Bs 7121 Part 5 (97) Tower Crane

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BS 7121 : Part 5 : 1997

BRITISH STANDARD

Code of practice for

Safe use of cranes Part 5. Tower cranes

ICs 53.020.20

PYING

SI PERMISSI

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BS 7121 :Part 5 : 1997

Committees responsible for this British Standard The preparation of thisBritish Standard was entrusted to Technical Committee MHE/3, Cranes and demcks, upon which the following bodies were represented: Associated British Ports Association of Lorry Loader Manufacturers and Importers British Iron and Steel Producers’ Association Building Employers’ Confederation Constsuction Plant-hire Federation Electricity Association Engineering Equipment and Materials Users’ Association Federation of Manfuacturers of Construction Equipment and Cranes Federation of Wire Rope Manufacturers of Great Britain Health and Safety Executive Institute of Logistics Institute of Mechanical Engineers Institute of Occupational Health and Safety Institute of Plant Engineers Institute of S t r u c m Engineers Lifting Equipment Engineers Federation Lloyd’s Register of Shipping Safety Assessment Federation LM. The foliowing bodies were also represented in the drafhng of the standard, through a subcommittee: Amalgamated Engineering Union (Constmction Heaìth and Safety Group) Federation of Civil Engineering Contractors Institute of Civil Engineers Oil and Chemical Plant Contractors’Association Ltd.

This British Standard, having been prepared under the direction of the Engineering Sector Board, was published under the authoriw of the Standards Board and comes into effect on 15 July 1997 O BSI 1997

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Date

Text affected

The foliowing BSI references relate to the work on this standard Committee reference MHEí3 Draft for comment 92/71042 DC

ISBN O 580 25805 X

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Contents

Committees responsible Foreword

page Inside front cover 11

Code of practice 1 1 scope 1 2 References 1 3 Definitions 1 4 Management of the lifting operation 1 6 Planning the lifting operation 2 6 Selection and duties of personnel 2 7 Attributes of personnel 3 8 Selection of tower cranes 11 9 safety 12 10 Siting of cranes 13 11 Erecting, dismantling and aiteration of height 14 12 Procedures and precautions 15 13 operating conditions 15 14 Testing and examinaton 16 16 Legai requirements 16 16 Ropes 16 17 Slinging and handling of loads 16 18 Raising or lowering of personnel 16 19 signalling systems 16 20 m g and guying 16 21 Signboards " Annex (informative) Specimen copy of informaîion sheet RA 195 published by A 17 the Radio Communications Agency Figures 1 Qpesoftower 5 2 of jib 6 3 mesofbase 8 4 Low mounted tower crane 10 Inside back cover List of references

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BS 7121 :Part 5 :1997

Foreword This Part of BS 7121 has been prepared by Technical Committee MHE#. It provides recommendations for the safe use of tower cranes. It should be used in conjunction with BS 7121 : Parts 1and 2, to which specific references are made. It is in the interest of all parties involved in lifting operationsto ensure that these operations are carried out efficiently and safely. This Part of BS 7121 has been written to provide recommendations for the safe use of the tower crane at all stages of its utilizaton.

This Part of BS 7121 is commended to owners and users of tower cranes, who are encouraged to observe all the recommendations, and where possible, upgrade emsting equipment and operating procedures accordingly. Whilst it is recognized that the recommendations given do not relate to the design and manufacture of tower cranes, designers are strongly advised to take them into consideration.

This Part of BS 7121 is one of a series of standasds entitled Code of pmcticefor safe use of c r a m as follows: Partl. GfYnEmL Part 2. Inspection, testing and exurnimttion Part 3. Mobile cranes1) Part4. Lorryloaders Part5. Towercmnes Part 6. Derriclc munes1) Part7. íhwhedunderhung tmvding and goliath mm') Part 8. High pedestal and portaE jib cranes1) part 9. Container h a d i n g maw') part 10. RU~Jmounted cmnesl> part 11. ûfls/tm-emnesl) It has been assumed in the draffing of this British Standard that the execution of its provisions is entrusted to appropriately qualified and experienced people. A s a code of practice, this British Standard takes the form of guidance and recommendations. It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading.

Annex A is reproduced with permission of the RadioconununicationsAgency. Attention is drawn to relevant legislation and, in pAcular, to statutory requirements for the testing and examination of cranes.

Compliance with a British Standard does not of itself confer immunity from legal obligations.

Summary of pages This document comprises a &ont cover, an inside h n t cover, pages i and ii, pages 1to 18, an inside back cover and a back cover.

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Code of practice 1 Scope

4.2.2 Other particulars

This Part of BS 7121 gives recommendations for the safe use of tower cranes. It should be read in conjunction with BS 7121 : Park 1and 2. Subjects covered include planning the installation, erection, testing, maintenance, operation and application, dismantling, and transportation, as well as safety measures to be taken during the execution of all the above functions. It also covers the appropriate selection of personnel for safe use of tower cranes. NOTE. Reference is made to different types of tower crane and it

On sites where there is more than one tower crane and there is a possibility of collision between cranes, a person, the crane coordinator (see 6.3.2), should plan the sequence of crane movements to prevent collisions. Any corresponding instructions from the crane coordinator to the crane drivers should be via the respective signallers. In such circumstances the signallers should obtain the agreement of the crane coordinator before canying out any operation. Where tower cranes inter-arc, a vertical distance should be maintained to prevent collisions. This distance should be either: a) a minimum clearance of 3 m; or b) a minimum clearance of 600 mm plus the manufacturer’s deflections where full details are available from the manufacturer. The positioning of the crane and components in the out-of-service condition, as specified by the manufacturer’s instructions, should be such that no collisions can take place (see 12.4b).

should be noted that these types are often combined, for example, seìf-erecting, raiimounteà, luffing jib.

2 References 2.1 Normative references This Part of BS 7121 incorporates by dated or undated reference, provisions from other publications. These nonnative references are made at the appropriate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this Part of BS 7121 only when incorporated in the reference by amendment or revision. For undated references, the latest edition of the cited publication applies, together with any amendments.

2.2 Informative references This Part of BS 7121 refers to other publications that provide information or guidance. Editions of these publications current of the time of issue of this standard are listed on the inside back cover but reference should be made to the latest editions.

3 Definitions For the purposes of this Part of BS 7121 the definitions given in BS 7121 : Part 1: 1989 apply, together with the following: zoning device An electromechanicaYelectronic device to control the zone in which a tower crane works.

4 Management of the lifting operation 4.1 Safe system of work Reference should be made to 3.1 of BS 7121 : Part 1: 1989. 4.2 Control of the lifting operation 4.2.1 General Reference should be made to 3.2 and 3.3 of BS 7121 : Part 1: 1989.

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4.3 Duties of the person appointed to control

the lifting operation Reference should be made to 3.3 of BS 7121 : Part 1: 1989. In the interests of safety the appointed person should arrange the lifting programme such that no one driver has to be in attendance at the control station or actually operating the crane for an unreasonably long period, taking into account environmental conditions. The driver should have breaks from the working activity in line with other personnel on the site. 4.4 Contractual considerations 4.4.1 Contract lfling operations Reference should be made to 3.4.1 of BS 7121 : Part 1: 1989. 4.4.2 User’s duties when using hired cranes Reference should be made to 3.4.2 of BS 7121 : Part 1: 1989.

5 Planning the lifting operation 6.1 General Reference should be made to clause 4 of BS 7121 : Part 1 : 1989.

6.2 Other particulars If the slinger or signaller is required to carry out a liftiig operation which is outside the existing plan, the appointed person should be alerted. The appointed person should delay that particular lifting operation until a plan can be prepared for it.

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6 Selection and duties of personnel

7 Attributes of personnel

6.1 Selection Reference should be made to 6.1 of BS 7121 : Part 1: 1989 and 6.1 of BS 7121 : Part 4 : 1997.

7.1 Crane driver Reference should be made to 6.1 of BS 9121 : Part 1: 1989. Tower crane drivers can be required to climb to considerable heights and to spend long periods of time in isolation. Thii should be borne in mind when selecting tower crane drivers.

6.2 Duties 6.2.1 Crane driver Reference should be made to 6.2.1 of BS 7121 : Part 1: 1989.

7.2 Slinger Reference should be made to 6.2 of BS 7121 : Part 1: 1989.

6.2.2 Slinger Reference should be made to 6.2.2 of BS 7121 : Part 1: 1989. 6.2.3 Signaller Reference should be made to 6.2.3 of BS 7121 : Part 1: 1989.

7.3 Signaller Reference should be made to 6.3 of BS 7121 : Part 1: 1989.

6.2.4 Crane erector Reference should be made to 6.2.4 of BS 7121 : Part 1: 1989.

7.4 Crane erector Reference should be made to 6.4 of BS 7121 : Part 1: 1989.

6.2.6 Maintenance personnel Reference should be made to 6.2.6 of BS 7121 : Part 1: 1989.

7.6 Maintenance personnel Reference should be made to 6.6 of BS 7121 : Part 1 : 1989. In addition, the maintenance personnel should be: a) fully conversant with the appropriate sections of the manufacturer’s instruction m a n w b) familiar with the ‘permit to work system where it is required by the safe system of work, and able to operate it correctly; c) familiar with all aspects of their personal protective equipment and capable of using it correctly.

6.2.6 Crane coordinator The crane coordinator should plan the sequence of operations of tower cranes on sites having more than one crane, to ensure that cranes, components and loads do not collide. 6.2.7 Crane erection supervisor NOTE 1. The crane erection supervisor is the ‘erector in charge’, as detaileà in 5.2.4 of BS 7121 : Part 1 : 1989.

The crane erection supervisor should have the responsibilities of a crane erector plus the following. a) The crane erection supervisor should be in control of ali crane erectors and of any additional cranage and lifting equipment which may be used in the erectionldismantling operation. b) The crane erection supervisor should provide a means for ensuring that the operation is carried out in accordance with the crane coordinator’s plan. c) Additional cranage and equipment should be in accordance with that specified and properly certified. d) All erectors should be equipped with the necessary tools and personal protective equipment. NOTE 2. The appointed person (see 3.2 of BS 7121 : Part 1 : 1989) retains overall responsibiiity for the erectioddkrnantling operation, including the planning.

If the crane erection supervisor has to leave the site of the operation, even for a few minutes, he or she should appoint another member of his/her team to be in charge during the period of absence, in order to prevent any ambiguity as to the control of the operation. NOTE 3. The crane erection supervisor should attempt to remain on site throughout the whole of the erectioddkmantiing operation.

7.6 Crane coordinator The crane coordinator should be: a) competent; b) over 21 years of age unless under the direct supervision of a person competent for the purposes of training; c) fit, with particular regard to eyesight, hearing, reflexes and agility; d) experienced for at least five years in the use of tower cranes; e) trained in the techniques of signalling and with a good understanding of the signai code in figure 2 of BS 7121 : Part 1: 1989; f ) capable of giving precise and clear verbal instructions where audio equipment (e.g. radio) is employed, and capable of operating such equipment in accordance with 19.2.

7.7 Crane erection supervisor The crane erection supervisor should have the same attributes as the crane erector and: a) have at least five years’ experience in the erection and dismantling of tower cranes or similar equipment, and be trained in the supervison of such operations;

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b) be fuily conversant with the manufacturer’s instruction manual for the particular crane (see note); c) be trained in the control of personnel carrying out the duties of erecting and dismantling tower cranes, and in ensuring that all persons use their personal protective equipment correctly; d) have knowledge of the certification requirements for all equipment used. NOTE.The crane erection supervisor should be in possession of the manufacturer’s instruction m u a i for the particular crane.

8 Selection of tower cranes 8.1 General Selection of a tower crane for a particular liftiig operation should be considered by taking the following into account a) clause 7 of BS 7121 : Part 1: 1989; b) prevailing wind-speeds, which can restrict the use of tower cranes in certain locations; c) principal features of the common types of tower crane, as described in this Part of BS 7121. NOTE. Sîatic and mobile tower cranes are available in a wide variety of types and conñgwations according to the particular combination of tower, jib and type of base which they employ. individual cranes can comprise almost any combination of the features shown in figures 1 , 2and 3.

8.2 Types of tower (see figure 1) Tower cranes have either a non-slewing or slewing tower. With a non-slewing tower, the slewing ring is situated at or near the top of the tower and the jib slews about the vertical axis of the tower, which itself remains stationary. With a slewing tower, the slewing ring is situated at the bottom of the tower and the whole of the tower and jib assembly slews relative to the base of the crane. Where non-slewing towers have to be tied to a fixed structure, it is imperative that the manufacturer’s instructions are followed. The ties should be designed by a competent person to withstand the loads specified by the manufacturer, and be attached to a structure capable of withstanding the imposed loads. 8.3 Types of jib (see figure 2) 8.3.1 Horizontal trolley j i b The jib is held by tie bars or ropes in a horizontal or slightly raised position, and the hook is suspended from a troiley which moves along the jib to alter the hook radius. A suitable allowance needs to be made for deflection when calculating the clearance between adjacent cranes (see 4.2.2). 8.3.2 Inclined trolley j i b The inclined trolley jib is similar to the horizontal trolley jib except that the jib may be set at a significant angle of inclination.

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8.3.3 L m n g j i b The jib angle can be changed to reposition the load at various radii. The jib may be single- or multi-component, and if multi-component, may be articuiated (goose necked) or telescopic. Due to the varying out-of-service conditions for these cranes particular care should be taken to observe the manufacturer’s instructions (see 12.4b). 8.3.4 Fixed radius j i b The radius at which the load is carried cannot be varied. Fixed radius jibs are usually only available on small tower cranes (self-erectors and similar), and it is generally desirable to be able to travel the crane in order to move the load. 8.4 Types of base (see figure 3) 8.4.1 Expendable base The crane is mounted on special foundation anchors or an expendable tower section, cast into a concrete foundation block. (see figure 3d). NOTE. It is important that the foundation anchors or expendable tower section are installed withii the maker’s tolerance of accuracy to ensure that the erected crane is within operational limits.

8.4.2 Crane base structure The crane stands on its own base structure with ballast (cil1 base) or with its base structure bolted down to a concrete foundation block (cruciform base). With this arrangement a larger area of ground floor space is taken up and, therefore this type of base is not always acceptable on small sites. Where the base is secured by ballast blocks there should be a notice attached detailing the position and weight of the blocks, and that the blocks should be adequately secured to prevent accidental displacement. The ballast arrangement should not be altered after the crane has been tested, for constructional or any other reasons (see 9.4.10). 8.4.3 Non-crane structure A base provided by a structure which is not a normal part of the crane (e.g. part of a bridge, a building or structure provided specifically for such a purpose). 8.6 Types of tower crane 8.6.1 Climbing crane A climbing crane is a tower crane that may be altered in height after initial erection. Where the crane remains on its original base this may be achieved by the use of internal telescoping equipment or external climbing frames. Another type of climbing crane can ascend through a structure using a climbing frame, the supported crane being provided by the surrounding structure. NOTE. This type of crane requires less initiai outlay due to the reduced quantity of mast required, but it has disadvantages in that the stnicture needs to have adequate strength and rigidity to carry the imposed loads, and the mast through the middle of the structure may interfere with the completion of the structure. Consideration should also be given to the dismantling of the crane once the structure is completed.

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8.6.2 Rail mounted tower crane A rail mounted tower crane is mounted on a chassis frame which is supported on rail wheels which are usually double flanged. There can be four single wheels on smaller machines or more usuaiiy four double wheel bogeys. The wheels or bogeys can have special mountings to enable the crane to negotiate bends. Rail mounted tower cranes may be of any of the types described in 8.2 and 8.3. Stability is normally obtained by means of ballast weights which should be adequately secured to prevent accidental displacement or removal, and the detail of the ballast should be on the notice near the base of the crane giving the crane capacities. NOTE.Rail tracks for tower cranes are in 10.3.2.

0.6.3 Lorry mounted tower crane (see figure 4) A lorry mounted tower crane is mounted on a truck or lorry chassis. These are particularly suitable when considerable inter-site mobility is required. Extra care should be taken in ensuring that outriggers, jacks, etc., are adequately supported for their imposed loads. 8.6.4 Wheel mounted tower crane Some very small capacity tower cranes are available on trailer mounts with pneumatic tyres. These machines need to be towed into position and should be properly mounted on their outriggers or jacks before erection or use. The manufacturer's erection instructions should be scrupulously observed and if the operator is to erect and dismantle this type of crane, he or she should be specifically trained and have the athibutes of an erector (see 7.4).

0.6.6 Crawler mounted tower crane Some tower cranes mounted on a crawler base have means of self-levelling. They are equipped with a sensing device to detect verticality. The seif-levelling function has a limited range of correction and great care should be taken when travelling over uneven ground. Crawler mounted cranes without self-levelling should not be moved over uneven ground when erected.

8.6.6 Micro tower crane Micro tower cranes are tower crane units complete for mounting on the top of either a special mast or a hoist mast. "hey usually have a radius of approximately 6 m, a safe working load always under 1000 kg and are remote controlled. Micro tower cranes are generally used for offloading materials and placing within a limited area of a building. 8.6 Remote controls Where cranes are available with remote controls, care should be taken in their use for the following reasons. a) The crane driver has no 'feel' for the machine and could, under certain circumstances, be tempted to handle the machine more dangerously than if the crane were operated via a cabin control. b) Infra-red remote control may be unreliable on tower cranes if the receiving sensor rotates with the crane and thus loses alignment with the transmitter. NOTE. Remote controls have one main advantage in that the crane driver can be at a point of safety when the crane is in use, especially during overload testing.

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a) Fixed tower

b) Slewing tower

Figure 1. Types of tower

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Fweá section of tower

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a) Saddle (horizontal) jib

b) Luffing jib

Figure 2. Types of jib

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Trolley moves along boom

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c) Fïxed jib

d) Rear pivoted luffing jib

Figure 2. Types of jib (continued)

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Sleepers

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a) Travelling base (raii type)

b) Cill base

Figure 3. Types of base

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Ballast weights

Cruciform base ballasted

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Cruciform base unballasted c ) Cruciform base

of crane tower

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d) Expendable base

Figure 3. Types of base (continued)

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Figure 4. Lorry mounted tower crane

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9 Safety 9.1 General Reference should be made to clause 8 of BS 7121 : Part 1: 1989. 9.2 Personal protective equipment 9.2.1 Personnel whose duties include working at heights on tower cranes should be provided with the necessary safety equipment, e.g. safety harnesses, as well as lifelines or similar equipment to attach to safety equipment. Such personnel should be instructed in the correct use and maintenance of such equipment and instruction should be given regarding the specific occasions and circumstances when these items are to be used.

which may interfere with each other’s freedom of movement. Such devices should limit the slew, the trolley motion, or the travel motion of the crane to ensure that coilision between the structure of one crane and the rope or load of another crane is impossible. NOTE.It may be considered preferable to have these devices equipped to warn or give information to the driver, rather than interfere with the operation of the crane.

Where t r a g cables run between one crane and another, consideration should be given to the means required to protect them adequately against interference or accidental damage. 9.6 Other safety provisions 9.6.1 Lightning protection Tower cranes should be completely and correctly earthed. Reference should be made to BS 6651 and BS 7430.

9.2.2 Personnel should be advised when and where helmets should be worn with respect to the Construction (Head protection) Regulations, 1989 [i]. 9.6.2 Base ballast design Heimets with chin straps should be used when When concrete ballast needs to be provided, working at heights. particularly in the case of new tower cranes, it is important that the ballast should either: 9.2.3 Personnel working on tower cranes should wear suitable footwear for climbing structures. a) have been constructed in accordance with the crane manufacturer’s design and specification; or 9.3 Fire extinguishers b) be of a design which has been approved by the Reference should be made to 8.6 of BS 7121 : crane manufacturer, and effectively secured. Part 1: 1989. Only ballast blocks having markings showing their Tower cranes should be equipped with appropriate correct weight should be used. types and quantities of fire extinguishers, which should be easily accessible to the driver. 9.6.3 Counterweight ballast The driver and any other personnel likely to be in Counterweight ballast should be constructed and the cab should be adequately trained in the use of marked in accordance with 9.6.2. Since the such fire extinguishers. counterweight ballast is at height and the blocks have a tendency to rub together during crane 9.4 Crane safety equipment operation, precautions should be taken to prevent Tower cranes should be provided with the following spilled concrete from falling (e.g. by containment in as a minimum: a metal box or frame). a) automatic safe load indicator, in accordance 9.6.4 Alarms with 8.7.1 of BS 7121 : Part 1 : 1989; R ail mounted tower cranes should be fitted with an b) load radius indicator, in accordance with 8.7.2 audible travel alarm. of BS 7121 : Part 1: 1989; c) motion limiting devices, in accordance with 9.6 Documentation 8.7.3 of BS 7121 : Part 1 : 1989 9.6.1 General d) overload cut-out devices, in accordance with Reference should be made to 8.8 of BS 7121 : 8.7.4 of BS 7121 : Part 1 : 1989 Part 1 : 1989. e) level indicator, in accordance with 8.7.6 of BS 7121 : Part 1: 1989; 9.6.2 Erectioddismantling and transport f ) anemometer, in accordance with 8.7.6 of All stages of transportation, erection and dismantling BS 7121 : Part 1: 1989; of tower cranes should be thoroughly documented g) machinery guarding, in accordance with 8.7.7 from initial enquiry to the final acceptance by the of BS 7121 : Part 1: 1989; user organization. h) zoning devices. 9.6.3 Drivers’ documentation Zoning devices may be applied to a single tower Records should be kept of tower crane drivers’ crane where there is an area which it should not training and experience, including such certificates oversail during operation, or over which it should of training as may be available. not cany loads. The principal use of zoning devices, however, is where there are two or more cranes

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9.6.4 Medical records Records should be kept of any medical examination for lifting operations personnel. 9.6.6 Plans and method statements The plan or method statement for the erection of tower cranes should be retained throughout the duration of a crane’s service on any one contract, together with calculations and plans for the tower crane base. NOTE. It may be necessary to refer to these in the event of a change of construction in the come of the contract requiring alterations to be made to the crane.

9.7 Access and cab safety 9.7.1 General if personnel need to be present on the crane whilst the machine is in use, they should always inform the driver. NOTE. It is recommended that access to tower cranes should be prohibited to personnel whose presence is not essential, wherever possible.

9.7.2 Crane access The appointed person should ensure that ladders, rest platforms and other means of access are in accordance with current regulations and standards. The erection supervisor should ensure that access equipment is correctly installed progressively as erection proceeds, so that the erection team have the benefit of their use. Particular attention should be paid to: a) ladder joint bolts, b) guard rails, particulaxly on rest platforms and inspection platforms; c) access from ground to the foot of the lowest ladder or to the chassis of the crane; d) access from levels of the construction to the crane. 9.7.3 Jib and counterjib access Access to and along jibs and counter jibs for inspection and servicing should be made safe. Catwalks should be provided with handrails. Where lifelines are provided, a suitable device should be used in codunction with the harness to permit full passage along the jib without detachment. NOTE. Personal carrying cages attached to the trolley may provide suitable aiternative safe access along the jib.

9.7.4 Cab sqfety The appointed person should verify that: a) vision panels in the floor of cabs or at the driver’s feet, in such a position that they may have to withstand all or part of the driver’s weight, are guarded, for example by a mesh of adequate strength to carry a person’s weight over the area concerned; b) window panels in walls of cabs are protected against being knocked outwards to prevent persons falling through the aperture;

c) panoramic and similas cabs of which the top part may be opened, conform to the Construction (Work places) Regulations, 1966, Regulation 28 [3].

10 Siting of cranes 10.1 General Reference should be made to clause 9 of BS 7121 Part 1: 1989. Attention is drawn to 4.2.2 of this Part of BS 7121. 10.2 Ground conditions Where tower cranes are to be erected close to the foundations of existing buildings or buildings to be constructed, the appointed person should ensure that the ground is consolidated as required by the designer. Where disturbance to the ground has occurred in the construction of adjacent foundations, a retaining wall should be constructed or deeper foundations used for the tower crane. 10.3 Tower crane foundations 10.3.1 Expendable base blocks Minimum dimensions for any expendable base block together with the overturning moment and other loadings during operation and out-of-service conditions should be as specified by the crane manufacturer. Having obtained from the crane manufacturer the loads imposed by the crane (noting that these may be nett and exclusive of any impact of safety factors), the foundation should be designed by a competent engineer so that the ground bearing capacity is not exceeded, including that caused by overturning moments. Where the base design limits the free standing height of the crane, the maximum permitted free standing height should be marked at the base of the crane and entered into the documentation. 10.3.2 Rail tracks f o r tower cranes Rail track should be made of suitable materials and strict control should be exercised to ensure that it is not in any way abused. NOTE. Rail track requires expertise in its design, layout and installation, particuìarly if it is to be curved.

The area between the tracks should never be used for the storage of materiais or for access to, from or across the site. The total area of the rail tracks should preferably be fenced off to prevent access by unauthorized persons. If there needs to be a point at which vehicles cross the rail track, this should be carefully controlled to prevent accidental collision, and precautions should be taken to ensure that the track is not overloaded by the vehicles crossing it. The gauge of rail tracks should be maintained by suitable means, e.g. tie bass. Rail tracks should not be welded or subjected to heating.

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End stops or buffers should be positively futed to the rail and precisely adjusted to ensure that the crane makes contact with both sides simultaneously. These end stops should be shock absorbing or sprung, and should be moved hard against the crane chassis if the machine is to be used in a static position for any period of time. Rail stops should not be taken into account when calculating the stability of the machine. Rail clamps which the crane manufacturer may provide to prevent the crane fi-om roiling along the track in storm conditions should be fitted whenever the machine is out-of-service. If clamps are not supplied, adequate means should be adopted to achieve the same result. Rail tracks of all types require periodic inspection, and should any defect or out-of-level become apparent, corrective action should be instigated immediately.

11.3 Control In the case of erection and dismantling of tower cranes, the person appointed to control the lifting operation should also take control of any additional crane which may be used in the course of such an operation, and be familiar with details of that crane, to facilitate the carrying out of the duties, as detailed in 3.2 and 3.3 of BS 7121 : Part 1 : 1989. He should also ensure that the operation is under the constant supervision of the crane erection supervisor. 11.4 Planning for erection and dismantling NOTE 1. The plan for the erection and particuiarly the dismantling of tower cranes requires careful consideration. Most organizations who erect tower cranes, either for themselves or for others, utilize some form of pro forma or check list to ensure that nothing has been overlooked at the planning stage.

A plan for the erection or dismantling of tower cranes should be drawn up by a person or persons having actual experience of these operations. The 10.3.3 Special base plan should deal with the following: Where the particular application calls for a special a) the format in which the crane is to be base arrangement, e.g. structural steelwork, then the transported to the site; appointed person should ensure that the base k. b) the selection of cranes that will be required to a) designed by a competent engineer, allowing for assist in the erectioddismantlingprocess, any appropriate factors (e.g. impact, dynamic), especially considering the removal of components with the details of the design verified by a from a height; e.g. when removing a section such competent third party; as a jib from an erected tower crane, the assisting b) constructed in accordance with the design. crane wiil be carrying the entire load with no opportunity for safely replacing it once the attachment pins have been removed. in this case it 11 Erecting, dismantling and may be desirable for the crane to have some alteration of height excess capacity to allow for any error in the 11.1 General slinging of the component concerned or its sudden release. Under no circumstances should the crane Reference should be made to clause 10 of BS 7121 : used in the dismantling operation be used to break Part 1 : 1989. a load free. A method of jacking should be used to Erection, dismantling and alteration of height of prise the load free after the initial tension is taken tower cranes should not be undertaken after dark. by the crane; 11.2 Personnel c) the availability of access to the site for the vehicles involved in transportation as well as the The erection, dismantling and alteration of the height crane(s) used for erection; of tower cranes should be carried out by specialist personnel under the continuous control of the crane d) the ground conditions for the erecting crane; erection supervisor and in accordance with the e) the free standing height to which the crane will manufacturer’s instructions. This supervisor should be erected be given the authority to stop the operation if he or f ) proximity hazards. Attention is drawn to 9.3 of she considers such action is warranted by ground BS 7121 P a r t 1: 1989; conditions, weather, obstructions or any other cause. g) any specialized Wing gear that will be required The crane erection supervisor should be in close in the course of this erection; liaison with the site management and should carefully consider any comments or warnings that h) liaison with occupiers of neighbouring management, any members of the site team, or any properties; other appropriate person or body may make. i) contact with local authorities or other bodies NOTE. The management may consider that this supervisor is the requiring statutory notification; appropriate person to be appointed to control any lifting j) arrangements for any necessary road closures; operations (see 3.2 of BS 7121 : Part 1 : 1989). k) the provision of a radio licence where required, available from the appropriate authorities;

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1) the availability on site of a comprehensive maker’s erectioddismantlingloperationmanual, in the language most readily understood by the erection team. NOTE. It is desirable that this information is available in advance of the operation so that the personnel concerned may familiarize themselves with the content.

11.6 Inspection before erection All parts should be inspected prior to erection to ensure they belong to the crane being erected and are in good condition, free from defect. Slinging points should be identified for all components. NOTE. Under certain circumstances it may be advantageous to carry out an inspection of the tower crane before it is delivered from the supplier to the user.

11.6 Weather Tower cranes should not be erected or dismantled in weather conditions likely to affect the stability of the crane, e.g. high winds (reference should be made to the manufacturer’s instructions for the maximum permissible wind speed for these particular operations) or under conditions of impaired visibility, e.g. fog. NOTE. More stringent restrictions on wind speed appiy to heightened cranes.

This type of work should be avoided if the conditions (e.g. ice on component parts, walkways) are likely to endanger the erectors.

11.7 Manufacturer’s erection and dismantling instructions Reference should be made to 10.2 of BS 7121 : Part 1: 1989. NOTE. Many tower crane manufacturers lay down specinc inspections and checks to be canied out in their erection and dismantling manual. For example, it is important to ensure that the lubrication requirements of tower joint bolts are met before applying torque.

11.8 Components and materials 11.8.1 Interchangeabilitu of components The interchange of structural components between one tower crane and another should onìy be permitted if the manufacturer has given approval. Having carried out such an interchange, a tower crane should be retested in its new combination, and the interchanged parts should be specified on the test certificate. 11.8.2 Materials Most tower crane parts are made from special steels and no repair or replacements other than manufacturer’s specification should be permitted. Welding or other heat treatments should be carried out under the manufacturer’s specified conditions. The re-use of high tensile bolts should be strictly in accordance with the manufacturer’sconditions. High strength friction grip bolts should not be re-used.

Bolts used to secure slew races should be renewed whenever they are removed. They should only be tightened in accordance with the manufacturer’s instructions. 11.9 Working area The area in which a tower crane is to be erected or dismantled should be roped or fenced off and all personnel not immediately connected with this duty should be excluded.

12 Procedures and precautions 12.1 General Reference should be made to clause 11 of BS 7121 : Part 1: 1989. 12.2 Working on cranes For tower cranes likely to sway or slew in the wind, appropriate precautions should be taken to prevent people from being displaced from their place of work by this movement, or being trapped by a rotating centre section of a tower crane under such conditions. 12.3 Working at heights A safe system of work should be used, in accordance with 3.1 of BS 7121 : Part 1: 1989. 12.4 Leaving the crane unattended When a tower crane is to be left unattended for even a short period, it is essential that the following precautions are carried out. a) No load should be left on the hook, and all chains, slings, etc. should be removed. b) The crane should be put out of service in accordance with the manufacturer’s instructions. NOTE 1. In nearly every case, this will involve turning the jib downwind and taking some action to ensure that the slew brake is left off, so that the crane is free to slew in the wind. NOTE 2. In the case of saddle jib cranes it is usual practice to bring the trolley or carriage to a minimum radius position. Tower crane jibs may infringe air space when left in the out-of-service condition.

c) In the case of luffing jib and similar cranes, the manufacturer’s instructions concerning the angle of the jib for out-of-service purposes should be strictly observed (see 8.3.2). d) Rail travelling cranes should be well secured to the rails, to make sure that in the event of a high wind the crane cannot be blown accidentally along the rails. When left for long periods (e.g. overnight), the power supply to the crane should be cut off and the door of the cab secured and locked. e) When a power supply is required to be maintained overnight for cab or control cabinet heaters, lights etc., separate arrangements should be made for the isolation of the power supply to the machinery.

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13 Operating conditions 13.1 General Reference should be made to clause 12 of BS 7121 : Part 1: 1989. 13.2 Mode of operation and control As the most common variation in mode of control encountered between different makes and models of tower cranes is the procedure for stopping the slewing motion, it is essential that the crane driver is made aware of which method of Carrying out this duty is applicable. NOTE. Failure to use the correct method can result in excessive structuraì stress on the crane as weii as causing failure in the electrical systems.

It is strongly recommended that the largest practicable bold notice should be displayed in the cab (in addition to the manufacturer’s instruction book) detailing the method of stopping the slew.

13.3 Multiple lifting Tower cranes should not be used for multiple lifts. 13.4 Special duties Tower cranes should not be used for carrying out special duties such as grabbing, lifting by magnet, balling operations, pile driving, or extracting. 13.6 Vacuum lifting devices Reference should be made to 12.6.3 of BS 7121 : Part 1: 1989. Tower cranes may be used with vacuum liftiig devices provided that the weight of the device plus the weight of its load does not exceed the safe working load of the crane. NOTE. The manufacturer may recommend some de-rating of cranes for this duty.

13.6 Weather 13.6.1 General No crane should be used or erected under weather conditions likely to endanger its stability. Reference should be made to 12.6 of BS 7121 : Part 1 : 1989. Attention is drawn to 11.6 of this Part of BS 7121. 13.6.2 Wind The manufacturer’s in-service wind speed should be strictly observed and cranes should be put out of service in accordance with the manufacturer’s instructions as soon as this wind speed is reached. In-service wind speeds should be carefully checked in the manufacturer’s instructions before putting a crane into operation. 13.6.3 Snow and ice Heavy accumulations of ice can make access along the jib extremely hazardous, and under these conditions consideration should be given to not

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starting work with the crane until the temperature has risen sufficiently to cause a natural thaw. Personnel in the vicinity should be warned of the likeliness of large lumps of ice falliig during the thawing. NOTE 1. Horizontal jib tower cranes are more prone to excessive loading from snow and ice than most other types of crane. NOTE 2. When there has been an excessively heavy fall of snow this should be carefully removed from the jib and counterweight jib before putting the crane into service.

13.6.4 Examination following adverse weather conditions After exposure to weather likely to have affected the stabiiity of a crane, the anchorage arrangements and ballast should be examined by a competent person as soon as practicable and before the crane is used, and any necessary steps taken to ensure the stability of the crane. NOTE. Attention is drawn to The Construction (Lifting operatioos) Regulations, 1961, Regulation 19 (7) [2].

Whilst the above examination is being carried out the whole structure should be adequately inspected to ensure that it has not suffered any damage or condition likely to lead to failure in the course of bad weather.

14 Testing and examination 14.1 General Reference should be made to clause 13 of BS 7121 : Part 1: 1989. Clause 14 of BS 7121 : Part 2 : 1991 should be studied in detail before any attempt is made to test a tower crane. 14.2 Age and utilization Tower cranes are not designed for a high intensiw of usage. Should a crane have been subjected to such usage, consideration should be given to the use of non-destructive testing to detect possible fatigue cracking. The assistance of the manufacturer or design authority should be sought to determine the vulnerable parts of the structure. Usage or storage of the crane in a corrosive environment may also cause deterioration of the crane structure and this may require more extensive examination. Fatigue damage and corrosion are also likely to be present on older tower cranes, which may require more detailed examination and testing as described above. Older cranes may remain serviceable, but particular attention should be given to these aspects on cranes more than ten years old. 14.3 Certification of cranes Reference should be made to 13.1.2 of BS 7121 : Part 1: 1989.

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14.4 Personnel safety Attention is drawn to 3.2.4 of BS 7121 : Part 2 : 1991 which points out that a test may fail and all personnel not essential for the test should be kept away from the area In this connection, it should be noted that if a crane is equipped with remote control, then this should be used for the purpose of carrying out the test with the driver in a safe position. Attention is also drawn to clause 14 of BS 7121 : Part 2 : 1991 which recommends that a clamp or similar device should be attached to the jib to limit the radius of the trolley when carrying out a maximum load test. Where safe access is not available to fit or remove the clamping device alternative safe means of limiting the radius of the tsolley should be adopted.

19 Signalling systems 19.1 General Reference should be made to clause 19 of BS 7121 : Part 1: 1989. Due to the distance between tower cranes and other personnel it is important that clear systems of identification and communication are used. Attention is drawn to 8.2 of BS 7121 : Part 1: 1989. 19.2 Radio communications Guidelines are given in annex A.

20 Tying and guying

16 Ropes

In certain circumstances a crane should be tied to the structure it is constructing, or held by guy ropes for any one of the following reasons: a) to obtain a height in excess of the available free-standing height; b) to restrict the movement of the tower when available space is limited; c) to comply with the requirements of the occupiers of adjacent properties, e.g. railways. In any of these cases the tyindguyjng arrangements should be in accordance with either the manufacturer's approval or calculations carried out by a competent engineer.

Reference should be made to clause 16 of BS 7121 : Part 1: 1989.

21 Signboards

15 Legal requirements Reference should be made to 14.1 and 14.3 of BS 7121 : Part 1: 1989. With regard to specific legislation, users of this Part of BS 7121 should acquaint themselves with the current national legislation that applies to the provision, maintenance, examination and use of tower cranes.

17 Slinging and handling of loads Reference should be made to clause 16 of BS 7121 : Part 1: 1989.

18 Raising or lowering of personnel Reference should be made to clause 17 of BS 7121 : Part 1: 1989. Tower cranes generally conform to the statutory requirements for raising or lowering of personnel by cranes, but due to the extra height often involved, special care should be taken to prevent the swing of the cradle carrying personnel, which could, in turn, cause the cradle to spin. It is not generally practicable to attach a tag line or similar equipment to such a cradle, and it is suggested that a cradle which is rectangular or square in plan would be easier to control when bringing it alongside a structure or building on which the occupants may be required to work. Care should be taken to ensure that the cradle is kept clean and in good condition and is not used to carry any tools, loads or equipment which may make a foothold difficult for the occupants.

Signboards, decorations, outline lights, etc. can impose additional loadings on the crane and should not be fitted unless approved by the crane manufacturer. Electrical supplies to such equipment should be restricted to 55 V max. Wiring should be protected to against damage and should not create a h-d personnel.

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Annex A (informative) Specimen copy of information sheet RA 196 published by the Radio Communications Agency NOTE.This publication is reproduced here for the convenience of the reader, but the reader is advised to check if this has been superseded and, if so,use the latest edition issued by:

The Raàiocommunications Agency South Quay Three 189 Marsh Wall London E14 9SX

Safer radio techniques

Radiocommunications for ‘hwer Cranes

Introduction %wer cranes often require communication as a means of signailing to ensure safe operation. This infomation sheet provides advice on the use of radio. Radio installation and operation in this environment calls for the observance of special requirements. Any radio system mounted high up on a stnicture is likely to receive and cause interference to other users over a wide radius unless it is carefully engineered. Since there are only a limited number of radio channels available, it is likely that a crane will be sharing a radio frequency within the same conurbation, and in worst cases on the same construction site. It is necessary, therefore, to engineer a ‘clear’ channel. A number of approved techniques have been developed to provide clear channeis. The consequence of not adopting one or more of these is that safety of life could be put at risk both on the construction site and elsewhere for other services using radio.

The Problem When a radio is used at ground level surrounding buildings and ground clutter soak up some of the signals and reduce the distance over which the signais can be received Any radio located high up on a crane is able to lmnsmit into free space and will be receivable many miles away At first sight this does not seem too much of a problem as most of the t a l h g is done by the banksman and the crane driver is mainly listening. However, not every banksman is located at ground level and often he wiìl obtain just as good propagation as the crane driver. W o communications between banksman and controller pose different propagation problems as constsuction progresses. On the construction site, the building itself may act as an obstacle to proper radio communication and it may not therefore be possible to reduce the output power to prevent interference to others. Often reducing output power does little to contain transmissions into free space but prevents communication into parts of the building such as a lift Shaft. O BSI 1997 COPYRIGHT British Standards Institution on ERC Specs and Standards Licensed by Information Handling Services ~

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Although, as the building goes up, the b a n h m wiii increasingly be liable to transmit nom a raised position he could stiU have transmissions blocked by the building in a particulas direction. The crane is likely to be above the construction and able to freely transmit in all directions throughout the duration of the work The area where it will be hardest to penetrate is the opposite side of the building should it be necessary to operate in that area

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1) Signalling systems The use of CESS (Continuously Tone Controlled Signalling System) or another form of Signalling will help lessen the effects of sharing. They can not, however, soive the problem. As a crane wiil receive signals from a large catchment area, tones will oniy reduce the transmisions which the crane driver has to listen to. 2) Special techniques There are several engineering techniques available which will alleviate the problems. These range from directional antenna or other means to restrict range which confine the radiation verticaiiy between operator and banksman to Merent types of communication on the up and down paths. It is possible to superimpose the radio traffic over the mains voltage. A leaky feeder from the rear jib will limit the radiation pattern. Whilst these are excellent solutions it should be noted that both systems have been patented. The use of a magmount aerial, because it is omnidirectional, will freely radiate. This causes problems in that communications wili be transmitted and received over a wide area. It is, therefore, essentiai to reduce as far as possible the radius for both transmission and reception. 3) Call signs One very simple way to improve the safety aspects of radio communication is to use call signs at the start of the message. When there is a danger that a radio frequency could be shared with another crane, and messages wili be of a similar nature, a unique call sign is a useful tool to ensure that a message is acted upon only by its intended recipient. Another reason why they should be used is that when an interference complaint is received, the Radio Investigation Service can more easily identify the users involved when call signs are used. There is much that contractom could do to help by ensuring their crane operators use call signs and explaining the benefits to them. It is &o a licensing requirement.

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me of n'equency The Agency can allocate either a single or dual frequency channel. If a crane is going to be at a site for a considerable amount of time the user will require a licence and it wili be necessary for the Agency to assign a channel. However, if the duration of the contract is less than twelve months, equipment may be hired from a Short Qrm Hire licensee.

Licensing requirements The use of all radio must be licensed but users are free

to choose either a single or dual frequency and the system employed The Radiocommunications Agency is not concerned about which particular system is chosen provided that interference to other users is kept to a minimum. Engineering trials have shown that it is possible to share frequencies much closer than had previously been thought possible providing the systems are carefully engineered. In defining what does or does not cause unacceptable interference, it has been decided to define a maximum signai strength at a distance from a crane no matter which techniques are employed. This shall be a maximum of 48 dB/uv per metre measured at 2 lan h m the crane at a height of 3 m above ground level. It is not intended that every crane radio should be required to conform with this figure. It would not, for example, be necessary in areas of the UK where use of radio communications is relatively light. However, if an interference complaint is received, and the offendmg radio system does not conform to these parameters then it will be necessary for that system to be reengineered so that it does conform.

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List of references ( ~ e eclause 2) Normative references BSI publications BRiTïSH STANDARDS INSTITUTION, London

BS 6651 : 1992 BS 7121 BS 7121 : Part 1: 1989 BS 7121 : Part 2 : 1991 BS 7121 : Part 4 : 1997 BS 7430 : 1991

Code of practice for protection of structures against lightnirq Code of practice for safe use of c r a m General Inspection, testing and examination Lorryloaders Code of practice for earthing

Informative references [ 11 GREAT BRITAIN. The Construction (Head protection) Regulations, 1989. London: HMSO.

[2] GREAT BRITAIN. The Construction (Lifhng operations) Regulations, 1961. London: HMSO. [3] GREAT BRJTAIN. The Construction (Work places) Regulations, 1966. London: HMSO.

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BS 7121 : Part 5 :1997

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