Prof Krishna's Answer Box
If you have any questions or comments to post in response to any of the topics discussed below, or something new, please send me an e-mail (email@example.com)
|22 Dec 2011||
You keep emphasising that Asians should not carry (especially lifting from a bent position) more than abaout 25kg.
[TO BE COMPLETED-- NK]
10 Feb 2009
Can you give us any guidance for lifting of persons by means of cranes beyond what is provided by Singapore's CP63?
ANSWER: CLICKING ON THE FOLLOWING UNDERLINED LINKS WILL TAKE YOU TO THE SOURCE MATERIAL:-
1. From OSHA (USA)
2. From Construction Forestry Mining Energy Union (Australia)
3. From Washington State Legislture (USA)
4. From California State Goverrnment (USA)
5. From "Lifting World - The world famous Lifting World web forums" (EUROPE)
EXTRACT FROM 'LIFTING WORLD'
Firm guidance on the design and use of man-baskets suspended from cranes comes with the publication of EN 14502-1 Cranes – Equipment for lifting persons - Part 1: Suspended Baskets. This European Standard was approved by CEN on 25 May 2005 and will be published by BSI within the next few weeks. The new standard has not been mandated under the Machinery Directive, which means that it takes the form of guidance rather than a legally binding document. However, anyone facing a law suit will be in a weak position if they have not adhered to published best practice,
Which the standard represents. Nor does the standard take precedence over national laws governing the use of man-baskets on cranes (France, for example, takes a much stronger line than the UK against the practice). Among the demands of EN 14502-1for the design of baskets are the following key points: Suspended baskets shall be incombustible and protected against corrosion. The basket shall have a minimum freestanding height of two metres. When the suspended basket is designed to be used in situations where falling objects may be a hazard, the basket shall have a roof, able to withstand the impact of a steel ball weighing 7kg, falling from a height of two metres. When calculating the rated capacity, the weight of each person shall betaken as at least 80kg plus at least40kg of equipment for each person .A safety factor of at least two must be used in design calculations. The basket must be attached to the crane hook with either steel wire rope slings according to EN 13414-1or chains according to EN 818-4with a safety factor of at least: eight for chains, and 10 for wire ropes, including the end termination. The slings shall be fitted to the basket in such a way that they can only be removed with tools. The vertical distance between the floor of the basket and the crane hook shall be no more that three metres. The floor of the basket shall be secured to the frame by welding or some other equally effective means. The floor must be slip resistant and have drainage.
Free space on the floor shall be at least 600mm x 600mm for one person, and at least 400mm x 400mm more for each additional person. Suspended baskets must be designed so that if a load 1.5 times the rated capacity is applied at the worst position on the floor, any resulting inclination shall not exceed 20°.
Any gate shall not open outwards and shall have an automatic catch to prevent it from being opened inadvertently. Baskets shall have anchorage points in accordance with EN 795 for personal protective equipment and people in the basket shall wear a harness with lanyard. The standard also sets out detailed requirements for handrails and contents of the instruction manual.
The manual must state that the suspended basket shall only be used in combination with cranes, which are designed for the lifting of persons. The only clue as to which cranes are considered" designed for the lifting of persons" comes with the proviso that cranes must have powered lowering and not free-fall winches.
The manual must also state that: The crane and the suspended basket shall only be operated by people trained in the safe use of the combination, including the operating procedures for egress in case of power supply failure or control failure.
A crane driver should always be present at the normal crane control station when the basket is occupied.
Visible and audible communication should exist between the persons in the basket and the crane driver at all times during the lifting operation. The required equipment necessary to perform an emergency rescue shall be available throughout the lifting operation. During operation the employer should not require the crane driver and signaller to do other work at the same time, or direct a second crane and/or Basket.
Lifting slings for suspended baskets should not be used for any other purpose. Suspended baskets should not be used in wind in excess of 7m/s (25km/h), electric storms, ice, snow, fog, sleet, or other adverse weather conditions that could affect the safety of personnel. Machines, which can be operated simultaneously in the same place with risks of collision, should be stopped. Unintended movement of the basket should, where possible, be prevented e.g. by means of guide ropes or anchoring.
The suspended baskets, hook, catch, and fixed load lifting attachment should be inspected prior to each use. The hook must have a safety catch .The basket shall be positioned on a firm surface when entering or exiting. The lifting and supporting should be made under controlled conditions and under the direction of one appointed person.
6 Oct 2006
"Is there an easy way to visualise the various categories of risks after we have done the assessment, and also what we should do with them? "
15 Aug. 2006
EXISTING CONTROLS IN RISK ASSESSMENT
Mr. T., a participant in one of my Hazard Evaluation and Risk Analysis courses, asks:
"In MOM's published Risk Management Guidelines, in assessing severity, it says that we should not consider the existing controls. It seems very unrealistic if we ignore existing controls in assessing the severity because the existing mitigation can be such that it actually lowers the severity and not just the likelihood."
1. With the exception of highly specialized processes under strict quality control, Risk Assessment (RA) for the most part is quite subjective and qualitative. Hence, various paths exist to achieve the goal of risk assessment and management.
2. There is no right or wrong way to do RA. But all procedures must include: (a) Hazard identification (HI), (b) Likelihood and consequence evaluation, (c) Risk estimation, and (d) Risk control. Certainly, by the time one reaches step (d), existing controls (EC) must be taken into consideration before the residual risks are determined and controls implemented.
3. The question is when the EC are recognized and accounted for. This too is a subjective matter, depending on various factors such as nature of activity, experience and expertise available, and regulations governing it.
4. In practice, EC can be considered at any one of three stages:
[QUESTION to readers: How about netting or air-bags around scaffolding as severity-reducing existing controls? Comment, please!]
(c) AFTER RA: Consider EC after doing the RA. Then check if and how much the EC reduce the risk level.
5. It is more important to account for EC at some stage, in such a way that unnecessary time and effort are not wasted in evaluating risks which are well-known and controls for which are commonly implemented, usually mandated by authority.It is also critical to check whether the existing controls perform as planned, and whether they are being adopted by the workers as expected.