Minimum thickness of large diameter steel pipes for handling/transport 2

[Bbird]

I am involved in a scheme of specifying large steel pipes, between 3 to 4 m diameter cast into reinforced concrete for a cooling water system of a power plant. I would like some advice on the minimum thickness of these pipes generally adopted by the industry. I know these pipes can be fabricated either by spirally welded, bent by a large press or other means to any thickness I want but for handling/transportation purpose and with the longest length possible (least leakage risk) there must be a common practice on the minmum thickness.

I know certain states in America specifies thickness as 1/240 and am interested to know more or any alternative.

I appreciate also any information on the internal coating available for such large diameter steel pipe, like is it possible to have a plastic liner applied in factory, and the cost ratio relative to the standard coal tar epoxy.

The pipe is to convey seawater up to 10 degree about the sea temperature.

There may be suggestion to sway my choice to other material but the current selection is based on years of experience and the fact the steel pipes and the concrete prices are well established whereas using GRP and steel cylinder mortor (Bonna) pipes etc always cost more with more subsequent maintenance problems

 

[yogibear1]

If you have access to the AWWA library I think you will find some useful information. They have a manual on thin wall steel pipe I think it is M41, but I'm not positive. One thing to consider if/when you use thin wall pipe is to provide internal supports during the installation of the overlaying concrete. If the pipe is not internally supported there is a real possibility that it could collapse from the overhead loads. After the concrete is cured the supports can be removed.

I am not familiar with coal tar applied internally, usually it is applied externally as a corrosion preventive. Internal lining include factory applied cementitious mortar. Around here (West Central Florida) we also use Protecto 401 (an epoxy) for internal corrosion control on our DIP sewer lines.

 

[dicksewerrat]

You could look at Hobas pipe. It is a modified concrete pipe that has excellent corrsion resistance. Or you could line the standard RCP with a aCured in Place liner. This is a polyester based resin, cured in the pipe. Lenght should not be a problem. where is this project? Maybe I can steer you to contractors in that area.

 

[Bbird]

Thnaks for the response.

The project is in the Middle East and there are abundant supply of manufacturers for GRP and steel cylinder RC pipes. I have a strange exerience that personally I have never come across a project in which GRP pipe was used and didn't leak. In my case most leakages took place when adjacent construction activities disturbed the installed GRP pipes which were typically about 2.6m diameter.

The propietary precast steel cylinder RC pipe typically has a thickness less than 2mm while the thickness I am seeking in this thread will be at least 6 times thicker. The cast-in situ method takes time but has been proved cheaper than the propietary products. Also for the diameters I am working on the precast steel cylinder RC becomes extremely heavy and can be supplied only in very short length of less than 0.5m. The large steel liner I am after can be supplied in 12m length that greatly reduces the number of joints.

 

[johnd43]

I am not sure I have understood all the implications of this discussion, because of differences in terminology, but I have understood that you are likely to be importing tube from some external manufacturing site, into the Middle East.

If that is correct, it is worth looking at a variety of diameters so that you can nest smaller pipes inside larger ones. That way you get closer to shipping on weight, not volume. The cost implications can be astronomical on a large order. Even if it is a more local manufacture, involving road freight only, there is still an advantage for large orders.

In the end, your finished installation may be the least taxing specification, as you could find that handling is the most arduous service condition and demands a particular wall specification. Talk to the manufacturers.

 

[Bbird]

johnd43,

The pipes are for a power project. The efficieny of such single cycle power plant is about 35% and the rest is dumped as heat. The pipes form a part of the cooling system and there are already 5 of them in a row at my suggested diameter. By decreasing the pipe size the friction goes up and so is the pumping cost which is already huge. Thus space and cost have already by optimised. The big diameter is due to a seawater based Flue Gas Desulphurisation system has also been chosen. Seawater is used to scrub the flue gas and its seawater demand can be comparable to the cooling system if the fuel conatins 4% sulphur.

 

[johnd43]

Bbird,

Sorry - I obviously wasn't clear in my earlier comment.

If you were using 3000 diameter pipes (for instance), you might think about having one third at 2800 mm diam, one third at 3100 mm dia and one third at 3400 mm dia so that net pumping head didn't increase (I can't do the sums without the detail). The point is that you can then slip a small pipe inside the next size and the nested pair into the largest so that you can get 3 lengths of pipe into each (say) 12m x 3.4m x 3.4m shipping volume. Its the difference between 12m delivered per wagon, and 36m delivered per wagon. The longer the lines the better it works. For instance, if you have 12 kilometers overall you need a thousand lengths so you would have 333 lengths at each size, with just two transition pieces to connect between the lengths of differing diameter.

As I suggested earlier, you need to plan it with your supplier and his needs for the most economic shipping formula are likely to drive (or at least contribute to) the final decision on wall thickness etc. If it produces a saving that is worth the (small?) additional effort, all well and good: take it. If not, then forget it!

Best of luck.

 

[Bbird]

johnd43,

Thanks for the suggestion. I haven't thought much of the transportation arrangement but I could certainly use your idea of nesting pipes during transporation. It is strange to suggest to designer to alter pipe size to suit transportation but your point is valid in my case.

 

[tommyclose]

moving your pipe one inside the other would be unusual i"m not sure about that ...however for a lining, cement mortar lining of the internal wall of the pipe in-situ would be quite acceptable and suitable and indeed in the middle east quite usual...

 

[stanier]

My understanding is that coal tar epoxy is a carciogenic compound. It certainly is banned by Sydney Water because of this parameter.