Welding supports directly on tube of heaters or boilers

[Joe254]

Greetings¡

My question is direct.

Is it forbidden to weld clips, supports or anything that works like a support directly on high temp tubes?

The tubes are located inside the heaters or boiler, it's to say, exposes to high temp.

My experience tells me that that not must.

thanks in advance

 

[XL83NL]

My answer is direct.

It depends. What’s your code of construction?

 

[Joe254]

The question is formulated on way general, but If it was used ASME SEC VIII Div 1 or SEC I, as code of construction...what could you comment to the respect?

Thanks in advance

 

[XL83NL]

Then I would suggest looking into the applicable code. Have you looked in any of the codes? Whats the reason for asking? Whats your situation?

 

[CuMo]

Just had some hairpin bundles in design and the existing ones that we are replacing
had impingement tubes tack welded to the tubes.

If your weld doesn't penetrate the tube wall, the support expands at the same rate as the main tube (same material), you eliminate any possibility for trapped air between them (vent the void),
and eliminate any potential vibration problems - I don't see a problem.

Can't you make it a sliding support to avoid any stress?

 

[Dhurjati Sen]

Dear Joe254,

Both welded as well as clamped supports exist. The supports have been designed by the manufacturer and are different for super-heaters, water walls, economizers, etc. depending on the temperature, pressure and geometry of the tubes.

Regards.

DHURJATI SEN
Kolkata, India

 

[saplanti]

In practice, if the tubes are in a furnace or in the path of high temperature exhaust gases we would not prefer welding anything on the tube.
We would not weld anything on the the radiation surfaces in case the ceiling tubes concern. The ceiling supports may require a risk analysis. Think about the failure of the support and consequence of it. This will take you to the right decision and the right support type.

Hope it helps.

 

[saplanti]

I probably mislead you with the first paragraph. In general you can weld high temperature materials on the tube in the high temperature exhaust gas path, however you need to be very careful with the temperature distribution on the welded material and the weld type. The calculation is very complex and requires an expert to work on it. As I understand you have not got this knowledge. So you need to consult someone near you for the calculation and selection of material with the chemistry of the exhaust gases, temperatures etc.

 

[saplanti]

An if you get away from the welded type support it is probably the best for the secondary stresses on the tube. This again require an expert for the secondary stress calculation of the tubes at support area. Welded supports mainly brings higher secondary stresses due to the load concentration, will be likely over-stressed. You may reduce the stresses by reducing support distances somehow by increasing the number of supports. Sometime it is better to use full U-clamps with stainless plates in case the tubes in horizontal. But these may require long hangers to compensate horizontal thermal displacements. Some cases, as suggested, sliding support can solve problems, but the type of it and location may require an expert to overview.