Pyrotec Pyrolyzer

Why Some Compounds Cannot Be Measured Directly

Worth understanding first, because it explains why this attachment exists rather than a tube.

A colorimetric detector tube works by chemical reaction. The target gas reacts with a reagent and produces a colour change, and the length of that change gives the concentration.

That requires the target gas to be chemically reactive. A great many are, which is why tubes cover more than 500 substances.

Refrigerants are not. Neither are most halogenated hydrocarbons or the volatile anaesthetics. Their chemical stability is the entire reason they are used, since a refrigerant that reacted with things would be a poor refrigerant and an anaesthetic that decomposed would be dangerous. A stable compound passing through a reagent does nothing at all.

So there is no direct tube for them, and until thermal cracking there was no field method either. Measurement meant taking a sample and sending it to a laboratory.

What Thermal Cracking Does

The Pyrotec breaks the molecule apart before it reaches the reagent.

A sample drawn through the pyrolyzer is heated to the point where the compound decomposes, which is the process known as thermal cracking. A stable chlorofluorocarbon becomes reactive fragments containing chlorine and fluorine, and those fragments react readily with a colorimetric reagent.

So the tube is not measuring the refrigerant. It is measuring the products of destroying it, in a known proportion, which gives the original concentration.

That is a considerably more elegant solution than it first appears, and it converts a laboratory measurement into a field one.

Three Things You Need

Worth stating plainly because they are ordered separately.

A measurement requires a Pyrotec detector tube, the Pyrotec pyrolyzer, and a Gastec sampling pump. Ordering the pyrolyzer alone leaves you unable to measure anything.

Assembly needs no tools. The pyrolyzer screws directly onto the sampling pump, and sampling begins straight away since it is ready to use in seconds rather than needing to warm up.

Five Pyrotec tubes work with it: numbers 51, 51L, 51H, 52 and 53. Each carries a direct read scale printed on the tube, so the concentration comes straight off the glass with no dual scales and no concentration chart to interpret.

Power is AA disposable batteries, which means nothing to charge and a spare set in the case rather than a flat instrument. The body is high impact plastic, corrosion resistant and built to be carried.

What It Measures

Four groups of compounds, and the coverage is wider than most people expect.

Refrigerants and fluorochlorocarbons, including R11, R12, R22, R112, R113, R114, R123, R124, R141b and R225. That covers refrigeration and air conditioning leak investigation, cool room and chiller work, and marine and transport refrigeration.

Halogenated hydrocarbons, including methyl chloride, methylene chloride, acetonitrile and methyl sulphide. These appear as industrial solvents, degreasers and process chemicals.

Nitroparaffins, used as solvents and intermediates.

Anaesthetic gases including halothane, which covers veterinary practice and older medical installations.

A separate Gastec Pyrotec system covers sulphuryl fluoride, which is dealt with below.

A Second System For Sulphuryl Fluoride

Gastec also produce a Pyrotec system specifically for sulphuryl fluoride, reading from 1 to 20 parts per million.

That is worth knowing about. Methyl bromide has been progressively withdrawn as a fumigant under the Montreal Protocol, and sulphuryl fluoride is the principal replacement for structural, timber and commodity fumigation and for quarantine treatment.

So a growing number of Australian operations are using a fumigant they need to measure, both for clearance before re-entry and for demonstrating residual levels. A field method for it is not easy to find. Talk to us about availability if that is your application.

This One Is Not Intrinsically Safe

Read this before specifying, because it reverses the rule that applies to the rest of the tube range.

Colorimetric tubes, Polytec tubes, dosimeter tubes and the sampling pump are all intrinsically safe by construction, because there is nothing electrical in any of them. They go into a classified area with nothing to check.

The Pyrotec is different. Thermal cracking requires heat, so the pyrolyzer is a battery powered heating device, and Gastec state plainly that it is not suitable for use in hazardous atmospheres.

That is a genuine constraint rather than a formality. A refrigerant leak in a plant room is often not a classified area and the Pyrotec is fine. A measurement inside a classified area is not something this attachment can do, and somebody who has learned that Gastec tubes go anywhere would reasonably assume otherwise.

Where the measurement point is classified, the sample has to be brought to the instrument rather than the instrument to the sample, or a different method used. Talk to us about the specific situation.

Where It Is Used

Refrigeration and air conditioning leak investigation. Cool room and chiller plant. Marine and transport refrigeration. Refrigerant identification and recovery verification. Timber treatment and structural fumigation using sulphuryl fluoride. Grain and commodity fumigation. Shipping container fumigation and quarantine clearance. Veterinary and medical anaesthetic gas measurement. Solvent and degreaser exposure assessment. Industrial process plant using halogenated compounds.