Liquid Inside Sprinkler Head

There are genuine mercury thermometers, but most straight thermometers contain a red alcohol-based liquid (easier to see, nonpoisonous). If the liquid expands enough to completely fill the tube, the tube breaks from hydrostatic expansion.

Think of a sprinkler actuator as a "short thermometer" that is designed to break at 65°C, thereby opening the sprinkler head.

There seems to be some secrecy about this liquid, the only reference I could find was on the Eurosprinkler.org site which says "This is usually a small glass bulb filled with a type of alcohol." The small bubble seen in the glass bulbs is to allow for liquid expansion under normal temperature variations.

The liquid within the ampule of the sprinkler head is a mixture of alcohol and water or glycerin and water. The % of each is changed to determine the activation temperature of the head. The color is from a dye and indicates the activation temperature. It is put in the liquid so that you can visually inspect the ampule to make sure it is still intact and the liquid has not evaporated or drained out without climbing up to the head to look. This is most often caused by the glass of the ampule cracking and the liquid evaporating. This would cause the head to go off at other than the stated activation temperature (either lower or higher depending upon the type of fracture of the glass).

As previously stated, the heating of the liquid creates an internal pressure within the ampule which breaks the glass at the activation temp.

Low melting metal alloys such as woods metal are also used.

Common temp ranges, based on maximum ceiling temperature are:

135-170 deg F, 175-225 deg F, 250-300 deg F, 325-375 deg F, 400-475 deg F, 500-575 deg F and 650 deg F. The faster the element is heated up the lower within the range it will activate.

Good Luck, Old Salt

Check out this out, look at the part about the operation, it has color codes listed also. Hope this might help. DJ

Thank you, but all I need to know is about the liquid. And I think I got the answer already.