Non-conducting locations

Non-conducting location as a form of protection is not much used in the UK because of the practical difficulties of providing it and then ensuring its integrity is preserved. It has an apphcation in the testing of electronic apparatus where the test area is specially designated for use by authorised personnel with the knowledge and skill for successful operation. 

Non-conductive locations referred to in Regulations 413-04-01 to 07, subsections 413-05, 471-10, and 471-11, are for special applications only where there is skilled supervision, such as in certain types of electrical testing, as described in Chapter 17 of this book. 

There is only limited use of Class II equipment in the fixed installation because in most cases it has to include the protective conductor for use elsewhere in the circuit to connect Class I equipment and this usage negates the Class II classification. Class II is more prevalent in portable apparatus. Protection by non-conducting location is not much used in the UK except for special locations such as test facilities. Earth-free local bonding, again, is used only in special locations where the necessary precautions can be taken to avoid importing an earth. Electrical separation s main application is also in electrical testing areas. 

If the installation includes any special facilities such as a test bench where it is necessary to establish and maintain a non-conducting location, the walls and floors must be made of non-conducting material. Their insulation value has to be proved by measuring the leakage current between at least three points on each relevant surface and earth. So a test bench against a wall would require a test at not less than three points on the adjacent wall and three on the floor. If there is an extraneous conductive part in the location, such as a metal window frame or service pipe, one of the test points should be not less than 1 m or more than 1.2 m from it. Check that the extraneous conductive part is separated from any exposed conductive part so that they cannot be touched simultaneously. If they can, the section of the extraneous part, within reach, has to be insulated to withstand a 2 kV a.c. test with a leakage current not exceeding 1 mA. 

Fixed CO2 systems are almost used extensively for protecting highly valuable or critical where an electrically non-conductive, non-residue forming agent is desired and where the location is unmanned. In the hydrocarbon industries CO2 systems are usually provided to protect... 

Although the whole-cell membrane is non-conductive, there are several redox proteins anchored on/in the membrane that confer nano-scale conductivity to the membrane and directly enable electron transfer across the cell membrane. These proteins usually assemble together in the periplasm and/or on/across the outer-surface membrane and act as an electron transfer chain to relay the electron across the membrane. For example, the membrane-bound electron transfer chain of Shewanella oneidensis is a trans icosa-heme complex, MtrCAB, that can move electrons across the membrane. The MtrC is a decaheme cytochrome located on the outside of the outer cell membrane that mediates the electron transfer to the extracellular substrate e.g, solid electrode). MtrAB is the transmembrane electron transfer module that is responsible for electron transport from the periplasm to MtrC. More interestingly, recent findings indicates that this electron conduit is capable of reverse electron transfer, ie., electron up-take from extracellular electrodes. ... 

Another interesting biological example that shows ferroelectric properties is voltage-dependent ion channels. These channels are glycoproteins located in the cell membrane, and they are found in either open or closed conformations. In the open conformation, these proteins are ion conductors. In the closed conformation, they become non-conducting, yet they still retain their ferroelectricity, even showing liquid crystalline properties [36,48]. 

Laboratories are normally classified as non-hazardous locations if the quantities of combustible materials are within the requirements of NFPA. Normally a vapor collection hood is provided when sampling and measurements are conducted with exposed hazardous materials. The primary... 

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