5 replies to this topic

[fallah]

Dears,

As per rectangular content of the attached regarding design temperature of the traced line (here steam tracing) in ASME B.31.3,please submit your viewpoint on below situation:

If temperature of steam in steam tracing system of an insulated line is 270 C,and maximum temperature of the fluid flowing inside that pipe raised up to ,let say, 100 C,then what would be the design temperature of the line?

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[Qalander (Chem)]

Dears,

As per rectangular content of the attached regarding design temperature of the traced line (here steam tracing) in ASME B.31.3,please submit your viewpoint on below situation:

If temperature of steam in steam tracing system of an insulated line is 270 C,and maximum temperature of the fluid flowing inside that pipe raised up to ,let say, 100 C,then what would be the design temperature of the line?

Dear Fallah
In My humble opinion

if the pipeline under discussion is throughly insulated & traced with 270 degree Celsius steam;

I will consider the whatever highest temperature of tracing steam may be encountered plus any radiant heat input from solar radiation

to benchmark for the design temperature of pipeline you asked for.

[achilles09]

Design temperature of steam traced pipe line should be its saturation temperature at maximum pressure.

If am wrong pl correct ??

[smalawi]

Hi,

for design temp above 242 you will pay for every temp incerase, since pipes are desinged in classes, I would check what is the pipe sch & flange class you should consider for your normal conditions. if the design pipe/flange class has limits exceeding your normal then would suggest you be conservative and design with margin eg max operating temp (from your max sat pressure)+ ~25C or whatever your local code calls for.

you might be able to put procedures in place to handle a maximum line temperaure conditions if your process line fluid velocity drops signifncatly to avoid a design temperaure that is significantly higher than your current pipe class

just some thoughts,

cheers,

sm

Edited by smalawi, 26 December 2009 - 12:03 PM.

[kkala]

""If temperature of steam in steam tracing system of an insulated line is 270 C,and maximum temperature of the fluid flowing inside that pipe raised up to ,let say, 100 C,then what would be the design temperature of the line?""

In the company I work, they would consider the max operating temperature of steam as design temperature of the line, that is a temperature higher or equal 270 C in your example. This according to their practice.

Note.
Electric tracing was once examined, since there was a big difference between fluid and steam temperature. It seems that electric tracing can control excessive temperatures (they can use even thermostats), although we have not found specific "rules" for design temperature. However the relevant Project was not implemented.

[kkala]

Design temperature of steam traced pipe line should be its saturation temperature at maximum pressure.
If am wrong pl correct?
---------------------

<http://www.cheresour..._tracing.shtml> supports tracing uses saturated steam, then your statement is OK.
Nevertheless another practice (of my work) specifies maximum operating temperature of steam as the design temperature of the traced line, which can be more conservative.

There are cases when available steam introduced to tracing line is superheated *. Even so, steam gets saturated after a while. For heat transfer calculations, steam temperature is accepted same as saturation temperature (normally not taking superheat into account).
So there must be not much difference between the two statements, especially for common cases of steam tracing.

*even if saturated steam is required, steam in transfer lines has some superheat to avoid condensation.