Frequent Start-up/Shutdown effects on Fertilizer Plant

[tabbymulla]

Dear All,

Can anyone guide me to some reference (books, web, etc) where I can find the negative effects of Frequent Start-up/Shutdown on Equipments Used in Fertilizer Industry such as pressure vessels, heat exchangers, piping, valves, compressors, pumps, turbine, etc? Please.

Regards,

Tabby

 

[metengr]

Negative effects from cycling - increased risk of thermal/mechanical fatigue damage and failure = increased O&M costs + increased capital equipment costs + loss revenue.

How's that?

 

[boilerone]

Like Metengr said, failure from fatigue is the major concern. One famous term is the 'S/N curve'. Fatigue should include mechanical, thermal and, particular to your chemical industry, corrosion fatigue. Here are some quick Wikipedia links:

http://en.wikipedia.org/wiki/Fatigue_(material)

http://en.wikipedia.org/wiki/Thermal_shock

http://en.wikipedia.org/wiki/Corrosion_fatigue

 

[unclesyd]

One point not mention above is that even for short periods of downtime you have to take care of any heat exchangers that have water on one side. Keep treated water flowing to prevent the water in the exchanger from becoming stagnant. This is to prevent MIC (Microbiological Induced Corrosion) from starting. The effects of MIC can and are generally additive over time once it starts.

 

[rmw]

All the information presented above is good information, but it didn't answer the OP's question.

Frankly, I don't think that it is taught as such (other than relationships like what a S/N curve is) in textbooks. In other words, in answer to your question, I don't think you will find a textbook teaching this per se.

What metengr, boilerone, and unclesyd have offered is practical advice based on common knowledge. The industry that metengr works in, for one, found out what happens to high pressure equipment designed for base load service when they were diverted to cycling and peaking duty.

If your plant was designed day one for cycling or repetitive start/stop cycles, then you might be alright. For one, details like unclesyd brings out would have been covered.

However, unless your plant is drastically different from the standard Kellogg and Braun plants, it was designed to be started and run constantly, with maybe one turnaround per year. Unexpected trips are another thing outside the the scope of the question as I understand it.

metengr, there may be some EPRI documentation re; the cycling effects on HP FWH's that would help the OP if he could get his hands on them. Do you know of any that specifically address that?

Tabby, you might google up some documents called GE GER's and rummage through them to see if any address cycling issues on turbines. Their turbines are larger than what you have in a fertilizer plant, but the principles will be the same.

You might also try googling HRSG's and look for cycling effects. They have found out the hard way that what the previous posters have stated is true.

rmw

 

[tabbymulla]

Thanks everyone. It was really helpful. I found some data in Urea symposiums and IFA conferences reports. Actually the situation wants me to have some literature reference.

Regards,

Tabby

 

[ColonelSanders83]

You should probably define frequency.

If the piping in your plant is designed to ASME B31.3 it is most liley design to the default 7000 cycles, or one sturup and shutdown cycle per day for a 20 year life expectancy. You should be able to find all the design data for all the pressure retaining components in you plant. The number of predicted cycles should be documented somewhere.

If not you are probably looking at gettting a specealist in to perform an evalution. It all comes down to what the plant was designed for and whether or not your current operational practices are still within that envelope.

A question properly stated is a problem half solved.

Always remember, free advice is worth exactly what you pay for it!

http://www.ap-dynamics.ab.ca/