Sealed gates

[2011dandd]

Hi guys

Finally got round to Welding up my box section gates. I was told to consider a small drilled pressure relief hole to allow for air pressure build up when welding it all up as they will be completely sealed owning to the fact they are mitred all way round.

Seemed a bit excessive to me. Is this common practice?

 

[Mark 2]

Yes, or they rust from the inside.

 

[nickk]

You’ll still get condensation inside.

 

[Onoff]

Squirt ACF50 inside the box sections I would.

 

[voipio]

If the structure is completely hermetically sealed, then no hole should be necessary. Any moisture trapped inside will react with the metal and with any remaining oxygen, to form a thin film of rust, and then the reaction should naturally run itself out. If the plan is to have the gates galvanised, then it's a completely different story, as the galvanisers won't touch it if there are no suitably placed vent holes. There have been too many explosions in galvanising baths in the past. The internal pressure would rise quite dramatically at the galvanising temperature and, with the added heat-induced stresses, any slight failure in a joint could have catastrophic consequences for personnel at the galvanising plant. .

 

[500e]

Did some hand rails round a flat roof patio was sitting in flat one Sunday afternoon LOUD bang like 12 bore.
Went out could not see anything amiss till 2 days later a HR upright had a vertical split over 50mm long on a corner of 50 x 3mm box

 

[2011dandd]

Cheers all much appreciated

 

[frank horton]

just get em galvanised.....
On something like that I use 6mm holes so the galve can get inside easily plus let the air out when dipping.....
Most galv firms will inspect for vent hole and charge extra if they have to do it...

 

[roofman]

How long are you planning to live

 

[pedrobedro]

Hi guys

Finally got round to Welding up my box section gates. I was told to consider a small drilled pressure relief hole to allow for air pressure build up when welding it all up as they will be completely sealed owning to the fact they are mitred all way round.

Seemed a bit excessive to me. Is this common practice?

I've never bothered it seems a bit of a non problem to me. The pressure inside the tube or pipe has never interfered with the weld.

 

[pedrobedro]

Did some hand rails round a flat roof patio was sitting in flat one Sunday afternoon LOUD bang like 12 bore.
Went out could not see anything amiss till 2 days later a HR upright had a vertical split over 50mm long on a corner of 50 x 3mm box

How f$%kin' hot was it that day ? You would need steam boiler pressures to do that kind of damage to 3mm