Dear All,
Please try AWWA C150(Thickness design for ductile iron pipe). It calsulates the thickness of underground pipe taking care of all types of loads (Internal pressure of pipe, Earth load, truck load, laying conditions, casting tolerances, Depth of cover etc.)
With Regards
Parmod Garg
SIEMENS POWER ENGG.
-----Original Message-----
From: <a href="/group/PipingDesign/post?postID=og6hVPhIQ5oJnu7Nkmkv4tRg8ue_ZHG19ko1turlh0NE5k9Qm9i4Zn-ZyoJM7DMdqYjYF32MhqxVw4IVRsk">Gordon.Reddek@Alcan.com</a> [mailto:<a href="/group/PipingDesign/post?postID=og6hVPhIQ5oJnu7Nkmkv4tRg8ue_ZHG19ko1turlh0NE5k9Qm9i4Zn-ZyoJM7DMdqYjYF32MhqxVw4IVRsk">Gordon.Reddek@Alcan.com</a>]
Sent: 09 June 2004 14:42
To: <a href="/group/PipingDesign/post?postID=s4L4XKSTRrhjgF4keke_F6Py0YN6rWY4d9Ns_0Uk9uXc68cL-ElEvcI8XxgtAixt0pVVLIMYFXS2MVBDGyJLO6bPXxig">PipingDesign@yahoogroups.com</a>
Subject: Re: [PipingDesign] Underground Piping
cckla,
Coming back to this one as promised.
I have looked at the information I have on this subject and can not find
the formula you are referring to. There is obviously more than one
approach to this problem and I simply do not have your formulas. Before I
comment on your formulas let me describe the approach the book I have
takes.
My book calculates the pressure on the pipe caused by the soil overburden
It uses a similar formula to yours. The formula is:
Wc=UsH/144 where Wc is the vertical soil load in psi, Us is the unit
weight of the overburden in lbf/cu.ft and H is the burial depth to the top
of the pipe. Notice that Wc is a PRESSURE.
The wheel load (WL) is more complex but can be summarised in a small
table. If you have a wheel load of 16,000 lbs then the pressure generated
below ground decreases with depth but has the following values:
at 2ft - 6psi, at 2.5ft-3.9psi, at 3 ft - 3.3 psi, at 3.5ft - 2.6psi, at
4ft - 2.2psi, at 6 ft - 1.5 psi, at 9ft - 1.0 psi. To find values for
your wheel loads simply multiply these figures with the ratio of your
wheel load divided by 16,000.
The total pressure on the pipe is therefore the sum of the overburden
pressure (Wc) and the pressure from the wheel load (WL).
What you need to determine now is if that PRESSURE will buckle the pipe.
The formulas I have are too complex to publish here. If you send me an
email I could email you a scanned page which describes how to determine
the buckling pressure of the pipe.
The problem I have with your formulas is that they both calculate load (lbf, or N) and not pressure. The one calculates the force of the overburden on the pipe and the other the force of the overburden on the bottom of the trench. It looks as though your approach uses the FORCE on the top of the pipe and not the PRESSURE. I need to see much more than just the formula to work out how it is being used. Can you scan the relevant pages and email them to me?
Regards,
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=eDK_2OD7TcmI3NlVohFZwNs8toeC8ZRSyAnTzYr1ymaIPY0mVtA75CjhWoJhOiRT40HUSAbPRFOBoeDjHNYPssg">gordon.reddek@alcan.com</a>
"cckla" <cckla@pd.jaring.my>
07/06/2004 03:38 PM
Please respond to
<a href="/group/PipingDesign/post?postID=s4L4XKSTRrhjgF4keke_F6Py0YN6rWY4d9Ns_0Uk9uXc68cL-ElEvcI8XxgtAixt0pVVLIMYFXS2MVBDGyJLO6bPXxig">PipingDesign@yahoogroups.com</a>
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cc
Subject
Re: [PipingDesign] Underground Piping
Dear Gordon Reddek,
My job are not only deal with fire fighting but I also involve in water supply system. In this case, I am in the position of dealing with water supply.
From your previous reply,
> 2) If the road is to be subject to abnormal traffic, like trucks
> carrying heavy equipment, one normally buries the pipe deeper
In my opinion, if the pipe was buries deeper, the buried laod on that pipe will be increased. Is it a normal practice to use larger diameter pipe ? Or there are some rules to be followed during the selection of the pipe ?
Do you know what is the difference in the usage of the formula CWB2 and CWD2 in calculating the dead buried load for underground piping ? Where C = coefficient and 2 indicate power of 2.
W = soil weight
B = trench width
D = pipe diameter
There are two ways of calculating the dead buried load. So, I believe that
there must be difference during the installing of the underground pipe.
Can you let me know the difference ?
Please guide me.
Thanks.
cckla
cckla,
I doubt it very much. I have never found a useful free standard on the web. The majority of those organisations are now private organisations bent on making a profit, so you can expect to pay. It looks as though you
are designing a fire water system. I suggest you surf the national fire
protection association (nfpa) website and look at the short descriptions
they give for each standard and take a punt on the ones that may cover the
subject of buried line. Once you know what you are looking for see if you
cant loan a copy from your national library or technical institution. I
did a quick google search and found the following site which you could
start with.
<a href="http://www.nfpa.org/catalog/home/index.asp?cookie%5Ftest=1">http://www.nfpa.org/catalog/home/index.asp?cookie%5Ftest=1</a>
Cheers,
Gordon Reddek
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=eDK_2OD7TcmI3NlVohFZwNs8toeC8ZRSyAnTzYr1ymaIPY0mVtA75CjhWoJhOiRT40HUSAbPRFOBoeDjHNYPssg">gordon.reddek@alcan.com</a>
"cckla" <cckla@pd.jaring.my>
03/06/2004 06:24 PM
Please respond to
<a href="/group/PipingDesign/post?postID=s4L4XKSTRrhjgF4keke_F6Py0YN6rWY4d9Ns_0Uk9uXc68cL-ElEvcI8XxgtAixt0pVVLIMYFXS2MVBDGyJLO6bPXxig">PipingDesign@yahoogroups.com</a>
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Subject
Re: [PipingDesign] Underground Piping
Dear Mr. Gordon Reddek,
Thank you for your informations. Anyway, is there any international piping
codes which are available online, such as nfpa for fire services ?
Regards,
cckla
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:
1) Steel high pressure oil and gas lines under roads with normal
traffic
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=eDK_2OD7TcmI3NlVohFZwNs8toeC8ZRSyAnTzYr1ymaIPY0mVtA75CjhWoJhOiRT40HUSAbPRFOBoeDjHNYPssg">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=s4L4XKSTRrhjgF4keke_F6Py0YN6rWY4d9Ns_0Uk9uXc68cL-ElEvcI8XxgtAixt0pVVLIMYFXS2MVBDGyJLO6bPXxig">PipingDesign@yahoogroups.com</a>
To
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cc
Subject
[PipingDesign] Underground Piping
Dear All Specialists,
1) What are the criterias, which determine the depth of the
underground
pipe ?
2) What should be considered in the selection of soil for the
underground pipe trench ?
3) Should there be any joint under the crossing road ? If yes,
what
will be the suitable joints ?
Thanks
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