Dear List,We need to control the flames of some furnaces, to shut down the gas when flames are out.There are some holes around the furnaces and technicians can observe inside by naked eye.I want to learn if we can use video cameras instead of flame detectors.And if we can, what kind of a system will be better for our purpose ?Thanks,A.Konyali

 

This sounds like a dangerous idea. Stick with UL listed flame safety apparatus. Don’t try and make your own. You are just asking for trouble.

 

Armagan,

Yes, it is possible to do this but not advisable. Several considerations make flame detectors the better choice.
First is safety. Unless you furnaces are continuously above the self-ignition point of natural gas (about 1100 F), an unobserved flame-out can rapidly dump raw gas into the furnace until it reaches an explosive concentration. An automatic system like a flame detector is far superior. They don’t take coffee breaks.
Second is the cost. A properly cooled and insulated industrial video camera will cost more than a dozen flame detectors. Then when you add the wages of someone to monitor the cameras you could buy even more.
As a backup to the flame detectors a video camera would be an excellent idea. It is a great help in maintaining the flame quality and PID tuning but as a primary means of safety I, personally, would run from that furnace.
Paul Butchart
Rolling Mill Electronics
Qualitech Steel SBQ, L.L.C.

 

Wouldn’t a decrease in light be enough to detect flame outages?
(Cadmium Sulfide Cells = photoresistors.) I think that a CDS cell in a black metal sleeve (perhaps with a glass bezel) pointed at the base of the flame would be simpler than a vision system.
Warren

 

------- Forwarded message follows -------
From: "Geoff Moore" <[email protected]>
To: "The Automation mailing list, managed by Control Technology Corporation" <[email protected]>
Subject: Re: APPS: video cameras instead of flame detectors
Date: Fri, 5 Nov 1999 20:54:01 -0000

Not quite on the subject but an amusing anecdote....

A while ago, a large and prestigeous bank we did some work for had a fire
alarm system which did not work.

One night, they had a fire.

Nobody knew until one of the security staff went outside to investigate some
strange noises.

He discovered that the noises he heard were the sounds of the windows in a
neighbouring building buckling from the heat of a fire inside the building
he was meant to be guarding.

There was a lot of damage done, both to the building and to the reputation
of the bank and serious questions were asked as to how, even without the
alarm system, a fire could go un-noticed for so long in a building with 24
hour security guards.

During the subsequent investigation an entry was discovered in the security
log, timed half an hour before the fire was detected, saying that one of the
CCTV monitors was faulty.

Sure enough, one of the CCTV monitors in the control room was found to be
switched off with a Post-It attached on which someone had written FAULTY!

On questioning the security staff who had been on duty that night, they said
they had to keep turning the brightness down on the monitor " 'cos it kept
flaring up".

The "flares" they had seen were actually flames from the fire licking up
around the camera.

So CCTV cameras do work as flame detectors, but people don't.

Geoff Moore
Straight Forward Solutions Ltd
Maynooth Road, Prosperous,
Naas, Co.Kildare, Ireland
+353 (0)45 892739
[email protected]


------- End of forwarded message -------

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> > We need to control the flames of some furnaces, to shut down the gas
> > when flames are out.
>
> Wouldn't a decrease in light be enough to detect flame outages?
> (Cadmium Sulfide Cells = photoresistors.)
> I think that a CDS cell in a black metal sleeve (perhaps with a glass
> bezel) pointed at the base of the flame
> would be simpler than a vision system.

With the burners I have worked with, most used Landis & Gyr controllers,
either using CDS style sensor or flame rod. The flame rod was the most
reliable
with good flame, but CDS did have problems with daylight and background
flames.
I recommend using a dedicated flame detection equipment as to build a
system
using video would not be cost effective and may not meet regulations.

Trevor Ousey