3 replies to this topic

[sukanta87]

HI All,

This is a water bath heater (Indirect fired heater). Natural gas has been used as fuel. Having problem with the burner system. The heater has two main burners and two pilot burners (see the attached figures). In a chamber there is a partition and in each section there is one pilot burner with one main burner. Air suction happens naturally from the bottom of the  chamber. Usually both burners works nicely but in separate time. Pilot burner starts burning firstly, then the main burner. The problem is when main burner is ON, pilot burner become OFF. It's recommended to keep the pilot burner ON always. In addition, the required voltage to keep the main burner's solenoid ON went down, when the main burner is ON. The voltage measured from the pilot burner ignition.

 

Is there any standard distance between pilot burner and main burner or how much the distance? As if the burners are very closer, oxygen deficiency may happen and the smaller ignition source may be stopped.

 

Attached Files

•  burners in WBH.jpg   80.29KB   3 downloads
•  Chamber.jpg   86.13KB   2 downloads

[PingPong]

It seems to me that this is a question for the company who built and installed the system.

 

In any case, one would need the P&ID of the system, plus Cause and Effect Diagram of the safeguarding system to understand the system.

[Art Montemayor]

We don’t know if this is a recent, new installation that is exhibiting the described actions.  We also don’t know if the burners are spared instead of working together:  in other words, is the heater designed to operate normally with one burner and have the other burner as a stand-by spare?  If both the burners are supposed to work together for the normal, designed capacity, why aren’t they operating together as described?

 

Also, if this is a new unit, it should have undergone an FAT (factory acceptance test) at the fabricators that was witnessed by the purchaser.  If so, did it function in accordance to the operating manual?  If so, were any changes (especially in the automatic controls and instrumentation) take place at the installation site after the FAT?  Also, are the described problems taking place recently after successfully working OK for a sustained time?

 

Has the designer/fabricator been advised?  It is not a process operating requirement to have the pilot ignition flame on 100% of the time.  Automatic instrumentation can be designed to ignite the pilot prior to starting the main burners and then turn off after successful startup.  It all depends on the logic and scope of the heaters design.  If you have only natural draft (as you describe), it is difficult to ensure that proper, safe, and thorough firebox purging is done after a shutdown or prior to a startup.  Therefore, there must be a safe, proper procedure to follow in order to ensure that there are no combustible gases in the firebox prior to igniting the pilots’ or burners’ flames.

 

 

In short, there is simply too much information that is unknown by the Forum to have an effective and accurate analysis of what is going on.  It is more prudent, safer, and efficient to notify the designer/fabricator and request their assistance in the field - as PingPong has advised.

[sukanta87]

Dear Art and pingpong,

 

Thanks for your comments.

The burner system is not spare, it's together. FAT was done successfully, also at site for some times it works. But it becomes OFF very frequently. From the beginning facing the problem. Yes, service time of pilot burner depends, mainly based on control philosophy.

Something identified to resolve this issue. There is a sizing mismatch of the burners which can withstand for a moment but not for longer time.