A client is irate. They are saying the retrofit fire protection system I designed (and that their contractors are installing) is malfunctioning. They have had two unintentional discharges of halon gas, a fire suppression element, and they are blaming my employer for the malfunctioning equipment, and more specifically, me for an improperly designed system. My employer, in a veiled threat, said I had better figure out what was going on. Cue that sinking feeling you get when you realize you may have really done something wrong.
The job was an electrical retrofit and extension. They replaced everything that had electricity flowing through it, and they were extending the existing piping system to protect a larger area. The new control panel and supporting electrical devices were installed, powered up, and tested. Everything checked out.
Illustration of how the panel was wired. The installers did not short the abort terminals.
These guys then continued to install the mechanical upgrade, while the system was active and armed. I was assured that the fire protection system had been locked out. Typically, locking out a system means that the tanks containing the agent cannot possibly discharge because they have been electrically and/or mechanically disconnected from the system. I soon learned that the contractors, professionals, had done neither of these. Instead, they tried to hotwire the control panel. Their crew had wired an alarm bell panel output into the abort input.
They thought that the 24V DC, which goes active for a preprogrammed discharge, would power the abort input and fool the panel into thinking someone was holding down the abort button, thereby preventing discharge. (A note about clean agent systems: They all have abort switches to delay the agent discharge. This is for someone who thinks the alarm may be in error, or is trying to hold off the agent release for people who have yet to exit the protected area.)
I found out what they had done the next day, but not before the system discharged a third time. Here is what they did not know -- the abort input is not looking for 24 volts. It is expecting a button mounted on a wall near an exit somewhere to electrically short the abort input terminals.
Fire control panels have supervised inputs. This works by applying a voltage to the input circuit. Each input circuit has an ELR or "end of line resister" as the last element in a parallel array of input devices. This supervisory voltage sets up a current that is monitored by the control panel. A switch closure results in increased current flow. No current flow indicates a severed circuit and will trigger a trouble condition at the panel.
Also, a broken wire on a parallel element wired after the ELR will not be detected by the panel. This is a common error during installations. For instance, ELRs are installed right at the panel terminal blocks for an initial panel check and then they will forget to put them at the end of a circuit during the rest of the installation, resulting in a circuit that is not being monitored for integrity.
The accusatory statements and threats of litigation against me stopped immediately following my explanation that their hotwiring did nothing. It was their fault for working a construction job while the alarm panel was active. It is hard to believe that so-called experts come in to do a job, and they pretend to know what they are doing. As my years in the fire protection industry continued, I encountered incompetence more times than not. When lives are at stake, shouldn't people's bonafides be tested?
Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.
I could not agree more. I used to build what I now design and have found both engineers and mechanics who are incapable of performing their assigned jobs if there is not someone there to hold their hands. The bigger the project or organization, the more likely these guys are to slip through the system and ride their way to retirement on other people's coat tails.
There were two additonal factors not noted above: 1) In the construction, the two rods were offset in a common block instead of inline. Then the load was side thrust as well as tension pull. 2) The people on the catwalks were dancing. Therefore when keeping time with the music all dancers feet were impacting at one time which greatly increased the dynamic load. Anyone who has ever marched across a suspended bridge understands the meaning of this and knows why the Rout Step command was issued, Once the bridge was crossed evryone was again put in cadence.
I have worked on both sides of this problem, as both a field technician and as a registered professional engineer.
This problem cuts both ways. Experienced field installers know that there are some engineers who rarely get away from their cubicles. These installers don't have time to get in to a war of words with someone who doesn't know the situation on the ground; so they deviate from the design.
This is why we have "As-Built" Drawings.
Sometimes, however, the installer did not understand what the Engineer was asking for. It used to be that a phone call from the job site was expensive. Well, that's no longer true. I always recommend communications. If the installer didn't plan a few phone calls in the schedule for the work they bid, that's their own fault.
All this regulations and licensing is worth... you name it.
This guys LICENSE should have been SUSPENDED immediately; their previous jobs INSPECTED for SAFETY. and recertification should have been a MUST for ALL responsible parties in that JOB.
HUMAN LIVES depend on this kind of SHODDY jobs.
That is why there are LAWS, REGULATIONS and INSPECTIONS, preventing Stupid, Lazy or Ignorant BOZOS from doing jobs where human lives are in DANGER. and PROTECTING the SAFETY of everyone.
RPCY, the original design wasn't even marginal; it was able to hold only 60% of the minimim load required by the city building code. The bad choice for redesign meant the 4th floor structure would hold only 30% of the load required by the city building code.
The original design wasn't strong enough, required rediculous threaded lengths, and was poorly considered because the rods passed through the welded joint of two C-channels (making a rectangular tube).
The deformations of the 4th floor beams is just plain scary.
My experiences with assorted contract installers have mostly been negative. Some of them got all of the connections correct but wasted huge amounts of wire, others have made errors in labeling wires, so that each end had a different number, one time a panelman skipped one terminal, and so half the wires were one terminal over from where they should have been.
I have been fortunate that when it came to working on live systems I was able to do that myself, since I could move a bit slower and be more careful than the people eager to finish and leave for the next job.
Fire panels are unique in that they are indeed supervised, and that does add a requirement to accomodate the supervisory function. Mostly that calls for careful attention to polarities and diode directions, so it is not hard, but tedious.
You (your company) has control of everything going into a product. That is where the limit of your responsibility (should) end.
If that product requires other "professionals" to correctly install / operate it... you no longer have any direct control. And you should no longer have any responsibility.
Unfortunately, that isn't the way our legal system works.
Have numerous examples of similar screw ups by other "professionals" involved in installing/maintaining systems.
Education, certification of skills, etc.. will mitigate some of this. But it will not eliminate it.
Interesting comment about Ft. Hood. The last company I worked for got the contract for some expensive custom products (to protect the guilty, I won't say what) that were going onto some buildings that were being decomissioned. I got the job to do the design work and enjoyed it. But I had to demonstrate that it would work before the Army Corps of Engineers would allow us to install. While they were in our prototype lab, I asked what I thought was an innocent question, "Why were they installing this very expensive equipment on buildings that wouldn't be used." They glared at me and said they had budget money to use up.
As an aside about the Army Corps of Engineers, I had found a substantial technical flaw in their standard bid document for our type of products. I wrote a letter to Huntsville, AL (pre-email days) detailing the problem. About a month later, I received a letter back stating that I was correct and they would update their documentation. Eight years later, when I left the company, we were still getting the erroneous bid requests.
THE FIRST THING I SUGGEST IS THAT YOU FIND OUT IF THE CONTRACTOR IA LICENSED AND CERTIFIED TO WORK ON FIRE ALARM/RELEASING PANELS. REQUIRED IN MOST STATES. A RANK BEGINNER SHOULD KNOW THAT ANY INPUT "ABORT" IS LOOKING FOR A CONTACT CLOSURE AND OPERATES IN THE MICRO OR MILIAMP REMGE. BY TIEING IT TO THE NOTIFICATION CIRCUIT YOU ARE DUMPING 1 AMP IN TO THE CIRCUIT. SO FAR AS INDICATED YOU HAVE BEEN LUCKY THAT THE ELECTRONICS HAVE NOT BEEN FRIED. FOR THE SAKE OF YOUR LIABILITY ON THIS PROJECT YOU SHOULD COMPLETELY TEST PANEL WHEN THE PROJECT IS DONE.
You're thinking of the Hyatt Regency walkway collapse in Kansas City MO, 1981. The original engineer's design was workable but marginal, calling for two suspended catwalks to be suspended from the same 40-ft threaded rods. When the builder got to that part of the construction, he balked at threading nuts and washers 20 feet onto each rod, so he made what he thought was a reasonable compromise: he'd use two 20 foot rods instead of one 40 foot rod. The top catwalk would hang from the ceiling, and the bottom catwalk would hang from the top catwalk. He ran this proposed change past the inspectors, the chief project engineer, and a few others, and they all approved the change. I use this example sometimes when talking to validation crews, because you don't have to know anything about civil engineering to realize that if the joints where the top catwalk transfers its load to the rod was workable in the original design, you now have two catwalks hanging from that stress point. Nobody seemed to realize this. And even at twice the weight, the joint held when first constructed. It was only when the catwalk was filled with holiday revelers that the joint finally failed, crashing the lower catwalk to the ground, and the upper one pancaking onto it. The contractor's original bonehead error managed to sneak by several other engineers and get approved. It is not clear that the original architect/engineer was ever consulted on this change -- you'd think that if anyone would have picked up on this gaffe, it would have been him/her.
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