Piping Material for Flashing Service

[curtis2004]

Hi Everyone,

I'm working on solving of the following issue:
Condensate return line has Condnesate Level Pot with 60 psig pressure. This pot has Level Transmitter which controls Level Control Valve, downstream from Condnesate Level Pot. Piping between Condnesate Level Pot and Level Control Valve is gravity feed. After Level Control Valve it goes to common header where two other condensate lines are tied-in in similar way. This condnesate header goes up 15 ft and connected to Condnesate Collecting Tank which has atmospheric pressure.
I have flashing going on at valve and after. There is severe erosion going on in all components of piping after this Level Control Valves.
I contacted Fisher and they recommended ES valve instead of EZ which was installed.
I calculated line sizes and they are undersized. I'm planning to split lines which will double line capacity and reduce velocities by half.
I also would like to recommend 2 1/4 Cr - 1 Mo CS piping material for all piping after those valves.
Can someone recommend certain ASTM material grade for this type of service? I need both for piping, and fittings (forgings).

Thank you,
Kurt

 

[StevenHPerry]

The ASME B31 codes include a nominal chemical composition of the materials in Appendix A. Otherwise, there are a number of pipe material cross references available on the web, pipe suppliers, etc.

ASTM A335 P22 - Pipe
ASTM A182 F22 - Forged
ASTM A234 WP22 - Wrought

Beware the class designations for F22 and WP22.

- Steve Perry
This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[curtis2004]

Hi Steve,
Thank you for your response. I also wanted to hear personal experinces solving these type of issues. Did you use these or other material in this operating conditions yourself? Can you quantify effect of these materials (let's say, it lasted 10 years instead of 5 when, for instance, SA53-B was used)? Are they readily available?
Thank you,
Kurt

 

[TD2K]

The steam condensate collection systems I've seen have just been carbon steel. These are pretty much all flashing services because of the very nature of the way they are designed. Armstrong, Spirac Sarco, TLV all have information on recommended practices for sizing collection systems. They essentially come down to sizing the lines based on the flash steam only (on a volumetric basis, the flash steam by far is the largest flow). I've seen too many systems where a plant has run a 1" line and tied in a pile of steam traps. Backpressure goes way up and the traps may not work, have reduced capacity, can't get into the return system if you trap multiple steam levels to a common system etc.

 

[StevenHPerry]

I'm on the EPC side so I don't get to see much of the aftermath. One coal plant I visited had a small mountain of worn-through small bore pipe that they have removed from service over the last several decades. The story is it came from small bore condensate and blowdown lines made of CS, almost all of it just downstream of an elbow.

Do some research on flow accelerated corrosion, erosion-corrosion, and impingement. Replacing CS with chrome >= 1.25% has been the common recommendation I found for addressing existing issues. That means A335 P11. That should be cheaper than P22, depending on availability and quantity.

For one:

http://www.power-eng.com/articles/p...ted-corrosion-a-critical-issue-revisited.html

I am pretty sure EPRI has info on this too for its members.

- Steve Perry
This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.