Multi-PID 2 photoionisation detectors from Draeger Safety Pacific
Multi-PID 2 photoionisation detector
Photoionisation detectors (PID) have featured in Draeger Safety’s product range for quite some time now. A while ago, the Dräger Multi-PID was presented.
Dräger Multi-PID 2: New device, new possibilities.
The Multi-PID 2 remains unchanged as far as its detector technology is concerned.
The Multi-PID 2 still offers high measurement sensitivity, accuracy, reproducibility of the measurement signal and low cross-sensitivity to water vapour (humidity).
The Multi-PID 1's familiar substance library and response factors have also been retained, meaning that no correction factors need to be taken into account when personnel switch to using the Multi-PID 2.
As regards handling and the instrument's display, however, the previous model has undergone some important changes:
Substance name displayed on screen:
The name of the substance currently calibrated is displayed in plain text on the screen, above the substance concentration.
If other substances occur at the site of measurement in addition to the one currently being detected, the total sum of organic substances is displayed, based on the calibrated substance.
Additional concentration information displayed on screen:
As well as the current concentration, the 15-minute average value (STEL), the 8-hour average value (TWL), the maximum recorded concentration (PEAK) and the elapsed measurement time are displayed on the screen in a smaller font size.
Data recording mode displayed on screen:
In the top right-hand section of the screen a symbol indicates whether the interval mode (i.e. continuous data recording) or the TAG mode (i.e. manual data recording) is activated, or whether no data are currently being recorded.
Just like its predecessor, the Multi-PID 2 can store 15,000 measured values. The Dräger GasVision then allows convenient processing and archiving of these data. GasVision outputs the maximum, minimum and average readings for each measurement interval.
One-key calibration:
Because PIDs generally require daily calibration, this process has been simplified in the Multi- PID 2 through the use of just one key. This means it is no longer necessary to work through several steps in the menu, so calibration could not be easier to perform.
Five languages in one device:
While users of the Multi-PID had to choose a language at the time of purchase, the Multi-PID 2 allows the operating language to be changed at will: German, English, French, Spanish and Italian are available, so personnel with different mother tongues can easily use the device too.
Applications:
PIDs offer multifunctional use when it comes to measuring organic and some inorganic substances.
The main difference as compared with other sensors (e.g. catalytic Ex-sensor or infrared Ex-sensor) is the fact that the PID is also able to conduct measurements right down to the sub-ppm range (with detection limits of approx. 0.5ppm). A number of typical applications are described below.
Leak detection and environmental analysis:
Due to its rapid response time and high level of sensitivity, a PID is well-suited to detecting leaks in many different settings, e.g. in pipelines in refineries, in tanks in chemicals factories, refineries and petrol stations and on ships and other means of transport.
If a leak is identified or an accident involving hazardous goods occurs, it is of course important to determine whether the soil in the vicinity of the leak has been contaminated.
Due to its high sensitivity, the Multi-PID 2 is also suited to such tasks, as well as to conducting a preliminary classification of soil samples (by way of a screening test to decide whether a laboratory analysis is necessary).
Arson investigation:
Arson investigations are often conducted to determine whether fire accelerants such as petrol, hydrocarbons or alcohol were used.
When police or fire officers inspect the scene of the fire, the Multi-PID 2 is used to search for any traces of such substances. In these situations the Multi-PID 2 is typically used with the sampling hose as a probe, allowing sites to be accessed which would otherwise be difficult to reach.
Entering aircraft tanks and other confined spaces:
Aircraft tanks constitute a particularly extreme example of confined spaces.
Since maintenance and inspection personnel have to conduct their checks right into the furthest corners of the tank, the use of respiratory protective equipment is only possible to a limited extent. This makes it all the more important to perform an all-clear measurement to ensure, for example, that the kerosene concentration is below 10ppm.
Because catalytic Ex- and infrared sensors cannot reliably measure such low concentrations of organic substances, this situation is also a typical example of a PID application.
In other tanks used to store organic substances too, an all-clear measurement should be conducted using a PID before personnel enter the tank. There is a clear trend towards assessing organic substances not only with respect to the explosion hazard they pose, but also with respect to their toxicity. This is something which can be done for a wide range of organic substances using the Multi-PID 2.
Fumigation Methyl bromide is still used, particularly when timber is transported overseas, but also during transport of textiles.
When unloading containers, or indeed when they are inspected by customs officials, it is important to ensure that concentrations of methyl bromide and any other fumigants are below the permissible limit values.
The advantage offered by the Multi-PID 2 here is that the instrument is able to cover an additional range of measurement.
Concentrations of between 0.5 and 2000ppm can be detected as standard, and the measurement range can be extended to 20,000ppm if the dilution probe is used. This makes the Multi-PID 2 suitable both for monitoring the efficiency of the fumigation process and for conducting measurements of relevance to health
Measuring diesel vapours:
Diesel is a mixture of different long-chain hydrocarbons and is used as fuel in cars, agricultural vehicles, trains and ships.
Up until now, attention was generally focused primarily on measuring concentrations of diesel fuels in the Ex concentration range (the lower explosive limit range, or LEL).
However, people's health may also be at risk below this concentration range. Bearing this in mind, the American Conference of Governmental Industrial Hygienists (ACGIH) issued a new limit value for the 8-hour mean value in 2002.
For the hydrocarbons in diesel, this limit is 100 mg/m3, equivalent to approx. 15ppm.
Diesel concentrations in the toxic concentration range are relevant when it comes to entering or cleaning tanks, and also during refilling and fuelling activities.
The Multi-PID 2 enables diesel concentrations in the ppm range to be determined. Because diesel is a mixture of different hydrocarbons, no universally applicable response factor can be stated.
For lighter diesel types the instrument can be calibrated to nonane and a response factor of 1.4 can be used. For heavier diesel types, such as those used in the shipping industry for example, a response factor of 1 can be applied.
Measurements in the chemicals and petrochemicals industry:
This is without doubt the main area of application for PIDs. Especially when personnel are to enter tanks, pipelines and other confined spaces, it is important to ensure that the concentration of the substances stored inside them is sufficiently low to prevent any harm being caused to the health of personnel.
The advantage of the PID, once again, lies in the fact that it allows measurements in the ppm range and that it can be calibrated to different substances.
Using the Multi- PID 2's calibration memory, different substance calibrations can be stored inside the instrument. This means that toluene can be measured first, for example, followed by an acetone measurement sometime later.
Calibration of the individual memories can be performed prior to the measurement process, so that only the calibration memory in question needs to be selected when it is time for measurement.
A further application in the chemicals and petrochemicals industry besides confined space measurements is of course classic workplace monitoring, for example when concentrations of hazardous substances need to be checked during particular work activities (e.g. filling of substances from one container to another).
In conclusion, it is clear that the Multi-PID 2 is able to perform measurements in many kinds of different applications and work areas.
Through Draeger Safety's technical applications service, users have access to far more response factors than those already stored in the substance library of the Multi-PID 2. For substances not listed there it is possible to determine whether they can be measured by means of PID.
The Multi-PID 2 photoionisation detectors are available from Draeger Safety Pacific.
15-Oct-2007