Conveyor belt steel truss repair 1

[SKJ25POL]

Does anyone have any article, reference book, source, manufacturer handout, seminar notes, or their own past work on repair of steel structure (trusses) of conveyor belts.

I have multuiple request of plants that have outdoor steel conveyor belts that the bottom chords or joints are rusted and need to be replced or reinforced.
I like to see what's the common practice is out ther. Any consideration while repair istaken place?

Is there need a crane hold up the truss to reinforce the truss?
How high you lift the truss, if is needed?

The projects are in States.
Any information will be greatly appreciated.


Thank you

 

[paddingtongreen]

I believe that you must treat each as an individual case unless there are duplicates or near duplicates in your backlog. The cases I have seen are sufficiently different that there is no "One size fits all" solution.

Do you need a crane? If you have a way to support the gantry while the required members are out of action, then no, otherwise yes.

Look at a case, put some ideas to work and then bring them here for discussion, we work better with real, rather than general or hypothesized problems.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[miningman]

What is common practice is for the operators of these structures to frequently load these conveyors dramatically beyond the original design loads. Make sure you get actual future loadings rather than historical design values

 

[Brad805]

These can be tricky projects. Rarely do you find the original drawings and like suggested, they make numerous modifications over the years. Many of these plants have experienced significant growth over the years, and operators can unknowingly exceed the original intent of the design.

Some of the basic keys to these projects are:
1. Tracking down reasonable drawings is always a challenge. If none exist it is a huge undertaking to measure all of the members and connections for a proper analysis. These are simple structural elements, but as all suppliers do, many try to optimize their design to save on steel weight and the number of bolts.
2. Site constraints. What size of material can you physically get to where it is needed? Do you have sufficient access for cranes or picker trucks and if so, how close can they get? Overhead constraints can be a problem as well.
3. How long can the client operate without the conveyor?
4. Is welding allowed on the site or are there special requirements to undertake welding (hot ticket)?
5. Establishing the design loads is not always easy. The basic wind, seismic, and gravity loads are well defined, but the material loads can be difficult to determine for a variety of reasons.
6. If the client has a working relationship with a contractor get him involved early. They can save you a lot of time by helping define the "how" part of the problem.
7. Assessing the extent of damage is another problem. A JLG is very helpful up to 120ft, but after that you need something different if you need to examine the U/S of the structure.
8. Is it being used as originally designed? If not, you can find fundamental flaws that turn this into a much larger project.

Unless you are dealing with bearing problems at the support bents or replacement, there is not usually a lot of need to lift the truss much more than inches. Lifting the truss represents a whole new challenge as the engineer. How they lift it can impose rather large stresses upon members unless they unbolt the assembly like it was originally installed.

I don't know if OSHA has started to define the safe particulate levels when working around lead paint. In Canada, the WCB has done so, and this has a major impact as many of these structures have been painted with a lead based paint at some point in their life. If the client is a union shop or has a strict safety policy this can be something to make sure to exclude in your proposal.

These are fun projects, but do not underestimate the time required if you are asked to quote the project. Be careful when you define you scope of works. Just like any renovation they are always full of little hidden treasures that take us time to figure out.

 

[SKJ25POL]

Brad805 (Structural)thank so very much for your valuable comments. I personally have faced your points.
The old drawing that cannot be read or they are not available, etc.

You mention JLG, what is the solution when the belt conveyor truss is 125ft in air and JLG cannot reach, what shall we do in this case/

Also, the consulting that I am reviewing thier work has asked to lift the truss with crane (I don't know how much) but they mention on dwg, "use crane to apply load on truss. Limit vertical load to 10 Tons upward. How do I check this?

The location that they are lifting truss is at the joint that has problem but how do I know the truss needs to be lifted at one location and not at two points?

Please if you have any reference or direction let me know. It sounded you very well know this subject of conveyors.

Thank you so very much and thanks all that have take their time and commented.

Sincerely,
Your fellow colleague

 

[Ingenuity]

"use crane to apply load on truss. Limit vertical load to 10 Tons upward. How do I check this?

Modern cranes have in-built mass-measuring capabilities, or alternatively you could use a on-hook crane dynamomoter like this one Link but it can be awkward to observe if the load is up high off the ground.

 

[Sawbux]

I've worked on a number of conveyor rebuilds in pulp and paper industry.

Are these deep, long span conveyors with through truss design or trussed conveyors with walkway on side? Different animals.

Major lack in most conveyors, unless they are the through truss design, is lateral bracing of the top compression chords. A lot of times it is omitted, missing or corroded away.

You may want to consider short term reinforcing using intermediate scaffold towers (if not too high off the ground). Or cables, harped to pick up the trusses at the 1/3 points.

Coming up with weights of product should not be too difficult. With belt width, trough angle and angle of repose of the material, you should be able to estimate it. There used to be some publications from conveyor equipment manufactures that had a lot of info Link-Belt, Rex, etc. Other factors to consider are start-up thrusts, belt tension forces and weights on gravity take-ups.

 

[SKJ25POL]

Sawbux (Structural, thank you for your response. Is it possible for you sharing some of the sample works you did. I like to learn but sources are very limited.

Thank you

 

[swearingen]

Recently did an emergency fix for a client that was losing money while the conveyor was down. $1.3 million. Per hour. No pressure, right?

We designed and built a cradle and lifted it into place, then loaded the truss with 40,000 lbs which was about 1/3 of the load it was supposed to hold. The internal braces were then fixed and a new support was added underneath.


-5^2 = -25 ;-)

http://www.eng-tips.com/supportus.cfm

 

[Bagman2524]

If the crane doesn't have a load cell on it, you should be able to purchase one separately and attached it to the hook.

https://www.google.com/search?site=...1119&dpr=1&cad=cbv&sei=4UfNU-TbMqOR8gGZ84GQBA

Faith is taking the first step even when you can't see the whole staircase. -MLK

 

[Sawbux]

Took a scan through what is available on the internet and it looks very sparse! But if you are doing only structural repairs, that doesn't matter that much.
Determine what the original capacity was and use your ingenuity to at least restore that.
If the operations is not suffering problems from belt misalignment indicating sagging or swaying in the trusses you might be able to reinforce while in service, depending on operations, flammable materials, etc.
Common problem I saw is that a lot of the older conveyors had rivetted back-back angle trusses. A lot of corrosion products in between the angles, where access for painting is limited. Repairs are dictated by the details of construction, many times there are connections of floor beams and other things that get in the way. I've many times used round bars nested into the fillet of the angles to get around the rivets and other obstructions. If the bottom chord is clear, you can add flat bar on the bottom of the chord.
Other problem was outriggers - extended floor beams which extend out from the conveyor sides and had diagonals which braced the top chord. Typically these were steel channel, which could be reinforced by doubling up with another channel or angle on the back side.

A lot depends on the configuration of the conveyor structure and accessibility. If the trusses are too far gone - then replacement is in order, requiring down time.

Hope this helps!