steam condensate conductivity - higher in new piping versus old?

[BronYrAur]

Would new piping cause the conductivity level of steam condensate to be much higher than normal? I have a new section of piping that was just installed. It was flushed with water and then steam was introduced. There is a conductivity probe on one of the drip trap condensate lines that is reading approximately 100 times higher than other probes that already existed in the old system. My first though would be a calibration issue with the probe, but I was wondering if the fact that the piping is brand new could be to blame? Does new piping liberate material for a while as steam condensate makes contact with it? That would possible explain my situation.

 

[EmmanuelTop]

You could easily check accuracy of the probes by switching between any two in the new and old piping systems, or performing a conductivity lab test on the sample from the new piping system.

The water used for flushing might also had been contaminated with corrosion products, rust, etc.

Possible reasons for the new piping elements to be contaminated are:
- Mill scale;
- General (atmospheric) corrosion, if pipes have been sitting for a long time before installation, and/or rust from corrosion caused by hydrotest water;
- Microbiological induced corrosion.

The good part is that you are seeing this only in the new piping section, so troubleshooting can be narrowed down.




Dejan IVANOVIC
Process Engineer, MSChE

 

[BronYrAur]

I did forget to say one important thing in my original post. After noticing the high readings we flushed this new section of piping again with plain water and conductivity went down to normal levels during the flush. But once the steam condensate returned, conductivity skyrocketed.

I have never monitored conductivity at the very initial startup of a new piping system which is why I asked my original question.

 

[georgeverghese]

Maybe the probe is reading right and you have a leak in the upstream HX - could that be why you've had to replace this piping segment - higher corrosion rates here due to process fluid leak into steam condensate?

 

[EdStainless]

It is possible that it will take a while for a stable oxide scale to build under steam conditions.
But it should happen rather quickly.
It sounds like you may have another issue.
Is your conductivity de-gassed?

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P.E. Metallurgy, Plymouth Tube

 

[bimr]

The ions responsible for conductivity come from electrolytes dissolved in the fluid.

http://www.emerson.com/resource/blo...eory-and-application-of-conductivity-data.pdf

The piping corrosion byproducts should not have a large affect on the conductivity.

 

[springrise]

Please mention what values do you measure and what units - both in normal and new piping.
As mentioned by georgeverghese, there might be a process leak.
Also, boiler water carryover can cause increased condensate conductivity which can under certain pipe configuration display itself selectively on one pipe branch only.
If you have conductivity measurement confirmed by another probe, chemical analysis (looking for distinct process and boiler water chemicals/minerals) can bring you on track.

 

[BronYrAur]

The units of measure are micro-S/cm. The readings are down now to roughly 5, which match all of the other conductivity sensors in the piping system. They had been around 500 when the system first went online. So, unless there was some unknown influence, I think the fact that the piping was brand new caused the high conductivity. As EdStainless suggested, I think it just took a little time for scale to build up and "seal" the internal pipe surface.

thanks for your input.

 

[IRstuff]

Pure water is quite capable of leaching all sorts of stuff from new pipes and equipment. There was a story, back when I was in high school, where a scientist announced the discovery of "polymerized" water that exhibited peculiar behaviors. It was later announced that the water had actually dissolved some of the glassware he use for experimentation.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529

 

[bimr]

5 micro-S/cm is demineralized water quality. 500 micro-S/cm is equivalent to 320 mg/L TDS or raw water.

To get a reading of 320 mg/L TDS, there must of been untreated water from the hydrostatic testing trapped in the piping/