nothing platform members 1

[picasa]

On platforms on towers, you are trying to get your pipe thru some area. You see a platform member interfering with the pipe. Notching the member to create room for pipe is a lousy way and I am against it. What does OSHA have to say about it or any other authority for that matter. Once you notch, you are talking about stress concentrations and vibrations transmitted to the member when tower is in operation etc. Let me know what you think.

 

[codeeng]

If this is still in the design stage I suggest you talk to your piping group to have the pipe relocated or move the beam. If this needs to be fixed in the field perhaps you could flip the beam to the other side of the vessel clip or bend the clip slightly. The last thing you want to do is notch the beam. Have a structural engineer look at it.

 

[picasa]

well the beam that I am talking about is the rolled L angle that goes around the vessel (It is a circular platform on a tower). So moving the pipe is the only solution. Any more thoughts?

 

[jte]

Ok, now we're getting some more details on this issue. So you are not talking about the brackets (the main cantilever beams which connect to the vessel clips) but about a secondary beam which carries the load from the checkered plate or grating to the brackets. In this particular case it is at the ID or OD of the platform. Chances are that the angle (L beam) has a 4.5" minimum leg pointed up. This construction is a frequently used combination which satisfies the need to transfer the load from the checkered plate or grating to the brackets and complies with the toe board requirement per OSHA. See

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9715

in particular, 1910.23(a)(2) and (e)(4).

Last time I checked, piping configuration governs platform design. You build the platform to access the piping connections, valves, and vessel manways. So the platform is built around the piping. Easy enough for new construction. Sounds like you have a retrofit issue. Deal with it. Make the notch, provide adequate beams to transfer the structural load, and add a bent flat bar collar to handle the toe board requirement.

Notching the angle will reduce its strength. Evaluate if the strength is necessary at the point in question and replace that strength or otherwise reinforce as required. I've never heard of a fatigue design on a ladder and platform. Yes, they shake, but for the most part they are loaded only by dead loads while they are designed for dead (roughly 20% of the total) plus live (roughly 80%)loads. So for most of their life vessel platforms are severely understressed. As with anything, someone will find an exception, but the generality stands.

Dealing with relocating a bracket on an existing vessel can be a bit more involved, but modifying secondary structural members to accomodate piping is routine.

jt

 

[codeeng]

Without specific info on the size of angle, span, loading and notch details you should still seek the advise of a structural engineer. There will be lots of options since you are not touching the vessel.

 

[jte]

As codeeng pointed out, a competent structural engineer provided with sufficient details and design data should be able to design a modification. So should a competent mechanical engineer who deals with vessel and L&P design.

jt