Coring 90mm MVHR holds in 254x254uc73 steels onsite - between posi joists - help :-(

[DeanAlan]

So, my mistake.

When working with the SE, SIPs designer and steel worker, and MVHR designer it was just looking too complicated to core the holes in the steel during fabrication to line them up with posi joists so, when I asked could that be cut on site to "yes", I deferred to gut those cores down in place.

 

Here I am and people sucking air between their teeth all over the place.

 

Any thoughts on how these can be cut? We don't have the height to run the ducts under the beams and there are 3 places where there are no stud walls to hide them in.

 

Some folks have said torch cutting would be possible but dangerous. Some have said a mag drill might fit.

 

Really appreciate some help here on suggestions. Thanks

 

[markc]

Hole saw, starrett ideally as a lot of the others just can’t hack it. Slow drill speed, plenty of water to keep teeth cool and well braced for when it snags, or use a drill stand held in place by a bolt.

we have done hundreds of service holes through webs like this

Edited November 7, 2022 by markc

[Moonshine]

What is the view like from the other side? is access better?

 

Assuming the that the SE is happy with holes in the beam, how about investigating putting rectangular holes in them, and changing from circular to rectangular ducting just in those sections (makings sure that the MVHR engineer is happy with the rectangular area).

 

That way a nice 4.5 inch grinder with metal cutting disc would make some progress through them. though lots of eye, hands and hearing protection needed.

Edited November 7, 2022 by Moonshine

[Mr Punter]

I have used a hole saw on steel beams, but only 40mm or so.  You may get up to 60mm with a mag drill but I don't think it will fit.  I would be pretty pissed off with your so-called professionals leaving you with such a ball-ache of a job.  Lazy bastards.

[DeanAlan]

@markcthanks - been looking at hole saw or annular cutter as a step up. Not sure there is enough space to get a mag drill so would need some other bracing. Doubt I could apply enough pressure.

 

You are based in west yorkshire 🙂 fancy a trip down to Cambridge.

 

The SE designed the beams for max of 3 90mm holes in centre of beam and we are less than than and off to the edge which is better. Challenge is just making the cuts.

 

@Moonshinerectangular cuts would be bad for the steel at the corners so I'll steer away from that but keep um coming. 

 

I was wondering about drilling needle holes and then hacksaw them connections. Labour intensive.

[Temp]

I've no idea if this is worth trying or waste of money but only £26...

 

https://www.amazon.co.uk/sourcingmap-Carbide-Cutter-Drill-Stainless/dp/B07FMQPXSQ?th=1

 

For pressure jury rig some sort of lever from 2x4. One man on the drill, one on the lever, third on the hose?

[Adsibob]

Have you considered getting a few adaptors that can split the tube into two or three smaller ones, go through and then coalesce into one again. A 90mm diameter pipe should have the same flow as three 52mm diameter pipes, or thereabouts.

[Moonshine]

1 hour ago, DeanAlan said:

 

 

@Moonshinerectangular cuts would be bad for the steel at the corners so I'll steer away from that but keep um coming. 

 

I am obsessed with grinders 🤣

 

This is probably too much work, How about metal cutting out slits of 100mm which rotate every 45 degress and enlarge the hole that way

[markc]

@DeanAlan no need for a mag drill, just an ordinary (decent size) rotary pistol type dril. You don’t put any weight on it, let the cutter do the work. Think the most awkward one I’ve done was on a ladder, 150mm diameter hole into a 300mm diameter steel tube with 20mm wall thickness. Took about 30 mins.

[DeanAlan]

2 hours ago, Moonshine said:

I am obsessed with grinders 🤣

 

This is probably too much work, How about metal cutting out slits of 100mm which rotate every 45 degress and enlarge the hole that way

I sense your obsession 🙂 

 

1 hour ago, markc said:

no need for a mag drill, just an ordinary (decent size) rotary pistol type dril. You don’t put any weight on it, let the cutter do the work. Think the most awkward one I’ve done was on a ladder, 150mm diameter hole into a 300mm diameter steel tube with 20mm wall thickness. Took about 30 mins.

Well Markc - you make is sound too easy. I hope you are right.

I'll let you know how I fair. Speaking with my fabricator tomorrow to see what he is thinking.

[Miek]

Your steel has a Web thickness of 8.9mm and at 90mm a HSS hole saw will do this easily. As @markc said, get a Starret one and use at low speed. Do not push too hard or you risk damaging the teeth and keep it straight. Get a can of aerosol cutting oil to make life easy. I reckon 5 mins per hole max. 

 

 

[DeanAlan]

Thanks all.

 

My steel fabricator came around today to take a look. He also says a hole saw will do it, it will take time, access might be awkward and I have 11 of them to do. I told him to do the first one and I'll do the rest with his kit!

 

I'll let you know.

 

cheers,

- Dean

[Andehh]

Good luck! 

[George]

Just to check... The structural engineer has given the OK to cut a hole in the steel beam? 90mm is over a third of the depth which is the point I'd get a bit wary. Plus needs to be away from point loads/supports 

[markc]

At 1/3 of web depth a circular hole is nothing. The web is only there to keep the flanges apart. But as above, they should not be a point loading locations

[Russell griffiths]

PEasy, done it before. 

Go and buy a cheap power drill with a clutch, slow cutting and lots of cutting fluid, get a squirty bottle for the fluid, and a mate to squirt it. 

 

Edited November 9, 2022 by Russell griffiths

[Onoff]

 

[markc]

I want one!

[saveasteading]

3 hours ago, markc said:

At 1/3 of web depth a circular hole is nothing. The web is only there to keep the flanges apart. But as above, they should not be a point loading locations

Good info, although a third is more a maximum than 'nothing' if the beam is economically designed.

To which I add that multiple holes are an issue too. Big holes need to be a long way apart, small ones  not so much. Say 1m. As with all holes in beams and joists..keep them at mid height, and towards the ends rather than central. Otherwise the web may fail.

[DeanAlan]

The SE designed the steels to accommodate up to 3 of these holes in the centre of the beams (worst location). In 2 of the beams I do need need to put 3 of these holes but they will be far apart from each other and not need and connection points.

 

As to economical designed - I think the general consensus is that SE don't do that. Tendency is to go to other way!

 

I'll let you know how things shape up (round and full of holes hopefully)

[saveasteading]

2 minutes ago, DeanAlan said:

think the general consensus is that SE don't do that.

Not fair. An SE can optimise the design if confident it will be properly installed, and not have holes cut in it.

I have seen electricians cut lumps out of the bottom flange of a steel rafter.

 

Default may be to design a size up when the contractor is as yet unknown.

If you want a lean design,  tell the SE you are personally supervising and then supervise. 

An SE working for a main contractor can more safely do this...but then the end user comes along.

 

So on second thoughts you are not wrong . SE generally assumes some overdesign is prudent....

 

 

[Pocster]

1 hour ago, Onoff said:

 

I asked for one at my local hss hire shop - they told me to (expletive deleted) off 

[markc]

Yes an SE dealing with buildings tends to (and rightly so) err on the side of caution. Asked to look at a sagging ceiling/cracks in plaster etc. and they had a 3m pool in a bedroom with around 500mm of water giving a mass of around 3.5tonnes. 
now I’m not a SE but do carry out a lot of design and testing of lifting equipment usually where transport weight is critical so optimising design is much more important.

[Dave Jones]

is there not a stud wall anywhere under that steel you could lose the duct in ?