My senior comments that I should make slope for steam line. I checked previous design in the existing plant and found that no slope. There are only steam trap and low point drain (from drip leg). Is this a good design practice to make slope? In my opinion, it is not standardized to weld the inclined pipe shoes for setting the line at the same elevation. Please comment.
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Slope for steam line 4
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What has primarily been discussed is co-current flow, both steam and condensate flow in the same direction.
What guidelines are used for counter-current steam/condensate flow?
This is a very interesting topic to me. The steam/condensate flow being discussed is two-phase flow (fluid/vapor), mostly vapor, with very little fluid (the intended condition during operation).
The guidelines Mr. Kirsner stated are typical for our designs, and the greater slope recommended by AJN can't hurt if installation costs aren't significantly hurt.
The guidelines seem appropriate to me, provided: the steam quality is high, piping is well insulated, piping is well maintained, system is thoughtfully operated, and if steam velocities are not too high. To the extent these parameters are not controlled or controllable, the design decisions for the line size, slope, and dripleg spacing may need to change. For two-phase flow, as the proportion of fluid increases for a given relatively high velocity, or as the vapor velocity increases for a relatively high proportion of fluid depth, the flow changes from stratified smooth, to stratified wavy, and then slug flow. If that happens the result will probably be water hammer, and in the case of stagnant sub-cooled condensate the result can be condensate-induced water hammer.
What guidelines are used for counter-current steam/condensate flow?
This is a very interesting topic to me. The steam/condensate flow being discussed is two-phase flow (fluid/vapor), mostly vapor, with very little fluid (the intended condition during operation).
The guidelines Mr. Kirsner stated are typical for our designs, and the greater slope recommended by AJN can't hurt if installation costs aren't significantly hurt.
The guidelines seem appropriate to me, provided: the steam quality is high, piping is well insulated, piping is well maintained, system is thoughtfully operated, and if steam velocities are not too high. To the extent these parameters are not controlled or controllable, the design decisions for the line size, slope, and dripleg spacing may need to change. For two-phase flow, as the proportion of fluid increases for a given relatively high velocity, or as the vapor velocity increases for a relatively high proportion of fluid depth, the flow changes from stratified smooth, to stratified wavy, and then slug flow. If that happens the result will probably be water hammer, and in the case of stagnant sub-cooled condensate the result can be condensate-induced water hammer.
Hi Gang,
These are great responses, and I'm inspired to chime in with my experience on steam trap maintenance. Several posters have noted that losing steam to leaks, etc..., only becomes a recognized problem when production capacity starts feeling the effect. I agree!
Many years ago, I made my living by carrying a hand-held infrared temperature sensor around plants and pointing out to the maintenance staff which traps were blowing thru. In my sampling of over 10,000 steam traps of all types, more than 20 percent of them were allowing live steam through to the condensate system, and thus to the air. I visited plants that looked like they had a hundred chimneys spewing steam into the air when seen from afar, and when all traps were repaired or replaced you could actually see the tops of the buildings and distillation columns!
My advice along these lines -- check the traps regularly.
Good luck with your project!
Old Dave
These are great responses, and I'm inspired to chime in with my experience on steam trap maintenance. Several posters have noted that losing steam to leaks, etc..., only becomes a recognized problem when production capacity starts feeling the effect. I agree!
Many years ago, I made my living by carrying a hand-held infrared temperature sensor around plants and pointing out to the maintenance staff which traps were blowing thru. In my sampling of over 10,000 steam traps of all types, more than 20 percent of them were allowing live steam through to the condensate system, and thus to the air. I visited plants that looked like they had a hundred chimneys spewing steam into the air when seen from afar, and when all traps were repaired or replaced you could actually see the tops of the buildings and distillation columns!
My advice along these lines -- check the traps regularly.
Good luck with your project!
Old Dave
rjstephens
Mechanical
This item has been going on for quite a while now, but I would like to add that when designing steam pipework for a BS power station, BS 806 stipulates that a slope of 1/100 with flow & 1/40 against flow at all operational cases is to be maintained as a minimum for condensate removal. In many cases this has not been adhered to and now the systems are bowed and deformed actually causing the situation to get worse, watching a 450 NB pipeline at 560deg c and 200bar smash into walls and steelwork 1 meter away is no fun.
rjstephens -
Your post was most helpful as it answers a question I asked in the Power Generating Facility Engineering forum. I wanted to know what codes, guidelines, or standards are referred to for power plant design. I see that BS 806 has been superceeded by BS EN 13480 - 2002, and is now in 5 sections.
Would it be possible that I could receive a copy of the page that describes the requirements you gave in your post? From either the older or current BSI standard would be helpful. Does the BSI standard also discuss velocity limitations for steam piping?
Your post was most helpful as it answers a question I asked in the Power Generating Facility Engineering forum. I wanted to know what codes, guidelines, or standards are referred to for power plant design. I see that BS 806 has been superceeded by BS EN 13480 - 2002, and is now in 5 sections.
Would it be possible that I could receive a copy of the page that describes the requirements you gave in your post? From either the older or current BSI standard would be helpful. Does the BSI standard also discuss velocity limitations for steam piping?
gxgovind777
Mechanical
As designed in many power plants, the slope depends on what kind of steam piping is that, whether a main steam or cold reheat pipe. Generally providing slope of 1: 100 is the recommended practice to avoid the negative slope which can be created when the pipe goes from cold to hot condition.
rjstephens
Mechanical
Hi Kann,
I have the BS806 copy and can fax you the page if you send me a fax no with all the area codes county codes etc. I will be faxing from JHB in RSA. The code stipulates that the slope is to be maintained in all operating conditions, cold, hot, cold to hot etc. That may mean using a 2-3 in 100 slope. The NWS 1451(ESkom Power Generation) spec that we use is more stringent i.e. 2/100 with flow as a minimum.
I have the BS806 copy and can fax you the page if you send me a fax no with all the area codes county codes etc. I will be faxing from JHB in RSA. The code stipulates that the slope is to be maintained in all operating conditions, cold, hot, cold to hot etc. That may mean using a 2-3 in 100 slope. The NWS 1451(ESkom Power Generation) spec that we use is more stringent i.e. 2/100 with flow as a minimum.
rjstephens -
I much appreciate the offer. I am interested in this information for my own personal growth, I can't afford to purchase the entire standard, neither have I found a lending source via interlibrary loan nor at our national engineering library. No doubt some corp. libraries in the US have it, but I haven't found good avenues to those sources.
My fax is 09-1-513-241-3659 from JHB to USA. Or if you prefer I can be reached by email at knislyna@fosdickandhilmer.com in which case a pdf file would be well received.
I would appreciate the page(s) which specifies/discusses pipe slope. If an adjacent page discusses the related issues of drip leg spacing and steam velocity that would be helpful too.
Would you say what the NWS abbreviation represents? I can find no reference to the meaning of "NWS 1451"?
Best regards,
Ken N-N
I much appreciate the offer. I am interested in this information for my own personal growth, I can't afford to purchase the entire standard, neither have I found a lending source via interlibrary loan nor at our national engineering library. No doubt some corp. libraries in the US have it, but I haven't found good avenues to those sources.
My fax is 09-1-513-241-3659 from JHB to USA. Or if you prefer I can be reached by email at knislyna@fosdickandhilmer.com in which case a pdf file would be well received.
I would appreciate the page(s) which specifies/discusses pipe slope. If an adjacent page discusses the related issues of drip leg spacing and steam velocity that would be helpful too.
Would you say what the NWS abbreviation represents? I can find no reference to the meaning of "NWS 1451"?
Best regards,
Ken N-N
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