EXP or pipe.

[itsmoked]

I need to run a couple of 50HP motors down a tunnel project. The distance will reach a mile - foot by foot.

Methane will be present so either EXP starters, controls and motors are needed or lots and lots of 1-1/2" to 2" hydraulic hose and pipe will be needed.

A little pro/con discussion if you please.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

I would do it electrically, but then again, I have a bias .

I don't understand the "foot by foot" reference. Are the motors moving? Are you concerned for the weight of the Ex Proof equipment? Hydraulic fluid in large hoses that long will be virtually impossible to move.

Is air a possibility? That's what a lot of mines do.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[TurbineGen]

Good point Jraef. We used compressed air and sealed cabinets in our Ethylene plant where size/weight/cost of anexplosion proof enclosure was too much. We used a pressure monitor and an alarm if the pressure dropped below 1/2 psi. This might be your best option. A mile of hydraulic line could get pricey, not to mention inefficient.

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If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[waross]

Is this a sewer cleaning or repair project Keith? Is there any access to the tunnel other than the entry?
A little more detail may help. I'm still thinking.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

It's a tunnel job so there are no additional accesses. "Foot-by-foot", is because it all has to move in steps of some dimension.

It isn't drilling or air would make tons of sense.

Hydraulic:
Straight hydraulic sounds simple. Just pipe and oil. You can get quick connects or valves for each length of pipe. Use a hundred feet of hose and once you've advanced 100ft add another hundred feet of pipe. Step and repeat. I would expect tunnel people to have the means to move 20ft lengths of that pipe with no problems. Add the hundred feet sections in 20 foot lengths. With a quick connect or valve at the last point to make it easy for the next cycle of pipe.

Electrical: The energy is much less cumbersome to transport. But it still seems to be a tougher solution to me. What size cable do you need for a mile of feeding 50hp at 480? A higher voltage would get us into MV which needs to be avoided for technical reasons. You have the same sort of issues with extending the cable as you do with pipe. Can you drag a mile of whatever you use or will you damage it pulling on it? If you add sections of it, you need someone on site capable of making the splices. Then as you add lengths you have additive voltage drops that must be dealt with.

All the EXP stuff I've done required rigid conduit. Can you use unprotected cable? I doubt it.(?) Armored cable probably. Is the required cable, with any connectors, going to actually be less expensive than hydraulic pipe?

Then you need the motor starters in EXP flavors. I guess you could leave the motor starters outside? You would probably still need disconnects at the motors. Are there EXP disconnects?

Large EXP enclosures are really pricey aren't they? Like many thousands of $$$?







Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Explosion proof starters.
I may investigate the possibility of using a purge system on the starters to avoid the cost of EXP.
Cables.
In Canada TECK cable is widely used and is available for use in hazardous locations. The construction of TECK is similar to ACWU 90 (Armoured Cable, Wet, Underground., NOT Aluminum Cable as some electricians will argue) In ACWU the armor is wound directly over the conductors. In a TECK cable there is a fairly heavy extruded neoprene jacket over the conductors. Then the armor is applied, followed by an overall jacket of PVC.
Voltage drop. I would limit the 480 Volt cable length to several hundred feet. The exact distance will be a compromise to be determined in the detail stage of the design.
I visualise a purge protected enclosure(s) with a transformer and motor starters. The supply voltage would be 4160V or more. Cable lengths would be joined by explosion proof connectors. There is a type of connector available that is similar to a welding plug. The female end is dead until the male end is inserted. When the male end is fully inserted, a mechanical interlock is released and a section of the body may be rotated to close the internal switch and energize the connection. (I hope that description gets by everyones IT filters ).
The cable lengths will be about the same as the 480 Volt working length.
Another advantage of this solution is that the switchgear may be kept back from the work area.
You may have serious environmental issues when the hydraulic system inevitably leaks.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[JohnWaa]

Either way you are going to have losses, but with electricity you can't easily add sections of cable (ever make up an armored cable? It's a bear).

As much as I hate hydraulics, I would say that in this case it's the easier of the two options.

 

[ScottyUK]

Keith,

You might want to Google "gate end box" and see where the links lead you. The GEB is the primary distribution at the end of (typically) an 1100V feeder from which mining plant is powered. It's usually a massive piece of hardware: 2" thick steel casing housing switches or breakers and a transformer, with connections made by armoured connectors.


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