accelerated flow corrosion
accelerated flow corrosion
(OP)
our condesate minuim flow recirc piping back to the condenser is a 4 inch sch.80 carbon pipe reduced to an 2 inch sch. 80 carbon pipe then back to 4 inch to the condenser. we are having problems with re occuring accelerated flow corrosion,original installation utilized an eccentric reducer. we have tried concentric reducers,
and other remedies to no avail,the reducers are 12 inches before the first 90 should we replace the 2
inch configuration to straight 4 inch ? need some remedie that will last longer than 6 mo. to 18mo.
condesate pump pressures around 350 psi. coming off 8 inch main pipe.there is vaccum pulled on the steam turbine condenser.
any recommendations greatly appreciated
and other remedies to no avail,the reducers are 12 inches before the first 90 should we replace the 2
inch configuration to straight 4 inch ? need some remedie that will last longer than 6 mo. to 18mo.
condesate pump pressures around 350 psi. coming off 8 inch main pipe.there is vaccum pulled on the steam turbine condenser.
any recommendations greatly appreciated





RE: accelerated flow corrosion
RE: accelerated flow corrosion
are you using a recirculation valve or an restriction orifice?
RE: accelerated flow corrosion
rmw
RE: accelerated flow corrosion
RE: accelerated flow corrosion
Cavitation....wouldn't you expect this to occur in this type of system..!!!
If you rename your pump "boiler feed pump" and GOOGLE recirc and "boiler feed pump" you can learn a lot.....
You could just buy one of these:
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or these:
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or these:
http://www.ccivalve.com/pdf/205.pdf
or these:
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or these:
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Where are you located and where is the plant ???
-MJC
RE: accelerated flow corrosion
RE: accelerated flow corrosion
The amount of piping downstream of the valve should be minimized. Locate the valve as close to the condenser as possible.
To increase wear resistance, change the material of the downstream piping to P22. I also suggest Schedule 80 for additional wall thickness.
To reduce velocity, make the downstream piping one or two sizes larger than the 4-inch piping upstream of the valve, i.e., downstream piping should be 6-inch or 8-inch. This means that the connection at the condenser needs to be increased to the same size as the downstream piping. A long diffuser rather than a standard pipe reducer will avoid abrupt changes in velocity. Mount the diffuser directly at the discharge from the valve.
Please note that adding another pressure-reducing device downstream of the control valve may restrict the valve's capacity. I would not recommend installing such a device unless you have analyzed the entire recirc line.
Best of luck,
RE: accelerated flow corrosion
we have not had to replace a valve yet but it is not far away.
RE: accelerated flow corrosion
You say that the valve body is deteriorating. If the body is carbon steel, you will need to change the material of the valve body to an alloy steel (P22) like the downstream piping.
You need a "severe service" valve with a torturous flow path or with multi-stage pressure reduction like the ones shown in the links from MJCronin above. Another alternative is a "severe service" valve and separate pressure-reducing device, like those from CU Services (links also from MJCronin above), located downstream of the valve.
I suggest working with a manufacturer (Fisher, CCI, DeZurik, Copes-Vulcan, etc.) to define a replacement for the existing control valve with or without a separate pressure-reducing device downstream.
Good luck!
RE: accelerated flow corrosion
greatly appreciated
RE: accelerated flow corrosion
Where are you located and where is the plant ???
-MJC
RE: accelerated flow corrosion
THANKS FOR THE INFORMATION YOU SUGGESTED
RE: accelerated flow corrosion
Consider fitting a Gem type steam trap, no moving parts and high efficiency with 10 year warranty
Offshore Engineering&Design
RE: accelerated flow corrosion
rmw
PS: mech-are you having a little trouble with that caps key?
PPS: and mech, remember one more thing. A young engineer at a combined cycle not far from you over in Arkansas once reminded me that I had to keep in mind that those plants (your generation of combined cycle plant) were the best plant low bid could buy. Plan to spend some money implementing the type fixes recommended above (better metallurgy control valves and piping) in your plant to bring it up to the standards to which it should have been built in the first place. I never did visit your plant, but I did get to Southhaven and Sterlington, so I am familiar with what you have to start with. Sad in some cases.
RE: accelerated flow corrosion
we have decided to try something very similiar to what you suggested.we are going to replace the 4''- 2''reducers and 2''valve to 4inch .put 1 4''- 2'' reducer close to the condenser as possible and run 2'' pipe inside the condenser with a baffle plate welded to the condenser wall or floor.hopefully this will help put an end to welding in new reducers every 6-8 months.
not very computer savy sorry about the caps lock deal
just a mech. trying to make it
appreciate the reply,s and information it has been very helpful in making a decision as what to do with this problem.
RE: accelerated flow corrosion
As I noted above, increase the size of the pipe downstream of the control valve to 6-inch or 8-inch, and use a diffuser between the control valve and the downstream piping. This also means increasing the size of the connection on the condenser to 6-inch or 8-inch.
Installing a 4-inch by 2-inch reducer downstream of the control valve increases the velocity in the pipe and may restrict the control valve's capacity. Also, there should not be a run of piping inside the condenser. The baffle should be located at the inside of the nozzle on the wall of the condenser. See HEI Standards for Steam Surface Condensers for guidelines on connections and baffle specing (escape area).