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Steam Tracing
- Thread starter amanites
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amanites
Are you just looking for general info on steam tracing or specific areas in a Biodiesel plant that need tracing.
If it is the first reason then the above post from gerhardl is a great place to start however if it is the second reason then a bit more information on your feedstock and ambient temperatures would be required.
Are you just looking for general info on steam tracing or specific areas in a Biodiesel plant that need tracing.
If it is the first reason then the above post from gerhardl is a great place to start however if it is the second reason then a bit more information on your feedstock and ambient temperatures would be required.
rocketscientist
Chemical
Be aware of heat transfer. Copper is best choice for heat transfer but lousy for reliability. Choose copper when:
* A tight space exists (where SS won't pass enough heat);
* High heat flux is required (BTU/hr/sq ft);
* Space can be easily taken apart when tubing corrodes; and
* Insulation can be cheaply replaced because it will not be damaged by leaking copper tubing.
Remember, if you use SS, use 316, and increase your tubing turns around the pipe by about 6: 60 BTU/hr-sf for copper and 9 BTU/hr-sf for 316SS at 212 F. Also, don't use steam traps with anything but SS guts. I prefer SS body and internals.
Personally, electric tracing is preferred unless you have the maintenance staff to support steam traps. Although the price of electricity and natural gas varies from place to place, at about 5$/1000 SCF and $8/100 kWh, the unit costs are about the same. However, if you factor in all the headaches, you will pay big bucks to maintain steam systems. The only drawbacks to electric are:
* Changes to electrical services (high I unless high E is available;
* Electric does a poor job of heating and is mainly for heat-maintenance;
If you need to heat something up initially, consider bumping it up with a steam heater and maintaining the temperature with electric tracing. Use mineral heat tracing for high heat flux; for plastic or fiberglass only heat-maintenance tape is available.
I hope this helps,
Dirk Willard
* A tight space exists (where SS won't pass enough heat);
* High heat flux is required (BTU/hr/sq ft);
* Space can be easily taken apart when tubing corrodes; and
* Insulation can be cheaply replaced because it will not be damaged by leaking copper tubing.
Remember, if you use SS, use 316, and increase your tubing turns around the pipe by about 6: 60 BTU/hr-sf for copper and 9 BTU/hr-sf for 316SS at 212 F. Also, don't use steam traps with anything but SS guts. I prefer SS body and internals.
Personally, electric tracing is preferred unless you have the maintenance staff to support steam traps. Although the price of electricity and natural gas varies from place to place, at about 5$/1000 SCF and $8/100 kWh, the unit costs are about the same. However, if you factor in all the headaches, you will pay big bucks to maintain steam systems. The only drawbacks to electric are:
* Changes to electrical services (high I unless high E is available;
* Electric does a poor job of heating and is mainly for heat-maintenance;
If you need to heat something up initially, consider bumping it up with a steam heater and maintaining the temperature with electric tracing. Use mineral heat tracing for high heat flux; for plastic or fiberglass only heat-maintenance tape is available.
I hope this helps,
Dirk Willard
rocketscientist - Steam tracing cannot be installed on horizontal lines by "coiling around the pipe". Only on vertical lines may the tracing be "wound around". Regarding the "leaking copper tubing" this problem stems most likely from water hammer damage (improper installation) or corrosion (improper water treatment.) Stainless steel is the material of choice, sometimes - under the right circumstances - copper can show up in the condensate system, and from there, back to the boiler. This is very bad news. The practical difference in heat transfer between copper and stainless steel is negligible for this application.
Steam traps should have no trouble operating for several years. I would suspect water hammer damage, or in rare cases, I have seen copper plating out on thermodynamic traps as a result of the condensate picking up copper from the tracing tubing. The plant people were busy blaming the trap manufacturer - but the problem wasn't his. It was the tubing material combined with water chemistry issues.
You only pay "big bucks" to maintain steam systems if they're not designed and/or installed properly.
Companies like Spirax Sarco, Armstrong, Nicholson, Hoffman, etc will be happy to provide design and application assistance.
Steam traps should have no trouble operating for several years. I would suspect water hammer damage, or in rare cases, I have seen copper plating out on thermodynamic traps as a result of the condensate picking up copper from the tracing tubing. The plant people were busy blaming the trap manufacturer - but the problem wasn't his. It was the tubing material combined with water chemistry issues.
You only pay "big bucks" to maintain steam systems if they're not designed and/or installed properly.
Companies like Spirax Sarco, Armstrong, Nicholson, Hoffman, etc will be happy to provide design and application assistance.
rocketscientist
Chemical
I am curious about the horizontal versus vertical application. Tell me where you get this information. As for the copper versus stainless steel, I could not disagree more. I have experience directly with this. You won't get sufficient heating if you replace Cu coils with the same number of loops of SS. Sorry, you're wrong. The water hammer issue seems wrong too. SS, though stronger than Cu has less resilience. Cu can endure thermal expansion and hammer than SS.
What you must NOT have, regarding steam lines, is low points that are not drained, or "trapped". With vertical lines, the steam tracing must flow downward. The tubing can be wound around the main line. If you have a horizontal line that requires tracing, you CANNOT wind the steam tracing line around it, or you'll create low points at the bottom every loop. You'll have a tracing system that runs half full of water - with resulting waterhammer - welcome to the world of split tubing and failed steam traps.
The waterhammer issue will be in addition to a steam system that will be running largely full of water. The reduction in available heat to be transferred will be HUGE, as there's no latent heat with a hot water system. I would suggest that the hot water vs steam issue was your problem, not the tubing material. If you've calculated the required surface area based on steam, and are now showing it hot water - you're going to be disappointed.
I should mention I used to work extensively with a manufacturer of stainless steel HXs for several years. In the real world, there's essentially practical difference between metals as far as heat transfer is concerned. The big considerations are 1/ delta-T, and 2/ surface area.
"Hook-Ups" by Spirax Sarco is an excellent reference. For those less familiar with steam, there's a more basic publication - also from Spirax Sarco - called "Steam Utilization".
In over 30 years, I have installed, operated & maintained literally hundreds of steam systems, including ones for tracing (carbon steel, copper, and SS). They were (and continue to be) cost effective to install, operate, and maintain.
The waterhammer issue will be in addition to a steam system that will be running largely full of water. The reduction in available heat to be transferred will be HUGE, as there's no latent heat with a hot water system. I would suggest that the hot water vs steam issue was your problem, not the tubing material. If you've calculated the required surface area based on steam, and are now showing it hot water - you're going to be disappointed.
I should mention I used to work extensively with a manufacturer of stainless steel HXs for several years. In the real world, there's essentially practical difference between metals as far as heat transfer is concerned. The big considerations are 1/ delta-T, and 2/ surface area.
"Hook-Ups" by Spirax Sarco is an excellent reference. For those less familiar with steam, there's a more basic publication - also from Spirax Sarco - called "Steam Utilization".
In over 30 years, I have installed, operated & maintained literally hundreds of steam systems, including ones for tracing (carbon steel, copper, and SS). They were (and continue to be) cost effective to install, operate, and maintain.
rocketscientist
Chemical
Thanks for the reply back on horizontal versus vertical. I dimly remember reading this several years back. Honestly, the last time I worked with steam tracing was in 1993.
In this business reference like those published by Sarco and Armstrong are absolutely necessary. They are also getting harder to get as vendors are not publishing online like they should.
As for the real world, I'm not really worried about the comparison of copper against stainless steel with regard to mechanical strength. Both copper and stainless steel will bust if hammered. But stainless will survive longer when the inevitable happens: the traps fail and the condensate (containing CO2 and therefore acidic) collects in the trace lines. The corrosion will happpen regardless of whether the lines are horizontal or vertical, straight or coiled. Replacing tracing will be required annually if you go with copper tracing, which is why I have it ripped out in every plant I've worked at.
Several years ago, Chemical Engineering ran an article on steam systems versus electric tracing. Electric tracing won. It is easier to control, which eliminates overheating issues. Steam tracing frequently leaks ruining fiberglass insulation. Trap failure is practically a cliche. The article concluded by summarizing the maintenance costs for steam, which quickly outstripped the higher investment cost of electric tracing. Perhaps traps have improved since I worked with them everyday in 1998. But, I avoid steam unless it's for a large system.
In this business reference like those published by Sarco and Armstrong are absolutely necessary. They are also getting harder to get as vendors are not publishing online like they should.
As for the real world, I'm not really worried about the comparison of copper against stainless steel with regard to mechanical strength. Both copper and stainless steel will bust if hammered. But stainless will survive longer when the inevitable happens: the traps fail and the condensate (containing CO2 and therefore acidic) collects in the trace lines. The corrosion will happpen regardless of whether the lines are horizontal or vertical, straight or coiled. Replacing tracing will be required annually if you go with copper tracing, which is why I have it ripped out in every plant I've worked at.
Several years ago, Chemical Engineering ran an article on steam systems versus electric tracing. Electric tracing won. It is easier to control, which eliminates overheating issues. Steam tracing frequently leaks ruining fiberglass insulation. Trap failure is practically a cliche. The article concluded by summarizing the maintenance costs for steam, which quickly outstripped the higher investment cost of electric tracing. Perhaps traps have improved since I worked with them everyday in 1998. But, I avoid steam unless it's for a large system.
Steam is a unique fluid that plays by it's own rules. Ignore them, and prepare to suffer...and suffer. Understand them, and you will have tamed a magic fluid that can do wonders ... usually at a very competitive cost.
I'm not familiar with the article you refer to. Magazines - and I've written a couple of articles for them - are published by - wait for it - publishers. I was amazed at the lack of hoops I had to jump through. It didn't appear that anybody checked anything - they just took what I wrote at face value.
Think a bit before ripping out the next steam tracing system (or any steam system, for that matter) you come across. I've seen cases where a LOT of money was being spent, and the problems could have been fixed with a dime. Not FOR a dime, but WITH a dime. The operating pressure was too high. All that was required was that the pressure control be turned down. It was a slotted screw head. You didn't even need a screwdriver. Just a few seconds with a dime - that could have been put back in your pocket as you walked away. It's absolutely unbelievable what gets torn out and tossed away because people don't understand it.
I'm not familiar with the article you refer to. Magazines - and I've written a couple of articles for them - are published by - wait for it - publishers. I was amazed at the lack of hoops I had to jump through. It didn't appear that anybody checked anything - they just took what I wrote at face value.
Think a bit before ripping out the next steam tracing system (or any steam system, for that matter) you come across. I've seen cases where a LOT of money was being spent, and the problems could have been fixed with a dime. Not FOR a dime, but WITH a dime. The operating pressure was too high. All that was required was that the pressure control be turned down. It was a slotted screw head. You didn't even need a screwdriver. Just a few seconds with a dime - that could have been put back in your pocket as you walked away. It's absolutely unbelievable what gets torn out and tossed away because people don't understand it.
rocketscientist
Chemical
I know exactly what you mean. Some companies have a handle on their steam systems. Others, most, do not.In the worst case I can recall (Ralston Purina)they bypassed the traps to keep the plant dryers running. Over $250,000/year of steam went up the stack while the superintendent told me not to waste time looking at his steam traps. The traps were working fine (He said). Management could care less. The company made $1/box in cereal --- pure profit. Combined, the plant could turn out >600 boxes a minute.
When it comes to high demand, steam beats electic. When it comes to control electric beats steam.
When it comes to high demand, steam beats electic. When it comes to control electric beats steam.
The issue of electric versus steam tracing must address system failure as well. In some geographic regions the system failure analysis dictates electric because of the catastrophic nature of ice damage. Even a large corporation can see these results. RS; you are correct on the cost analysis side: steam will beat electric.
rocketscientist
Chemical
Veman1,
I think you missed my point. It is the cost of maintaining steam systems that generally makes them too costly for most users. Unless your company is really dedicated to traps,with a good plan in place, steam traps quickly become a problem. First, they fail, then condensate builds up, then corrosion begins, pretty soon, flow through the header itself is a problem. My point is that electric is the way to go for simplicity, though it too will require maintenance, typically in 2-3 years. Another area of concern is safety. Refiners sometimes prefer steam, especially in Div 1, Div 2 areas. Besides, steam is usually available, is used for other things, like purging in place of air; electrical service may require significant upgrade of the entire utility for a large implementation of electric heaters or even one large one.
Steam is expensive to maintain. Electric is expensive to install and may not be acceptable everywhere. Steam is more expensive overall, because of the manhours that require dedication to traps. Electric costs are generally higher than steam, especially for large plants (economy of scale).
So, in the end, you decide but remember Crane's rule: "There's no such thing as a free lunch."
I think you missed my point. It is the cost of maintaining steam systems that generally makes them too costly for most users. Unless your company is really dedicated to traps,with a good plan in place, steam traps quickly become a problem. First, they fail, then condensate builds up, then corrosion begins, pretty soon, flow through the header itself is a problem. My point is that electric is the way to go for simplicity, though it too will require maintenance, typically in 2-3 years. Another area of concern is safety. Refiners sometimes prefer steam, especially in Div 1, Div 2 areas. Besides, steam is usually available, is used for other things, like purging in place of air; electrical service may require significant upgrade of the entire utility for a large implementation of electric heaters or even one large one.
Steam is expensive to maintain. Electric is expensive to install and may not be acceptable everywhere. Steam is more expensive overall, because of the manhours that require dedication to traps. Electric costs are generally higher than steam, especially for large plants (economy of scale).
So, in the end, you decide but remember Crane's rule: "There's no such thing as a free lunch."
Rocketscientist - I must disagree on the cost of steam trap maintenance. If the proper traps are selected for the service, and the steam & condensate systems are correctly designed & installed, then traps - and all other components - will last literally years, and often decades. A proper steam system will beat an electric tracing system any way you want to slice it, 9 times out of 10.
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