SAFETY PHONE GUARDS AGAINST EXPLOSIONS (Mar, 1935)

If they had already perfected explosion-proof telephones in 1935, why can’t I use my cell phone at the gas station? Has this miraculous technology been lost?

SAFETY PHONE GUARDS AGAINST EXPLOSIONS
A new type of explosion-proof telephone, exhibited in Chicago, is a recent addition to the roster of curious safety appliances developed especially for use in industries where dust, gunpowder, or inflammable gases present the constant hazard of a blast. Not only does the construction of the instrument guard against the possibility of an electrical spark igniting any combustible material in the surrounding air, but even the mechanical working parts have been designed particularly with a view to reducing friction so that a spark cannot be produced.

9 comments
  1. Rick Auricchio says: June 30, 200811:19 pm

    1. Explosion-proof equipment is quite different from the normal stuff. It includes sealed electrical contacts to avoid any type of spark, special metal choices to avoid metal-to-metal sparks, etc.

    2. The cell phone/gas station scare is totally false. There is no problem.

  2. Gazzie says: July 1, 200812:01 am

    I agree with you Rick.
    It’s not the cell phone, it’s static electricty. People slide into their seat to answer their phone, slide out and touch the gas nozzle or their vehicle… and … boom!

  3. Darrel says: July 1, 20085:13 am

    It is almost impossible to avoid producing sparks in any electrical equipment that operates by means of a mechanical contact at the voltages used in industrial installations, rather it is the enclosure design that prevents any flame-front initiated by a spark from the opening of a mechanical contact from reaching the outside environment and, thereby, producing a larger, more wide-spread combustion/detonation event. The principle used is to create a very long, temperature reducing path to the external environment by making the junctions at the casing very wide and very tight and making the enclosure strong enough to survive any internal explosion. Explosion-proof enclosures typically have junctions on the order of 2 inches in width and are tightly held in close contact with many, many bolts. The entryways for wiring are also sealed using kapok and a plug of very fine cement or some other means. The enclosure is designed to contain and survive an internal explosion while preventing the propagation of the resultant flame-front to the external environment.

  4. Mat Hall says: July 1, 20087:40 am

    The problem with mobile phones in gas stations is not, as is often believed, due to the risk of explosion; you’re not supposed to use them because of the possibility of it interfering with the electronics in the pumps. Dull, huh?

  5. sweavo says: July 1, 20088:24 am

    Interesting post Darrel, thanks

  6. fluffy says: July 1, 20088:42 am

    @ Mat Hall: That is absurd and implausible. Those things are designed to withstand a hell of a lot more interference than the couple of microwatts which come from a cellphone. They get more interference from the towers themselves (as does everything else, for that matter).

    The actual explanation is #2.

  7. Don says: July 1, 20089:47 am
  8. StanFlouride says: July 1, 200811:08 am

    The real danger in using a cell phone in a gas station comes from the stressed-out guy who just got off work at the Post Office and is waiting in line behind you with his .45 in his lap…

  9. docca says: July 11, 20087:46 pm

    Will you still have FINGERS to dial after an explosion?

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