What is the difference between wet pipe fire fighting system and dry pipe fire fighting system?

In Wet Systems, the pipes contain water up until the sprinkler for immediate discharge of the water in case of fire.
In Dry Systems, the pipes contain air or nitrogen under pressure.
when the sprinkler opens, the air is released causing a pressure drop which opens a valve call "dry pipe valve" that lets the water into the system.
Dry pipe sprinkler systems are installed in areas where wet pipe systems may be inappropriate such as areas where freezing temperatures might be expected.

Wet pipe systems

Wet pipe systems are the fire fighting systems installed for firefighting and contain water with pressure every time inside the pipes/system i.e. sprinklers etc.

Dry pipe systems

Dry pipe systems are installed in spaces in which the ambient temperature may be cold enough to freeze the water in a wet pipe system, which make the system inoperable. Dry pipe systems are most often used in unheated buildings, in parking garages, in outside canopies attached to heated buildings (in which a wet pipe system would be provided), or in refrigerated coolers. Dry pipe systems are the second most common sprinkler system type. Mostly, installed where the ambient temperatures reaches above40F.

- (wet system) نظام شبكه حريق يكون ممتلئ بالكامل بالمياه المضغوطه8 بار و يفضل استخدامه فى الاماكن معتدله الحراره

- (dry system) نظام شبكه حريق يفضل استخدامه فى المناطق البارده عند وصول درجه الحراره الى اقل من4 درجه مؤيه و له نوعان:

1- نظام مضغوط بالنيتروجين او الهواء الجوى و يستخدم رشاشات مغلقه

2- نظام غير مضغوط و يستخدم فيه رشاشات مفتوحه

Wet Pipe FF System: It is live with fire water, pressure & flow (Control), ready to work when open or fire fighting needed.

Dry Pipe FF System: It is manulal start and set up system of fire water, pressure & flow for fire fighting.

wet system : pipes in this networks filled by water 

dry system : pipes contain air or nitrogen pressurized used in cooling environment

 

Dry risers are advise in areas where temp is less than4 deg C.
Also, it is installed for fire brigade inlets.

ya

It is possible to get any kind of bar from the pump tube

wet pipe contain H2O

&

dry pipe contain air and nitrogen to control the fire 

A wet system is always charged with water so when a sprinkler is activated water immediately flows.  A dry system is not charged with water, hence the term dry.  A dry system is used in high rise buildings where for insurance purposes do not require a wet system or in cold conditions where freezing may occur.  The Fire appliance is need to charge a dry system and under pressure it will act as a wet system.

Watch this ....Fire Fighting Webinar...i think its help full.

 

https://www.youtube.com/watch?v=5x0Tz-1zSOw&index=1&list=PLgwFrn4WS09Fx2-3l2xD55eLFmyVREVLe&t=1s