Design life of some ACFB boiler components 1

[wayuu1981]

Hello, the company where I work is hiring a Chinese EPC contractor for a new 164 net MW coal fired utility. The last week we received the specifications of the proposed CFB sub-bituminous B coal fired boiler of 605 t/h steam production at 540°C and 13.7 MPa, natural circulation, once through reheat, single furnace, balanced draft, with economizer and tubular air heater.

I wonder where I can find reference values of the estimated design life for some boiler components such as: air heater tubes (cold end), de-superheater spray nozzles and convective heating surfaces in low temperature zone, as the Chinese company is offering 50000 hours, 80000 hours and 100000 hours respectively and I would like to compare these values to western standards or at least to a rule of thumb.

By the way, I live in South America where ASME is not mandatory, so we can accept GB (Chinese standards) or any other code or standard for designing, manufacturing and testing the boiler.

Thanks everybody for your responses.

Javier Guevara E.
Projects, Mechanical Engineer

 

[davefitz]

first, ASME sect I has inlcuded a note that states that use of their code does not provide any warranty or expectation on equipment life ( damage factors of corrosion , erosion, and fatigue are not inlcuded in the code).

second, the components that seem to wear out first on cfb's include non pressure parts such as refractory, fuel and limestone feed components, heated supports, etc. You might be beter served to get a life warranty on those parts.

finally, no matter how ironclad you think the warranty statement sounds, the vendor will claim any failure is due to operator error, feedwater quality , fuel or limestone quality being off-spec, or other excuse.

 

[wayuu1981]

Thanks davefitz for your response,

I understand what you say, now I'm asking the Chinese Company to specify the estimated life of the fluidizing nozzles as well as the estimated life of refractory to be applied to lower zone of furnace, cyclones, platen superheater, platen reheater and particle recirculating valve and spout. Coal, limestone and ash handling systems will be provided by other subcontractor.

But, and now it looks a little suspicious to me, the company only specified the life in hours for those 3 components described in my last thread, so I really need to find some information about estimated life of main CFB boiler components, specially those 3.

By the way, the boiler specifications also say that "main" parts of the boiler will be designed for a live of at least 30 years.

I know this kind of things are only words, and it will be almost impossible to claim a compensation if they are not achieved in the future.


Javier Guevara E.
Projects, Mechanical Engineer

 

[adamuk]

50,000 hours seems low (remember there are 8760 hours in a year so that's just under 6 years life. Really you should be aiming for 100,000 hours life as a very minimum and really aim for 250,000 (see BS1113 for an example)

My experience of boiler operation and maintenance is that in the design stage I would go for the maximum life you can otherwise you end up doing endless fitness for purpose work and technical reviews to justify keeping the thing going and it just becomes a PITA.

Adam Potter MEng CEng MIMechE

http://www.ax-ea.co.uk

 

[rmw]

Depends on which side of the table one is sitting on. If you are on the user's side, you want it designed to last one day past your retirement date (assuming that is many years away) but if you are on the supplier's side, you want it to last one day beyond the end of the warranty period.

I knew of manufacturers of auxiliary equipment that wouldn't put their company logo on stuff they sold to boiler companies because it was so cheaply built. All the boiler OEM's specified for and wanted was to survive the warranty period.

They sold on the basis of lowest cost, not longest life.

rmw

 

[GenB]

Being in SudAm means no ASME but why not get an American Made equipment?
Why not, we buy your Oil? I imagine you're in Venezuela or Brazil, Ecuador, Peru.
The life of American Equipment will at least double compared.
do not forget that you get what you pay for.
San Francisco Port bough Chinese Cranes that lasted six months then start cracking, so repair after repairs... It was an open bid and they had to pay the lowest. Country of El Salvador bough many Chinese Trash collection trucks, all ended up in the river in a couple years of use and the list goes on and on.
Good luck.

 

[athomas236]

I have been involved in a number of projects with Chinese EPC contractors and comment as follows:

1. The advantages of using Chinese contractors are lower prices and shorter delivery times.

2. The disadvantages of using Chinese contractors are:

(a) The quality of manufacture and there are some real horror stories.

There have been attempts to overcome this by using third party inspectors but these have to be Chinese speakers trained in Europe/US to avoid the China Inc syndrome. In my experience such attempts have not been successful because of clients unwillingness to pay for such inspectors.

(b) We have never accepted GB standards but have always specified ASME Section 1 for boilers with ASME stamping for both works and site. Most GB standards are not available in English and those that are and that I have read do not have the equivalent level of detail as ASME.

Your local statutory boiler inspector may have an opinion about the acceptability of GB standards.

(c) Chinese contractors are often not familiar with international practices with the consequence that they do not plan there work, do not understand co-ordination with the client and his consultant.

On one project told us that drawings "approved for construction" were for guidance only.

Hope this helps.

athomas236