Flame contact cracking rear section

Turbo Dave

Hello. I need to find information about flame contacting a rear boiler section causing it to crack. I know this is true, but I need to find it written somewhere. I have searched at length on the wall and have not found anything yet. Googling didn't help so far either. I had an issue where the tips of the electrodes were in the pattern, causing drips of fuel to be thrown and flame to contact the rear section. The section cracked after 2 months of this being unnoticed, following a tune-up. Any information or direction where to look is appreciated.

Robert O'Brien

Flame impingement can cause combustion issues but will not cause a wet base CI boiler to crack.

njtommy

Sounds like the boiler is over firing. I'm assuming its oil. I would check to see what size nozzle and spray pattern is currently installed along with what pump pressure it's set at. You could simply be running too much pressure with the wrong nozzle for your boiler.

Steamhead

What njtommy said, and-

What make and model is the boiler?

What make and model is the burner?

Was there a "target wall" installed on the back section?

STEVEusaPA

As you're checking all the above, make sure:
A) If there is a target wall, it's tight to the back section
Check your 'Z' dimension as an incorrect setting can make the flame 'longer'

Turbo Dave

The boiler is a Burnham P509. According to Burnham, this originally came with a Carlin 801CRD w/ 5.0 & 5.5 gph 60 nozzles. It currently has a Carlin 601CRD w/ 7.0gph x 45SS. The section has been replaced and the flame issue corrected by properly adjusting the electrodes. At this point, I only need to find verification that the flame contact can or cannot cause the section to crack. (I am aware of the many other reasons for this occurrence). I subcontracted the burner service and now need to educate myself and determine responsibility. The customer has boiler professionals on staff that are adamant that flame contact can cause cracking. Robert O'Brien, you seem quite sure that it can't. While I am confident in the professional opinions of members here, my customer likely desires something published. I've not found anything conclusive either way, so far. However, if I can gain the understanding of why or why it is not likely, that will get me much farther ahead of where I am. Thanks.

STEVEusaPA

If it never ran out of water and was dry fired, then that would not be the cause. Think of a pot of water on a gas stove. Does the flame damage the pot?

Steamhead

Turbo Dave said:

The boiler is a Burnham P509. According to Burnham, this originally came with a Carlin 801CRD w/ 5.0 & 5.5 gph 60 nozzles. It currently has a Carlin 601CRD w/ 7.0gph x 45SS.

What pump pressure is the 601CRD running? This will affect the firing rate. Nozzles are rated at 100 PSI but some of these large commercial burners might run at 150-300 PSI.

Robert O'Brien

Is it steam or HW? A surging over-fired steam boiler can have a low water condition in a rear section while the front, where the LWCO is commonly located is fine. 509 boiler has no combustion chamber but does have a firewall, I believe?

Turbo Dave

Steamhead, the fuel pressure is 150psi per spec. Robert, this is a HW boiler. It is supposed to have a liner on the right side of the firebox only, to enable "thermal pumping" through the sections, per the install instructions, attached. That is one of several reasons why the section could crack, but I need to address whether or not flame contact specifically can do so. This is not the first time this customer thought a service tech cracked a section. The previous example a nozzle with too wide of a spray angle was installed, the flame then cracking the side of a center section. They have 10 of these boilers. They are PF-509, forgot the F earlier. From the responses so far, it seems nobody thinks this is possible. I just need help in proving this to my customer.

Robert O'Brien

What does Burnham say? Their opinion is the only one that matters

Steamhead

A 7.00 nozzle at 150 PSI gives a firing rate of 8.57 GPH. The PF-509 is rated at 12.6 GPH, so over-firing is not the problem.

You say the section was replaced. Was there evidence of overheating on the failed section? Was there an accumulation of sludge in the old section that would keep water from carrying away the heat?

Turbo Dave

Steamhead said:

You say the section was replaced. Was there evidence of overheating on the failed section? Was there an accumulation of sludge in the old section that would keep water from carrying away the heat?

I have not seen the section since removed, but a long vertical crack was evident when looking at it through the inspection port, directly center in front of the flame path. I will try to get pictures Monday.

Turbo Dave

Robert O'Brien said:

What does Burnham say? Their opinion is the only one that matters

I will talk to them Monday and let you know.

Firecontrol933

Sounds to me more likely to be stress cracks from shocking the boiler(s) with cold water return. I've never seen a CI boiler fail due to impingement of a flame....... soot up so bad it plugged it solid, yes!

It'll be interesting to see what Burnham has to say about it.

Brings to mind science class in high school where you boiled water in a paper cup over a Bunsen burner.

Turbo Dave

We are waiting for the ground to firm up in order to move the section. It is currently laying on it's face. Burnham is going to review the pictures. More to follow.