Minimum Head Room for maintenance only access in process plant 1

[Jaanos]

Hi all,

I have spent a couple of hours searching for this answer but cannot find anything solid.

I have a piece of equipment that requires access for maintenance only. The mechanical location with regards to other equipment and vertical space constraints means we have to minimize the headroom available for maintenance activities (replacing wear parts, etc). It is not a means of egress.

The project is in Idaho USA so falls under AISC and OSHA which I have searched to no avail.

What, if any, other parameters are important to this? Any help or advice would be much appreciated.

Cheers.

http://www.eng-tips.com/viewthread.cfm?qid=16567

 

[SlideRuleEra]

What you are describing could be considered a "confined space". OSHA does not require a minimum size for a portal to a confined space but does make recommendations:

(3) Portal size.

(a) Restricted -- A portal of 24 inches or less in the least dimension. Portals of this size are too small to allow a rescuer to simply enter the space while using SCBA. The portal size is also too small to allow normal spinal immobilization of an injured employee.

(b) Unrestricted -- A portal of greater than 24 inches in the least dimension. These portals allow relatively free movement into and out of the permit space.

Since recommendations could be made into requirements in the future, I suggest going with the unrestricted size, a little over 24" in the least dimension. (A thin wall, nominal 26" diameter steel pipe has an inside diameter of a little over 25").

Here is the link to the OSHA criteria, near the bottom of the page: Non-Mandatory Appendix F -- Rescue Team or Rescue Service Evaluation Criteria

Edit: Rereading your post, I see that you are asking about headroom, not a portal. However, IMHO, the same criteria would apply. Minimum (unrestricted) headroom would be just over 24", as long as the horizontal clearance is greater than 24".

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[Jaanos]

Thanks so much for the reply.

I am Australian and new to the 'American' way of doing things so please bear with me..

Regarding an area that is classified as an 'unrestricted confined space' - what additional controls are required by OSHA when entering this area to perform maintenance works, etc? Would a safe work permit need to be in place prior to any work being performed? If so I am assuming the area would need to be isolated to prevent unauthorized entry?

The process plant is also part of a mining operation so would fall under MSHA - whos guidelines and website is even harder to navigate than OSHA's..

Thanks again for your help, most appreciated.

 

[Jaanos]

From OSHA:

https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9797

1910.146(c)(7)

A space classified by the employer as a permit-required confined space may be reclassified as a non-permit confined space under the following procedures:
1910.146(c)(7)(i)

If the permit space poses no actual or potential atmospheric hazards and if all hazards within the space are eliminated without entry into the space, the permit space may be reclassified as a non-permit confined space for as long as the non-atmospheric hazards remain eliminated.

So I'm assuming such a space (platform area in a process plant) is adequate to be classified as non-permit and therefore does not require a permit or any other restriction?

From the post referenced above though:
under 1910.179, "Overhead and Gantry Cranes", the statement is made "Where footwalks are located in no case shall less than 48 inches of headroom be provided."

7'6" is too high but I think 48 inches is a bit low for the work to be comfortably performed. A number around the 60 inch mark (5 foot) should be ok as the operators will need to be inside the machinery (isolated obviously) anyway and this number fits the current vertical height constraints. I just want to make sure we are not designing something outside code - or something that is going to require an hours worth of permits and safety briefings in order to enter.

Thanks again.

 

[SlideRuleEra]

You are welcome. There are specific confined space entry requirements. Most of them are pretty much common sense. Using Google will take you to many. Keep in mind that OSHA rules are for safety. Design of equipment for reasonable accessibility is another field, Human Factors & Ergonomics Engineering.

Also, there is nothing mandatory that requires maintenance to be performed while standing. For example, consider some heavy equipment maintenance:

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[racookpe1978]

Confined space access DOES require hours of permits and controls (and continuous monitoring) for access. But those rules are set up because of the many deaths that have occurred when maintenance, surveys, instruments, valves are put in limited access areas with POTENTIAL dangerous or hazardous or flammable gas buildup, or gas stagnation (no oxygen) in the confined space access area.

What exactly IS the maintenance, and who have you talked to on the maintenance teams that will be doing the work?
How often will it have to be done?
How much does lost time (wasted or extra time doing this job) cost per hour of shutdown time?
Is this maintenance EVER the critical path on the plant outage?

A poorly planned maintenance area COSTS LOTS OF MONEY, time, and effort that will make your maintenance costs skyrocket. Or not get done at all. Or not get done the right way.

 

[thaidavid40]

If this is an ope structure, and access is the only consideration, I would use 6'-6" as the minimum headroom - if conditions will allow. That would allow 95% of all workers, with hard hats on - to comfortably access the work areas underneath, standing erect. Anything less than that is a judgement call, and it would be up to the end users and the engineer to come to a consensus understanding of what will be provided.
Dave

Thaidavid

 

[SAIL3]

the OP mentioned a platform....where on the platform is this headroom problem?....is it a walk-thru or deadend location?....what min headroom height are we dealing with?....alot of times these process plants are able to get fast code exemptions ....so, if it looks like one is needed then contact the plant and local code entity to start the ball rolling.....

 

[bridgebuster]

As racooke1978 pointed out, talk to the maintenance crew. I've done quite a few small renovation projects for WWTP's and it's always been beneficial to talk to the foreman and crew about their needs.