Design of industrial Suspended Scaffolding Under Pipe Rack.

[tarekdata]

dear All Scaffolding Experts.

We are doing a project in UAE - Abu Dhabi , the project is surface facility plant or central process plant , oil & Gas pre export treatment.


the plant contains 3,500 Lm of multi layer and story pipe rack.

we need to erect a scaffolding under each layer, therefore, we need to construct suspended scaffolding or floor decking where the welders, Painter, inspector, insulator can stand on.


See the attached pictures inside excel file.

Does any one have a knowledge in design such similar model.


Regards
Tarek

 

[RHTPE]

In the US OSHA scaffolding rules would apply, assuming that this scaffolding is required for construction and not for plant operations. OSHA requires a 4:1 factor of safety for scaffolding. Simply put, if your design live load for workers and their tools/equipment is 50 PSF, then design the scaffolding for 200 PSF.


Ralph
Structures Consulting
Northeast USA

 

[CANPRO]

tarek, scaffold design isn't overly complicated when you get down to the numbers, its more about your experience and having an eye for the details. My first suggestion to you would be to outsource this to someone familiar with scaffold design as this could be a daunting task for someone not familiar with scaffold.

If you're going to do this yourself, I suggest taking the following steps:

- Get a copy of all local and national standards that relate to scaffolding and suspended platforms
- Find out which specific manufacturer of scaffold will be used. Each manufacturer will have slightly different components and capacities available. The major suppliers should have online catalogs.
- Talk to the foreman/supervisor/contractor who will be responsible for erecting the scaffold (if one hasn't been chosen yet, find someone local you can talk to). These guys almost always have an idea how they want to build the scaffold. You will have to take their concept and check the numbers, but in my experience, if you can get a quality contractor, hes going to give you a great start on the concept.
-For a project this size, you're never going to be able to draw the scaffold as it will be built. There is just too much to work around. Best you can do is provide concept drawings for as many scenarios as necessary and then perform onsite inspections.
- Make sure you have a full understanding of the workers requirements before you start the design. Will the scaffold be hoarded in? If hoarded in, what is the maximum wind speed (wind speed to can be limited with break away tarps)? How long does it need to be erected? What are the live load requirements? Will there be any concentrated or lateral loading? Will there be a material hoist attached to the scaffold? Are you responsible for providing access (stair tower)?

I don't know if those pictures are of scaffolds that are already erected on your project. If I saw the larger picture of the suspended scaffold in my area, some of the first notes I would make are:

- There a no cleats on the underside of the planks to prevent slippage
- There are no check clamps on the suspended components. If a load bearing element (ledger, tube, truss) is suspended by a clamp, you should have a 2nd clamp (check clamp) on the supporting vertical, below the main clamp, in case the main clamp slips.
- Is the single tube supporting the decks made of aluminum or steel? If its aluminum you're not going to get much of an allowable span.
- Typically the scaffold trusses are rated for point loads at their panel points (where the webs meet the chords), it appears the tubes could be off center.
- Doesn't look like there are toeboards at the edges.

Like I said, when it comes down to checking the loads vs. allowable loads, scaffold is fairly straight forward. But you need to get a working concept before you can do the easy math. Hope this helps.

 

[RHTPE]

Canpro nailed it. There is a lot to be considered.

The best concepts are a combination of field input (they gotta build it) and good engineering knowledge of all the components used. I lean heavily towards the former, and start from there with the numbers (member size v. capacity). Then we compromise as the details come together.

Repeat as required.



Ralph
Structures Consulting
Northeast USA

 

[tarekdata]

Dear canpro, ralph

Thanks indeed for you participation .

Dear Ralph, the steps and notes you provided is so useful.

Mostly we are going to buy , so we need to budget the QTY. I've already done it based on 1 meter pay span. see the attached file, since we are in UAE, the currency used is AED.

Now the real dilemma in estimating the productivity. I was going initially to use my previous experience with tower scaffolding system using cup lock standard probes and ledger, by building the tower from bottom to top. but the Vol. and QTY of members found extremely high " hit 10 Million USD " , since by this assumption, we are going to build a net of tubes beneath the entire pipe rack area " 50% of Pipe rack length " assuming that we will dismantle a 50% of QTY and re- Build it.

the UAE productivity for this type of Cup lock is 20 m3 of scaffolding per Day per labor. assuming 10 hrs working shift.

then it cross in mind that we might be able to go with suspended scaffolding, where the volume and QTY of Scaffolding is less but and productivity is extremely low due to one fact, that labor will erect and clamp the pipes and trusses on Air. also Clamps QTY will be much more.

Wooden Planks QTY wont be affected neither by using tower nor Suspended System.


Please let me know if you have any rough estimate or rule of thumb for Scaffolding productivity.

Regards;

Tarek