Steam lines in publicly accessible areas

[Yobbo]

Hi,

Referring also to thread378-260783, that I found very usefull, I am looking for a guide line that tells me what is the best way to position the steam line in public areas. What I am interested in is whether it is feasible to have the steam line running underground or at ground level. This should reduce costs compared having the steam line running on high supports. On the other hand I think that public safety requires measures that disable people to access the steam line. I never saw steam lines running underground or at ground level, but that is not much of a fact to decide on. Are there any guide lines for this particular situation? Your help or tips are appreciated.

Karel Postulart


Karel Postulart, The Netherlands
Nuon Power Generation

 

[LittleInch]

Public safety and what you need to do to satisfy regulations vary with each country. An analysis of failure modes, frequencies and consequences will normally be required to assess the risk. Protection to the line by burial, additional wall thickness / double skinned lines, concrete, all reduce the failure frequency.

Of course Steam lines are buried - See New York for an example.

http://www.coned.com/newsroom/energysystems_steam.asp

Insulation is key as are condensate drains.

Ground level - no. Too much risk of damage and too many consequences if it fails.

What sort of size and pressure are we talking about here? Where is this - a city / town steam distribution system or running steam from one industrial facility to another across public land?

the previous post gives some excellent points to address.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KevinNZ]

This a pubic safety question and needs to be addressed by the local regulations.

Geothermal steam lines are run over ground all the time. These can be right next houses,roads etc.
We find hot surfaces and traffic collision to the biggest risk. So insulation and vehicle barriers are important, so is keeping the public away from steam traps.

 

[MJCronin]

" I never saw steam lines running underground or at ground level, but that is not much of a fact to decide on." ....... Really ?

There are many, many district heating systems all over the world. Some systems are well over 100 years old. District heating systems are a good choice for cities, hospitals, Universities, prisons and many other locations where the generation and use of steam is the best method to distribute heat from centralized boilers to remote facilities.

DH systems, almost universally run their steam piping underground in tunnels, vaults and sometimes in double walled buried systems.

Tunnels are configured and designed to tolerate occasional system leaks, but can become deadly.

There are more people near district heating steam and condensate piping systems than any other circumstance.

http://www.districtenergy.org/

MJCronin
Sr. Process Engineer

 

[bimr]

I have been in some countries (Russia for example) where the district heating steam pipes are run at grade.

 

[Yobbo]

Thanks for the answers.
First I realise that I hadn't mentioned temperature and pressure. It is superheated steam with a pressure of 8 bar abs and a temperature of 195 Celsius (374 Fahrenheit).
I think the local regulations and societal culture is very determining for the right way of running pipe lines through public area. I did see steam pipes run at grade as well in Mongolia, but I wouldn't be the one to recommend it. Not just for the risk of exposure to steam, but definitely too for exposure to asbestos. Safety culture there is quite backward to put it mildly. So I wouldn't take this example as promising option. In western densily populated areas vandalism is not to be dismissed as a safety factor.
I would be interested whether the underground option is a desirable option for a new application. Weren't those underground steam lines concipated in a time where the disadvantages were not well known? I have experienced problems with distribution heating lines with superheated water where the lack of accessibility caused quite some difficulties and costs. I suspect that steam lines underground are even more problematic. Therefore I would not be inclined to choose this option. But maybe I am not aware of any other advantages that would make me change my mind.

With best regards,

Karel Postulart


Karel Postulart, The Netherlands
Nuon Power Generation

 

[LittleInch]

Hmmm,

Advantages of buried lines:

Ability to walk, drive, farm above the pipe with very little risk of damage to the pipe
No need for supports,
Reduced impact of pipe break or leak to the public (compared to A/G)
Reduced risk of impact damage from vehicles / people
Can be cathodically protected from corrosion (insulated pipes might not be able to to)
Coating not damaged by sun or wind
Much more attractive

Each location will have different weighting in these factors.
An industrial plant will have many lines running on pipe racks or low level supports and work will be controlled around them to prevent damage. Generally few people around to impact in the event of failure

In public areas, visual intrusion, impact on the operation of cars and trucks and impact of any release will be much more important as will the interest of the safety authority.

Quite frankly running superheated anything or high pressure steam in a public street strikes me as a risk not worth taking. The benefits versus merely hot water would have to be very significant before I think many authorities would allow it with many additional safety features ( multiple shut off valves, perhaps double wall pipe or conduit, monitoring features to prevent someone digging it up by accident etc etc). Whether those still make it worthwhile is up to you.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.