feedwater pump failure modes ?
feedwater pump failure modes ?
(OP)
just getting started on a feedwater pump failure problem which "has been gong on for years" according to the onsite team, the problem description starts out like this: we are regularly replacing pumps due to "pinholes" in the housings and recirculation piping, we switched to a high purity (demineralization system a few years ago and have had problems since.
Question: does anyone have a recommendation on where to go to research water chemistry and it's impact on high pressure feedwater pumping systems?
my initial thoughts are that this is a flow accelerated corrosion situation but i am short on technical data to support the theory or offer alternative possibilities.
Thnaks in advance for any and all ideas and helpful comments.
Best Regards
co-gener
Question: does anyone have a recommendation on where to go to research water chemistry and it's impact on high pressure feedwater pumping systems?
my initial thoughts are that this is a flow accelerated corrosion situation but i am short on technical data to support the theory or offer alternative possibilities.
Thnaks in advance for any and all ideas and helpful comments.
Best Regards
co-gener





RE: feedwater pump failure modes ?
Nominal temperature & discharge pressure?
RE: feedwater pump failure modes ?
Johnny Pellin
RE: feedwater pump failure modes ?
Johnny Pellin
RE: feedwater pump failure modes ?
the water is deaerated prior to enerting feedwater pumps, we have residual sulfite in boilers, so we should be good there, will check curves and min recirc rates to see if we have ultra high velocities @ recirc lines.
one other note, the recirc lines feed back into pump suctions and not back to the tank, not sure this is a problem but it is not what we usually see witht these set ups.
thnaks again for the feedback.
RE: feedwater pump failure modes ?
I would always recommend 11-14% chrome materials typically 13%chrome/4%nickel for impellers on larger high pressure feed pumps certainly above 100hp.Wearing parts i.e. impeller wear rings in hardened 17/4ph material running against 420 stainless steel casing rings with a good differential hardness between the 2 components to prevent galling.
I was told once by a chemist that demin. water has a memory and always looks for ways of extracting certain minerals out of the materials in close contact to it. Hence the pitting experienced.
Andy
RE: feedwater pump failure modes ?
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: feedwater pump failure modes ?
Johnny Pellin has given you some superb advice.
Seemingly small variations in water chemistry can produce very large effects on corrosion in pumps. You may want to check on the variations in your water chemistry. It may be much less stable than you think.
I would want to pay particular attention to water chemistry variations in the flow from the demineralizer trains. There may be something in the configuration of your piping and tanks that may allow for "hide-out" problems that could provide slugs of "non-compliant" water chemistry.
Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.
RE: feedwater pump failure modes ?
PH levels in the feedwater that range from 10 to 5, dead legs where chemicals "reside" until pumps are cycled into service, high turbulence in pumping and recirc lines, and probably a fair measure of flow accelerated corrosion. perhaps some chemical control issues as well. it seems we have the deaerators working well though.
can i forward a few pictures in an attempt to identify other possible causes?
RE: feedwater pump failure modes ?
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: feedwater pump failure modes ?
RE: feedwater pump failure modes ?
RE: feedwater pump failure modes ?
RE: feedwater pump failure modes ?
RE: feedwater pump failure modes ?
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: feedwater pump failure modes ?
Are the last two files supposed to be e-mails or pictures?
Patricia Lougheed
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