Work In Manhole With Energized Cables

Cables of that age will most likely be lead sheathed so water shouldn't be a problem. But try to avoid moving them in any way.

TonyS,

Where they enter the switchgear, I do not see any lead. Thanks for the input.

--JMM

What level of protective clothing are you planning after the cables are blanketed? I know that 40cal is bulky and hard to work in, but even blanketed, there is significant hazard from a flash/blast. Even blanketed, the requriement for the 40cal might not be relaxed.

Be sure you run an air monitor to measure O2 levels as well as possible noxious gases. I assume this would be part of your confined space procedures, as would be the use of an external rescue system (tripod, winch/cable, and harness) to pull out an unconscious worker if for some reason he were to collapse. Safety first!

PeterT (& also KJK/USA),

Site is pretty strict about following confined space rules. Already opened lid to look in (but not enter), then closed after look/see. O₂ is 20.8%, % LFL 0.0, CO 0.0%, H₂S 0.0%. We will use a tripod & harness, of course.

We have 40cal and 12cal suits, plus 15kV gloves. We have not calculated available fault energy, but suspect is would be quite large. However, with concentric shielded cables, wouldnn't a fault through the dielectric be mostly (if not entirely) confined within the cable? I'm hoping someone could cite rules or policies that are in place where they work, regarding these questions. Range of policies can be from no entry until all cables de-energized & locked-out, to . . . . If shutdown is required, the problem is in trying to plan or schedule any outage long enough to do some work. If that's what has to be done, then that is what we will do; however, I always like to explore the range of possibilities or options before proceeding.

I find it hard to conceive of an installation with a sump pump that requires occasional service and allowing that only with a complete shutdown of a facility that runs 24/7.

Thanks--JMM

Along with the great suggestions above, you may also want to consider one of these.

They are ABSOLUTLY required in my local.

Be safe!

Link: http://www.northernsafety.com/Product/162-7738/DBI-SALA-Confined-Space-7-Two-Way-Tripod-and-Salalift-Winch-System-with-1-4-x-60-Cable

Do you open the re closing circuit to the breaker(s) that feeds these cables?

wareagle,

I assume you are talking about utility line automatic reclosers. This is a customer-owned and customer-maintained site. All breaker operations are manual, with lockout & tagout procedures in place and working.

Mechnical protection of the cable is not a UK requirement but the manholes I've been down, we've used 1 inch marine ply to lay over the cables to offer a further degree of protection to the cables. It stops dropped tools damaging the outer sheath of the cables..

How much work can be completed without going into the hole?

use vacuum device clean and dewater

use camera to perform inspection

if work involves feeding through the manhole can you excavate outside and intercept the conduits you need to use?

Thanks, Natfuelbill,

The manholes are nominally 6'x6'x9'deep. Sump pumps are hard-wired with cords, no plugs; discharge piping cannot be disconnected without being on the fixed rungs in the manhole. Duct bank is concrete encased, so interception is not possible. Inspection with a camera may be possible, but snaking a camera into a duct bank opening 7-8' below and then working with it may be difficult. Clean & dewater with vacuum (and hose to wash muck to vacuum pickup) is a good idea.

--JMM

I have found the best resource is your utility supplier for procedures to handle the job like you've outlined. There are others out there that do high voltage maintenance etc;. I would suggest that given the question you are asking I would contact an outside party to make these repairs. It would be much safer for you and the employees who might be called on to preform a task they are not familiar with.

I like your answer.. GA from me...