The C Factor of Pipe, What Exactly is It??

Often times in designing our sprinkler systems, we need to use formulas to arrive at a value that is useful to us and our work.  In these formulas there are variables and constants that we may or may not understand but we mindlessly plug them into equations anyway because we know them by heart.  The Hazen-Williams formula is the formula we will most often use when calculating our sprinkler system.  In Hazen-Williams we need to input the inside diameter of the pipe be used, the flow in gallons per minute, and the C Factor of the pipe to derive the friction loss for 1′-0″ of pipe.  From memory we can probably recite the C values, 150 for CPVC, 120 for black pipe used in a wet system, and 100 for black pipe used in a dry system, etc, etc.  Perhaps in the course of our experience we learned that the C Factor represents the roughness on inside of the pipe, which is true.  But what does the number actually represent and how does it actually affect our calculations? Continue reading “The C Factor of Pipe, What Exactly is It??”

Low Flow Test Pressure? Try High Efficient Sprinkler Head Spacing

Inevitably we all design a project where the pressures from the flow test are less then desirable.  We layout our fire sprinkler heads and pipe to do a preliminary calculation and input our flow test into the calc program.  It’s then we realize, we can’t get a safety factor on the system…our calc fails.  So we do our normal routine of increasing pipe sizes, changing k-factor of heads, and changing the pipe schedule of pipe to be used but nothing seems to work.  After every trick in our bag is exhausted, nervousness sets in…..thoughts of fire pumps and an uncomfortable meeting with the general contractor cross our mind. Continue reading “Low Flow Test Pressure? Try High Efficient Sprinkler Head Spacing”

A Helpful Way to Get Aquainted with a New Project

When the inevitable new project gets handed off to the fire sprinkler designer, many of us feel tempted to immediately open up the drawings to the reflected ceiling plan to get an idea of the project scope.  However, just referencing these drawings is not sufficient enough to familiarize yourself with the entire project.  Over they years, I have developed a simple and helpful way  to become familiar with a project during the start-up phase and it may help youtoo.  What I do is simply follow the architectural sheet index/table of contents in order.  If you look at one, it’s organized in a fairly logical order and flow of work.  It usually begins with some kind of general information sheet, and life safety plan, then to the site/civil information.  Next the architectural drawings and then to the structural and mechanical trades.  I will explain why following this flow of drawings can be very helpful. Continue reading “A Helpful Way to Get Aquainted with a New Project”

CPVC – Overlooking Expansion and Contraction is a Big Mistake

I would say the number one most over looked issue with CPVC fire sprinkler systems most fire sprinklers designers fail to address is dealing with expansion and contraction of the CPVC pipe.  All CPVC pipe is made from plastic which has many advantages over steel pipe;  plastic pipe is non-corrosive, lighter weight, cheaper then steel, and has great hydraulic characteristics.  However, it does have its draw backs.  One of which is its ability to expand and contract with the swings in ambient temperature due to the highly elastic nature of plastics.  As the sprinkler system expands and contracts over time, it puts additional stress on the fittings and joints holding the system together.  To much stress and the pipe or fittings may crack creating a slow, dripping leak in the system or may shatter the pipe joint completely. Continue reading “CPVC – Overlooking Expansion and Contraction is a Big Mistake”

Gather Your Tools, Pt.3 – Fire Sprinkler References

As fire sprinkler designers, most of our time looking up codes is spent reading through NFPA-13, the fire sprinkler designers bible.  However, after a short amount of time reading through 13, we notice that not everything we need to know about a sprinkler system is contained in the book.  Standpipe systems need to be designed according to NFPA-14.  Fire pumps needs to be designed according to NFPA-20.  Many times it is often necessary to reference NFPA-101 for life safety purposes.  We could go on and on with water tanks, foam systems, residential systems, etc, etc.  This is just a brief list of NFPA references and I haven’t even touched on building codes and local ordinances.  Before we know it, we have a reference list of code books that is longer then we care for it to be and the costs of all those books would break the bank of many design department’s budget. Continue reading “Gather Your Tools, Pt.3 – Fire Sprinkler References”

Gather Your Tools, Pt.2 — Your Computer

In the previous post in this series, Gather Your Tools, Pt.1 — The Fire Sprinkler Design Software, I explored the necessary design software to get you up and running.  However, that software needs a machine to run on which is your next critical decision.  Whether you purchase a desktop computer or a laptop computer, this is the second largest investment money wise you will make to outfit a designer.  I chose a laptop for a number of good reasons but your needs may be very different.  To make this decision you need to ask yourself some key questions.  Would you like to bring your computer out on a job site survey? How important is upgrading a computer to you?  If you work in an office, would you like the ability to bring your computer home with you?  What is your computer budget?  Lets discuss each of these questions in a little more detail. Continue reading “Gather Your Tools, Pt.2 — Your Computer”