A flexible coupling of approved make is recommended to take care of shocks due
to movement of the traffic. Also, in case of minor settlement in the soil, this
would be helpful. This is recommended for fire service passing under the roads
in India.
Regards,
Rajendra Bajikar.
<a href="/group/PipingDesign/post?postID=LGv_CpdqUdWKglBRYwnZblM2CXiJmlmlTEmHJN0LHTYCJkL8Ue8NAyOK3IHjB2mfZ3SR72W8lSp7syKqLucDXiUq">Gordon.Reddek@Alcan.com</a> wrote: Banerjee,
The 1200mm cover was used in Australian codes some years ago. Since then those codes have been withdrawn and replaced with a code called AS2885.1 Pipelines - Gas and Liquid Petroleum Design and construction. I have had little to do with that code for some years however so I am not sure about the contents of the current revision. I was very disappointed when they introduced it because they changed if from a code that provided prescriptive information, like the one you are looking for (1200mm cover), to one that listed endless things that an engineer must do with no concrete and useful information. If I remember correctly it had no more than three equations in it. So I would give that one a miss and look for something more positive in its approach. ASME advertises the following codes which I do not have access to:
Gas Transmission and Distribution Piping Systems
B31.8
Published 2000
Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids
B31.4
Published 1998
Gas Transmission and Distribution Systems
B31.8
Published 1995
If I was you I would get hold of one of them. The Americans are generally much more practical and prescriptive. Regarding the high traffic load. Yes it is always permissible to pull a pipe through a square culvert or a round casing installed below a road that is designed by a competent civil engineer to carry the traffic. If you are pushed for space you can use a culvert at road surface and the pipe laid just below it. The culvert will take the full traffic load. You must however protect the pipe on both sides from damage by vehicles leaving the road so the standard practice to drop the pipe down to the 1200mm cover ( or whatever turns out to be the accepted depth at that point), and to protect the pipe with concrete slabs etc until it has reached the safe depth of cover.
Gordon Reddek
Specialist Mechanical Engineer
Alcan Engineering, Level 3, 443 Queen St, Brisbane, Qld 4001, Australia.
Tel: +61 7 3328 6424
Fax: +61 7 3328 6990
Email: <a href="/group/PipingDesign/post?postID=29MM47CcxotYwhfcTPnjXUQITsKeIvXxTcagTKF1L0cNTMJbr3mnkl2r6qxKOPkqsefTHoNYzfuVaSOhV_QKkRhP">gordon.reddek@alcan.com</a>
Banerjee Sudipta SPEL-T1 <Sudipta.Banerjee@siemens.com>
04/06/2004 01:17 PM
Please respond to
<a href="/group/PipingDesign/post?postID=3cPru8l_8th5_R9UvaVjeskJot_cU_Mf17-_JZ9ZT59aeVDveDiPHi5KhPLjaxkmOQE-UbBf99AvFnKOMc4MBxly7tZN">PipingDesign@yahoogroups.com</a>
To
"'PipingDesign@yahoogroups.com'" <PipingDesign@yahoogroups.com>
cc
Subject
RE: [PipingDesign] Underground Piping
Hello Mr Reddek,
Please can you specify the code where that
figure of 1200mm is been mentioned? Suppose if it is a 10" Stainless Steel
Fuel Gas Pipe running below a road subjected to abnormal traffic will a
concrete casing work if that 1200mm is not possible to maintain??
Regards
Sudipto
Dear Thanks,
The criteria for buried pipe depends on the code that has jurisdiction
over the facility you are designing. These days one seldom designs a
pipeline from first principles, you have to design to the requirements
of
either a national, or international standard. As always you guys give
insufficient information to give good advice. What are we talking about
here. High pressure steel oil or gas line, plastic or a concrete sewer?
What is the diameter? two inches or six feet? For what it is worth:
are normally buried with 1200mm cover, that means from the top of the
pipe
to the road surface.
2) If the road is to be subject to abnormal traffic, like trucks
carrying
heavy equipment, one normally buries the pipe deeper, or , the pipe runs
in a culvert designed by civil engineers to take the load, or a slab is
cast over the pipe to distribute the load to the ground on both sides of
the pipe.
3) Very large diameter low pressure lines like sewers require special
treatment. That is the area of a specialist and you should not touch it
if you are not qualified.
Regarding bedding material. The soil below the pipe is commonly called
bedding and that above the line is called shading. Normally it has to
surround the pipe with a layer of at least six inches (or 150mm). The
specification normally calls for clean loose sand free of stones and
extraneous material. Some specs may even nominate a sieve size that the
sand must pass through however it is not uncommon to see clauses like
"the
sand may contain stones of a rounded shape and with a diameter no
greater
than (say) 10mm." The details will depend on the pipe coating. If the
pipe is a steel pipe coated with a fairly soft coating the spec will
have
to be stringent to protect the coating from damage by the bedding and
shading material. If the pipe is a concrete monster you would most
probably call for a loose sand bedding so that the pipe can be levelled
properly and shading with the excavated material provided the lump
size
is on average no greater than (say) 100mm. What you specify depends on
the pipe you are installing.
Sure you can join pipe under roads. If you are running gas or some
other
dangerous material you will not want a leak there so one tends to be
more
stringent regarding joints in that area. Some Authorities may require
that the line under a road is jointless, however in general pipe codes
require the pipe in that sort of area to be thicker so that they are
more
lightly stressed. Flanges are generally not allowed on buried
installations so I would expect that a full penetration butt weld which
is
subject to 100% NDT would be considered to be acceptable.
Once again, you must find out what code governs the way you design your
line and you must be guided by the requirements of that code.
Gordon Reddek
Specialist Mechanical Engineer
Alcan Engineering, Level 3, 443 Queen St, Brisbane, Qld 4001, Australia.
Tel: +61 7 3328 6424
Fax: +61 7 3328 6990
Email: <a href="/group/PipingDesign/post?postID=29MM47CcxotYwhfcTPnjXUQITsKeIvXxTcagTKF1L0cNTMJbr3mnkl2r6qxKOPkqsefTHoNYzfuVaSOhV_QKkRhP">gordon.reddek@alcan.com</a>
"cckla" <cckla@pd.jaring.my>
02/06/2004 03:40 PM
Please respond to
<a href="/group/PipingDesign/post?postID=3cPru8l_8th5_R9UvaVjeskJot_cU_Mf17-_JZ9ZT59aeVDveDiPHi5KhPLjaxkmOQE-UbBf99AvFnKOMc4MBxly7tZN">PipingDesign@yahoogroups.com</a>
To
<PipingDesign@yahoogroups.com>
cc
Subject
[PipingDesign] Underground Piping
Dear All Specialists,
Thanks
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[Non-text portions of this message have been removed] Received on Fri Jun 04 01:42:00 2004
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