TomHoward Posted January 17, 2017 Share Posted January 17, 2017 Evening allApologies for a fairly well-trodden subject but most of the advice seems to be on motor hoists. We've got a sports hall, which we propose to rig a couple of short, relatively lightweight truss in.Imagine each one is say 4m truss, with 2x 1000kg manual chain blocks, one at each end. Roundslings over a 600mm RSJ at the top.Each truss has say 4x LED cans and 4x generic fixtures. That's about 60kg of fixtures plus truss and cabling.The height to the ceiling is about 9m max and the truss will hang at about 6m. The truss will be over seated audience or an area accessible by audience.Hoists and all accessories have been LOLER inspected within the last 12 months. Both ends of the truss are on the same beam of a sloping roof so the hoists are at different lengths to get the truss level. What are your initial thoughts on the need for secondary suspension in this system? My thoughts are-Secondary suspensions are likely to be difficult given the unknown distances, unless there is a shortening system, but these only seem to work under tension-Secondary suspension adds working at height-Assuming the hoists are rated at 5:1 for PUWER, I could derate them to 10:1 to 500kg per hoist and either hoist would still hold the entire system, although not nicely after one had failed. Link to comment Share on other sites More sharing options...
ontoprigger Posted January 17, 2017 Share Posted January 17, 2017 The rules are the same regardless of a manual or electric hoist, if the load is to be left suspended above people then it will need to meet the relevant standards, in the UK you can use BS7905, BS7906-1, 'lifting for the entertainments industry' and its code of practice. This will require the hoist to be of the 'Type A' and designed and specified by the manufacturer for suspending loads above people. As the UK is still part of Europe, EU standards can be used and if the hoist complies with VLPT.SR2 and is D8+ or C1 rated then they are also able to be used. If you don't want to follow or comply to any standard then you could produce a lift plan and in your risk assessment state that you are down rating the hoist by 50% (1000 Kgs > 500 Kgs) and that should cover you in the terms of showing you have tried to comply with the various reams of legislation, but if there was an accident you would have to go up against the HSE in court and prove what you did was OK. All equipment must comply with LOLER as must the lift plan. With Motorised hoists to the relevant standard we often sight not putting worker at risk at height as one of the reason for not using safeties, and you could use the not working at height as part of your defense, but I guess if it the only one they will throw the use of adequate access equipment, PPE etc. at you Personally I would always back up a manual chain hoist, they don't have brakes as such they rely on a clutch to hold the load, and you are more likely to have an issue with less weight than more on these type of hoists as they can free run if the load was not enough for the clutch to engage properly. If you are using them lock the operating chain together as close to the unit as possible to avoid accidental lowering or movement once the load is secured. You can use a number of devices to back up the hoist, including chain, steel cables with a wedge socket, Reutlinger Cable Gripper or similar, also remember that the rigging equipment used to suspend loads above people must be suitable for the task and have a higher factor of Safety I.e 8:1 or 10:1 and above. Link to comment Share on other sites More sharing options...
Seano Posted January 17, 2017 Share Posted January 17, 2017 What are your initial thoughts on the need for secondary suspension in this system? If I'm reading the OP correctly, you're talking about a 100kg-odd load on two mutually redundant 1000kg hoists?I wouldn't be putting any secondaries on that unless I was humouring a ludicrously risk-averse client. By, paradoxically, engaging in some entirely unnecessary work at height. Secondary suspension adds working at height It does. Though presumably you do still need to re-visit the hoists once the truss is at trim to tidy up the hauling chain. Careful with those chain bags - the most common accident by *miles* involving hoists, whether manual or electric, is a chain spill. Link to comment Share on other sites More sharing options...
TomHoward Posted January 17, 2017 Author Share Posted January 17, 2017 Well they're kind of redundant, except that failure of one the load would end up sideways at the very least. To be honest the chain block itself is probably the heaviest single element of the whole system and the one I'd least want falling on me. I'm struggling to find many manual hoists that have certification like the motor hoists do. I'll ask the manufacturer. It is true we need to revisit anyway for the hauling chain. If they were at the same height I'd just get some long steels and bypass the hoists once in place, but it's the adjustment that's got me a little bit stumped. And unless you were going to put in a second roundsling at both ends you're only bypassing one part of the system. Link to comment Share on other sites More sharing options...
ontoprigger Posted January 17, 2017 Share Posted January 17, 2017 quote name='TomHoward' timestamp='1484639698' post='546540']If they were at the same height I'd just get some long steels and bypass the hoists once in place, but it's the adjustment that's got me a little bit stumped. And unless you were going to put in a second roundsling at both ends you're only bypassing one part of the system. The easiest way to bypass the hoist would be to use a second point, have a steel close to the correct length and use a length of STAC chain to give you the adjustment, possibly only needed on one end if you have the correct length of steel for the other. I would dead hang the truss on the steels and use the hoists as the back up, that way no issues as long as the factor of safeties in the steels are enough. if putting them at the same time as rigging the hoist should not take too much longer. it is possible to get something like this, that will give you a more adjustable length that can be used to bypass the motor, often used to bypass electric chain hoists. http://www.safetyliftingear.com/products/1-5-tonne-rigging---clutch-chain--1-25mtr/rigging-chain-7mm Link to comment Share on other sites More sharing options...
TomHoward Posted January 17, 2017 Author Share Posted January 17, 2017 Careful with those chain bags - the most common accident by *miles* involving hoists, whether manual or electric, is a chain spill.Just on this - the chain bags are decent sized and have proper rims and the top and all that. Feeling in from the dead end of the chain, and having the hand chain on top, is there anything else to avoid? Link to comment Share on other sites More sharing options...
Seano Posted January 18, 2017 Share Posted January 18, 2017 anything else to avoid? No just the obvious, nothing clever. Link to comment Share on other sites More sharing options...
mac.calder Posted January 18, 2017 Share Posted January 18, 2017 The only other thing - don't feed the hauling chain in from the bottom of the chain - collect the chain and then sort of put it in from the section of chain closest to the block. So dead-end of the lift chain goes in from the bottom first (if your lucky/position the bag correctly, the bag should gather the lift chain as it goes up correctly) so that it 'debags' itself nicely when the truss comes down and then the haul chain, from the section closest to the block first. Then with the tip of the hauling chain you can 'tie' it around one of the chain bag's straps. This serves 2 purposes - the chain can only drop half way (which generally means in a chain spill - the hauling chain is not going to hit someone in the head) AND it is easy to retrieve when you need to drop the truss. If your chain bag is gathering the dead end of the lift chain, just make sure your operators watch the chainbag as the line goes up. If the chain stops falling into the bag and starts sagging below the bag they need to be extra vigilant for that chain to start making its descent towards the ground. Chain spill tends to happen in 3 situations - when the truss gets moved/bumped after it is at height because it has been poorly bagged, when the truss is being raised and when removing the hauling chain because it has been poorly bagged. Link to comment Share on other sites More sharing options...
TomHoward Posted January 19, 2017 Author Share Posted January 19, 2017 Something's just struck me about this, I was putting 2x 4m sections, spaced along the same line across the room. There's about 2.5m space between them but no requirement to hang anything in this space. If I joint the two trusses into one length it'll have 4 hoists on it and then they will be truly redundant. Link to comment Share on other sites More sharing options...
MarkPAman Posted January 19, 2017 Share Posted January 19, 2017 Though you will need a team of 4 working well together to raise and lower it each time. One person going at a different speed can easily lead to only 2 of the hoists taking all the weight. Link to comment Share on other sites More sharing options...
Seano Posted January 19, 2017 Share Posted January 19, 2017 If I joint the two trusses into one length it'll have 4 hoists on it and then they will be truly redundant. Depending on the spec of the truss - 10m odd is a long span for a flimsy lightweight pub truss.If the truss is up to it (CPL at span of entire length of truss > weight of truss plus fixtures), may as well make it 3 hoists. Link to comment Share on other sites More sharing options...
TomHoward Posted January 19, 2017 Author Share Posted January 19, 2017 I thought that but the middle one is a pain as there's services down the middle of the room (big air handling units down the apex), plus I'd rather be belt and braces.Knowing the room, there's little doubt that some of the permanent fixtures are more suspect than this. Link to comment Share on other sites More sharing options...
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