steam drum

[rgrokkam]

Dear All,
Of late two steam drums in boilers of our power plant have shown cracks during RLI. Can the forum throw some light on the possible reasons for cracks in steam drum and how to go about a preliminary investigation.

Thanks

 

[MrMyers]

What is the material and where are the cracks? In welds, nozzle branches etc?

Does the unit see much cycling?

 

[EdTeach]

You need to look at the crack and determine if it is a mechanism from bad boiler feed water condition or fatigue failure.
If you are unsure I would investigate the H2O quality. I would look for CO which would be a likely cause of corosion, erosion, or cracking. You could take some test of your water (PH,CO,O2,etc) to determine if your water treatment is working correctly.

 

[0707]

A current industry concern is the increasing number of incidences of utility boiler header and steam drum cracking, found in units which have typically been in service more than twenty years.
The cracking is associated with both high temperature steam and lower temperature water carrying components. The failure mechanisms of stress rupture and fatigue are associated with the high temperature components, while fatigue due to thermal shock and/or corrosion are applicable to steam drum and lower temperature (water carrying) headers.
Stress corrosion cracking of boiler components is a well known phenomenon and is easily controlled by the use of proper water chemistry during boiler operation. Occasionally water chemistry can go astray and stress corrosion cracking can occur

Check your water quality

Make ndt testing such as magnetoscopy and TOFD

Make metallographic replicas

luismarques

 

[chicopee]

You should shed some light as to where the cracks are. Also check out the NBIC booklet on the types of cracks and their possible causes.