Main Panel Block Diagram The fire alarm system continuously monitors the detectors. Detectors are divided into zones. (Using Software configuration file in the base board). Detectors are connected to the system through loops. (physically) The Loops are connected to the loop boards. Each Board can have 3 loops. Each loop can have 254 detectors. (Depending on the address size) Each Loop has an address and each device has an address given using DIP switches. (These are stored in the Software config file) Devices send digital data packets containing the Addresses and the Data. The digital data packets are sent digitally using analog signals through the twisted pair cables. ( Analog Addressable Signals ) ID address on DIP switches All addressable loop units must be given an address between 1-254 to be operational. The loop units located on the same physical loop must all have unique addresses. The address is set by a 8 pole DIP switch located on each addressable unit
Galvanic Corrosion Can occur due to Oxygen attack or contact of two dissimilar metals in an electrolyte (eg: Copper + Steel). Oxygen Attack (Pitting Corrosion) At the Anode: Metal goes into solution Fe ⟶ Fe 2+ + 2 e - OXIDATION At the Cathode: Oxygen is reduced ½ O 2 + H 2 O + 2 e - ⟶ 2 OH - REDUCTION The variables pH, temperature and the concentration of oxygen affect the rate of corrosion. To avoid this alkaline conditions are maintained in the boiler. Oxygen reacts with iron to give ferric oxide (rust) Fe 2 O 3 which will not protect the metal from further attack and metal is continuously dissolved. 4Fe + 3O 2 → 2 Fe 2 O 3 Hematite (ferric oxide) Oxygen corrosion is usually observed as localized pitting on a metal surface. (Pitting Corrosion) This form of corrosion can be reduced by: 1.by reducing the level of oxygen as far as possible using mechanical means which include deaeration and/or judi