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Standpipe Ops: NFPA 14 - Small Talk About A Big Subject

This week we will be discussing NFPA 14 “Standard the Installation of Standpipe and Hose Systems”.  Over the next two weeks we will discuss nozzle tip size and hose sizes for standpipe operations.  This information from today will help set a background on the numbers that will be used over next few weeks.

 

Warning: This post may be lengthy and somewhat boring but the information is crucial to understanding weapon selection.  This is a small talk about a big subject.

 

I first started studying high-rise buildings and systems four years ago. I was assigned downtown and at some point I began to realize just how complicated these systems were and how little most of the guys, across the fire service actually know.  I chock it up to the “you don’t know what you don’t know” rule.  I became intrigued and have read as many books and taken as many classes as I can get my hands on, getting the information from some of the smartest in the business.  The following is just a brief overview of NFPA 14 and how it affects your operations when it comes to fighting fires in buildings with standpipes.  As always with the fire service, you need to continually learn and I learned something new this week.  Brian Brush posted an excellent article the other day and the link is included at the bottom.  Hopefully one can see just from reading about NFPA 14 the need for smoothbore nozzles and 2.5” hose but brother Brush points out a whole other NFPA recommendation, NFPA 13E.  Take the time to read his article afterwards.

 

There are two different versions of NFPA 14 that are important to know about.  They are generally referred to as Pre 1993 and Post 1993.  Pre 1993 NFPA 14 required a residual pressure of 65 psi at the top most or most remote standpipe hose outlet (usually the roof).  Post 1993 NFPA 14 the minimum pressure has been changed to 100 psi. These are minimum pressures.  It is quite possible that the outlets may produce more pressure but unless you are out testing every outlet in the building, in every building, you have no way of knowing.

 

Either Pressure Reducing Valves or Pressure Restricting Devices, collectively called Pressure Regulating Devices, are required by NFPA 14 to reduce pressures when excess pressure is in the system.  If you think about it, the pressure imposed on the second floor outlet will be much more than the pressure imposed on the 30th floor outlet because of the head pressure.  The fire pump may be putting out 300 psi to get 65 psi at the roof.  The pressure on floor 2 is going to be a lot higher than 175 psi. These devices are required and installed to combat this effect.

 

NFPA 14 states that when the static pressure at a 2.5” outlet exceeds 175 psi, a pressure regulating device must be installed to limit the static AND residual pressure to no more than 175 psi.  However, the valves can be set to any number as long as it is above the minimum 100 psi (65 psi pre 1993) and below the maximum 175 psi (100 psi pre 1993) residual pressure.

 

Pressure restricting devices reduce pressure and flow by interfering with or restricting the size of the orifice.  They may be metal rings placed inside of the standpipe outlet to create a smaller orifice or they may be a stopper added to the standpipe wheel to keep it from opening past a certain point.  There are multiple different types and you should research and become familiar with them all.  These devices are not favored due to the many incidences where they have been improperly adjusted and severely hampered the firefighting efforts. When encountered they should be removed prior to connection fire department hoses or appliances.

 Above Photo: A Pressure Restricting Device

The more accurate and reliable devices are the pressure reducing valves. These are spring-activated valves, which maintain a constant flow pressure and gpm despite the system pressure. These valves can be either pre (factory) adjusted or field adjusted. The units that are factory adjusted are specific for each floor and great care must be taken during installation to ensure that they are on the proper floor. The field adjustable units are field calibrated once they are installed on the floor by a technician.  Another small subset of field adjustable are what some people refer to as fireground adjustable.  These can be adjusted by fire department personnel with the right know how and they require specific rods to manipulate. Pressure reducing valves are usually distinguishable by a large rim on the body of the outlet.  Also, once the end cap has been removed the presence of a smooth stem is a direct sign of a pressure reducing valve.  A non-pressure reducing valve would have a threaded stem.  Pressure Reducing Valves (PRV) can also be installed at ceiling level, reducing pressure before water flows to the hose outlet or sprinkler system.  Once again, there are plenty of different types of PRV’s and you should research and be familiar with each. If you jurisdiction has fireground adjustable PRVs you should make sure the adjusting rods are present during your PIPs and possibly carry some in your standpipe bag.

Above Photo: A Pressure Reducing Valve - Notice the large rim around the  outlet.

One of the most famous high-rise fires where PRVs caused severe problems was One Meridian Plaza in Philadelphia, where three firefighters were killed in the line of duty. Due to improperly installed factory preset pressure reducing valves, firefighters had standpipe outlet pressures around 45 psi.  This case study is an important one in the history of high-rise tactics and equipment and showcases the need for low pressure weapons such as 2.5” hose and smoothbore nozzles.

 

Lastly, we will talk about distance of travel.  NFPA 14 requires that the distance of travel from an outlet be no more than 130 feet in non sprinklered buildings and no more than 200 feet in sprinklered buildings.  If the distance of travel exceeds these numbers, then outlets are required to be placed in the hallways.  All that is to say that if the building is built according to NFPA standards, any part of the building floor should be accessible with no more than 200 feet of hose from the standpipe outlet.

Let’s throw a wrench in it though.  Best and accepted practice is to make your standpipe connection on the floor below the fire.  This easily adds a full 50 feet to your hose lay changing your maximum lay to 250 feet.

 

Thanks for taking the time to read. Next week will apply all this knowledge towards making our hose and nozzle selections.

Brian Brush's Article Link

http://community.fireengineering.com/m/blogpost?id=1219672%3ABlogPo...

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