double brake motors

[Ben]

I have been told that at the coledge we neve use any safetys on double brake motors, however we have been told that we have to find evidence that this is not a problem before using the motors on monday, so can anyone point me in the direction of anything about safteying motors used in rigging? even if the documentation says we should safety them it would be a great help.

 

thanks

Ben

[Tom]

I've always been told the same (most recently by Unusual who hired me some).

 

Try asking the manufacturer of your motors.

[Rob]

The whole concept of safeties seems to be a bit of a grey area to me, with lots of people having different opinions. I've had a quick looks through Chris Higg's book and I can't find anything about double braked motors.

 

I think the jist of what Chris does say about safeties is that there is no hard and fast rule, but you have (as ever) to asses the risks, and if necessary provide safeties or enough redundancy to cope with any eventuality.

[Bryson]

My understanding is that you need two ways to stop the point "going": one brake and a safety or: two brakes - if one lets go, the other holds.

 

I have 8 VBG70 (Now called BGV-C1) motors with double brakes which I'm assured do not need safeties.

[Ben]

is there anywhere that this is written down (LOLER?) or is it just word of mouth?

[Tomo]

The way I've always understood it was that the system must be able to lose any single suspension component and not fall or swing in a dangerous manner.

 

The actual LOLER statutory instrument is available from Her Majesty's Stationery Office (online).

Statutory Instrument 1998 No. 2307

 

Part 6 appears to be what you're looking for, but it isn't specific.

[Chris Higgs]

Refer to the Approved Code of Practice for LOLER for quite specific and precise info. which is also the model of best practice that would be used in court. (See inside front cover of any ACoP).

I am unaware of any law that requires any specific conditions in terms of 'two means of stopping the point going' and similar traditional views.

Most hoist manufacturers will distance themselves from any concrete discussions about secondaries, simply advising use of adequate auxilliary measures.

Preventing 'unintentional release of a load' is the idea expressed in LOLER.

Precautions to be taken when working under suspended loads is mentioned specifically as is the idea of enhancing the factor of safety in certain circumstances to reduce risk to people who need to be under or near loads.

Double brakes alone do not mean you comply with BGV-C1 (VBG70), there is a lot more to it than that, although they do have their uses. It is a valuable reference, but was intended only to help in specific circumstances.

Most riggers worth their salt will rely on redundancy rather than separate 'safeties' wherever possible because of the difficulty in eliminating slack vs. time taken, often using more hoists than necessary. The integrity and strength of the load is equally important and in many cases more likely to fail than any rigging.

Each situation needs to be looked at individually, it is impossible to provide a general set of instructions or guidance.

It's all down to competence again (also defined in the ACoP).

The structure that supports the rigging may be the first thing to look at ............

[Chas at Halls]

We've recently been looking at the exact nature of the BGV C1 classification system as part of our envolvement with a German motors manufacturer.

 

There are many subdivisions of the C1 category and the system goes into greater depth than Loler and other standards we work with.

 

The most important aspect for us is that the C1 'mark' covers all aspects of the installation ie; you must have a C1 control system ( and the equivelent of C1 shackles, C1 truss etc) as well as C1 motors.

 

In addition to the C1 grouping, there are further 'AK' (Standards Class) sub-divisions and 'AK-5' covers the use of motors, moving scenery & flying artistes etc over the heads of public/audience etc without secondarys. It appears that many of the hoists in common usage here are not in this group, but are OK for general rigging with a secondary. Its not the motor they're worried about, but the brake system itself as the 'common' failure point, in their experiences.

 

Many ASM motors were designed without brakes....and have full AK-5 certification.

 

We are currently investigating the whole BGV standards - as our friends at ASM are all on the various standards committees - and hope to produce an English translation for reference soon.