Factor of Safety - Lift Turn Move

Unit 6, Appin Road, Argyle Industrial Estate
Birkenhead, Merseyside, CH41 9HH, UK
Tel : + 44 (0)151-649 0467
Fax: + 44 (0)151-649 0099
Email: sales@liftturnmove.co.uk
Web Site: www.liftturnmove.co.uk
Suspending Loads in Entertainment Applications- Version 3, September 2010
A guide to suspension of loads above people prepared by LTM- Lift Turn Move Ltd.
1/. Safety Wires (Safeties)
When the truss is in position, the rigger accesses the roof/ truss level and installs steel wire
ropes (safeties) at each lifting point these are attached to the load; there is generally one
safety wire alongside each lifting point/ hoist.
Rated lifting points for mounting of the safety wires are required in the roof.
Work at height is generally involved.
2/. Load Arresters
The Load arresters (that LTM offer) are rated at either 500kg or 1500kg and are attached at
high level alongside each hoist/ motor with the rope extended and attached to the load.
In the event of catastrophic failure, the load arrester detects movement and an increase in
speed of the load and when the arrester reaches a certain speed the brake operates to stop
the descent. This is similar in operation to a seat belt in a car.
Rated lifting points for mounting of the arresters are required in the roof.
Summary- If standard hoists are used with either safeties or load arresters there is no
need for any additional hoist safety features to be incorporated.
This is a simple suspension system and with the addition of safety wire rope suspensions
or load arresters meets UK Entertainment standards (BS 7905/ 7906) for suspending loads
above people.
3/. Hoists with Double Brakes
The use of double brakes fitted to hoists for lifting or suspending loads above people is
sometimes advocated in place of other solutions.
There is no UK law, Health & Safety Executive (H&SE) regulation/ acceptance, or any UK
safety standard which approves the use of double brakes only as safety features that allow
hoist use above people without secondary suspension.
Summary- LTM do not recommend double braked hoists for suspending loads above
people without additional secondary suspension.
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Hoists with Special Safety Features- The Options for suspending or moving loads above
people
The following has been prepared using the British Standard and the BGV specifications from
VPLT in Germany (VPLT is an association similar to PLASA and ABTT).
Use
Use
Origin of Regulation
BGV D8/
Normal
Hoist
Hoists to
BS 7906:
Part 1
Category A
BGV D8/
Normal hoist
with
Secondary
Safety
Component
BGV D8
Plus
BGV C1
Use According to BGV Regulations
When people are present below the load
UK/Europe
/ Germany UK Germany Germany Germany
Assembly/disassembly,
set up
Not
Permitted
Permitted
Not
Permitted
Not
Permitted
Permitted
Load–holding
Not
Permitted Permitted Permitted Permitted Permitted
Staging processes
involving movement
Not
Permitted
Permitted
Not
Permitted
Not
Permitted
Permitted
4/. Chain Hoists to BS 7906 Part 1: 2005- Category A, Use of Lifting Equipment for
Performance, Broadcast and Similar Applications
This is a British Standard which details Electric Chain Hoists suitable for lifting or suspending
loads above people without additional safety measures.
The standard divides hoists into Category A and Category B hoists.
Category A Hoists are declared by the manufacturer as intended for use by the
entertainment industry for lifting and suspending loads over people and meeting the
requirements of BS 7905-1 or DIN 56925. Category A hoists are suitable for lifting or
suspending loads above people without additional safety measures.
The following features are required.
Double Brakes - Essential
Brake Position - Brake acts directly to stop the load (the overload clutch is not in the drive
train)
Limit Switches – Normal top and bottom and emergency limits are essential
Mechanical Stops - End of travel (mechanical) stops essential
Emergency Stop - Essential
Secondary Suspension - Not necessary
Controller – Desirable
Chain Container - 50% fullness maximum
Note- We often receive enquiries for hoists to this standard but with increased factors of
safety, for ease we detail 3 safety factors with permissible loadings in our catalogue, we are
asked for these different factors on a regular basis.
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Category B Hoists are normal hoists which do not meet Category A requirements, these
require a secondary suspension system for suspending loads above people. (These could be
designated as hoists to German BGV D8 or normal hoists.)
5/. Hoists to BGV D8 plus: VPLT SR 2.0, Code of Practice for Event Technology
This is a German safety regulation published by VPLT, for hoists used for lifting loads during
setup and with the special characteristics of being able to hold loads at rest above people
without using a secondary safety component.
These hoists allow the following (when people are present below the load):
Load holding when loads are static
The hoists do not allow (when people are present below the load):
Assembly/ disassembly during set up
Staging processes involving movement.
The hoists have the following features:
2 separate brakes
Limit switches not required (but available on some hoists)
Overload monitoring – shutdown. A friction clutch is permitted if it is not within the
load path when the Electric Chain Hoist is disconnected from the power supply.
Underload monitoring- not required
Factor of Safety – 10:1, the lifting capacity is de-rated*.
Note* According to instructions from the German employer's Liability Insurance Association
the ratings of BGV D8 Plus and BGV C1 Hoists have to change. The Lifting Capacity now
becomes Rated Lifting Capacity, this is calculated by dividing the maximum lifting capacity
(with 10:1 safety factor) by the dynamic factor; this has the effect of reducing all the
previously stated Lifting Capacities.
Note- the standard calls for Direct Control Hoists (without controls and limit switches),
outside of Germany we generally offer Low Voltage Hoists with limit switches as we
consider this a safer unit which still meets the standard.
Summary- When hoists to BGV D8 Plus are used for load holding, a secondary suspension
system is not required and people are allowed to work below a raised load when in a set
position. Hoists to BGV D8 Plus are not rated for moving loads above people.
Although this is a German regulation, there should be no doubting its safety. BGV D8 Plus
hoists are not officially approved for use in the UK and selection is subject to a risk
assessment being carried out.
6/. Hoists to BGV C1: VPLT SR 2.0, Code of Practice for Event Technology
These hoists allow the following - when people are present below the load:
Assembly/disassembly during set up
Load holding when loads are static
Staging processes involving movement
These hoists are adapted to have the following features:
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2 separate brakes
4 position limit switches – limit switches & emergency limit switches
Shutdown at 120% of rated load (using a loadcell)
Underload monitoring – (using a loadcell)
Factor of Safety – 10:1, the lifting capacity is de-rated*
Note* According to instructions from the German employer's Liability Insurance Association
the ratings of BGV D8 Plus and BGV C1 Hoists have to change. The Lifting Capacity now
becomes Rated Lifting Capacity, this is calculated by dividing the maximum lifting capacity
(with 10:1 safety factor) by the dynamic factor; this has the effect of reducing all the
previously stated Lifting Capacities.
Hoists to this regulation are tested and approved by TUV offices throughout Germany and
relevant certification issued. Control systems do not require an official BGV C1 approval
certificate. Each BGV C1 system has to be approved on site by a special theatrical engineer
when integration tests are carried out.
The only exception is SIL 3 control systems; these have to have a separate official approval.
Control systems monitor the special features and in the event of any of the safety features
being breached- overload, slack chain or emergency limit being contacted, the entire system
shuts down. A bypass for the emergency limit is required so that an inspection engineer is
able to test limit switches and brakes of the hoists individually
Control systems operate manually or can operate via computerisation using encoders which
can monitor the position of the hoists/ load. Often encoders are required to control hoist
positions etc.
Summary- When hoists to BGV C1 are used, a secondary suspension system is not
required and people are allowed to work below a raised or moving load.
Although this is a German regulation, there should be no doubting its safety. BGV C1
hoists are not officially approved for use in the UK and selection is subject to a risk
assessment being carried out.
7/. CWA 15902- 1, Lifting & Load- Bearing Equipment for Stages and other Production
Areas within the Entertainment Industry- Part 1.
This is a relatively new CEN agreement dated December 2008 to try and standardise on
procedures for entertainment lifting equipment. The document states- The CEN Workshop
Agreement can in no way be held as being an official standard.
(LTM thoughts- This seems to call for single brakes and the lifting capacity needs to be
derated to 50% of the normal working load limit. No other safety features or other
regulations are required. This is for suspension only, not for moving loads above people.
I refer below to specific details in the document to help users assess the agreement.
Page 31 – 7 Overhead suspension of loads- states that where standard lifting machinery
and accessories compliant to Machinery Directive 2006/42EC are used to provide overhead
suspension of loads and where it is not required to move these loads above people, the
following applies after a satisfactory risk assessment has been carried out.
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7.2 Lifting Equipment- Standard lifting equipment should be loaded to no more than 0.5
times the safe working load as given by the manufacturer.
(LTM thoughts- This equates to an increased safety factor of around 10:1)
7.3 Direct acting force limiters- Direct acting lifting force limiters lying in the kinetic chain
between the load and the securing devices are admissible.
(LTM thoughts- This indicates that an overload clutch within the drive train is permissible,
unlike the other standards detailed above)
7.4 Single components- Single components in the kinetic chain (e.g. a single brake) are
admissible providing they are rated for a minimum of 200% of the applied load.
(LTM thoughts- Single brakes are allowed when the load is de-rated as in 7.2- unlike the
other standards detailed above)
7.5 Lifting accessories- Standard lifting accessories shall be loaded to no more than 0.5
times the safe working load as given by the manufacturer. Examples of lifting accessories
are shackles, roundslings, wire rope slings, O-rings, beam clamps, clutch chains etc.
7.6 Precautions during the lifting and lowering operation- arrangements should be made to
secure the working area and appropriate measures shall prevent unauthorised starting.
(LTM thoughts- no one below a moving load)
7.7 Secondary suspension- When an equivalent secondary suspension is used, lifting
equipment and accessories can be loaded to the safe working load as given by the
manufacturer.
(LTM thoughts- if a hoist is de-rated to 50% of its Safe Working Load or working load limit it
can be used to suspend loads above people (not move loads) without secondary
suspension)
Note- We understand that if this CEN workshop agreement operates for five years it can be
changed into an official standard.
Please Note:
This document is under copywrite to LTM – Lift Turn Move Ltd, Birkenhead; please consult
us before you circulate the document, please contact JohnJones@liftturnmove.co.uk
This is a guide only and is based on UK practices. It is not meant as an exhaustive list – the
validity of the statement made should be independently checked.
All load points should be the subject of a Structural Engineers Report and certification.
Use a professional qualified company as your supplier; they can provide you with the back
up and support that you need.
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