LPG Burner Completely destroyed

[moobe]

Hello Experts,

We have four LPG burners in the oven. Each burner is 275 KW . One of the burners was completed destroyed.Please check the pics attached. Now I need to know the reason behind this. Also, a list of maintenance things to be done to avoid the problem in future.Burner Model is RS 34/M MZ from Rhielo.

 

[moobe]

Some other pics

 

[IRstuff]

Shouldn't you ask the manufacturer to look at it?

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[itsmoked]

Most likely scenarios are:

1) The fan failed. This left a dirty flame operating in the bore of the burner instead of launching directly into the combustion chamber.

2) The igniter is in the bore of the burner and it's mount failed and it fell deflecting part of the burner flame into the side of the burner housing. Often the ignitor just reaches in thru a simple hole in the side of the burner tube. The air always gets sucked into the burner tube thru that hole unless the blower is not running.

3) That fourth burner failed to run at all and the other three pressurized the burner box. Some of the flue gases backtracked thru the one non-running burner since it isn't a positive pressure source like the running ones if it's not running. Again possibly back out the igniter hole.

Could be those burners are not supposed to be run in a ganged mode unless they're equipped with some sort of electrical link to stop them all - if one fails.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[moobe]

Thanks Kieth,
Yes I doubt of the blower failed ,the thing is my burner controller does not give a signal if the blower is running or not to my plc.The only way i will know if the blower failed is when the burner is commanded to start and the burner fails to ignite as the blower has failed. Can i know what is other way of preventing this type of incident

 

[itsmoked]

moobe; I listed a bunch of possibilities for you to pursue. You must figure out why exactly it happened before you have any hope of protecting the system from it.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[georgeverghese]

To add to Keith's list , also check if this burner was the only one left in operation at low heating load. If heating load was below the turndown limit for this remaining burner for a long time, you may have had burner backburn or even a single flashback / explosion event. Modern fuel gas runs for industrial heaters/ furnaces would have a min op pressure limiter on fuel gas supply to prevent flashback.

Heating load turndown a typical gas burners is 5:1 when compared to max rated burner heating load for the design case operating fuel gas supply pressure. On an installation with 4 burners, the safe operable limit would then be 20:1. A special high turndown gas burner can operate at loads as low as 8:1.

Strange that the burner PLC doesnt trip the entire heater if the FD blower has tripped during operation. You could ask a process controls engineer to configure a trip loop external to the burner PLC to do this if you cannot get the burner supplier to help you out.

 

[EngrPaper]

You say that your controller does not know if the burner has failed? Your burner really should be equipped with a self-checking UV flame detector. These will sense the UV light from the flame and feedback to the burner management system as a safety check. Normally, your BMS will have to verify that the flame lit as part of its startup procedure in order to move to a high-fire position. Then, as the burner operates, the self-checking feature of the flame detector will every once and a while intentionally interrupt the signal to verify that the sensor has not failed in the on position.

Another way this is done is with flame rods, though these are not self-checking.

 

[moobe]

Thanks . We do have flame rods to check the flame and in case burner doesnt fire the burner controller gives an alarm to plc but the problem is in my case I dont require to run one of the burners depending on the temperature and in this condition the combustion fan on the burner should always run to prevent heat flow back to the burner . So in such condition I do not have a signal for the fan status running/not running . The only way i will know is when the burner is commanded to start up and obviously it will trip because the fan is not running

 

[EngrPaper]

Part of our startup procedure in the BMS is a flow switch proving combustion air. Perhaps if you have one of those (which I assume you do) you could run that separately to your PLC as a double check.

 

[itsmoked]

The more I look at that picture of the melted burner the more it looks like it didn't run and the others cooked it back feeding it. You should definitely have some air flow switches as EngrPaper suggests to alert the PLC to shut down the others. It should also indicate to the users which one is 'not flowing' to give quick troubleshooting information. There are a whole bunch of air flow switches out there that are pretty inexpensive. Four will cost probably 1/20th the price of a new burner. They'll pay for themselves the first time one trips. There is probably somewhere obvious that the air is sucked into the blowers. Find that location and an airflow switch that can monitor it without interfering with flow and you'll be set.

Keith Cress
kcress -

http://www.flaminsystems.com