steam tracing

[gelsi]

Hi,
I have a line of incondensables+condensables at 40°C that is bare, without insulation and with pockets. The fluid reduces its temperature because it exchanges heat with the ambient (convenction, wind action, radiation, etc) and condenses, so it needs to design a system to avoid liquid accumulation and surge phenomenons. What can be done?
1- Insulating+tracing of the whole line (very expensive)
2- Insulating of the whole line and Insulating+tracing of liquid pockets
3- leave the line bare and Insulating+tracing of liquid pockets (cheapest)
4- Which other?
I think the 3 is interesting but don’t know if someone has never done (who knows?), so I would try to design the 2 + adding a pot in each pocket to solve some failure event
Anyone can give me other solutions or suggestions about design methods and procedures?
Thanks for whichever help

 

[hendersdc]

Another option would be to run a resistive heater along the line to counter the heat loss.

 

[lilliput1]

If the steam system is not shut down and if the piping is sloped to avoid liquid accumulation all you need to do is insulate the piping. No need to heat trace.
At start of condensate line, provide check valve and elevate piping so remainder can slope down without pockets to accumulate liquid. Either locate the riser in heated space or insulate and electric heat trace.

 

[EdStainless]

Can you re-plumb to eliminate the pockets?
Option 3 is a waste, why heat some areas if you are just going to let it cool off again.
Option 2 is a minimum.
I am with Hendersdc on this, I would use electrical tracing so that you only heated when and where it was cold.
Be careful when you insulate. Selecting the correct insulation and surface prep is critical, Corrosion under insulation is a serious issue.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[lilliput1]

I forgot to add you have to make sure the pressure in the line is adequate to meet the trap and check valve operating pressure and to lift the condensate up the riser.

 

[gelsi]

Tx,
so there are two options:
2- insulating of the whole line and Insulating+tracing of liquid pockets;
5- use electrical tracing so that you only heated when and where it was cold.
Suggestions about design methods and procedures?

lilliput1, I can't elevate the line (it goes from piperack to ground and from ground to rack many times). But one question: when you said "At start of condensate line, provide check valve and elevate piping..." what is the function of check valve upstream the first riser?

What do you main about "adding a pot in each pocket", say 4"x600mm (the line is 2")?

 

[lilliput1]

Maybe the solution would be to add a condensate pump, discharge all low condensate lines to it them pump it up to the elevation required so downstream piping can slope down to the main condensate receiver. The check valve at the discharge of the trap and at the bottom of the riser would prevent condensate from backing down the riser.

 

[gelsi]

I think a check valve upstream a riser-pipe is not a good idea: when the line is "no flow", the condense is accumulated downstream the c. valve and when the flowrate begin and the c. valve opens, a slug can start.
Maybe i didn't understood your suggestion: see att.

 

[lilliput1]

You will get the slug with or without the check valve but the check valve minimized the force on the trap. See Sarco Hook-up Designs for Steam and Fluid Systems Figure Z-15 Section II.

 

[georgeverghese]

My opinion - if there is no way to drain out all the condensate collected at these low points on a continous basis, think the only way is option 1 - it simply wont be possible to boil up all the liquid collected at the low points, especially when the traced low point lengths are short relative to the length of the untraced high point sections - re startup operations will also be a problem with surging and liquid hammer.

 

[25362]

If possible, bring down the dew point of the mix, at some point upstream.