I just did a google search on "
chain motor overhead lifting" and it doesn't really confirm that chain motors are fine for
overhead lifting - implying movement over people. from CM FAQ:
"
Can a CM Lodestar be used to hang loads over people's heads?
It is preferred that the load always be tied off (
dead hung) with auxiliary chains or cable before access to the area beneath the load is permitted. As an alternative, the
system may be designed such that malfunction or failure of one
hoist's load bearing components does not cause load loss and/or overloading of any other
hoist in the
system. Note that in such a
system,
hoist performance and function must be monitored visually or with the use of load cells.
However, both the
CM Lodestar D8+ and
CM Lodestar BGV-C1 feature a 10:1
design factor that allows them to be used for suspending loads above people without a secondary support."
A lot of cracks there.
PLASA here :
http://www.plasa.org/nrag/load_suspension.pdf doesn't make it all so
clear and limitless as your statement. In any case, your statement should be more qualified like: "A limited number of really special chain motors are sometimes acceptable for
overhead lifting." At least the
current literature from CM acknowledges the requirement for alloy chain, something they use to resist.
http://blog.cmworks.com/understanding-the-difference-between-chain-grades-and-how-theyre-used/
I am not so concerned the use of these by really qualified people, but the problem is - especially with the unqualified "chain motors are fine for
overhead lifting" attitude, is that less than really qualified people will try it. We saw it with indoor
pyro.
Pyro use to not be permitted indoors then some folks - most of whom who happen to benefit form the sale and use of
pyro - got a standard approved and accepted. Well, then even common john and jane doe decided if they read the standard they could do it too. And then we have 100 dead in Rhode Island.
Its the attitude that injures and kills. There needs to be a very high bar to jump to be allowed to use chain motors for
overhead lifting, with a lot of safeguards and very deep pockets behind the work so when it does go fubar, the victims are compensated.
David - I'm not saying you shouldn't do it - but you are making it sound too easy for any high school teacher (or student) that frequents CB as well as many other unqualified individuals to believe they can do it too, and that's not safe.
I agree and disagree, respectfully.
I concur we need to be careful with how accessible potentially dangerous equipment (and partial information) is to unqualified or inexperienced users , especially students, but I didn't say
chain hoist lifting operations were easy or without risk. To the contrary I stated that it needed to be done "properly" implying that this is not as simple as it may sound and that a further understanding is required. Hopefully this would help push your
point home to the less-experienced reader; that there is a right way and a wrong way.
The Kinesys
chain hoist control systems are designed to increase
safety, assist experienced professionals and electronically prevent unqualified users from making potentially dangerous errors. This completely supports the notion of improved
safety and risk reduction. I don't think my attitude is one which promotes unsafe practices whatsoever. Righting off chain hoists as unsuitable to all newbies is misleading as they will see them at events and performances which surely is a mixed message and rather confusing.
If anyone read my post and assumes that, based on that post alone (or really only a part thereof that you responded to), I have a lax attitude towards
safety and it is all the training they need to have a go at multi-hoist lifts then that is the strongest argument for more regulations. I agree with you that we need to be proactive and responsible as professionals, but I don't agree that I made it sound overly simple to the
point of putting lives at risk. I was arguing the
point you made about chain hoists, versus winches, not being robust enough or suitable for
overhead lifting and that, IMHO, is untrue. Given the number of chain hoists in operation around the world in entertainment applications, I would say they are a widely accepted means of safe lifting. The fact that there are standards and legal regulations for their design and use is a fundamental acknowledgement of this.
On the matter of the regulations, you mentioned BGV D8, BGV D8+ and BGV C1 directives, which are not mandatory standards in the US, but we do work to these standards as required in other markets. They help people quantify what is acceptable and safe and this acknowledges chain hoists as suitable. This directive includes the controls as an integral part of the
system safety. The
design factor of the
hoist is only a part of the directive. Other elements such as
encoder reading and load cells to avoid failures as well as a specified
level of
E-Stop safety integrity (
SIL) are all important factors. A
hoist designed to be "BGV C1" , be it
winch or
chain hoist, cannot be "certified" on it's own and must have a suitable control
system and data acquisition components to conform. More on this below for those who want further information. The
ANSI standards also acknowledges chain hoists as suitable in
ANSI E1.6-1 – 2012 Entertainment Technology – Powered
Hoist Systems, which also includes
wire rope drum winches.
With all due respect Bill, chain hoists are suitable for
overhead lifting but what that statement doesn't mean is that you don't have to read the
manual or learn about their proper use. Kinesys makes winches too and don't misunderstand me, they are the right tool for some jobs.
There are many chain hoists on the market, most of which offer BGV D8+ and C1 levels of conformity, but you mentioned CM which is a very popular and respected brand in our industry. These hoists meet strict guidelines and are proven to be robust and dependable. From the CM
manual: "Each Entertainment-Lodestar
Electric Hoist is built in accordance with the specifications contained herein and at the time of manufacture complied with our interpretation of applicable sections of the *American Society of Mechanical Engineers Code B30.16
“Overhead Hoists”, the National Electrical Code (
ANSI/
NFPA 70), the Occupational
Safety and Health Act, British Health
Safety Executives, TUV and CE Directive." ...*American Society of Mechanical Engineers Code B30.16
“Overhead Hoists”.
From the Kinesys DigiHoist brochure: "Achieving BS7906-1:2001 (British Standard) and D8+ (SQ P2:2010) Compliance with the DigiHoist
System.
The DigiHoist controller may be used as part of a BS7906-1:2001
Category A
system, for lifting and suspension of
loads above people, and as part of a D8+(SQ P2:2010)
system, for suspension of loads above people without the
need of a secondary suspension. In order to achieve full conformity with the above codes of practice the following
conditions must be respected:
Category A and D8+ Systems
D8+
Hoist must be compliant with DIN 56950:201 SQ P2-2010.This must include but is not necessarily limit the following:
• Double brakes
• Brakes must act directly to stop the load
of statically indeterminate loads
• Top and bottom limits are recommended
• End of travel stops
•
Safety Factor 10:1
Category A
Hoist must be compliant with BS7905-1:2001 and
BS7906-1:2005
Category A.
This must include but is not necessarily limited to the
following:
• Double brakes
• Brakes must act directly to stop the load
• Top, bottom and ultimate limits
• End of travel stops
• Chain container must be no more than 50% full when
the hook is fully retracted
•
Safety Factor 8:1