Beam web penetrations

Date 10-22-2013 17:48

We are being told by the EIC on a structural building to perform some beam web openings for piping in the field. The problem is that he will not allow us to use a oxy-acetylene cutting torch " You can't use it because your going to destroy the steel around where you cut out the hole". He will only let us use a plasma system. Of course the erector doesn't have a plasma out-fit, so to him it would be a huge extra. We cut beam web openings in the shop all the time with oxy-fuel, along with copes per AWS D1.1. How would you handle a case like this?

By G.S.Crisi (****)

Date 10-22-2013 18:27

My opinion, based in several years spent in erection of heavy industrial plants.
The expression "destroy the steel" is too heavy. What you're going to do at using oxyacetylene is to increase the steel grain size and its carbon content. This, however, will take place in a very narrow thickness around the hole wall, say a few tenths of a millimeter.
So, to avoid endless discussions and keep your client happy, what you can do is to grind those few tenths of a millimeter off with a grinding wheel. Now, your client should know that by using plasma you'll avoid the increase of carbon content, for there is no carbon in plasma, but not the grain size increase, which is due to heat absortion by the base metal.

Comment nº 1. Does the structural steel designer know that you're going to cut holes in the beams webs? You better make sure.
Comment nº 2. You say that you cut beams web openings in the shop at all times. The reason is that there are no naughty inspectors fooling around.

Giovanni S. Crisi
Sao Paulo - Brazil

By Superflux (****)

Date 10-22-2013 20:54

Keep him happy and just rent one for a day or two?

By 99205

Date 10-22-2013 22:00

Might want to check to see if there is, cut hole, roughness language in the contract documents also. I was happy to point that wording to a rude, condescending contractor a few years ago.

By jwright650 (*****)

Date 10-23-2013 11:27

We had to purchase several plasma torches for jobs just like the one you speak of...in our case, it was the EOR who specified in the job specs that all beam penetrations(web openings) were to be cut with a plasma torch, no oxy/fuel unless we were to cut 1/2" long and grind the last 1/2"...nobody in their right mind is going to grind 1/2" off of every cut.

By 803056

Date 10-23-2013 02:28

Is there a prohibition against using an oxy-fuel cutting torch in the project specification? I know of none in AWS or ASME.

It sounds like the individual is imposing his personal preference. Let him know you will purchase a plasma torch and charge it to his employer. Ask him to sign the authorization for the work and the means he has specified to be used.

Best regards - Al

By SCOTTN

Date 10-23-2013 12:46

The answer from your EIC was "you're going to destroy the steel around where you cut out the hole". As opposed to an oxyfuel cut, a plasma cut should be faster, thus reducing the the heat input on the beam web, which, in turn, would reduce the width and depth of the HAZ. Still, a bit extreme in my humble opinion.

By Milton Gravitt (***)

Date 10-23-2013 23:15

Is the beam wide enough for a mag-drill.

M.G.

By jwright650 (*****)

Date 10-23-2013 23:19

Milton,
Web penetrations usually are rectangular(not always though), sometimes they even have stiffeners to frame out the opening.
Ductwork, plumbing, and electrical chases run through these openings.

By Milton Gravitt (***)

Date 10-25-2013 11:23 Edited 10-25-2013 11:25

John , I guess I learn something everyday. Do you think you could use hangers for things like that.
M.G.

By jwright650 (*****)

Date 10-25-2013 11:41

Hi Milton, Yes, they still use hangers to support the plumbing, electrical, or duct work....these penetrations are to save headroom where the plumbing, electrical, or ductwork runs perpendicular to the structural frame steel.