While all points made in this thread are valid, I think that the reality is that if the cables are laid in conduit or pipe which will allow replacement cables to be drawn through if needed later it will probably last for a long time and be cost effective.
Rob On Wednesday, 22 January 2014, Helmut Walle <[email protected]> wrote: > The silicone is not the issue. The point Yuri has been making possibly was > the simple old principle that applies to any sealed cavity: somehow water > will get in, possibly quite slowly, and it may take a long time. But once > it is in there, it will start accumulating at the bottom, and there is no > effective way out. Two very common ways for water to get into hermetically > sealed cavities are condensation of air humidity on the inside walls of the > cavity, and breathing of the cavity due to temperature and pressure > changes. And either means that the water just gets more and more over > time... It just happens sometimes, in spite of best materials and > workmanship. Periodic inspections can make it worse, as there always is a > risk of damaging a seal. There are ways around it: > > * Drain holes at the bottom (but if the pipe is buried in the ground keep > in mind that the holes may turn into artesian wells when the rain saturates > the soil). > * Ventilation / airflow - this is good for removing moisture, even if > sometimes a little bit of water gets in. Obvious drawback: dust and bugs > can get in, unless the intakes are filtered; but in that case you need to > replace filters periodically. Passive ventilation is fairly easy to > implement and has good long-term reliability. However, if the pipe is long > and thin and filled with cables it may not be sufficient to remove all > humidity. > * An automatic pump to remove any water once detected. Disadvantage: > long-term reliability may be questionable. > > YMMV... > > Kind regards, > > Helmut. > > On 22/01/14 10:24, Volker Kuhlmann wrote: > >> On Wed 22 Jan 2014 00:27:22 NZDT +1300, yuri wrote: >> >> Since changing career from sparky to telco tech, I've learned a few >>> things. >>> One of them is that all outdoor conduit will eventually fill up with >>> water, no matter how good you think you've waterproofed it. >>> >> I find it hard to believe that a good layer of silicone sealant will >> last for less than 10 years. If you just stick the pipe pieces together, >> sure, and I wouldn't assume that PVC pipe glue is watertight unless >> there is assurance that all surfaces have been covered fully and are >> resting wihtout gap against each other while the glue sets. >> >> Outdoor rated grease-filled cat6 is a must if you're looking for a >>> long-term solution. >>> Maybe some single-mode and multi-mode fibre if you *really* want to >>> future-proof. >>> >> My really future proof solution fit for long term is to keep the pipes >> accessible. >> >> Volker >> >> > _______________________________________________ > Linux-users mailing list > [email protected] > http://lists.canterbury.ac.nz/mailman/listinfo/linux-users > -- Robert Fisher
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