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Suspended Scaffolds Archives | DH Glabe & Associates

Suspended Scaffold Mysteries

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My experience indicates that people easily get confused about suspended scaffolds.  I’m not sure why that is other than it may have something to do with their knowledge, or lack thereof, of suspended scaffolds and how they work.  This shouldn’t be surprising since most people base their knowledge on what they have seen on the evening news.  Here are a few questions that occur about suspended scaffolds:

What is a suspended scaffold?  This is a fundamental question that has an easy answer.  A suspended scaffold is any temporary elevated platform that is supported by a non-rigid means, such as by rope or chain.  For example, if you have a platform hanging by your mother’s clothesline, it is a suspended scaffold.

Do all suspended scaffold platforms have to be supported by wire ropes?  No.  You can use anything you want as long as the support is strong enough.  This can be clothesline (see answer above), wire rope, cable, manila rope, chain, string, duct tape, bungee cords or rubber bands.  As long as it has the required strength, and you can prove it, you can use it.

What is the required strength of wire ropes?  It depends on what you are trying to hold up.  For temporary suspended scaffolds used in construction and general industry, the safety factor must be at least 6; that is, the suspension line must be 6 times stronger than the load you are placing on it.

Can I really use duct tape?  Well, if you can prove that it will hold 6 times the load you put on it, then you can use it.  I have no idea how you would prove that so I strongly recommend against using it, even if it is “professional grade” duct tape!

Is there a difference between temporary suspended scaffolds and the scaffolds that commonly called “permanent installations”?  Yes there are considerable differences.  Different regulations and standards apply.  For example, temporary suspended scaffolds used in construction in the United States must comply with the applicable OSHA construction standards [29 CFR 1926].  A Permanent Installation, (also known as a “P.I.”), must comply with OSHA standards that specifically address P.I.’s.  The significant differences are in the areas of safety factors and fall protection requirements.

I have a 5/16” wire rope but do not know anything about it.  Are all wire ropes of the same diameter the same?  Absolutely not; wire rope strength varies based on the tensile strength of the steel used.  Therefore you must have the data on the wire rope to determine its strength.

Why are wire ropes twisted?  They aren’t twisted but rather are “laid” into strands.  The strands make up the wire rope.  There are a variety of “lays,” such as the Regular Lay and the Lang Lay.  Different lays have different handling characteristics which means that you should select the wire rope with correct lay for the job.

The safety factor for temporary suspended scaffolds used in construction is 4.  Does this also apply to the suspension rope?  No.  The minimum safety factor for the suspension rope is 6.

Why are suspended scaffolds so dangerous?  They aren’t. If you utilize properly designed and maintained equipment, erect the scaffold correctly, and use it correctly, it’s no less safe than any other construction or maintenance activity.

I saw a worker on a suspended scaffold not connected to a vertical lifeline.  Is this legal?  Who cares if it is legal—is the worker safe?  Typically, a worker on a single or two point temporary suspended scaffold is required to utilize both a guardrail system and personal fall protection equipment.  However, on some temporary 2 point scaffolds the personal fall protection system may be built into the scaffold and rigging.  Depending on the design of Permanent Installations, vertical lifelines may not be required due to its design.  Obviously, before you use a suspended scaffold you must know what the fall protection requirements are.

Can I ride on a suspended scaffold without knowing how to operate it?  Yes you can.

What do I need to do to be safe on suspended scaffolds, whether or not they are permanent or temporary installations?  You need training in the specific type of equipment you are using.

Where can I get training on how to use and operate suspended scaffolds?   Well, that should be evident if you are reading this magazine!  The Scaffold Industry Association.

How Much Luck?

By | OSHA Standards & Regulations, Resources, Safety Hazards, Scaffolding | No Comments

This month’s topic is suspended scaffolds.  As I started writing this article I thought about what I have written in the past.  Sure enough, several years ago I wrote about suspended scaffold safety.  As I reviewed the article, I realized that not much seems to have changed; we still have spectacular accidents involving suspended scaffolds.  The subject is still applicable and the points in the article are still the same.  So, in case you missed the article the first time around, here it is again.  (I’ve change the title.  Last time it was “How Much Safety?”  Now I’m thinking people are trying their luck at suspended scaffolds.)

 

Suspended scaffolds, such as window washers scaffolds, make spectacular news items for the local television stations when things go wrong.  Based on my familiarity with the standards, regulations, and recommendations regarding the installation and use of single and two point suspended scaffolds, it is amazing that any suspended scaffold accident can happen, much less a spectacular one.  The OSHA standards are almost fool proof!  Perhaps that is the problem; only a fool would choose not to comply with the available information.  The Federal Occupational Safety and Health Administration (OSHA) has very specific standards regarding the erection and use of suspended scaffolds.  They address all aspects of suspended scaffolds.  In fact, if you compare the suspended scaffold criteria to the other standards, you’ll quickly realize that the suspended scaffold standards are very specific.  If that’s the case, then why are there so many suspended scaffold accidents?

 

Tough question, no easy answer.  Perhaps the typical untrained user just doesn’t recognize the hazards.  Perhaps the untrained user just doesn’t recognize that there are two types of safety systems for his/her protection and used on all suspended scaffolds.  The first system incorporates engineering safety in the design and manufacture of the scaffold and its components while the second system incorporates specific safety products, such as a guardrail.  Tampering with either system is asking for trouble.

 

The parts and pieces that a scaffold erector and scaffold user must install and use prior to operating the scaffold, such as tieback ropes and personal fall protection equipment are examples of specific safety products and are well known to trained erectors and users.  Not so well known are engineering safety systems that are “designed into” the scaffold.  This would include the strength of the components, safety factors, and types of materials.  As an example, a properly engineered suspended scaffold might use aluminum for certain structural components.  The aluminum would have a material content that would ensure a sufficient factor of safety.  The scaffold erector would not give this too much thought since all this work was done in the design of the component.

 

What does this have to do with safety in the scaffold?  A lot if the erector decides to substitute an inferior strength material for the original.  Or maybe the user decides that a certain component needs modification because of a certain condition.  The modification may alter the strength of the component resulting in a modification of the safety factor.  In other words, the component isn’t as strong as it used to be.  Since it doesn’t fail on the first use, it is assumed to be safe; but is it?  How much strength is left?  Does it meet the standards?  Good questions.  If you feel lucky, you don’t think about that margin of safety.  Too bad because the odds, and statistics, indicate that luck probably isn’t on your side.

 

The same principles apply to wire rope supporting suspended scaffolds.  By law this rope is to have a six to one safety factor.  That means it has to be six times stronger than the load that will be on it.  The strength is engineered into the product at the time of manufacturing.  The manufacturer verifies the material strength, size, and fabrication to ensure that a certain strength is always obtained.  If the load on the rope is expected to be 1,000 pounds, the rope has to hold 6,000 pounds.  Since the six to one safety factor is rather substantial,  31% of scaffold fatalities should not be due to suspension rope failure.  But they are.  Could it be that the scaffold erector isn’t installing the scaffold correctly?  Could it be it was never designed correctly?  Could it be the user is abusing the rope?  Could it be the rope has been damaged?  My experience would suggest that incorrect installation and abuse are the main causes.  If that is the case, the solution is training; training that the engineering systems should not be field modified; training in the proper installation of suspension ropes; training in the proper maintenance of suspension ropes; and training in the proper use of suspended scaffold equipment.

 

For any quality product, including suspended scaffolds, it can be assumed the original engineering is correct.  Qualified engineers and manufacturers don’t make a habit of producing faulty products.  It can be assumed that trained erectors install safe suspended scaffolds.  They don’t make a habit of trying to kill people.  It can also be assumed that trained users don’t abuse or modify suspended scaffolds.  They don’t like falling to their deaths.  So who are those workers who get injured and killed?  If it isn’t the trained and the qualified, who is it?  Could it be the untrained and unqualified?  If you don’t know the answer, call 303.301.2646 and ask about the certified suspended scaffold training program.

Hang In There

By | Resources, Scaffold Components, Scaffolding | No Comments

  Suspended scaffolds, that is, those elevated platforms hanging by wire ropes, have several key components. The first key component is the wire rope.  The second key component is the equipment at the upper end of the wire rope that holds everything in the air.  The third key component is the platform and hoist that keeps the occupant in the proper location while hanging from the wire rope up in the air.  The fourth key component is the tie back system so if component 2 doesn’t work so well, the operator won’t experience a cataclysmic failure, just a subtle one that suggests that something isn’t quite right with the world.  And finally, the fifth key component is the personal safety system the occupant wears in case components 1 through 4 don’t work so well.

 

It should be reasonably apparent that the wire rope in a suspended scaffold only works if the end at the top of the building remains at the top of the building while it is being used.  A sudden loss of the attachment point is not a good thing.  Therefore, while all the components of a suspended scaffold are critical to the welfare of the scaffold user, it is my opinion that the rigging at the roof is most critical.

 

There are a variety of ways to secure a wire rope at the top of a building.  One frequently used method in temporary situations is the cantilever beam.  The basic concept here is to take a long “stick”, rest it on the roof of the building and stick it out far enough so the wire rope can hang vertically.  If the building face is straight, the cantilever is small, not more than a couple of feet.  However, if the building steps in (or out), the suspension rope must be positioned further away from the edge of the roof, and, in some cases this could be ten feet or more.  The bigger the cantilever, the bigger the stick has to be; the bigger the load, the bigger the stick has to be.  Of course, in addition to the fact that the stick has to be the right size, the roof has to support the loads the stick exerts on it.

 

The roof, or whatever is holding the stick, sees two loads.  One load, at the edge of the building, is pushing down on the roof.  The other end of the stick wants to lift up.  Therefore, the roof has to restrain the uplift force.  If the stick is attached directly to the roof with, say a big bolt, the roof has to restrain the uplift load.  If, on the other end, a counterweight is used to hold down the rear end of the stick, then the roof has to hold up the weight of the stick and the counterweight.

 

What is a scaffolder to do?  Well, one thing is to make sure the stick is big enough.  Another is to make sure the roof is strong enough.  And finally, if you are using counterweights, make sure you have enough.  Fortunately, the SIA has the answer for the number of counterweights that are needed.  It takes into account the length of the cantilever, the length of the stick, the location of the fulcrum (the location of the front support), and the load that is being put on it.  Contact the SIA office; they can tell you all about it.

 

A little more problematic is the stick.  We in the profession prefer to call the stick a beam as in outrigger beam or cantilever beam.  Choosing the correct size requires an understanding of engineering principles and mechanics of materials.  For standard setups, scaffold suppliers have “pre-engineered” beams that address most typical loading circumstances.  (How can something be pre-engineered?  Either it’s engineered or it isn’t!)  The non-standard setup requires a different approach.  For those who like more excitement in their lives, a wild guess as to the correct stick may work.  For the rest of us who don’t like living on the edge, but don’t mind hanging from it, consultation with a qualified person is recommended.  Any situation can be addressed.  Just remember, the bigger the cantilever, the bigger the stick and the bigger the counterweight.  Building elevators are limited in size and typically don’t go all the way to the top.  That means you have to carry the counterweights the rest of the way and somehow you have to get that stick into the elevator.

 

The roof is the final issue.  Most scaffolders estimate the strength of the roof prior to the rigging installation.  Read that word estimate to mean guess.  Most of the time the guess is good, sometimes it isn’t.  Watch out for deterioration of the roof members, additional loads such as ventilating machinery, and other conditions that will affect the ability of the roof to support the rigging.  Remember that a 700 pound pile of counterweights can easily overload a roof designed to only support 40 pounds per square foot.

 

Suspended scaffolds are a beautiful thing, when they work correctly.  Make sure the stick is big enough and the counterweights are right.  Don’t guess—there are plenty of qualified scaffold suppliers to help you decide which stick is right for your application.  As for the roof, I suggest you don’t accept any responsibility for its strength unless you really do know how strong it is.  Suspended scaffold rigging is not guesswork!

How Much Safety?

By | OSHA Standards & Regulations, Resources, Scaffolding | No Comments

Unfortunately, suspended scaffolds, such as window washers scaffolds, make spectacular news items for the local television stations when things go wrong.  Based on my familiarity with the standards, regulations, and recommendations regarding the installation and use of single and two point suspended scaffolds, it is amazing that any suspended scaffold accident can happen, much less a spectacular one.  The OSHA standards are almost fool proof!  Perhaps that is the problem; only a fool would choose not to comply with the available information.  The Federal Occupational Safety and Health Administration (OSHA) has very specific standards regarding the erection and use of suspended scaffolds.  They address all aspects of suspended scaffolds.  In fact, if you compare the suspended scaffold criteria to the other standards, you’ll quickly realize that the suspended scaffold standards are very specific.  If that’s the case, then why are there so many suspended scaffold accidents?

 

Tough question, no easy answer.  Perhaps the typical untrained user just doesn’t recognize the hazards.  Perhaps the untrained user just doesn’t recognize that there are two types of safety systems for his/her protection and used on all suspended scaffolds.  The first system incorporates engineering safety in the design and manufacture of the scaffold and its components while the second system incorporates specific safety products, such as a guardrail.  Tampering with either system is asking for trouble.

 

The parts and pieces that a scaffold erector and scaffold user must install and use prior to operating the scaffold, such as tieback ropes and personal fall protection equipment are examples of specific safety products and are well known to trained erectors and users.  Not so well known are engineering safety systems that are “designed into” the scaffold.  This would include the strength of the components, safety factors, and types of materials.  As an example, a properly engineered suspended scaffold might use aluminum for certain structural components.  The aluminum would have a material content that would ensure a sufficient factor of safety.  The scaffold erector would not give this too much thought since all this work was done in the design of the component.  What does this have to do with safety in the scaffold?  A lot if the erector decides to substitute an inferior strength material for the original.  Or maybe the user decides that a certain component needs modification because of a certain condition.  The modification may alter the strength of the component resulting in a modification of the safety factor.  In other words, the component isn’t as strong as it used to be.  Since it doesn’t fail on the first use, it is assumed to be safe; but is it?  How much strength is left?  Does it meet the standards?  Good questions.  If you feel lucky, you don’t think about that margin of safety.  Too bad because the odds, and statistics, indicate that luck probably isn’t on your side.

 

The same principles apply to wire rope supporting suspended scaffolds.  By law this rope is to have a six to one safety factor.  That means it has to be six times stronger than the load that will be on it.  The strength is engineered into the product at the time of manufacturing.  The manufacturer verifies the material strength, size, and fabrication to ensure that a certain strength is always obtained.  If the load on the rope is expected to be 1,000 pounds, the rope has to hold 6,000 pounds.  Since the six to one safety factor is rather substantial,  31% of scaffold fatalities should not be due to suspension rope failure.  But they are.  Could it be that the scaffold erector isn’t installing the scaffold correctly?  Could it be it was never designed correctly?  Could it be the user is abusing the rope?  Could it be the rope has been damaged?  My experience would suggest that incorrect installation and abuse are the main causes.  If that is the case, the solution is training; training that the engineering systems should not be field modified; training in the proper installation of suspension ropes; training in the proper maintenance of suspension ropes; and training in the proper use of suspended scaffold equipment.

 

For any quality product, including suspended scaffolds, it can be assumed the original engineering is correct.  Qualified engineers and manufacturers don’t make a habit of producing faulty products.  It can be assumed that trained erectors install safe suspended scaffolds.  They don’t make a habit of trying to kill people.  It can also be assumed that trained users don’t abuse or modify suspended scaffolds.  They don’t like falling to their deaths.  So who are those workers who get injured and killed?  If it isn’t the trained and the qualified, who is it?  Could it be the untrained and unqualified?  If you don’t know the answer, call 818-610-0320 and ask about the certified suspended scaffold training program.