Galvanised Mild Steel Pipe

[BRIS]

Galvanised mild steel pipe with screwed or flanged connections is used extensively in developing countries for water supply transmission pipelines and distribution systems. Often it achieves service lives of little over 10 to 15 years. When whole life costs are comapred with more durable materials then it can be shown to be more expensive. However, when you have limited funds you consider only what you have to pay out now not what may nedd to be paid out in 10 years time. I am looking for arguments to support my case for using more durable materials (ductile iron, PVC, GRP (FRP) etc). - any papers on the performance of galvanised mild steel pipe and its suitability (unsuitability) for potable water supplies.

 

[JedClampett]

When ease of installation and supporting equipment is considered, I can't believe that PVC is more expensive than galvanized. With a hacksaw or cutters, fittings, primer and glue, one worker can install many feet of PVC. I don't have any studies to prove this, but I bet you could easily go to a supplier, buy both types of pipe and compare installed costs.

 

[oldcorreng]

I have to agree with JedC as plastics will last longer than most metals used for potable water. If you select plastic, be certain to select a plastic that is approved for potable water use.

A lot will depend on the size of the piping and thickness of plastic to be used, is it going to be buried, is it going to be in harms way where it could be easily damaged by heavy equipment or personnel, is the location a safe one so as not to cause colatteral damage if it is broken, what about having to support it in long runs?

What are water composition and temp as this could have a seriuos effect on corrosion of the metal used. Usually pitting and/or under deposit corrosion will occur which are the worst types so that average corrosion rates of the particular material in that service would not be useful for determing it's life.

 

[JStephen]

I know if I run down to the local Lowe's, PVC pipe is a bunch cheaper than galvanized steel pipe. Is that different elsewhere in the world? In larger sizes, C900 PVC is normally cheaper than DI pipe.

I'm sure not aware that galvanized pipe would have service life of 10-15 years, though- that sounds awfully low. Isn't this what's been used in houses extensively?

I'm not aware of anything besides PVC really being competitive in the sizes that galvanized pipe is normally used in (2" or less).

 

[BRIS]

Sizes of galvanised pipe used in potable water transmission and distribution systems are typically 6" and 4". House connections which are invariably above ground are 1/2" and 1". My observations are that with unprotected buried pipe the galvanising breaks down after 5 to 10 years and pitting corrosion can result in leakage in 5 to 10 years after that. The case for PVC in terms of cost, installation, long term durability are overwhelming yet galvanised mild steel continues to be the only material used in many developing countries. (low cost, low spec material from India and China). One obvious problem with PVC is its deterioration when stored exposed to sunlight. I could show photographs of acres of 4" galvanised MS pipe manufactured in India and stockpiled at the local yard of the rural water authority ready for installation in small town distribution sytems.

Brian

 

[Zambo]

For developing countries there are some advantages of GI pipe, which is why it is so often used. 1. It doesn't have to buried very deep to protect it from light vehicles and the pipe surround can be selected excavated material. 2. It can be installed on the surface where this is more convenient without being affected by UV. 3. It is easily installed and no change of material is needed between the storage tank and the outlet, which would often be a street supply tap.

Zambo

 

[stanier]

In may parts of malaysia the GI pipe has been replaced with ABS. This is not the ABS formulation that created so much angst in the USA but a formulation from Australia or Europe. This product made to Australian Standard AS 3518 is tough and easily slovent cement welded. it is available in sizes up to DN800. It is approved for use with water to AS 4020.

ABS has been used in exposed environments for over thrity five years. It has a greater fracture toughness than PVC-U. It is cost competitive. The product is manufactured by Tyco, Georg Fisher or Durawills. It is also used extensively for pure water in the electronics field.

Its toughness and resistance to UV allows its use in above ground applications.

 

[BRIS]

Zambo you have given the clear advantages - also it is readily available on the local market, easy to stock, easy to transport, needs no special skills and screws directly to low cost Eastern manufactured valves. The problem is its short service life - maybe 20 years. how do developing countries develop if the infrastructure collapses every 15 to 20 years. Do I try and introduce more sustainable materials - which in the long term are more cost effective or do we go with the flow and replace the corroded galvanised pipe with new galvanised pipe!

 

[Rich2001]

One should be concerned with Lead (Pb) in the galvanizing alloy. Many galvaniziers add a small amount of low melting point alloys (Tin, Bismuth and Lead) to the zinc to improve the wetting of the steel by the galvanizing. Alway obtain certified test results on the galvanizing on piping that will be used for potable wtare service.

Vita sine litteris mors est.

 

[jherbert]

BRIS,
From my experience the reasons GI is used is simple, availability. When I arrived in Hong Kong (from UK) I was shocked to find that GI was used for everything! potable water chilled water, everything was GI. Primarily because that was all that was available and the importers didnt want to gamble buying the new fangled copper and plastic's since none of the fitters knew how to install it.

Thankfully that has all changed, with copper and plastic potable water is commonplace. However, the old GI handover continues, we have GI covered pvc here, yup, a perfectly good pvc pipe inside within a GI pipe.

Anyway to answer the OP, if the market conditions i.e. dealers stock the material , and provide the necessary support i.e. warantee, tools, etc. you too amy get mdpe.

Locally two factors effected change, change in regulations and a large utility started installing mdpe mains. And I agree if you install GI today, they will be replacing the mains again very soon.

 

[lochan017]

the usage of GI pipes is not that arbitary in India as some of the member have said. the available site conditions guide the usage of material in the rising/distribution mains. they may underlying strata which may be rocky.in Many of the places the in southern India the rock strata may be mat at a foot depth or so which is far less that the minimum priscribed minimun depth for laying of PVC /hdpe pipes.also due to unplanned construction at the local level such as at village level roads especially CC roads are constructed without any engineering guidance.these constructions necessitate usage of GI pipes. since cost of excavation in such conditions may be costlier than laying GI pipes. hence GI pipes are used.

also you don't only get low cost and low spec pipes from India and China. they are cheap because the production cost are are low in India and China. you do have a minimum standard below which you cannot go and those things are adhered in all the water supply Projects.

 

[BRIS]

What we are saying is that although GMS (GI) pipe has a short life span there is no alternative low technology material for developing countries. As long as the World Bank and other agencies continue to fund projects which utilise short life materials We will continue to see the cycle of replacement of unsustainable infrastructure. The developing countries of the world will continue in a cycle of development.

 

[stanier]

ABS to AS 3518 has been used in Malaysia and Indonesia for water reticulation. It is manufactured in those countries. The skills required to fabricate and install piping up to DN200 are easily taught. Larger diameters require more extensive equipment but the techniques are the same. No the ABS is not that product from the USA that has caused so many problems. It is a material developed in the UK but now manufactured in Australia up to DN800.

It is comparable in cost to GI.

The tradesmen in SE Asia are just as capable of learning new techniques as other countries. The assumption that they are some way inferior and incapable is offensive. Look at many of your building sites in so called developed world and it will be tradesmen from these very countries.

Let engineeers educate the World Bank on sustainability. It takes six times as much energy to produce GI as it does ABS. What does that do for global warming?

Let the engineering institutues and standards bodies in the developed world encourage the use of ISO standards in less developed countries.

Give a man a fish and he has a meal for the night. teach him how to fish and he will have a feed forever. Invest & teach him how to build a fish farm and he will have a thriving business, feed the community and challenge the big companies in the developed world.

Perhaps thats what the western world is a fraid of doing!

 

[rconner]

Those interested in this thread might also want to see the current posts reportedly involving similar subject on the AWWA Public Discussion forum at

http://www.awwa.org/forums/messageview.cfm?catid=22&threadid=8998