentation staff to be trained, as the performance of the instrument is highly dependent on the selection of the sensor or technology (like photoionization versus electrochemical for instance), calibration of the instrument and general maintenance and upkeep. My question to all of you is, do we have a winning model of a handheld gas detector that has excellent performance, is easy on today’s shrinking safety budgets, yet does an exemplary job of sniffing gases? If so, please name it and the reasons why.
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Yet another welding related fire-now in a nuclear plant!
As if we did not have enough of welding related fire accidents in conventional plants (read my last post on the issue here ), now we have a report of a similar accident in a Japanese nuclear plant.
Here is the incident reported by various agencies:
A fire broke out at a nuclear power plant in northern Japan on Thursday, injuring one worker but causing no radiation leak, the operator said.
Firefighters put out the fire about an hour after white smoke was spotted coming out of the reactor, which was already shut for a regular check-up, Tohoku Electric Power said.
“One worker sustained minor burns but was not exposed to radiation,” a company spokesman said, adding there was no leak to the outside environment either. The fire started at around 2:00 p.m. at the plant’s No. 1 reactor, which has been undergoing regular checkups since February, Tohoku Electric said.
Kyodo News Agency which first reported the incident said the worker was in a welding operation inside the building, and the filter in the air conditioning system might have caught sparks from the welding.
The plant is located in Onagawa town, some 350 kilometres (220 miles) north of Tokyo. The plant has two other reactors, which are operating normally.
The nuclear power complex, which suffered extensive damage in an earthquake last year, has been out of service and undergoing repairs.
The incident occurred just days after a Dec. 1-5 inspection by a team from the United Nations nuclear watchdog. The team of 10 experts from the Vienna-based International Atomic Energy Agency assessed safety measures designed to deal with the continuing threat of earthquakes.
I hope the investigation is completely impartial and gives us some better ideas to prevent such incidents in future. I know that the nuclear industry is a highly regulated and procedure-driven industry so this incident is shocking. Secondly, this is the second such fire in a Japanese plant (the earlier one was supposed to be because of an earthquake). However as usual, the investigation reports are pretty sketchy and certainly not as detailed as the ones from the chemical /hydrocarbon processing industry (Well, if they are I have not seen many in the public domain). I wonder what kind of combustibles are present in such installations and what kind of gas detection systems are used. Anybody from the nuclear industry who is reading this could be kind enough to throw some more light on this issue.
Comments as usual are welcome.
Not doing a gas test before welding is criminal negligence
I wonder why many plant owners & managers cannot do some simple things to prevent accidents and save innocent workers’ lives? Shockingly, in many of the recent accidents, that have been reported as “welding accidents”, the root cause is not doing a “gas test” before starting the job. As all of you, who are familiar with the oil & gas, petrochemical and related industries know, it is essential to do a “gas test” (in other words, use a gas monitor to check the presence of explosive or flammable gases) before allowing “hot work” in any area in the plant. Apparently, this simple fact is not known or plainly ignored by many owners/operators of such facilities.
The recently released US Chemical Safety Board investigation into the Jackson, Mississippi oilfield accident, clearly indicates that the owner company failed to do this basic test, before allowing workers to do the welding work. The result was a very predictable explosion, with an unfortunate fatality too. This, in a developed country, supposedly industrially advanced, like the US of A; we’re not talking about some Timbuctoo in some remote corner of the world.
The latest such incident is an oilfield explosion in Ohio. Just about three weeks ago there was another similar accident in Honolulu. The US Chemical Safety board has sent a team to the site for an investigation into the Ohio explosion ( the Honolulu investigation is still on) and we will know only later whether this too, was the result of not conducting a “flammable gas test” at the site before allowing such work to start.
I wonder whether the managements are incompetent or plain negligent or ignorant about the hazards of allowing hot work, in areas known to have flammable vapors and gases. This is because explosive gas monitors are not at all expensive , easily available everywhere and are also pretty easy to operate. Training is available in many forms, including an excellent e-learning course on Gas Monitors, as well as from other sources such as vendors.
It is time that the authorities made it loud and clear to all owner/operators that there will be zero tolerance for such negligent acts. I understand that the US Chemical Safety Board can only make recommendations, not issue penalties, so this has to be done by some other federal agency.
As always your comments on this issue are welcome!
Gas Detector calibration & testing-ideal frequency
In a typical large chemical manufacturing plant or facility, typically there may be hundreds of gas detectors and gas monitors that warn operators about lurking hazards related to leaking chemicals and vapors. These detectors are installed during the plant startup or possibly are added after a few incidents or as the result of HAZOP or safety studies. So far so good. How do you, as the plant engineer or plant manager or the safety manager, ensure that they continue to work as intended?
Well, you calibrate them or just “bump test” them with a known gas mixture in a gas bottle. Fine, but after how many months or years?
How often should you check, whether your installed gas monitors & gas detectors are working OK? In order words, what should be an ideal calibration frequency for these instruments? This is one of the questions that many engineers and technicians ask us, after they learn about gas monitors (from our excellent e-learning course on gas detectors and gas monitors).
Nobody seems to have a common answer.
Some experts suggest every year, some every half year and others, every quarter. So who is right? Some may feel the more the frequency, the better. However, the catch is, that in most electrochemical type gas detectors, every time a calibration or even a bump test is carried out, a small amount of the electrolyte is depleted. This means that the useful life of the gas detector gets reduced , the more you test it. It may so happen, that on a particular test (say the fifth one on the same sensor since its installation), almost all the electrolyte will get depleted. However because sufficient electrolyte was present during the test, the detector will pass out with flying colors. BUT, suppose the next day there is a gas leak AND the electrolyte is now depleted, the instrument that was just declared healthy yesterday will fail in the actual emergency !
Does this bother you? It should. Probably some manufacturer will start indicating the level of useful electrolyte left (there are some models that have this, but I am not sure) or there is some kind of other sensor diagnostic available, but in the vast majority of these detectors, it does not seem to be present.
What about the catalytic combustion type? Well, frequently exposing them may to %LEL gas mixtures may cause damage of the bead (repeated explosions taking place on the bead) and could render them ineffective in an actual gas leak.
The only types that can escape this “destruction by calibration” seem to be the semiconductor and the optical/infrared types, that may be unaffected by frequent exposures to gases to which they are sensitive. Does it mean that we should replace all of the electrochemical types and the catalytic combustion types with IR sensors and semiconductors? Not really practical as they are much more expensive than the electrochemical type and the catalytic combustion type.
So do we use the “lightbulb replacement method”, that used to be present in many factories in the 80s (for those who have forgotten about it, here is a refresher-some smart guy had calculated that replacing all light bulbs-even the working ones-every six months was cheaper than replacing only those bulbs that failed, due yto the inventory carrying costs, the payroll costs of the “light-bulb-changers” ,etc, etc).
Do we simply replace all the electrochemical sensors and catalytic combustion sensors every two years? Any thoughts on this issue?
Please use the comments form below.
(P.S. BTW if you wish to know more about gas detection or have a good training course on gas monitors, why don’t you download our excellent e-learning course ? )
