Manhole for existing ductbank

[greenspark1]

Hi. We have a job with an existing 15kV underground ductbank (4x 4" conduits) that we want to splice to a new building. Minimizing downtime is of course a priority so I'm looking for a manhole we could drop over the existing ductbank and then expose the conductors to splice into. I haven't had much luck finding this online. Anyone had luck with similar situations?

 

[dkidd]

The only time I had to do that they had to cast the new manhole in place.

 

[NewtonLaw]

Hi. We have a job with an existing 15kV underground ductbank (4x 4" conduits) that we want to splice to a new building. Minimizing downtime is of course a priority so I'm looking for a manhole we could drop over the existing ductbank and then expose the conductors to splice into. I haven't had much luck finding this online. Anyone had luck with similar situations?

We did this exact type of work many times in the LTN systems located in most major cities with manhole and duct systems. I would suggest you purchase a pre-cast manhole, http://www.utilityconcrete.com/Handholes?catid=26#!, and install it such that the incoming line is on one side of the new manhole. If using precast, you will have to dig a hole both under and around the existing duct to allow for maneuvering the precast in place. We would under dig the duct, the hole to one side was as big as the hole to be placed around the existing duct, pour a new concrete pad. This pad becomes the slide pad to move the lower half of the manhole in place. Cut the necessary notches on the upper half and lower it into place.

No cheap and not easy, but since yo do not take an LTN out of service, an option. Last of course, build a new manhole around the existing duct work. Consider that cost versus taking an outage or running a temporary over-ground supply. (Cheapest option if you must remain in service.)

Hope this helps,

Newton Law

 

[greenspark1]

We did this exact type of work many times in the LTN systems located in most major cities with manhole and duct systems. I would suggest you purchase a pre-cast manhole, http://www.utilityconcrete.com/Handholes?catid=26#!, and install it such that the incoming line is on one side of the new manhole. If using precast, you will have to dig a hole both under and around the existing duct to allow for maneuvering the precast in place. We would under dig the duct, the hole to one side was as big as the hole to be placed around the existing duct, pour a new concrete pad. This pad becomes the slide pad to move the lower half of the manhole in place. Cut the necessary notches on the upper half and lower it into place.

No cheap and not easy, but since yo do not take an LTN out of service, an option. Last of course, build a new manhole around the existing duct work. Consider that cost versus taking an outage or running a temporary over-ground supply. (Cheapest option if you must remain in service.)

Hope this helps,

Newton Law

??LTN??
Thanks for the responses, definitely helps. It does sound like an involved job, but avoiding downtime is worth big bucks.

 

[NewtonLaw]

LTN

LTN

LTN - Low Tension Network - a term used by most Utilities to describe an underground supplied grid usually connected as a four wire grounded Wye system at 208Y/120 volts. The smallest one we have consists for 15 transformer vaults supplied by four primary cables. Each of the transformers are connect via an NWP (Network Protector - large amperage switch relay controlled to close on differential voltage and open on reverse current to the transformer). All secondary cables are connected together making up a low voltage (low tension as opposed to high tension, 69 kV to 750 kV overhead transmission lines) grid. The grid is often made up of multiple conductors running from manhole to manhole. Most manholes have a ring bus from which a service is supplied to the customer. The grid is always hot since dropping it out of service will mean loss to an entire city, like New York or Philadelphia, etc.

Hope that explains it well enough.

Newton Law