Re: Electrically Conductive Tubing
By John Grant
John Tuttle's recent story about his experience with slightly conductive neoprene tubing was quite an eye-opener for me and I am grateful for his having shared the information. I have, for a number of years, known that materials such as this are, in fact, conductive but I think there is an additional explanation for it. While the conductive "ingredient" in neoprene may indeed be carbon black, it's concentration or proportion may actually be different from that required to achieve uniform coloration. Although I cannot quote you specific documents or regulations, many materials which have the potential of being used in hospital operating rooms, are intentionally made to be electrically conductive, even though they might ordinarily be considered as insulators. The rationale here is that in that environment, it is VITAL to prevent the build-up of static electricity charges to the point where an electrical spark could be generated. Since "tubing" of all sorts is used in these environments, many manufacturer s add conductive substances to their tubing material during the fabrication process. I believe that even "clear" and other non-black tubing will, in fact, be found to electrically conductive so that it can be certified for this use. Hind-sight being 20-20 of course, it would be wise to use the truly non-conductive "heat-shrink" spaghetti insulating material for similar applications such as John's in the future.
Here is some more food-for-thought: The power cords and plugs for many, if not most reproducing pianos do not carry the modern "safety ground" (green) wire. Frequently, the plugs themselves are non-polarized, and can be plugged into the wall outlet either way. Try performing this test: Lightly slide the knuckles of your fingers over the tracker bar of the piano, then reverse the power plug in the wall outlet and repeat. If there is modern neporene tubing in the piano, chances are that you could feel a slight "tingle" sensation when the plug was in one position or the other. If so, there is an electrical shock hazard there! You should modify the power cord and connectors such that you are able to carry the safety ground through to the motor housing, pump plate, and tracker bar. While I don't wish to complicate anyone's lives, there may be a liability issue here for those of us "in the business", and perhaps someone who is familiar with the NEC (National Electrical Code) and Underwriter's Laboratories can inform us authoritatively about what standards we need to observe here.
Stay safe! -John Grant
"Beer: It's not just for breakfast any more."
[ Editor's Note:
[ The discussions about electrical and fire safety seem very timely.
[ I live in a "historic" community. Julian was a gold mining community
[ at the turn of the century. Virtually allof the buildings
[ "downtown" are preserved from that era. Many of them had no
[ electrical wiring at all when they were built. Many of them
[ have had a patchwork of electrical "improvements" performed on
[ them over the years, and obviously not all of it to "code". Last
[ weekend a 107 year old building housing a grocery store burned
[ to the ground. Speculation is that it was some electrical
[ problem. We are all greatful it did not take the
[ entire downtown area with it. Our volunteer fire department
[ did a terriffic job. But back to the point.
[ Many people involved in instrument restoration want
[ to "preserve exactly" the original implementation. Not all
[ original implementations would be considered "safe" by today's
[ standards. I've heard some horrible stories about shocks
[ from Mill's Violanos. The recent postings here raise some
[ other interesting, if not frightening issues about "improvements"
[ to designs. Please give consideration to electrical and fire
[ safety. Sometimes well-intentioned alterations actually
[ make things worse. Failing to make some alterations (such
[ as proper grounding) could be considered negligent. If you
[ are not sure, PLEASE consult a qualified electrician, electrical
[ technician, or engineer.
(Message sent Sun 11 Aug 1996, 00:02:33 GMT, from time zone GMT-0700.)