Trenches vs. Duct banks

[Okpower]

I am designig the electrical installation of a Gas Compression Plant, and I decided to run 13.8 KV, 4.16 KV and 480 Volts cables, in sand trenches with concrete covers. But the client wants concrete duct banks. I am compiling my arguments to defend my sand trenches decision and I can mention:
- Quicker installation.
- Lesser cost.
- Better cooling or temperature behaviour.

The client says that cables replacement or future cables installation in sand trenches is more complicated than in duct banks.

Some arguments to defend (or to discard) the decision will be appreciated.

Regards

 

[rbulsara]

Why argue with the client? Is he not willing to pay?

Duct bank is superior and safer to direct burial. I would not try to "defend" it. You can gracefully say you see the value in client's opinion and will confrom to his/her request.

Plus your client's argument is right one too. Your arguements are for a cheap and dirty job not for a better and safer installation.

 

[davidbeach]

Why are you arguing with the client, and why oh why would you even think of direct bury in an industrial installation?

Maintenance and serviceability far outweigh the transitory benefits(?) of a cheap installation.

 

[dpc]

The only possible technical advantage for your sand trench might be higher cable ampacity if supported by Neher-McGrath calculations.

Otherwise, I agree with your client. Don't forget to include spare conduits and apply appropriate de-rating factors. Also, you will need to isolate the 480 V cables from the med-voltage cables in manholes, etc. Or preferably, use separate manholes.