Returning to the foundations - Firefighting in protected structures

Sprinklers and standpipe systems

CarolinaFireJournal - By Mike Coffey
By Mike Coffey
07/05/2011 -
A firefighter’s best friends in protected structures are sprinkler and standpipe systems. These systems offer suppression and containment for firefighters to make stands to protect life and property — in that order. Knowing what these systems are capable of and their use makes life easier on all involved. image

Most of the wet systems we come in contact with are control systems that are meant to keep the fire under control until we arrive and do manual extinguishment.

Sprinkler systems have their humble beginnings. The first patent for a system, issued in 1723 to Ambrose Godfrey, was a pewter chamber of gunpowder attached to a cask of water. A fuse system was connected. As flames reached the fuse, it ignited the gunpowder and dumped water on the fire. Sounds strange, but given the time frame, it was a working system with some “bang.”

The year 1806 witnessed the development of perforated water pipes, courtesy of one John Carey. Water was supplied from elevated tanks through a system of pipes. Valves were kept closed with a system of weights and cords. Burning through a cord released counterweights that allowed water flow. This system tended to leak, valves became stuck with failure to open and overall performance lacked. The first patented automatic sprinkler head is credited to Mr. Henry Parmelee in 1874. He continued to refine his product. By 1881, the Parmelee system had been installed in 214 plants.

Since those first attempts at automatic fire protection, the systems of today are efficient at what they do, work with little problems and do the job asked of them. These systems work 96 percent of the time without major problems. The times they don’t work are attributed to human error such as shutting the system down, up to something catastrophic — explosions taking out parts of the system.

Automatic sprinkler systems evolved into five different classifications: wet systems, dry systems, deluge systems, preaction systems and residential systems. There are several subsections involved within these classifications, the ability to identify and recognize the system involved continues to be advantageous to firefighters in the trenches.

Wet Systems

Wet systems are the basic system all the others have evolved from. A basic wet system contains check valves not allowing system water back into a potable (drinkable) water system, alarm check valve that sends an alarm when water flows through the valve, retard chamber to hold water surges from tripping the alarm valve with risers, pressure gauges noting water pressure coming into the system and the system above the alarm valve, feed lines, cross lines, and then the branch lines the heads are attached to. Being a wet system means water is always in the piping and ready to be used to control the fire’s progression.

Most of the wet systems we come in contact with are control systems that are meant to keep the fire under control until we arrive and do manual extinguishment. There are systems in place that are suppression systems, designed to kill the fire with large volume discharge — as much as 1¾” lines per head. These systems are known as Early Suppression — Fast Response (ESFR). The difference is the piping to allow large flows and the fast-acting elements in the heads to allow for quicker discharge of water onto the fire.

Dry Systems

A dry system distinguishes itself as having air in the piping rather than water. These applications are usually located in areas subject to freezing temperatures. Most of the same components used in a wet system are in the same places on a dry system. A larger alarm clapper valve is commonly used in the riser to separate air on top of the valve and incoming water supply and kept from freezing. The pressure gauges with these systems monitor air pressure above the alarm check valve and incoming water pressure on the bottom of the valve. Priming cups are added to put a small amount of water on top of the clapper valve to “prime” the system. The clapper also is designed to have air pressure — and a little water — hold the clapper closed until a head opens to release air and begin water flow.

The ratio of air to water on the clapper valve is one pound of air pressure to hold back five pounds of water pressure. Exhausters and accelerators are used to exhaust the air from the piping in larger systems. Because air is in the system prior to water, there is a delay in putting water on the fire and more heads are figured to activate over a wet system.

Deluge Systems

Deluge systems are dry systems that have open heads to drop large volumes of water over a high hazard area. This system uses fire detection — flame/heat/smoke — to activate the clapper valve for water flow to the area. The clapper valve release uses hydraulic, pneumatic or electric means. The biggest difference in this system is that with the open heads — all heads drop water on the problem to control or suppress a potentially quick growing fire with the quantity of water the system can dump in the area of concern. These systems can be modified to become foam systems. Slight modifications to the heads and additions of protein or AFFF concentrates have successfully been used.

Preaction Systems

Preaction systems are the next variation of dry systems. They require some kind of detection — smoke/heat/flame — to trip the deluge-style valve and send water through the system. This system has traditional closed heads and at this point acts like a traditional wet system where the heads fuse and put water on the fire.

The way I teach this system — it takes an action (the detection system senses a fire) to get the reaction (system going wet and depositing water) for fire containment. These systems are designed to limit water damage to the area being protected and are found where that same water damage is detrimental to the operation.

Residential Systems

Residential systems have become popular — usually in wood-frame apartment buildings. They also have been put into single and two-family complexes as standard equipment. These systems are designed to prevent flashover in living areas along with giving the occupants a fighting chance of escape — not suppression, but life safety. Most of these systems are wet systems supplied by the appropriately sized line coming from the domestic water supply, with some sprinkler companies developing a dry valve.

Residential systems utilize residential sprinkler heads having to meet different requirements than standard sprinkler heads. These heads also are not placed like commercial systems — they are placed to the probable location of fire origin to meet National Fire Protection Association (NFPA) 13D and 13R. These standards provide a complete list of where heads are to be placed in these occupancies.

Standpipe systems are divided into three classes: Class I for fire department use or those trained to operate heavy streams only, Class II for occupant use and Class III which is a combination system for both fire department and occupant use. These systems meet NFPA 14 based on protection required and purpose of use.

There are also instances where sprinkler and standpipe systems are combined with the standpipe system flows figured into the total flow of the system. Factors indicating if a standpipe system is used are: occupancy and occupancy load, products and commodities, processes and storage conditions, building height, building area and size of fire area. There are also sub classifications within these as well: wet standpipes, automatic dry standpipes, semiautomatic standpipe systems, manual standpipes and manual dry standpipe systems.

Class I standpipe systems are designed for 2½” hose use with hose connections where all portions of each story/section of building within 150 feet of connection in unsprinkled buildings (200 feet in sprinkled buildings). Don’t be surprised to find 1½” reducers on these connections. Minimum risers for these are four inch pipe up to 100 feet and minimum flow requirement of 500 GPM. Each additional riser adds another 250 GPM up to 1000 GPM maximum. Flows are for 30 minutes with 100 PSI at top outlet at 500 GPM flow. These systems are usually found in high-rises, open parking garages, covered malls and underground buildings.

Class II systems are designed for occupant use or initial fire department operations with 1½” outlets. All portions of building/story are within 130 feet of connections. Minimum risers on these systems are 2” up to 50 feet, 2 ½” over 50 feet. Flow requirements are 100 GPM per building for 30 minutes minimum with 65 psi at top outlet with 100 GPM flowing. These lower requirements allow for better hose control with the logic of controlling the fire during the initial stages.

We discourage the occupants from firefighting for life safety reasons. Using these systems do not provide us any protection. These systems were designed for the occupants) which begs to ask if they are useful to us. Check your policy for use requirements.

Class III systems are basically combination Class I and II systems with the requirements of Class I systems. They can have 1½” hose connected as well. These systems are often substituted for Class II systems. Reducers can be removed easily — usually.

Automatic wet systems must supply water to system demand automatically and has water in the system at all times — hence the “wet” system. Fire pumps and other pressure maintenance devices can be involved in the system to maintain pressure in the system. These systems are found in heated buildings, just like wet sprinkler systems. This type of system also is the preferred system for us in the trenches — water already available and ready to go to work.

Automatic dry standpipe systems work in the same way as dry sprinkler systems. Pressurized air is in the pipes, waiting on an opening of a valve/nozzle to bleed air and bring water to bear on the fire. These are found in unheated buildings, similar to dry pipe sprinkler systems. Dry pipe or deluge valves are also used in these systems. Same requirements that wet systems meet must be met here as well — readily available water. These systems are commonly found in open stair towers, breezeways and corridors in apartments or condominiums.

Semiautomatic standpipe systems can be pressurized or have atmospheric pressure for supervisory purposes with little or nothing to do with system operation of water being admitted into the piping. A remote control device is required for water to enter the system, usually consisting of a manual release of some kind. This type of system is commonly found in industrial complexes or public areas where the system is exposed to the elements.

Manual standpipe systems has water in the system at all times coming from the building’s domestic water supply and not from a dedicated fire service supply. Water pressure is not enough to supply any attack lines and must be supported by a fire department pumper through the fire department connection. These systems were common in older high-rise and mid-rise buildings. Don’t be surprised if this system is called a “dry system” requiring a pressurized water source to supply system and provide fire flows to attack lines.

Manual dry standpipe systems do not have any attached water supply. Atmospheric air fills the piping system. This system totally relies on fire department support for water supply. This system is commonly found in freestanding structures or parking garages — areas that weather conditions and tampering are hard to monitor.

This little refresher on sprinkler and standpipe systems can open up some of the brain pathways or open new gateways to these protective systems. Valuable learning comes from touring your area and learning the systems in use that you respond to. Understanding their capabilities better allow us to utilize them in times of need to protect life and property. Let’s continue working on the “foundations” so we don’t crack under pressure. Be safe out there in the streets and roads!

(Extra historical and technical information derived from: Automatic Sprinkler and Standpipe Systems 3rd Edition by John Bryan 1997; NFPA and Fire Protection Systems by A. Maurice Jones Jr. 2009; Delmar Cengage Learning)

Captain Coffey currently serves as one of the training officers of the High Point Fire Department. He has been an instructor with the NC Community College system and the Office of the State Fire Marshal since 1990. He can be reached at
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