Brian Posted November 25, 2009 Share Posted November 25, 2009 In general if a motor is rated at, say, 500kg what does that refer to? Is that the SWL? And if so what derating factor is used? The reason for the question is to know if a motor is already derated by 8:1 to meet industry practice. Link to comment Share on other sites More sharing options...
Snailtrail Posted November 25, 2009 Share Posted November 25, 2009 In general, it would be the SWL. Industry standard motors would be around 8:1 safety factor but the manufacturer specific information is generally easily obtainable. The only thing to be careful of is if you're using an industrial hoist which may well do the job but the factor of safety would possibly be less (5:1?) and should be de-rated accordingly. Check with the manufacturer. Sam Link to comment Share on other sites More sharing options...
Joe Betts Posted November 25, 2009 Share Posted November 25, 2009 . Industry standard motors would be around 8:1 safety factor What industry are you refering to? Most lifting equipment is identical in both industrial and entertainment use, save the color. To use a fairly good example, the CM Lodestar, one of the most widely used hoists in entertainment rigging has a safety factor of 5:1, and while its an "industry standard" hoist for entertainment, CM sell far more lodestars to the industrial market than to entertainment. The only difference between the Entertainment and industrial models is the color. There are 2 ways to find the answer to your question easily: 1) Contact the manufacturer 2) Contact the person who performs your anual inspection Cheers, Link to comment Share on other sites More sharing options...
Brian Posted November 25, 2009 Author Share Posted November 25, 2009 Thanks guys, that's what I thought, but sometimes someone says something that makes you doubt.... Link to comment Share on other sites More sharing options...
Alan McGregor Posted December 2, 2009 Share Posted December 2, 2009 Sorry, but its quite simpleSWL is Safe Working Load, end of storyThere is then the EN classification of what the equipment may be used for (eg. lifting people or equipment)But you cant look at the classification, say I'm doing something else, and recalculate the SWL(eg its rated for people at 8x, so you recalculate the SWL based on 5x for lifting equipmewnt)SWL is just that, end of story Link to comment Share on other sites More sharing options...
Tom Posted December 3, 2009 Share Posted December 3, 2009 I do not think you are correct. The SWL is the breaking strain divided by your safety factor - that's why they tell you what the safety factor is. If you are having steels made up for you, you can specify the Safety Factor you would like them to use when certifying them and stating their SWL (or certainly you can with Rope Assemblies). There is nothing stopping you de-rating something to a lower safety factor (e.g. when lifting people), particularly if that's what your Risk Assessment or standard industry practice requires. You could, I guess, go the other way and up rate something, as long as you knew its breaking strain and were competent to make that assessment. T Edit: This post by Chris Higgs though quite old, explains it all much better that I ever could. Link to comment Share on other sites More sharing options...
lightsource Posted December 10, 2009 Share Posted December 10, 2009 Sorry, but its quite simpleSWL is Safe Working Load, end of storySWL is just that, end of story Sorry, but from a non-rigger's point of view, and thinking of 'scarry scenario's ' (better known as a more in-depth risk assesment :unsure: ) where the sh*t may hit the fan.... If it is quite that simple, then how do you adjust your SWL figures for an outdoor event in (let's say for example) Gale force winds. Structures are up, then out of the blue, winds arrive! Brian asks a simple question, but what other factors need to be addressed to actually obtain good (reliable) figures for the harsher side of the uk weather. ( If it's relevant in his case). A lot of manufacturers quote various figures but never seem to factor for extremes. Sorry if I'm deviating from the OP a little, just looking more at the overall SWL vs real life scenario aspect of this topic. Link to comment Share on other sites More sharing options...
johnlinford Posted December 10, 2009 Share Posted December 10, 2009 Loading due to environmental conditions is not something that will affect the SWL of a structure. It is a load to be taken in to account when working out the total load on the structure - for example additional loading on a roof due to snow is part of the design calculations of the total load on the roof. There are guidelines available for wind loading of truss structures but once you get to that scale of event you really ought to have someone on your team with the knowledge and the experience to make the calculations. Link to comment Share on other sites More sharing options...
Psychedelic Theatre Posted December 13, 2009 Share Posted December 13, 2009 This is purely my understanding of the regulations, correct me if I'm wrong. As far as I know, the ABTT suggest a 8:1 safety ratio for equipment used in the theatre, whilst the standard safety ratio for lifting equipment used in other industries such as construction is 5:1. Therefore one could assume that the vast majority of hoists use a 5:1 safety ration. As it is never safe to assume, it would seem the only way to find out the safety factor and thus answer your question is to contact the manufacturer. Link to comment Share on other sites More sharing options...
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