Nozzles in a stack - Corten Steel

[waliq]

Hi,

We want to cut 02 nozzles of NPS 3" each in an existing stack. The nozzles are instrument nozzles

Diameter of stack : 1350 mm
Design pressure : Atm
Operating Pressure : 280 Deg C
MOC Stack shell : Corten steel (Grade not available in drawing)
Thickness of shell : 10 mm

My questions in this regard are as follows
1) Can I use SA 106 GrB and SA 105N flange and blind flanges for nozzle material?

2) Should we perform a stress analysis for cutting holes in an existing stack to install 02 nozzles?

 

[hacksaw]

What sort of analyzer are you using that requires a NPS 3 connection,
You might also indicate the elevation above grade your connections are planned.

 

[Maslov]

Design pressure : Atm

Are you following a code?

I wouldn't consider an open stack a pressure vessel, so requirements are going to be up to your jurisdiction, client, and sound engineering judgement.

There's not nearly enough information here to answer this for you. Like hacksaw asked, how high up are the connections (are we concerned about wind loads?)? How heavy is the instrument you're attaching?

You could do WRC nozzle load calcs to check the nozzles for stress. And a calc on the stack base/connection should be easy enough.

As for welding, without a code (nor a material spec/grade given) it's hard to say. You're main concern is weldability, best proven with a qualified weld procedure.

 

[LittleInch]

What nozzle connection are you using?

Pipe or weldolet?

Should be fine, but depends on load and how your connecting the nozzle.

You might be better if with a support welded to the flange to avoid vibration.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mk3223]

It's typically to add new nozzle on the furnace stack with a heavy wall pipe with or without reinforced pad, if needed, depending on the instrument weight on the nozzles.
As the operation temperature at 280C, verify if any refractory lining is existed inside the stack and needs to be repaired for new nozzle.

 

[waliq]

The nozzle is to be attached 7M above grade.

The nozzle shall be blinded and a probe shall only be installed to analyze the flu gases occassionally.

The connection of nozzle to stack shell is a full penetration weld

The material grade of stack itself is unknown. The drawing only mentions the stack shell material as Corten steel. The drawing is quite old (about 15 yrs) and we do not have any contact with the vendor now.

 

[GD2]

waliq,
Did you say the flue temperature is 280C? 280C seems too low for flue gas.
What is the height of the stack?

Find out if the stack is internally coated/double-wall and externally painted/insulated? What's the ambient temperature?

The reason I am asking these questions is if the metal temperature falls below the dew point of the acid gases, the new connections would be corroded.

You are allowed for instrument port connections with adequate repad on the stack shell but it will be important to protect it from the corrosion from the acid gases.

GDD
Canada