Wednesday, September 26, 2007

Conduit for the gas network in St Nom / Conduit pour le réseau de gaz a St Nom

Yellow gas conduit Large gas conduit in St Nom

I left the house this evening with the car and drove past the church right at the bottom of our residence. There was a whole area cordoned off around a fresh dig and a roll of yellow conduit. The dig was ready to go under the exact street that we would have to cross to get to the exchange.

In France (and probably other places) builders are required to use a certain color of conduit to put in the ground so that other workers will know what it is if they come across it in their own digs.

I knew that red was for electricity and blue was for water but I wasn't sure what yellow was for. If it was for telecom I would have taken the day off tomorrow and asked the construction crew how I could possibly lay my own conduit quickly next to theirs. If I could get across the main street the next little bit to the exchange would be much easier.

I was already planning on calling Vincent MONVILLE for something unrelated and thought if anyone could tell me what the yellow color represented he could. I asked him about the conduit and he explained that is was for gas. He chuckled when he said that it's not a great idea to try and mix fiber and gas. :)

So close...


Zed said...

Can't say why Vincent thinks gas and fiber do not mix. You can actually even install fiber optic cable within a gas pipe.

Obviously you need a non-metallic cable construction and ahere to safety codes and other directives, but different utilities are often installed in the same trench due to the cost savings.

- Zed

Tad said...


Thank you for the comments. I probably didn't explain well in the post.

Gas and fiber wouldn't work in my circumstance (with my contacts and my resources). I assumed at the time that's what Vincent was referring to.

There certainly are some interesting and innovative ways people are laying fiber. They're just beyond the scope of my little project.

Stéfan said...

Can you give more details about why you couldn't lay your duct next to the gas conduit ?
In theory there's no problem in having gas and telecom ducts in the same trench, so it's interesting to know what the difficulties are in real cases like yours.

Zed said...

I surmise Tad meant that he didn't have the time or the resources to do a co-location deal with the gas company.

Tad said...

Zed's right. It's a little too early for me to be trying to negotiate with the gas company for them to allow me to lay conduit next to theirs.

I think I'd probably need the business license ready before I could approach any other infrastructure providers about working with them. The mayor certainly made it clear that I couldn't get any permits to cross streets myself without it.

I was going to walk down tonight to see because I figure they've probably filled back in the hole already. It's just a bit too early for me...

Vincent said...

I meant that it is never a good idea to install whatever in the same trench as gas. Not only fibre.
There is no technical difficulty, for fibre is filled with light and not electromagnetic field, electricity and so on.

Gas companies require a security distance between their network and any other for safety reason. They don't want maintenances to take place around their network for they are responsible in case on accident.
For water ducts, for example, there is another technical constraint : No other network above. This time, it is for their repair conditions : They use machines to pick up their ducts from above.

Hope it is clearer now ;-)

Zed said...

For the record: I am not familiar with French construction regulation. I no not work with gas companies, as gas is a secondary energy supply in my market.

With regards to gas, I understand safety concern and sympathize with the gas company's plight. However from an economical point of view trench sharing is so effective that it would make sense to place fiber optic ducting at a safe distance in the same trench with enough access points at a safe separation distance. Thus if there is need for restoration or rerouting you could just use the access points and if need be abandon any damaged trench between access points and retrench just that bit. You end up with huge savings even if you have to do a bit or retrenching now and then.

All of the above is in the end a bit of overkill. You could just use the same contractor that the gas company uses to do your restoration. No need to retrench and no worries that an unexperienced contractor would damage the gas utilities.

Now water is another story. We've placed 300+ km of fiber optic ducting in the same trench with water and sewage without any problems.

- Zed