HPS inlet temperature of steam turbine 1

[Jack Nicholson]

Dear all.
Hello.
I have a question. would you please help me?
Normal/min/max steam temperature to the steam turbine is 410/400/430 C (pressure: 40 barg). But right now inlet steam temperature is 360C!!! due to operating limitations.
What is the mechanical and operating effects of this condition on steam turbine?

 

[georgeverghese]

As long as discharge remains in the superheat region for all operating cases, doubt there will be any mechanical or blade erosion issues. Obviously, you'll need more steam flow to deliver the required power, so the turbine power delivery may be limited by the high speed set on the speed controller.

 

[Jack Nicholson]

No, there is about 4% increase in liquid fraction, outside of the rurbine.

 

[EdStainless]

Check your HP outlet conditions.
If there is any liquid then you are in trouble.
An HP is not designed to handle the droplets and they can (will) cause serious blade damage.


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P.E. Metallurgy, consulting work welcomed

 

[RVAmeche]

I'd vote for turning off the turbine if your operational limitations mean inappropriate steam is getting to the turbine. Better to have a bit higher elec bill versus repairing an expensive turbine, especially these days.

 

[MJCronin]

What does it say in your Operating Manual about steam pressure/temperature limitations ?

Why don't you have the OM anymore ??

Can you tell us details of the specific Steam turbine make, model and vintage ? ... Perhaps there is someone out there with the same model steam turbine ?

Can you take a picture of the nameplate ?

Why won't your boss let you take pictures of any equipment ?... He expects you to answer questions, doesn't he ?

MJCronin
Sr. Process Engineer

 

[georgeverghese]

So the plant manager thinks there is no choice but to allow short term operation under these conditions ?
What is the cause of this low temp in superheated HP steam supply ?

Abstract from Perry on this topic:

"In a turbine that is running, erosion-corrosion is pretty much confined to units that are operating on saturated steam with inadequate boiler-water treatment. This type of erosion takes place behind the nozzle ring and around the diaphragms where they fit in the casing."

So maybe your plant manager is confident BFW is of good quality; ie TDS and dissolved O2 and silica are well within spec, so he has taken on this short term risk to avoid production loss?

 

[shvet]

I have a question. would you please help me?
Normal/min/max steam temperature to the steam turbine is 410/400/430 C (pressure: 40 barg). But right now inlet steam temperature is 360C!!! due to operating limitations.
What is the mechanical and operating effects of this condition on steam turbine?

No, there is about 4% increase in liquid fraction, outside of the rurbine.

It looks like you know inlet/outlet conditions before/after limitations appeared so you can calculate a deterioration in the efficiency.

https://www4.eere.energy.gov/manufacturing/tech_deployment/amo_steam_tool/equipTurbine

 

[georgeverghese]

Also from Perry on the loss of power, thrust bearing failure and blade erosion, all related to saturated steam exit conditions coincident with offspec BFW quality:
"Loss of power is another item generally tied to water treatment. With dissolved salts in the steam these salts stay in solution while the steam is superheated. After the steam has expanded through several stages and become saturated, the salts condense out with the moisture. Silica and other salt deposits build up on the blading and the nozzles. The stage pressures increase, and the load drops. The thrust load increases, and the thrust bearing may fail. Depending upon the nature of the salts, it is possible to have corrosion associated with the deposits or corrosion only in the region where the steam changes from superheated to steam with moisture "

 

[TiCl4]

Georgeverghese,

Far be it from me to question Perry, but how do the salts stay in "solution" if the steam is superheated (i.e. no liquid fraction remaining)? There is no solution in the superheated steam into which they can dissolve, yes? So they would either scale out on the heat transfer surfaces as the steam is being superheated or are carried along as solid particles/grit in the superheated steam as the entrained droplets evaporate, correct? I don't quite understand the beginning of the quoted statement, which seems to indicate some sort of "solution" is carried along with the superheated steam.

 

[EdStainless]

TiCl4, I have helped inspect steam turbines which were being run correctly.
I have seen salts on the roots of HP turbine blades, and I have seen Cu on HP blades.
Both of these were from the condensers and made it through the entire system.
I can see the salts being volatilized, but Cu. And yet there it was. Enough to cost about 6% of the output power.

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P.E. Metallurgy, consulting work welcomed

 

[georgeverghese]

@TiCl4, Think the author is implying there are fine salt solids (and silica salts too) entrained along with the superheated vapor. This is probably quite likely since the "saturated vapor" that goes into the upstream superheat tube bank in the boiler inevitably carries some liquid mist.

 

[pierreick]

Hi,
Please consider reading the info in the link attached :

https://www.watertechnologies.com/handbook/chapter-18-steam-turbine-deposition-erosion-and-corrosion

Good Luck
Pierre

 

[georgeverghese]

As pressure increases, interfacial tension for liquid water drops off, making it more difficult for liquid drops to agglomerate in wiremesh demister pads, hence liquid carryover into saturated vapor rises with increasing pressure.