How to choose the best gas detector

CAC Gas & Instrumentation

Wednesday, 01 May, 2019

How to choose the best gas detector

Gas detection instruments are lifesaving devices. It is essential that you choose the best product to meet your specific application and working environment. CAC Gas & Instrumentation has reviewed some of the critical issues to focus on when choosing your instrument, to ensure you are buying the best product for your business.

Gas sensor specifications

The reason to purchase a gas detection device is to measure gas, so the sensor is the first and most important consideration.

What’s the application and what are the correct sensors required?

The key here is not to overburden the instrument. If you need a two-gas instrument, buy a two-gas instrument. Don’t buy a four-gas instrument because the sales rep says it’s cheaper. Whether it’s a two- or a four-gas sensor they both require calibration and bump testing and, ultimately, it will cost you more for the four-gas instrument.

Are the sensors being used consistently or do you only need them in one or two areas of the plant site? If this is the case, minimise the number of instruments with the full fleet of sensors and make sure your core requirement is in the bulk of the instruments. Use single-gas instruments if that meets the application.

What are the specifications of the sensors in the instrument you are considering?

Not all sensors are the same, despite having been manufactured by the same company. In fact, the major sensor manufacturers produce many different sensors for any one gas. For example, one manufacturer produces 14 different sensors for carbon monoxide, each with slightly different specifications. Those specifications are critical in determining if your environment has background gases, which could create cross interferences with the sensor you are considering. The specifications will also assist in determining how poisons or inhibitors will impact your catalytic sensors. Do your homework and find out which sensor is the best for your environment. Selecting the incorrect sensor for your environment could lead to an increase in false alarms, shortened sensor life or a workforce losing confidence in the instrument you selected.

Will the sensor respond in the time frame you require?

Sensor performance is based on laboratory results with just the raw sensor. Adding filters, a case, electronics and possibly a pump will change the speed of performance. Test the instrument that you are considering before you purchase. Challenge the instrument with or without a sampling pump to see just how fast it responds to calibration gas.

Sensor life

Sensor life impacts the long-term costs of the instrument. Look at the specifications, but also ask for proof sources from customers in your industry who are using the instrument. What are they achieving in sensor life? Your environment will dictate sensor performance both short and long term.

Sampling pump specifications

The specifications and performance of sampling pumps, whether internal or external, are often overlooked. The pump can make the difference between whether your sensors perform or not. Poor performance of the sampling pump can change your sensor’s response significantly. Consider the following:

How is the pump designed? What is its expected life span? How long will it run continuously? What is the sample draw distance and with what water column pressure? How are contaminants stopped from entering the pump/instrument? How do you maintain and repair the pump? How easy is it to repair?

These are all important questions that impact the performance of the pump and running costs.

Is my instrument easy to use?

The instrument needs to be easy to use, as today’s workforce must deal with multiple tasks and responsibilities. Ease of use includes the user but also should include the service technicians who need to calibrate, test and repair the instrument. Even if you outsource your maintenance, make sure the instrument is easy to repair and calibrate so your repair bills remain low.

Size and ergonomics are part of ease of use. You need the instrument to be comfortable to wear and not interfere with the user’s work functions. Controls and buttons should be user-friendly and most importantly easily accessible. Smaller is not always better, but size should not be a deciding factor unless all other critical elements are the same.

Is my gas instrument durable?

Durability cannot be overstated. The best technical instrument is of little value if it gets damaged easily and is often out for repair. Be careful though not to trade off durability for key technical requirements. You need the most technically competent instrument in as durable a package as possible.

Training the end users on the use, care and operation may assist in reducing damage to instruments.

Calibration and function/bump test gas specification

It doesn’t matter if you are manually calibrating and bump testing instruments or using the latest in docking station systems, you must determine the total volume of gas you will consume over one or two years. By doing so, you will be able to maximise your calibration gas efficiency and minimise cost.

Selecting the correct cylinder size(s) and mixture contents will allow you to minimise cost/litre of calibration/bump test gas while maximising the supply efficiency. Get a qualified gas expert involved in your decision-making when it comes to cylinder mixtures, cylinder sizes and gas distribution systems.

Docking or calibration/testing system specifications

Selection of your gas detection device should be based, first, on the instrument’s capability in meeting your requirements as outlined above.

Managing your fleet of instruments has a significant impact on long-term costs and should be a key part of the overall cost/benefit analysis of each gas detection device you are evaluating. Although, it should be the second stage of the evaluation after you have determined the best instrument choice or narrowed it down to two.

Key considerations with docking stations/calibration systems include:

Is the system easy to set up, commission and maintain? Do you need specialised individuals to run the system? How does the system deliver gas to each module? Does the system deliver gas by flow or pressure? How long does the system take to calibrate and bump test? What volume of gas is consumed with each calibration and bump test? What is the maximum number of instruments you can calibrate/bump test at one time? How does the system accomplish multiple calibrations at one time? Can the system easily manage growth in your fleet? Can the system be used for all the gases you must monitor?

Service and repair specifications

In-house or outsourcing your service and repair needs depends on your resources/manpower and costs. In either case you must determine how difficult your instrument is to repair. If the instrument is extremely difficult to repair, then your costs will be high. Many suppliers provide service contracts or total cost management options. All of these have value but need to be evaluated against the actual costs of you maintaining the instruments yourself, if possible.

Training specifications

Training is a key step to implementing your gas detection program. It should not be overlooked or be an afterthought. The best instrument in the world not introduced, trained and implemented correctly will be a failure. Be prepared to pay for a qualified trainer who has the skills and knowledge to provide value-added training.

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