PCB dielectric oil testing
This information originally came from Tredi New Zealand Limited ©1997. Tredi was a hazardous waste consulting company. Unfortunately, this company appears to no longer be in business. Their web site has been closed for over 10 years. I am reproducing one of their old pages on PCBs here for education purposes. These two tests are some of the simplest I have seen for spot checking for the presence of PCB contamination in oil. I have not tested these techniques myself yet. I frequently come into contact with oil in old electrical devices. I wonder about PCB contamination, but I have no way to test, so I just rely on the date of manufacture and any information I can dig up about the company and device.
Identification of PCBs
Tredi New Zealand Limited ©1997
PCB's range in appearance from colourless, oily liquids to more viscous and increasingly darker liquids, to yellow and then black resins, depending on chlorine content. Viscosity varies from highly mobile to very thick and syrupy. Flash points can be as low as 140 C to 200 C; however, most have no flash point at all as measured by standard test. The vapour is invisible and there is a characteristic strong odour.
DO NOT SMELL THE VAPOUR IN ORDER TO IDENTIFY PCB'S, INHALATION SHOULD BE STRICTLY AVOIDED.
PCB's used a dielectric fluids are usually mixed with organic solvents such as chlorinated benzenes which change the chemical and physical properties of the fluids. In addition used PCB fluids may be contaminated with dirt, moisture, black carbon particles and pieces of insulation from the inside of the equipment. This contamination may change the appearance of the fluids.
SIMPLE TESTS FOR PCBs
Simple test of specific gravity/density
PCBs are heavier than water whereas mineral oils are lighter than water. This can be used as a simple test to help identify PCBs. Density Test (Please observe all relevant electrical safety precautions)
Clean the drain valve at the base of the transformer with a clean rag. Drain a few drops of the liquid into a clean glass bottle and add a small amount of water. If the liquid sinks to the bottom, it is a PCB fluid. If the liquid is mineral oil it will float. If the oil does neither, it may be contaminated mineral oil and will need to be tested by another method. DO NOT POUR TEST MATERIAL BACK INTO THE TRANSFORMER - WATER WILL DEGRADE ITS ELECTRICAL PERFORMANCE.
Rather than rely on appearance or density, a test for the presence of chlorine can be made.
Simple test for Chlorine
Heat one end of a length of clean un-coated heavy copper wire (preferably 2 to 3 mm diameter) in a pale blue gas flame. If the wire is initially clean there will be no colouration of the flame until the copper reaches red heat when an orange hue will be imparted to it. Allow the wire to cool, somewhat below re heat, then dip it in the unknown chemical and again heat it. There may be an initial bright yellow and smoky flame - but as the copper nears re heat,. The presence of chlorine will be indicated by a bright green colouration (the yellow should have disappeared at this stage), as it reacts with the copper to produce copper ions in the flame. NOTE: When PCBs are decomposed at high temperatures, gases are produced which contain a high proportion of hydrogen chloride, a highly irritating and corrosive chemical. CONDUCT THIS TEST IN A WELL-VENTILATED PLACE.
The above test for chlorine is not infallible. However, it will usually suffice to distinguish between chlorinated hydrocarbons and non-toxic mineral, vegetable or silicone oils, greases or waxes. If these screening tests are positive the material should be dealt with as if it is a PCB liquid, but the composition of the PCB liquid can only be determined by laboratory analysis. This can be carried out by various laboratories.
MANUFACTURER'S TRADE NAMES
PCB fluids are often known by the term askarel, which is a generic name for synthetic electrical insulating material. Askarels generate only non-explosive gases or gaseous mixtures when decomposed by an electric arc. Commercial mixtures contain PCBs, chlorinated benzenes and contaminants, in a range of concentrations. Manufacturers have used a wide variety of trade names, including:
- NO - FLAMOL
- SAT-T- AMERICA
- SAF-T- KUHL
Other PCB products and their possible applications are:
- SANTOTHERN FR (UK) - Heat transfer (prior to 1972)
- THERMINOL FR (USA) - Heat transfer (prior to 1972)
- PYDRAUL (USA) - Hydraulic applications (before 1972)
These three trade names are still in use but now refer to non-chlorinated products. For SANTOTHERN and THERMINOL only the FR series contained PCBs and present day products are not labelled as FR. For PYDRAUL, the present series of hydraulic fluids which do not contain halogenated compounds are designated E.