×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Fall Protection Monorail

Fall Protection Monorail

Fall Protection Monorail

(OP)
thread507-447086: Fall Arrest Anchorage

I'm designing a monorail that will be used as a fall protection device over a train car. The owner wants the system to be designed for an occupancy of 2 people.

My understanding from reading OSHA is that each anchor point needs to be designed for 2 times the MAF, which for a full body harness would be 1,800 lbs. To me, this means that the factored load is 3,600 lbs (i.e. no other load factors applied).

My question is in regards to multiple occupancy. OSHA does not seem to land firmly on this issue. Should a system with 2 occupants assume that both occupants fall simultaneously (applied load of 7,200 lbs)? Or should it be a single occupant (applied load of 3,600 lbs) Or should the assumption be that one person has fallen and another is falling (3600 lbs + a static load)? 7,200 lbs seems excessive, but a single load of 3,600 lbs doesn't seem correct either. I'm looking for something like a multiple presence factor that exists in bridge design and I can't find it.

Also, the system will be need to be load tested. Should it be load tested to 2 times the MAF, or to the standard 125% of the MAF - 2,250 lbs. Similarly, should it be for 2 occupants at 2,250 lbs or one static load of 250 lbs and one load of 2,250 lbs.

Any input would be appreciated. Thanks!

RE: Fall Protection Monorail

In the CSA (Canadian) standards for a flexible horizontal lifelines, it says that it is statistically unlikely that you'll get the MAF from both users at the same time (after all, the MAF is only applied for a fraction of a second) , and does not need to be considered in design - EXCEPT if the circumstances make that scenario likely, i.e. workers are on a suspended platform that if failed, both would fall simultaneously.

RE: Fall Protection Monorail

abuchman,

I can't pull up the passage at the moment, but all the HLL systems on the market have test data that shows that for multiple occupants, the system needs to be designed for 2 simultaneous falls + the additional dead loads from the occupants. In the case you describe, we would require harnesses and yoyo's or shock packs to bring the FAL to 900-lbs per occupant (or a design force of 1800 lbs per occupant). Then you should still apply standard load factors to the live loads.

For testing, in the past we had the contractor drop a 300# mass off the side of the building connected with a shockpack. If you are going to do a static test, then I agree that you should support the design force as a dead load - so 1800 lbs masses.

Good Luck!

RE: Fall Protection Monorail

I think the horizontal lifeline is left to engineering judgement see II.B.4 Link

Here is the quote from OSHA.

Quote (OSHA 1926.502(d)(8) Horizontal lifelines shall be designed, installed, and used, under the supervision of a qualified person, as part of a complete personal fall arrest system, which maintains a safety factor of at least two.)

RE: Fall Protection Monorail

In my opinion (and what I was taught) is that the static load of one user (usually 310 lbs in US) should be combined with the 1800 lbs MAF so that should one person fall, the system has sufficient reserve strength for the remaining user. It is possible that the rescue/recovery operation will partially involve the non-fallen user, so their safety needs to be protected even after the first fall. Of course then use a safety factor of two per OSHA. With that being said, if the fall of one user is likely to cause the fall of the other, simultaneous falls should be a design consideration. This is common in flexible HLLs since the displacement of the line during a fall will carry with it significant load (enough to knock over the other worker).
Finally and equally important, be sure to consider the rescue of the fallen worker be it additional strength in the monorail or a separate anchorage.

RE: Fall Protection Monorail

(OP)
Thanks for the input - all very helpful!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

eBook - Integrating the Engineering Ecosystem
Aras Innovator provides multiple options for integrating data between systems, depending on the scenario. Utilizing the right approach to meet specific business requirements is vital. These needs range from authoring tools, federating data from various and dissimilar databases, and triggering processes and workflows. Download Now
Research Report - Simulation-Driven Design for SOLIDWORKS Users
In this engineering.com research report, we discuss the rising role of simulation and the paradigm shift commonly called the democratization of simulation. In particular, we focus on how SOLIDWORKS users can take advantage of simulation-driven design through two analysis tools: SOLIDWORKS Simulation and 3DEXPERIENCE WORKS. Download Now
White Paper - Industry 4.0 and the Future of Engineering Education
With industries becoming more automated, more tech-driven and more complex, engineers need to keep their skills and knowledge up to date in order to stay on top of this wave—and to be prepared for the Industry 4.0 future. The University of Cincinnati offers two online Master of Engineering degree programs designed specifically for practicing engineers. Download Now
eBook - The Design Gridlock Manifesto
In this eBook, you’ll learn 6 ways old CAD technology slows your company down and hear how design teams have put those problems to rest. “The Design Gridlock Manifesto” shares first-hand modern CAD experiences from 15 companies around the world. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close