Steam tracing effectiveness on 40" acid gas line

[thermmech]

Greetings!
A 40" LP acid gas line (normally no flow) with 130 degC temperature is LP steam traced. Steam 4.1 barg (140 degC) is used to keep the pipe wall at 130 degC. Internal corrosion occurred die to water condensation.

Two questions:
1. During no flow condition, should the steam tracing (if adequately sized) be able to keep the pipe at 130 degC? The pipe leads to the incinerator burner.
2. For the above conditions and small dT between steam and acid gas (10 degC) seems like a large number of 1" steam tracers is required. Any thoughts on whether steam tracing is an adequate choice?

 

[mk3223]

1. With no flow, the heat is to conduct inside the pipe through the air slowly along the pipe to reach the temperature as specified.
2. To use multiple steam tracers along the 40” pipe or wrap it around to have the constant surface temperature around.
3. Consider a temperature monitor with the steam tracing to prevent the pipe corrosion due to water condensation.

 

[1503-44]

Probably going to need much less heating capacity at no flow.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[hacksaw]

You'll need to check where your steam traps are located along your line, to insure proper heating the entire length of the line, as well as temperature monitoring.

 

[LittleInch]

"Internal corrosion occurred die to water condensation."

So clearly the trace heating isn't fully effective if you're trying to keep this line > boiling point although how low is Low Pressure?

Anything more than 2.5 barg and you're above 130C in BP

Insulation?

Some sort of electric trace heating might be a better option but first work out what temperature you need.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

This recent post from @pierrick, which references the spirax sarco tables, tells me 4.1barg steam is too low for 130-135degC maintain temp - see the second table which lists the heat output for steel or copper tube tracing

https://www.eng-tips.com/viewthread.cfm?qid=522259

If you cannot get higher pressure steam, electric tracing may be the only practical solution. Temp limit for self regulating cables is 120degC, so it may have to be HPT cable style if you go with Thermon.

 

[hacksaw]

Ref OP
you have described a gas line that is improperly designed. There is no quick fix.

 

[Dhurjati Sen]

I have come across such acid lines which are jacketed with LP steam passing through the outer pipe. I always thought this as a standard design practice.

DHURJATI SEN
Kolkata, India