Has anybody ever seen the very old fire alarm systems where there was a small hollow copper line that was pressurized. When there was a fire, the pressure in the pipe would increase and set off an alarm. There was no electric to the system, except at the main panel. The way you would trouble shoot a leak was, you walked all around the building with a bottle of soapy water. You would lay the soapy water on the pipe until you found bubbles. Then you had to solder the pipe and close the hole. You would see these types of systems in schools a lot of the time.
I saw something similar to that at an old clothing factory in Park Ridge, NJ that was converted to a lighting store. They had this "capillary" tubing run throughout the place to sensor bulbs. They ran down to the basement annunciator panel. When the heat from a fire approached the sensing bulb, the pressure in the tube would increase to the extent that it would cause a lever to trip in the panel. This would cause a number plate to pop up and "ding" an internal brass bell. My guess is that this system was installed in the late 1800's.
Later on (probably in the 1920's), someone had done a retrofit with some switch contacts that allowed this bell to be located upstairs. What is strange is that this system was still fully intact well into the late 1970's. I'd be willing to bet that remnants of it are still there.
They rate of rise on gas stationfire suppression in the canopy. You see them sticking thru the roof. The company I do some work for use a cup of hot water to see if they function.
Fenwall,pendant heats: We use a large solder iron,remove the tip and it slides right over the heat, works great. On the HIDs',the copper line systems, we use the hot water trick,I've found no better way.This can be tricky on top of a ladder with a pot of very hot water. These are still in use in alot of our chemical/paint customers places.
