Steel Pipe laying 1

[emanc]

Is it proper method to lay steel pipes (500mm dia. x 9m long) by pre-fitting up every 2 pipes at ground level then lift and place into pipe trench then full weld. What are advantages and disdavantages. Any opinion would be very much appreciated.

Is laying 1 pipe at a time better than 2 pipes.?

 

[zdas04]

Welds inside a ditch cost 5-10 times the cost of welds on the surface. Consequently, the normal technique is to weld the pipe on the surface as long a underground obstructions allow (i.e., from one foreign crossing to the next). One caveat is that open ditch is a liability--it can fill up with rain water and have to be redug; pregnant, prize racing cows can fall in and die, etc. so having ditch more than 2-3 days ahead of the welders is a bad idea. In the area where I live we have been busily building pipe for 75 years, we rarely get 1/2 mile between underground obstructions, but I once had a string 1.5 miles long that we could lower in all at once.

Having one ditch open is best. If you open a ditch and lay two lines in it your lay costs will be somewhere around 75% the cost of digging two ditches and laying the same pipes.

David

 

[BigInch]

Why not weld up joints continuously at the surface at the front of the string and lower the end into the trench in an "S" lay configuration.

(Copyrights: Virtualpipeline)

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[zdas04]

Purty pictures, lot of yellow iron. That technique is absolutely the best on long cross-country lines with few pipeline/road/river/railroad crossings. Crossings kill the profitibility of that sort of lash up.

David

 

[BigInch]

Crossings are a source of profits. Just makes the pipeline a little tiny bit more expensive, but what's the alternative, not build it.

But that's right, for sure you can't open cut everything. Some push crossings will have to be made somewhere, and you wouldn't want to slow down the main lay with crossings. You can reserve those couple joint welds for the speciality crossing crews, then let a tie-in crew come in and weld them into the main line which has probably passed them up and is long gone by then.


**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[emanc]

Thanks guys for your usefull inputs, BigInch thanks for the pictures.

 

[bimr]

There is no question that petroleum pipelines are installed according to the procedures previously mentioned by BigInch.

However, you are posting in the water forum. Steel piping is not used extensively for water piping. And most of the water piping in underground applications is installed with flexible push-on joints.

Is your project a water pipeline?

 

[coloeng]

On the contrary, steel piping is used extensively for water transmission piping. Typically in the diameters of 18-inch and larger. Many water transmission mains, both raw water and treated water, are steel and use not only gasketed push-on joints but also welded joints. Our system has around 100 miles of steel transmission main and within the next 10 years that number will probably be doubled.

 

[cvg]

depending on geographic regions steel piping is used extensively or not at all. For instance, southern california has hundreds of miles of CML&C steel municipal water lines generally 16" or larger. Just two hundred miles east in Arizona, concrete pipe (with steel reinforcing) or DIP are used and steel pipe is rarely if ever used. Aggressive soil conditions or political pressures may be the reasons...

 

[bimr]

Ductile iron (and cast iron) pipe has been the standard for water distribution systems for many years worlwide. There are more miles of this pipe in use today than any other pipe.

Steel pipe and reinforced concrete pipe are sometimes used as large feeder mains in water distribution applications.

 

[emanc]

The project involves installation of about 5 km steel pipe transmission line and about 7 km HDPE main distribution line. Contractor proposed full penetration butt weld joints for steel pipes.

We have another issue on lining of weld joints inside pipe as the contr proposed manual application of epoxy lining, meaning worker have to go inside the 500mm dia pipe which we consider unsafe. Any opinion on this?

 

[emanc]

The project is extension of municipal water supply system, water willbe drawn from a lower level reservoire then pumped to a resrvoire about 130meter at higher level through the transmission line. Water supply will then be distributed by gravity.

 

[Zambo]

emanc,

which country are you in? I am sure that in Europe and North America 500mm diameter is not considered "man entry". There must also be fume issues.

 

[bimr]

A 500mm diameter pipe does not allow adequate working space for a worker to properly install an internal coating on a field joint. Inadequate surface preparation and surface contamination before applying the field joint coat will lead to internal coating failure.

The coating applicators use automated equipment that will do surface preparation and apply coatings to field joints without the need for entry. The type of automated equipment depends on the selected coating.

You should request additional information from the Contractor on the coating application.

 

[emanc]

We are in south east asia. Contractor intends to use somewhat like a roller skateboard where worker can slide himself inside the pipe. We already rejected this methodlogy due to safety issues, we are looking at automated method, bimr, have you done any automated lining method before? the lining is epoxy, another issue is how do we check if joints were applied with correct thickness of epoxy lining, we have to device a method to insert DFT gauge up to the joint then be able to press the button to activate the DFT gauge. any further opinion on this?

 

[dicksewerrat]

Why not use HDPE for the whole line?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[SJones]

http://www.nov.com/Tubular_and_Corr.../Internal_Coatings/Line_Pipe/UB_Fittings.aspx

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04