conduit work

[Billythekid]

Some basics:

For 90 degree bends (back of bend)

Start with a scrap piece of conduit preferably >1m. make a mark at a set distance from end (say 500mm). Put conduit in bender and line up with the start of your former, bend to 90, and remove from bender. Place conduit on floor and measure from back of bend (floor) to the end that you measured from. Say it's 448mm, this will give you a 'take up' of 52mm. Next time you simply add this 'take up' to your required distance, and you should be within a gnats tadger . Would note above only applies if you are measuring from rear of bender (handle end).
If measuring from front of bender make your mark and slide through untill level with back of former + your conduit size (use an offcut of same sized conduit and level if unsure).

For offsets using 30 degree bends

Firstly the multiplier for 30 degrees is 2. So however much you need to offset conduit by, simply times it by two. i.e if you have a 200mm obstruction/level change, mark your bends 400mm apart (200 x 2).

For 45 degree bends just change multiplier to 1.41.

There truely isn't a set of instructions for conduit bending, and as previous members have stated "practice makes perfect". Gain and shrinkage should also be considered, but is often forgotten. hope this helps to reduce your wastage a little.

Kind Regards

Billy

 

[Engineer54]

Sadly a lot of these skills are now dying off. Too easy to buy pre-made bends and angles an just screw them all together, a run comprising solely of bends looks a hell of a lot more professional.

I haven't been on a project for donkey's years now that allowed ''inspection bends or T's of any description (apart from T conduit boxes) to be used in conduit installation. They can rip the cables insulation to shreds. Another thing to remember, every screwed fitting in a conduit run will add a potential snagging obstacle for draw lines and cables alike. They should always be kept to the bare minimum....

Saying that a conduit installation looks more professional with these pre-formed bends etc has to be the joke of the week. They look anything BUT professional!!!
They look what there are, ...a conduit system that's been installed by Amateur that hasn't got a clue about conduit work!!

 

[Silly Sausage]

They look anything BUT professional!!!
They look what there are, ...a conduit system that's been installed by ammeter that hasn't got a clue about conduit work!!

Hardly surprising, currently they're only good for electrical work!

 

[Richard Burns]

Saying that a conduit installation looks more professional with these pre-formed bends, etc. has to be the joke of the week. They look anything BUT professional!!!
They look what they are ...a conduit system that's been installed by an amateur that hasn't got a clue about conduit work!!

I think Strima was agreeing with you and saying that a properly bent conduit system looks more professional than pre made bends.

 

[Engineer54]

I think Strima was agreeing with you and saying that a properly bent conduit system looks more professional than pre made bends.

Didn't come across to me that way, but if i was mistaken then i whole heatedly apologise.

Perhaps i need another coffee this morning, to wake me up... lol!!!

 

[Engineer54]

Hardly surprising, currently they're only good for electrical work!

Never seen conduit used to carry water, or anything else come to that... lol!!!

 

[somersetsparks]

I haven't been on a project for donkey's years now that allowed ''inspection bends or T's of any description (apart from T conduit boxes) to be used in conduit installation. They can rip the cables insulation to shreds. Another thing to remember, every screwed fitting in a conduit run will add a potential snagging obstacle for draw lines and cables alike. They should always be kept to the bare minimum....

Saying that a conduit installation looks more professional with these pre-formed bends etc has to be the joke of the week. They look anything BUT professional!!!
They look what there are, ...a conduit system that's been installed by Amateur that hasn't got a clue about conduit work!!

Indeed, even on the prisons 'special permission' has to be gotten to use inspection elbows, Tee's and inspection bends I have personally have hardly ever used in fact only when wiring a conveyor as there was just no room for besa boxes.

 

[Engineer54]

Indeed, even on the prisons 'special permission' has to be gotten to use inspection elbows, Tee's and inspection bends I have personally have hardly ever used in fact only when wiring a conveyor as there was just no room for besa boxes.

Inspection elbows were/are the worst for shedding solid core singles insulation. Though, i expect the reason for not allowing them in HMPS hotels, is to stop inmates from gaining access to wiring, rather than anything else!! lol!!!

They were designed for just such situations that you describe above , ...for tight connections on machinery and the like, normally on entries to accessory boxes such as em stops etc...

 

[somersetsparks]

Inspection elbows were/are the worst for shedding solid core singles insulation. Though, i expect the reason for not allowing them in HMPS hotels, is to stop inmates from gaining access to wiring, rather than anything else!! lol!!!

They were designed for just such situations that you describe above , ...for tight connections on machinery and the like, normally on entries to accessory boxes such as em stops etc...

All screws must be replaced with security ones, the spec for which changes from job to job, pretty much every one they use though is included in the £1.99 toolstation set!

I personally hate inspection elbows, bends and tee's as they make for more awkward wiring even with stranded singles, however sometimes they are the only option.

 

[dpiers1980]

i got a load of scrap out of bin at college and had a good go at it first before doing a set we were going from consumer unit into garage unit i put a set at both ends and it looked mint i wont lie i got it right the second time but on those small bays they have at college nobody bothered they just used hospital saddles. But when asked why i did like that i said in the real world you would have it set into unit then into consumer unit and i wanted to learn i was right they were wrong. On a 90 bend i bent to what i thought was 90 then went past a little and put it against a plum wall and it looked good. There is a good book JTL installing Electrotechnical systems and equipment has a good section on it

 

[johnboy6083]

im pretty good with conduit, in fact all steelwork, but the one thing im not 100% on is bubble sets. I can do them, but doing them to fit in an exact place, without cutting the tube to measure is a pain. Its not something i have to do often, so i dont get to practice it. It still looks ok, but i can see its 5-10 mm one way or the other, not central.
Im the only spark on site most of the time, and the others sprks are worse than me anyway, so its not like i can ask for pointers. Ill wait till i see an old boy about at some point and get him to walk me through it, so i get it perfect

 

[cogsey133]

Conduit work is a skill...the old boy who taught me bent it using a piece of wood with a hole the size of the conduit drilled in it; then i had to copy what he showed me before i was allowed near a conduit bender! remember it becomes slightly different beast (regards your way of thinking and approach) when you have to put the conduit in the bender and bend it upwards instead of down.....lol Using the bender to take out over bend or put a bit extra into it or to straighten your bend is also a good skill to have.

 

[Bick]

What's the shrinkage values for 20 and 25mm conduit? anybody know? the vids and pages i've looked at mostly give imperial measurements for shrinkage.

 

[Bick]

Should've put for 30 degree and 45 degree angles .......I've worked it out to be 25mm/1cm rise for 30 degrees and 40mm/1cm rise for 45 degrees, someone let me know if that is accurate or not.....also trying to get my post count up to post a couple of pics that could be helpful.

 

[somersetsparks]

im pretty good with conduit, in fact all steelwork, but the one thing im not 100% on is bubble sets. I can do them, but doing them to fit in an exact place, without cutting the tube to measure is a pain. Its not something i have to do often, so i dont get to practice it. It still looks ok, but i can see its 5-10 mm one way or the other, not central.
Im the only spark on site most of the time, and the others sprks are worse than me anyway, so its not like i can ask for pointers. Ill wait till i see an old boy about at some point and get him to walk me through it, so i get it perfect

Bubble sets are difficult to me as well, I can get them reasonable, but only if I start with bubble and put any other bends in after and double bubble..... well lets say I have only managed it perfectly once! I work with an old boy who can do even double bubbles perfectly every time with just the measure between the tubes! However he's not much of a teacher and as with most conduit work a lot of it is experience and hard to teach