Cable tray install

[Isaiah]

The design calls for four 12” cable trays vertically stacked with a concrete wall on one side. The trays are 6” apart with the bottom tray being 5’-0” above the finished floor. All cables are #10 TC cable with an OD of app 0.64”.
I feel like 6” is insufficient vertical space between trays and may result in cable damage during the pulling process
The E&C firm doesn’t want to change their design even though there’s room to do so by lowering the bottom tray etc
Comments?


Sent from my iPhone using Tapatalk

 

[paulengr]

The design calls for four 12” cable trays vertically stacked with a concrete wall on one side. The trays are 6” apart with the bottom tray being 5’-0” above the finished floor. All cables are #10 TC cable with an OD of app 0.64”.
I feel like 6” is insufficient vertical space between trays and may result in cable damage during the pulling process
The E&C firm doesn’t want to change their design even though there’s room to do so by lowering the bottom tray etc
Comments?


Sent from my iPhone using Tapatalk

Can’t be done unless you install and pull one at a time. I’m not even concerned about cable size. But the requirement issue is going to be access. The only thing you did not specify is rail height. On true ladder with 5” side rails it’s impossible except one tray at a time. On say wire trays or the small thin trays that are just a single sheet of aluminum with the sides bent up that’s different and maybe not so bad. It depends on the distance between supports and total weight which you can use. Regardless, what derating are they using? Can you lay cables side by side or do you need to maintain 1 cable width in between? How are you doing this with tie wraps? How are the hills? Do you need rollers in the trays? Any bends? What kind of mess will the supports make doing this? What about stubs? If so you need plenty of access to get your hands and equipment in and out.

I really don’t care if the engineer has to do more work. Constructability is a consideration. Normally you just do one wide tray. Stacking trays is done either to avoid Tees or on a later modification where you can’t just widen the supports easily, so you under/overbuild. It sounds like they messed up the width of the structure. Why not just go to one 36-48” wide tray at 8 feet or multiple trays side by side so it’s not a head knocker? Much easier to build, inspect, and maintain. You can even hang lights on/below it.

 

[Isaiah]

Can’t be done unless you install and pull one at a time. I’m not even concerned about cable size. But the requirement issue is going to be access. The only thing you did not specify is rail height. On true ladder with 5” side rails it’s impossible except one tray at a time. On say wire trays or the small thin trays that are just a single sheet of aluminum with the sides bent up that’s different and maybe not so bad. It depends on the distance between supports and total weight which you can use. Regardless, what derating are they using? Can you lay cables side by side or do you need to maintain 1 cable width in between? How are you doing this with tie wraps? How are the hills? Do you need rollers in the trays? Any bends? What kind of mess will the supports make doing this? What about stubs? If so you need plenty of access to get your hands and equipment in and out.

I really don’t care if the engineer has to do more work. Constructability is a consideration. Normally you just do one wide tray. Stacking trays is done either to avoid Tees or on a later modification where you can’t just widen the supports easily, so you under/overbuild. It sounds like they messed up the width of the structure. Why not just go to one 36-48” wide tray at 8 feet or multiple trays side by side so it’s not a head knocker? Much easier to build, inspect, and maintain. You can even hang lights on/below it.

Great points and I agree completely. The trays can be spaced at 9” or even 12” since they won’t be a head knocker, ie there’s a concrete wall in one side and a walkway directly above the 4 trays.
Rail height is 6” overall with a 5” depth to the ladder rungs.


Sent from my iPhone using Tapatalk

 

[Julius Right]

IEEE 527-2007 E.3.2 Tray system design

In general, vertical spacing for cable trays should be 30 cm (12 in), measured from the bottom of the upper tray to the top of the lower tray.

A minimum clearance of 23 cm (9 in) should be maintained between the top of a tray and beams, piping, etc., to facilitate installation of cables in the tray.

 

[Isaiah]

IEEE 527-2007 E.3.2 Tray system design

In general, vertical spacing for cable trays should be 30 cm (12 in), measured from the bottom of the upper tray to the top of the lower tray.

A minimum clearance of 23 cm (9 in) should be maintained between the top of a tray and beams, piping, etc., to facilitate installation of cables in the tray.

Yep. 12 inches. That’s exactly what I told them in engineering


Sent from my iPhone using Tapatalk