Mine Dewatering Vertical Shaft 1000m

[stanier]

Hi,

I have previously posted this in the Pipelines Forum and it was suggested that it be bettter posted here. Your assistance would be appreciated.

A project on the drawing board features a mine dewatering facility. The pumps at the base of the mine will pump vertically up to the surface into a tank.
It is proposed to use 808 Double Grooved Victaulic couplings of the high pressure variety. Supports will be rockbolted into the wall.
Please comment on the following rationalization.
There is a concern that the tolerance in the groove of the coupling will allow the pressure thrust to be transferred to the supports. These forces should be balanced either side of the support apart from the mass of the pipe & water. It would only be a problem if there was a pipe burst and the unbalanced forces would shear the support.
Thermal strain is yet to be determined as the mine temperature is to be assessed.
Have you any direct examples of this type of installation?

 

[miningman]

Something is not right here. 1000 metres is 3300 feet which implies the hydrostatic head at the base of the shaft is in excess of 1300 psi. Ive used an awefull lot of victaulic pipe in my career but I've never tried to use vic systems at this depth or pressure. This crys out for flanged pipe.

Additionally if this is anything close to a standard dewatering exercise, you're going to be be dealing with a continually increasing head as dewatering progresses, assuming you are dewatering the shaft directly and not using something cute like borehole wells. You'll almost certainly be bolting the pipes to the shaft steel, not directly to the rock.

Ive never yet experienced thermal strain in a shaft piping system, and Ive worked at depths of 6000 feet+. Get yourself the assistance of an experienced shaft engineer.

 

[stanier]

Hi Miningman,

Your advice is very relevant welcomed.

Until I see the documentation I do not know how this is going to go.

As far as the Victaulic couplings go the style 808 is rated to 17.25MPa which appears to sdatsfy the pressure requirements.

The stress analysis can be done to determine the pipe wall stresses. If there is a difference between installation temperature and operating temperature then there will be thermal strain. Of more concern is that the pipe may expand and take up the tolerance in the coupling grooves.

Flanged pipe makes sense but would take up more room in the shaft.

There is an existing dewatering system at a higher level and the mine is going deeper. It is not as if they have not done it before. If the design is done logically and the numbers are there then the design can be certified. If not then an experienced shaft engineer has to do the design.

 

[miningman]

This is starting to get interesting. So here's a few more considerations that may be relevant. The OP seems to be based in Australia and I am based in Canada. I personally have never used the Victaulic 808 clamps but they do appear to meet the basic hydrostatic requirements and I do have some experience working with Australian personnel (not all positive I might add) but I must concede that there are a number of techniques which are widely used in Australia and are unknown in Canada (and vice versa of course). Some are legitimate differences... how many Australians have to deal with minus 35 degree weather for example...but maybe hi pressure victaulic systems are more common in Australia
than North America.

And I say North America rather than Canada since one relatively undisputed fact is that Canadians possess somewhat more deep mining expertise than Americans. I personally have worked in shafts at over 5000 and 6000 feet deep in the last few years. Interesting things can occur at depth which arent always well understood or appreciated by personnel without direct knowledge of these things. Perhaps Canadians use flanged pipe simply because they have learnt by bitter experience that the apparent savings in initial capital costs in using victaulic are more than outweighed by increased operational / maintenance costs over a mine life. How does one put a dollar value to the inevitable water hammer that will occur at some point during the life of the mine??

And while discussing capital costs, if the owner insists on using victaulic type clamps, make 1000% sure that the purchasing agent does not save a few $$ by going to an alternative supplier who makes a similiar product which appears to meet the specs.... you dont want to know how much money Ive wasted changing out defective product... stick to Victaulic!!

So that brings us to the mining engineers who seem to have specced out the system todate. If they are competant and experienced in this type of installation, why arent they being asked to sign off on the design with all the issues of thermal strain and support mechanisms ?? I've always been very reluctant to get into a p***ing contest with owner's engineers unless they are clearly unskilled.

Of course if they do not have the skills and experience , then we are back to the potential gong show I previously alluded to.

And to be fair, this sounds as if it is the dewatering of an existing shaft which is then going to be deepened which is a vastly different exercise to just dewatering an existing shaft. There is an awefull lot to consider here. And I hope this isnt a copper mine with all the increased corrosion that inevitably exists after a few years of flooding

 

[stanier]

Hi Miningman,

Thanks for the response.

I have done some analysis for a deep mine previously. I specialise in waterhammer studies and pipe stress analysis. The mine in question had vibrations issues and I had to do the waterhammer and vibration analysis of the piping. It was installed already so the design of supports was already someone else's domain. Anyhow that worked out alright with additional supports being strategically placed.

The concern I have with the Victaulic is that the salesman tend to profess how wonderful they are but take no responsibility. My approach would be to get all the technical information. If it fails to materialize insist on some test results or FEA using upper bound limit strain analysis of a joint under pressure and compressive load.

You are right this is in Oz. The local piping code would require radiographic examination of the couplings which I doubt has occurred. This because they are a ductile fitting.

I am curious to know hwy you cannot rock bolt to the shaft providing that the column can be aligned to avoid lateral forces.

I too am concerned about cdorrosion but as yet have not received the water analysis to comment on. Has the use of GRE pipe grouted into a bore been used in Canada? This would appear to be eminently safer than running a pipe up a shaft and would solve the corrosion issue?

Do the flanges leak at the gasket? I would imagine the compressive load from the pipe/water column would compress the gasket down to the retaining ring?

Usually posts in the piping forum gives references to texts and papers/websites/books so we can all learn. Do you have any?

 

[miningman]

Stanier, with all due respect, I think you are in danger of becoming involved in areas outside your area of expertise. However in an attempt to assist you please consider these adfditional comments.

Pipe can indeed be affixed directly to the rock if the mounting brackets are designed to have say 50mm of adjustment. A standard rock bit is 32mm and if you have ever watched a miner collar a hole, you will understand why we dont work to millimetres when working with rock. Once the rock is excavated , yes we can install steel sets and other infrasture to tight tolerances but again, this is not surface construction, and unless you have witnessed this type of work, I think it would be very difficult to comprehend some of the practical difficulties miners have to overcome.

You dont say if the shaft is concrete lined or not. If conctete lining is in planned, then yes it is relatively easy to engineer the placment of threaded inserts into the formwork to which the pipes can be clamped. But this must be done at the design stage, doing it after the concrete is in place is tough. And remember, you are not dealing with just one pipe, sight unseen I would guess there are at least 5 pipes in the shaft and as previously stated, space is at a premium.

I cant comment on standards and technical specs because alho this might seem unusual, the mining industry here seems not to rely heavily on these things. Dont get me wrong, the last major deawtering exercise I was involved with was specced I believe to B33.1 ( does that sound right??) but Im afraid the engineers who designed the system did not earn much respect from my colleagues and myself who installed it and had to deal with the errors and ommissions in the design. As an example, if youve ever seen the volume of water that tends to be running completely uncontrolled in a shaft, who really cares if one or two pipe joints have minor leaks... we are not dealing with H2S here.

Additionally, if I understand your prvious post, you are dealing with dewatering (AND rehab) of an existing shaft which is to be deepened. These are two totally different tasks but it does imply you are dealing some some existing infrastructure in place. How are you going to use it?? Does it have to be ripped out and replaced?? If some of the existing pipes are inadequate for ongoing use , can they be used for something else???

I cant see anyone without practical mining background being able to answer these questions or recognise the significance of something apparently insignficant on the existings drawings. Hope this helps.

 

[micalbrch]

Miningman I would give you a start if I could but I'm happy for the recommendation to post this in the Mining Engineer forum. And I hereby offically withdraw the dwarf and replace it by Giant! Good advices you give here!

 

[stanier]

Hi Miningman,

I am taking on board all you have said. i am not alone in this exercise and am working with another design group. I am seeking all the information knowing that some of this is new to me. To ally your concerns I have designed systems below ground before and have experience of anchoring vertical pipe systems in rock shafts and high rise buildings. I am proceeding with great caution and asking the questions of others. I do respect your position on a number of matters you have raised.

i do the know the mining industry having been the engineering manager for McNally here. Their work was mainly surface mineral processing plant and equipment. Ore winning was by use of draglines/bucket and shovel rather than deep mine. The below ground folk are another breed.

This system has been specified to a piping code which is not dissimilar to AMSE B31.3 that you mentioned. It has rigorous requirements for design and analysis, quality control of welding and definition of system risks/hazards. I respect the fact that the mining industry does not always use such codes.

I take your point about groundwater ingress making minor leaks of little consequence.

Until I get the design documents I cannot begin to address the infrastructure needs. But I have taken notice and anything outside my area of expertise will be referred on. I do wish to learn on the way so this dialogue has been truly helpful.