Nov 2003

Sprinkler System Design Data

There was a time when hydraulic design of automatic sprinkler systems was unusual. The process was cumbersome and time consuming even for the simplest of pipe arrangements. Access to computers capable of assisting in this work was expensive. So the cost and effort limited this method to very specialized sprinkler systems – usually those protecting severe hazards.

Things have changed. Computers are commonplace. Programs for conducting hydraulic analyses abound. The cost has become so low that it is outweighed by the capability to design sprinkler systems that are hydraulically efficient, resulting in the ability to tailor a sprinkler system to a particular occupancy or hazard with minimal over design. This results in cost savings from smaller pipe sizes and lower weight. The natural progression of these factors has led us to an almost universal use of hydraulic designed sprinkler systems.

These hydraulic sprinkler systems present a problem that did not exist before their proliferation. You can not tell much about the design or performance capability by looking at them. Of course there are rules and guidelines for information to include with installation drawings that enable the hydraulic analysis, so the design data is available. For a few years this was relied upon – until it became evident that the drawings tend to disappear, and with them go the data – lost to history.

In an effort to solve this problem authorities have required each sprinkler system to have a permanently affixed sign indicating the appropriate data and information. In theory, the design data will be readily available as long as there is a system of pipes. This was definitely a good idea, and admittedly the practice has been widely accepted. A fairly universal example of the sign and the data it must contain can be found in the National Fire Protection Association’s Standard NFPA 13-2002 “Installation of Sprinkler Systems.” Specifically, the paragraphs are 16.5.1 and 2 and Figure A16.5.

So by now you may be wondering, what’s the problem? Well, our experience has been that one piece of the required information is being consistently omitted. That piece is important to the occupants, local authorities, and fire protection engineers. That piece is the record of the occupancy classification or commodity classification or the maximum permitted storage height and configuration. Basically it records the status of the facility for which the sprinkler protection was designed – at the time it was designed. This baseline is needed to determine the impact of proposed or incidental plant changes that may take place.

There is not much required information, just five basic items. Here is how it fits together:

1. Design area location.

2. Water discharge density and area of application.

3. The required water flow and pressure.

4. Occupancy or commodity classification or maximum storage height and configuration.

5. The allowance made for fire hose use.

Items 2, 3, and 5 are all related to the sprinkler system performance. Items 1 and 4 tell where and what was originally protected. That is the piece we sorely miss – what was in that space. We can tell what is in that space by visual observation, but is it the same as it was when the sprinkler system was designed? What was in that space prescribed the needed performance? While it is relatively easy to determine that system performance is the same, the missing information is what you need to tell if the performance is still adequate.

We need to be partners to make this happen. Designers should show the sign on their sprinkler drawings, complete with the required information. Reviewing authorities should request this and comment on the completeness of the sign and information. Owners, occupants – the group that is there when the sign gets placed on the pipe need to be demanding and not settle for missing information. And once again, reviewers checking completed installations for conformance to drawings need to insist on replacement of inadequate signs.

If you are reading this and wondering…go ahead, take a look. We will wait – and please, let us know what you found when you get back. We would love to hear from you.