# Heat Trace



## Wiresmith (Feb 9, 2013)

any heat trace aficionados out there?

1)why do you offset the heat trace slightly off center-line on outside radius', to reduce chance of damage? or so hard/heavy over-sized insulation doesn't put excess pressure on trace?

2)is wrapping the outside of flange better? i would think you would be getting the heat to the coldest part and keeping everything closer to the same temperature that way, everything would be more of an even temperature and with self-reg your heater would produce more heat when/where it is actually needed.

thanks


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## 99cents (Aug 20, 2012)

It's not really an offset, you just want extra around the flange in kind of an exaggerated "S", keeping in mind that you don't want to overlap self reg.

Edit: I see what you're saying now that I look at it closer. I am not sure why they are suggesting a different orientation around the bend other than there is a little more surface area to cover.


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## just the cowboy (Sep 4, 2013)

I think
#1 is for motion so it has room to move if needed. 


#2 is dual purpose extra heat for flange base, and extra cable for opening pipe at later date.


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## joebanana (Dec 21, 2010)

1) more surface area?
2) more slack for changing the gasket, installing a blank?


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## Wiresmith (Feb 9, 2013)

1) it is for more surface, what i mean is they say in technical note 2 "do not install heater on on very back or throat of pipe"

2)yes it is for service and additional trace, both ways require the same amount of allowance(extra trace at flange) but one shows the trace on the outside of the flange and the other shows the extra trace beside the flange, isn't outside much, much, better?


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## glen1971 (Oct 10, 2012)

From what I know...
1) Heat trace is installed at the 4:00 or 8:00 position on a pipe for a few reasons:
a) Liquids lay in the bottom half of any pipe, so this will prevent it from freezing.
b) The heat will radiate out and has a tendency to rise, so if it is on the lower half of the pipe it will radiate up.
c) Protect it from damage from things falling on or stepping on it.
d) It is usually on the outside of the radius as it is the longer side, and will heat the inner diameter easier than a shorter length trying to heat a larger area.

Their note about not on the very back of the pipe, may have to do with thermal expansion of the piping, in some cases. Steel will expand at a different rate than the copper in the heat trace..

2) Flanges have additional heat trace because:
a) They are a giant heat sink and will take more heat to ensure that any liquids that rest in any low spots will not freeze. This is similar to valves, pipe shoes, etc.
b) Makes it easier to replace a gasket or install a spade. On valves to remove the valve.

When I've done flanges, I tape close to the flange, then pull a loop so that it can almost wrap the flange. Then tape the trace to the pipe on the other side of the flange. Tape the flange and move on.

Crossing self regulating heat trace is not as critical as MI trace. It will cause the trace to prematurely (falsely) reduce the heater output and could cause process issues..

If heat trace isn't insulated or isn't touching the pipe, it won't be as effective if it was installed properly... I know it seems basic, but....


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## glen1971 (Oct 10, 2012)

Remember that you may have to double up the runs of heat trace depending on the pipe diameter.. That would change how flanges, valves, etc are done..


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## Wiresmith (Feb 9, 2013)

glen1971 said:


> From what I know....


that expansion of the pipe makes sense for putting it on 4 or 8 o clock too and not 6 o clock, if you have vertical bends in a vertical run of pipe the pipe could expand and put tension on the trace. i never thought of that, thank you all.

i think the expansion damage is more of the reason for calling 4 and 8 than just saying bottom of pipe or other way of saying it, the expansion of the pipe is possibly more likely to damage it/strain it then something falling on it.

glen,
which pictorial most looks like how you tape the flange, the black and white(top) one or the orange(bottom) one, i'm thinking the orange way would be better because it would keep all of the pipe and its parts all at a closer temperature to each-other. the thing that is coming to mind is expansion and contraction at a gasktet, you would want the piping members temperature(because of size change (expansion and contraction)) to stay rather stable, i think it might make the joint seal more reliable over the long run. have any thoughts on this? i know i'm just splitting atoms here but that's just something i do, if there's a best way to do something why not do it the best way.


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## glen1971 (Oct 10, 2012)

Wiresmith said:


> that expansion of the pipe makes sense for putting it on 4 or 8 o clock too and not 6 o clock, if you have vertical bends in a vertical run of pipe the pipe could expand and put tension on the trace. i never thought of that, thank you all.
> 
> i think the expansion damage is more of the reason for calling 4 and 8 than just saying bottom of pipe or other way of saying it, the expansion of the pipe is possibly more likely to damage it/strain it then something falling on it.
> 
> ...


 

The amount the pipe would expand and contract would depend on lots of factors, such as length, operating temperature, temperature fluctuations, and if there bends in it to allow expansion or not. And depending on how long your heat trace is could influence strain issues..


Personally, neither of them. The orange one has the trace on the top of the pipe, and the black it doesn't really look like it's hitting the thickest part of the metal.. If I'm tracing a line and I'm on the same side as the trace, I'd tape just before the weld on the flange. Then form the loop so it passes on the underside of the flange and comes back around to just past the top of the flange, so it is nearer to me. Then I'd tape a couple of spots past the flange, to continue the tracing run and hold it in place. Then in roughly the center of the loop, put a couple of wraps of tape, and use that to help pull the trace around the flange and hold it in place and tape it over the gap by the studs. The rest of the trace I'd tape to the edges of the flange, as the orange picture shows. Keep in mind, it is real easy to draw something that looks nice and pretty, but lots of times the heat trace won't bend anywhere near as neatly for you, so you make it touch the flange or fitting the best you can.


As for expansion and contraction at the joint, I doubt that would be an issue. The studs will be torqued and it shouldn't move a bit.. The excess on the flange is more to add the heat that the excess metal in the flange absorbs.


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## Byron J Kessler (Oct 20, 2018)

We offset because of hydrates. This becomes important in high pressure most of the time explosive gas transport. On the back side of the elbow is where the heavy wet gas pushes to as it travels the bend of the pipe. If this is a cold spot it can form ice on the inside of the pipe. Once ice is formed it can let go and be propelled down the pipe like a bullet. Not a good situation. 
Dry gas pipes are not traced. 

The second topic about flanges and valves. Follow the client spec or bible. It changes for all of them. Different liquids or gases different wattage of trace number of passes all feed into what is done and requested. But yes valves and flanges are heat sinks or the reverse of that cold sinks. They need more trace on them.


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## glen1971 (Oct 10, 2012)

Byron J Kessler said:


> We offset because of hydrates.


Never heard of that being a reason before, but could be.. 


From Thermon's guide:


Elbows: Locate the cable on the outside of an elbow to provide sufficient heat to compensate for the added piping material.


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## Byron J Kessler (Oct 20, 2018)

glen1971 said:


> Byron J Kessler said:
> 
> 
> > We offset because of hydrates.
> ...


When reviewing the thermos quote and break it down the elbow when compared to a piece of straight pipe has more metal per length. Which in turn yes needs more heat. Without the heat could cause freezing of the fluid inside the pipe. In the case of hydrates, water causing ice. The Thermon quote is totally correct and general. I agree the description I gave is in particular for oilfield construction and describes the results that can occur. 90% of my experience is in oilfield construction. Hydrates moving inside a pipe have been known to shake and move pipes of 36” diameter laterally up to 12”. A very dangerous situation.


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## Lone Crapshooter (Nov 8, 2008)

The true reason for insulating heat traced pipe is to cover up bad heat trace jobs.

I have put that stuff on by the mile not good work. We also had to cover our tracing with aluminum foil tape.

LC


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