Fixed Installations (Water) Flashcards
7 main principle controls installed
Describe when a wet pipe sprinkler system is normally installed and the principal controls of the system.
valves, heads, supplies, max area protection
- Installed in premises where there is no chance of the water freezing and the water in the system will not exceed 95c.
Principal controls in place:
- a stop valve on each separate source of supply.
- a non-return valve on each source of supply.
- must have two supplies, town main and secondary supply (to maintain pressure and fire cover in event of town supply being compromised.
- installation main stop valve to cut off the flow of water to the system (once fire has been extinguished).
- an alarm valve.
- sprinkler head (normally fusible link of glass bulb).
- a test and drain valve (for testing and to empty the system).
Max Area of Protection:
12000 m/sq LIGHT hazard
10000 m/sq ORIDINARY hazard
9000 m/sq HIGH hazard
Describe when a dry pipe sprinkler system is normally installed and the principal controls of the system.
- Installed where temperature condititons are artificially maintained sloe to or below zero, where there is a chance of the water freezing in the pipes (basement/parking garage) and where the temperature of the structure is maintained above 70c.
- Pipes charged with air or N at all times to hold back water
- ONLY upright of pedant heads fitted.
Contolling valves:
* Main stop valve
* Dry pipe air valve (sub for alarm valve on wet system)
There is some delay in water reaching the heads due to time required to release sufficient gas to allow valves to open
Therefore an accelerator is normamly installed, two types:
(i) Mechanical
(ii) Electric
Describe where a alternate wet/dry sprinkler system is normally installed and the principal designs/controls of the system.
Installed where the premises may not have adequate heating year round to stop water freezing in the sprinkler pipes.
- Spring/summer can operate on wet system, winter operates on a dry system.
- When wet system in use the dry valve is placed out of commission or changed over.
- Sprinklers heads ALWAYS placed above the distributing pipes and given a SLIGHT SLOPE (so that water will not be trapped in pockets when system is drained).
- TAIL END Systems can be used in areas:
(i) where there is a possiblity of frost danager in an otherwise adequately heated building (eg basement parking).
(ii) in high temperature areas or above stoves.
Tail end would be on an alternate wet/dry for (i) and dry pipe for (ii).
7 requirements
Describe a Life Safety sprinkler system is and the requirements of the system.
Basic sprinkler system enhanced to give a higher standard of reliabilty and continuaity of service.
Life safety requirements may include:
* Must be a WET pipe system.
- Should be zoned (each zone controlled by a seperate stop valve, max area 2400 m/sq).
- Zones my require duplicate or bypass valves so the system can be serviced without taking it offline.
- No zone shall extened further than one floor level can include mezzanine (max 100 m/sq)).
- Only one zone of a multi-zone system shall be shut down at any one time (FRS must be notified).
- Stop valves should be accessible at the floor level of the zone they control.
- Visual and audible warnings must initiate when the pressure in the sprinkler tank falls to the point at which the pump would start and this should only be able to be CANCELLED MANUALLY.
Describe a Pre-action sprinkler system.
This is a system conbinationof a standard dry sprinkler system and an INDEPENDANT, approved heat or smoke detection system.
THe heat/smoke detection systems operates prior to the sprinklers, activating the pre-action valve allowing water to flow into the system before the first sprinkler head operates.
Normally rquires 2 detection zones to operate then a sprinkler head for water to flow.
Max Area of Protection same as wet pipe:
12000 m/sq LIGHT hazard
10000 m/sq ORIDINARY hazard
9000 m/sq HIGH hazard
Describe the operation of a Recycling Sprinkler System.
• In this system the sprinklers heads are turned on and off repeatedly by a heat section system which opens and close the main valve.
• once actuated the sprinkler system operates and cools the fire to a predetermined temperature, at which point the heat detection system would close the main valve.
• at this point there is a delay mechanism which maintains the water flow for another 5 minutes.
• if the temperature rises again to the predetermined level the heat detection system re-activates the sprinkler system and the process is repeated.
Used where there is a need to:
• reduced total amount of water required to extinguish the fire.
• prevent unnecessary water damage.
• avoid the need to close the main valve to replace sprinkler heads.
• reduce the risk of water damage through mechanical damage to the system.
Describe the operation of Drencher systems and the different types.
Placed on roofs and above windows/openings to protect the structure from exposure to fire from adjacent building.
Roof Drenchers:
Have a deflector similar to sprinkler head, through a curtain of water upwards which falls back down onto the roof.
Wall or Curtain Drenchers:
• Throw water to one side of the outlet in the form of a flat curtain over the opening likely to admit fire.
• usually place just below the eaves and fitted to every window/opening on the top 2 floors.
• those on lower floors are then fitted on every alternating floor other than ground and basement.
• fitted so water stream must come into contact with window 600mm from top.
• also used in theatres on the stage side to protect the safety curtain.
Window Drenchers:
• placed horizontally level with the top of the window with deflector 100mm from surface of the wall.
• Tail of deflector throws a water stream inwards on to the glass near the top while two streams are directed at a 45 degree angle to the lower corners.
Explain how high velocity water projection systems work to extinguish fires.
Used to extinguish oil fires using water by:
(i) cooling
(ii) dilution of oxygen supply
(iii) dilution (or removal) of the Liquid (fuel) supply.
Cooling:
• oil burns as a vapour from the surface.
• cooling the liquid decreases the rate of vaporisation and so the rate fuel can reach the fire.
Dilution of O2 supply:
The steam formed by vaporisation of the applied water displaces air from the zone of combustion, smothering the fire.
Dilution of the Liquid (fuel)
• under certain conditions oil and water can for an emulsion, this requires energy however;
• supply via the water striking the surface of the fuel;
• water droplets surround the oil droplets forming an emulsion, which has a low flammability because the heat from the fire must pass through the water envelope surrounding the oil.
Describe where a Deluge sprinkler system is normally installed and the principal designs/controls of the system.
Designed for special hazards where intensive fire with a very fast rate of propagation are expected and water needs to be applied simutaneously over a complete zone.
It is a system of open sprinklers controlled by a quick opening valve operated by heat detectors or sprinklers installed in the same area as the open sprinklers.
(i) Quartzoid bulb operates,
(ii) compressed air escapes,
(iii) rapid decrease in pressure on diaphragm
(iv) casues deluge valve to open and water to discharge.
Describe how a Glass Bulb Sprinkler Head Operates
(i) An aritight glass buld holds the valve assembly in place, preventing water flow.
(ii) as temperature increases the liquid in the buld expands and the size of the buld decreases until it disappears.
(iii) further rise shatters the bulb (into small pieces to not obstruct water flow).
(iv) head opens and water flows to deflector.
Describe how a Fusible Solder Sprinkler Head Operates
metal cap, strut, hook, key, solder, valve cap
(i) Metal cap fitted over the valve into which the STRUT is inserted and supported by the HOOK (which engages the deflector end of the yoke) and KEY.
(ii) All 3 parts held rigidly in place by a special fusible solder, keeping the valve cap in position against the water pressure.
(iii) temperature increases to a level at which the solder is heated to its fusing point.
(iv) Strut, hook and key fly apart
(v) valve cap is released allowing water uninterrupted flow to the deflector.
