Back in 2008 i once had a period of time where i resolved to understand PLUMBING. i thought it would be nice to declare one week "UNDERSTANDING PLUMBING WEEK" and spend all that week googling and reading up on PLUMBING (the following week could be "UNDERSTANDING ELECTRICAL WIRING IN THE HOME" or something like that. or "UNDERSTANDING GAS MAINS" week, you get the idea). at the time i also went to hackney library and took out a book about plumbing and sewage symbols. however life intervened and my library books went overdue and i never did learn all i needed to know about plumbing.
Now we will rectify that.
A dry riser is a main vertical pipe intended to distribute water to multiple levels of a building or structure as a component of the fire suppression systems. The pipe is maintained empty of water. The dry riser is the opposite of a "wet riser" or "wet standpipe" system where the pipes are kept full of water for manual or automatic fire fighting operations. Dry risers have to have fire engine access within 18m of the dry riser inlet box.
"The opposite of a wet riser, it is used in instances where the immediate environment can be so cold as to freeze. This could apply to an unheated area or refridgerated space, for instance. The piping is pressurized with air, at a "maintenance" pressure which is relatively low compared with the water supply pressure. To prevent the larger water supply pressure from forcing water into the piping, the design of the dry pipe valve (a specialized type of check valve) intentionally includes a larger valve clapper area exposed to the maintenance air pressure, as compared to the water pressure. The connection point is on ground level to give the Fire service easy connection straight into a water supply"
Qn: why is it more common to see dry risers in singapore then, since our climate is constant?
is it because: "Some view dry riser sprinklers as advantageous for fire protection of valuable collections and other water sensitive areas. This perceived benefit is due to a fear that a physically damaged wet pipe system will leak, while dry pipe systems will not. However, dry pipe systems will only provide a slight delay prior to water discharge while the air in the piping is released prior to the water filling the pipe." ?
From another source: Dry risers are systems of valves and pipework which enable the Fire Brigade to deliver water onto upper floors of a building. Generally, a dry riser system will be required where any floor of a building is over eighteen metres above ground level. Since dry riser systems are used by the Fire Brigade, particular attention must be paid to the design of the system to ensure the valves are correctly sited, with adequate space to enable efficient use of the equipment. A typical dry riser system will comprise a vertical 100mm diameter pipe, with a twin inlet connection at street level, an outlet valve at each landing and an automatic air release valve at the highest point.
A wet riser is a constantly pressurised water pipe supplied by a storage tank with pump, a mains pump or from a mains pressure supply.
"By a wide margin, wet pipe sprinkler systems are installed more often than all other types of fire sprinkler systems. They also are the most reliable, because they are simple, with the only operating components being the automatic sprinklers and the automatic alarm check valve. An automatic water supply provides water under pressure to the system piping. All of the piping is filled with water. Until sufficient heat is applied, causing one or more sprinklers to fuse (open), the automatic sprinklers prevent the water from being discharged."