METHOD STATEMENT FOR FABRICATION OF STEEL WORKS The Primary goal of Arewa Metal Containers Limited (ARMECO) is the satisfaction of customers, we design, detail and fabricate our structures, machines, tanks etc using sound principle of engineering and we fabricate every component with utmost attention to quality and detail. Below is our company site erection process: 1
PURPOSE The purpose of this manual is to ensure that site erections are carried out according to specifications and in a safe manner.
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SCOPE The scope of this manual shall include: Understanding the Engineering Documents Basic sequence Site organization Erection Procedure Quality control programme Safety procedure
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RESPONSIBILITY The Site Engineer is responsible for the effective implementation of this manual on site and shall ensure that: The workforce is aware of and implements the relevant standards and regulations. Changes in procedures, which become necessary during the erection stages, are agreed by him and/or design engineer, and that the technical document are corrected in order to be consistent. Hoisting equipment of suitable capacity is available for any preassemblies which must be lifted. Means of access, such as scaffolding, stairs and platforms, are installed to enable bolting and welding to be carried out satisfactorily.
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REFERENCE Erection/assembly drawings Loading/dispatch list BS 5950: Structural use of steelwork in building AWS D1.1: Structural Welding Code
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UNDERSTANDING THE ENGINEERING DOCUMENTS Anchor bolt Setting Plan This drawing shows the layout of all anchor bolts, it is normally presented in one sheet, but for relatively large buildings, this layout may be presented on two or more sheets. Erection drawings are not made to scale. All drawings appear in millimetres unless noted on the drawings. 1
Cross section The cross drawings indicates columns and rafter references, connection details, bolt schedules, flange brace schedules and other information as applicable such as strut tubes and flange and flange brace details Roof Framing Plan Roof framing plan illustrates the purlins, bracings and related details. Part numbers are indicated on this drawings for purlins, bracing, sag rods (where applicable). Other Drawings Other drawings include roof sheet layout, sidewall and end wall sheeting and framing, crane beam layouts and details, accessories such as sliding doors, roll up doors. Bill of Materials The B.O.M supplied with the erection drawings is the client B.O.M. The B.O.M.begins with cover sheet indicating the job number, project Number and phrase, clients name, location and job size. The second page indicates the various sub areas of the phases, on the next page the detailed B.O.M list of items included in each phase begins
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BASIC SEQUENCE OF ERECTION The basic sequence for erection have been determined and documented for various project types and are as contained in appendices A, B and C; and shall be strictly adhere to by erectors on site.
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SITE ORGANIZATION Site shall be adequately identified and project signboard erected before commencement of project. Adequate supply of drinking water shall be provided in all places of works. When sanitary sewers are not available, one of the following facilities, unless prohibited by local codes, shall be provided: chemical toilets, recirculation toilets, combustion toilets, or other systems as approved by state/local governments. Prior to start of work, arrangement shall be made for medical facilities and personnel to provide prompt attention to the injured and for consultation on occupational safety and health matters. All projects, activities, installations, or contracts at the site of work where neither a firstaid station nor medical centre is available, shall be provided with a first-aid kit. All the restricted areas on site shall be clearly identified as such and all necessary PPE required accessing such areas indicated. Construction site shall have a muster point for headcount in the case of emergency.
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ERECTION PROCEDURE When work at the factory is finished, only one final operation remains, ERECTION: the erection method statement will set out the procedures for delivery and assembly including 2
the phasing of the erection, bolting, welding and methods of erection and safety of the steel work package Delivery A construction sequence relevant to the particular project shall be agreed prior to delivery of any material to site, from which a delivery schedule shall be produced. Particular attention shall be paid to the logistics of the erection process to prevent members being missed out, double handling of materials on site, trucks being under-utilized, and the positioning of steel in the wrong location. Delivery of the steelwork shall normally be in 30-tonne semi trailer trucks on “just in time” delivery sequence in order to alleviate site congestion, and minimize double handling and on-site damage. For transport and delivery to site of bolts, nuts and washers the following shall be noted: They shall be provided with adequate packing, sufficiently protected to avoid damage during transport. In the case of high strength bolts, both bolts and nuts shall be adequately greased. Each package shall contain only one type of bolt, nut or washer of the same diameter, length and quality. Each package shall be provided with a label, indicating the manufacturer’s mark, the type (bolt, nut and washer), the quality and the number. High strength bolts are indicated by coloured labels, according to the type and quality (4.6 = green, 8.8 = red, 10.9 = blue) Reception of Materials Reception and unloading of materials always take place as near as possible to the place of erection, the lay down area are cleansed and levelled. A suitable forklift or mobile crane is use for unloading. Care are executed in handling the various components and bundles to minimize damage to paint.Any damaged material, which should be repaired or returned, shall be separated immediately after arrival and documented. The project engineer shall be informed, to allow him assess what effect this might have on the construction programme. Handling of Materials When handling individual members the following shall be noted: Parts with different reference marks shall not be mixed or packed together. On large or heavy parts the lifting points shall be indicated, including where possible the location of the centre of mass of the component. All parts that can be easily damaged shall be adequately protected during transport and handling. Components in the storage area shall be kept off the ground, protected from damp and dirt by means of sleepers or battens. When using steel wire cables as lifting strings the following shall be noted: Care shall be taken to ensure that the sharp corners of beams are packed with wood in order to protect the sling, the surface treatment and any prepared edges. 3
Slings shall be regularly inspected, and the maximum safe load shall be shown on a steel tag. When using double-leg slings it shall be appropriate that the lifting capacity diminishes as the angle between the legs increases. The Site Engineer shall ensure that the load in the legs shall not exceed that calculated from R= P x 1 2 cosa Where R is the load in a leg, P is the total leg and α is the half-angle between the legs of the sling. Maximum safe load shall not exceed 1/6 of the breaking load of the steel wire cable from which the sling is made. The hoisting slings shall be regularly inspected and taken out of service as soon as the number of broken wires in a metre’s length reaches or exceeds 20% of the total. The slings shall not be bent over diameters less than six times the diameter of the cable. If necessary rounded cushions shall be put in place to support the sling.
Regarding the storage and use of welding consumables, the following shall be noted: The electrodes shall be packed in closed and sealed packages or tins; storage shall be in closed and dry place to prevent condensation and special care shall be taken to avoid damaging the coating. When basic-type electrodes are used, they shall be dried or baked in accordance with the welding procedure. Once the sealed packets have been opened, the electrodes shall be placed in a portable drying oven. Mobile drying ovens shall be provided with an insulated quiver in which he keeps the electrodes, taken from the nearest drying oven. In very special cases and in very damp conditions the welders shall be provided with individual portable drying ovens, from which they remove the electrodes one by one, as they need them. For general purpose a complete list of erection element shall be available on site indicating their code-mark, weight, and size and specifying the locations where they will be used. Foundations Levelling and Measuring An inspection of the foundation, to check the levelling and alignment of the anchor bolts, shall be made before erection commences. A fixed levelling point and three fixed alignment points shall be established for this purpose. Errors in the foundation identified at this stage, shall be corrected using packer plates. The foundations shall be cleaned prior to erecting the steelwork. We shall ensure that the cavities for holding down bolts are completely free from contamination.
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Assembly and Erection Planning for the erection of our jobs commence at the design phase, the steel structure is erected quickly to programme to the lowest possible cost. Questions concerning the construction sequence and its effect on stability shall be resolved. The designer shall position the braced bays in a way that they shall be the first to be erected. The structure shall be braced and true as the erection proceeds. Works at a height shall be minimized by the use of sub-assembly units where practicable. Where sub-assembly shall be carried out on site, it shall be done behind the lifting equipment in order that the assembly can be lifted straight off the ground and into position. During lifting damage shall be minimized on the paint treatment by the use of softwood packers and to ensure that the load will not slip as it is being lifted and that the sling-chains or wires are not damaged. Where the structure needs additional rigidity during erection temporary stiffening shall be used to ensure the rigidity of structure until the permanent connections are made. Where a particularly awkward or heavy lift has to be made, special cleats shall be fabricated for this purpose. Holding-down bolts To facilitate the erection of the structure, holding-down bolts are normally positioned by our civil engineers. Movement tolerances are accommodated in the foundation to ensure that correct alignment takes place. After checking and confirming that holding-down are acceptable, typical 100mm x 100mm steel packs (1-20mm thick) or similar are placed on the base to the required level. Bolting Connections on Site Before carrying out any bolted connections checks shall be made to ensure: The bolts, nuts and washers to be used shall be exactly as indicated on the drawings. Bolts, nuts and washers shall be cleaned and undamaged. The parts to be connected shall be cleaned and without defects. In connections with tapered flanges, tapered washers shall be placed under the nut, the bolt, or both. In the case of a hole with a vertical axis, the bolts shall be inserted from above, with the nut at the bottom. Welding Connections on Site Where welding is necessary on site, careful pre-planning shall be required as follows: Provision shall be made for temporary alignment of the adjacent components which are to be welded together, and to hold them in position until they are welded. The methods adopted for the alignment shall be able to carry the weight of the components and in some cases a substantial load from the structure. 5
Safe means of access and a secure working platform shall be provided for the welder and his equipment. All welding shall be carried out by qualified welders in accordance with approved procedures. The earth return of the electric current must be made through the steel structures, cranes, or through metallic parts of installations but must be directly connected to the construction part being welded. The surface of zone to be welded shall be clean and dry.
Painting Surface Preparation Where oil and grease are present remove in accordance with the SSPC Surface Preparation Specification using No. 1 Solvent Cleaning (SSPC-SP1). Perform cleaning prior to blasting. If contamination remains after blasting, reclean with solvent Blast cleans all steel to a commercial blast condition, as defined in SSPC-SP 1085 equivalent to grade Sa2 ½ of Swedish Standards SIS 05 5900 and Second Quality of British Standards 4232. Mixing Paint Mix the primer with a high shear mixer in accordance with the manufacturer’s recommendations to smooth, lump free consistency. Mix in the original containers. Continue mixing until all of the metallic powder or pigment is in suspension. Assure that all of the coating solids that might settle to the bottom of the container are thoroughly dispersed. Mix each subsequent coat to achieve and to maintain a homogenous mixture. Strain the mixture through 500µm - 250 µm (30-60 mesh) screen openings to remove large particles. Equip paint containers with a mechanical agitator so the mixture is in motion throughout the application period. Thinning Paint Thin the paint only as recommended by the manufacturer. Conditions for Painting Apply paint only on clean and dry surfaces and only during periods of favourable weather. Do not paint when the temperature of the air, paint, or metal is below 5˚C, and at no time below that described in the technical data sheet; when the air is misty; or when conditions are otherwise unsatisfactory. Do not paint damp or frosted surfaces or surfaces hot enough to cause the paint to blister, to produce a porous paint film, or to cause the vehicle to separate from the pigment.
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Paint only when the surface temperature is at least 3˚C above the dew point. Determine the dew point with the use of a psychrometer and psychrometric tables. Allow each coat of paint to dry before applying the succeeding coat. Follow the manufacturer’s recommendations for drying time, unless a longer drying time is required.
Application Before paint is applied, clean dust and dirt and other contamination from the freshly painted surfaces. Apply primer and subsequent coats immediately after inspection and acceptance of the surface. Apply primer the same day the metal is cleaned. If the metal is blast cleaned and remains unpainted overnight, blast clean it again prior to priming Spray applies primer in accordance with the manufacturer’s recommendations. For application for intermediate and finish coats, wet stripe all edges, bolts, welds, rivets, corners, and other irregularities either by brush or by a separate and distinct spray operation, prior to the application of the full coat. Provide safe access for inspection, as required by the Engineer, prior to application of the full coat over the striped areas. Do not apply the full coat until approval of the striping is provided. Apply intermediate and final coats to areas of steel that will be inaccessible prior to the stage of construction that prevents access. Thickness of Coats The cumulative dry film thickness will be determined by the use of a Magnetic Dry Film Thickness Gauge, or equal. Increase the thickness of coating, if directed by the Inspector in-Charge. 9
QUALITY CONTROL PROCEDURE Quality Assurance Manual The Quality Assurance Manual (detailed sequence of work for the project type and erection procedure) defines the appropriate procedures required to ensure the particular project is up to specification. The erector responsible for the erection shall be informed of all the variables affecting the quality of the assembly, so that they can be monitored. Quality Control Programme A Quality Control Programme shall be in place identifying all materials and workmanship from purchase to delivery and subsequent incorporation into the works. It is essential that monitoring is carried out to ensure performance of materials and workmanship incorporated into the final works is not inferior to those specified by the designer. The Quality Control Programme shall be based on the following: The Quality Assurance Manual The general contract condition of the project The general standards applicable to the project 7
The company’s standards, procedures and specifications.
Inspection Programme Within the method statement, an approved testing and inspection programme shall be agreed to ensure that, the as-built structures conform to specification and design intention. The inspection programme shall monitor the following: The structure position is in accordance with the tolerance laid down. The erection has not deviated from the design requirements or specification without all changes being approved by the appropriate body and a full record kept of those changes. The method of construction have allowed for process quality control of welding, heattreatment of welding, non-destructive testing, alignment and plumbing. Non-conformance Procedure All variations after the work has started shall be accompanied by a Non-Conformance Report (NCR), traceable throughout the entire process and signed off by the design engineer. Any damage or discrepancy shall be reported using the NCR system (appendix D) and repaired or replaced following this approved system. 10
SAFETY PROCEDURE Safety of the workforce Every individual working on site shall take responsibility for safe work practices, regardless of job title. Safety is everyone’s responsibility. Before start of work, all workers shall attend a structural steel erection best practice review for the project. Weekly safety meetings shall be held and the sub-contractor shall be kept informed, in writing, about discussions and issues that may affect safe erection of steel (e.g., weather conditions [such as wind], access, and site conditions). Risk Assessments General hazards Site safety There can be assorted hazards associated with working on any site and site regulations as laid down by the OWNER/Facility Operator should be observed. Manual handling risks
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Equipment and associated items may be heavy and care should be taken when handling manually. It is generally preferable to reduce any risk by avoiding manual handling altogether. When unavoidable, correct lifting procedure should be used. Heavy items will include, but not limited to, roof and floor plates, stilling wells and rolling ladder. Arrangements should be made for items such as these to be delivered as close as possible to the intended point of installation and be moved subsequently as much as possible by machine. Personnel Protective Equipment The minimum personal protective equipment is as follows:
Approved safety helmet Approved earplugs Safety footwear Eye protection Gloves Overalls Respirators
And any other equipment deemed necessary by the specific task involved. Risk of falling If any installation or activity needs to be done at a height above 2m, care should be exercised to prevent personnel falling from height. Scaffolding/Man lifting equipment should be used for such activity/installation.
Specific hazards applicable to Erection of Pre-Engineered Steel Building Crane and Lifting Equipment All cranes and lifting equipment shall undergo relevant test and thorough examination and certified okay. They shall be operated with the use of
manufacturer’s handbook. Only certified operators and trained riggers authorised by the contractor shall be
allowed to operate cranes/lifting equipment. Crane/lifting equipment operators and/or safety personnel shall carry out daily
inspections and this shall be entered into the crane/equipment register. Cutting and Welding Personnel involved with this operation shall use respirator Welding shield shall be worn 9
Mains Voltages Care should be exercised when working with mains voltages (240V or 380V AC). All appliances, equipment, and materials used for temporary electrical installations shall be constructed, installed, protected, worked and maintained, so
as prevent danger All work on electrical equipment shall be carried out by, or under the immediate
supervision of a qualified electrical craftsman Power in excess of 240V shall be transmitted by armoured cable, which shall either be buried or strung overhead
Workers Orientation Prior to starting work, every worker shall attend a site orientation to be informed of and becoming familiar with: Site rules and regulations Erection plan and procedures Equipment to be used Hazard assessment Work area and emergency procedures (including the rescue plan) Work areas of other trades and the need to communicate planned work activities to them when working in close proximity
Lifting and Handling Loads Manual handling of loads or materials by workers should be minimized. Sub-contractors must provide, where reasonably practicable, appropriate equipment to help workers lift, lower, push, pull, carry, handle, or transport heavy or awkward loads. Housekeeping Store all supplies, such as bolts in proper containers and set away from areas where they can pose tripping hazards. Do not leave loose bolts and nuts lying on steel or on ground. Perform ongoing cleanup as required. Do not string hoses through high traffic areas or stairs. Instead, hang the hoses up to eliminate the hazard.
Steel Fabricator’s Responsibility The steel fabricator shall be responsible for: Providing detailed connection information to ensure that the structure can be safely erected. Providing, where required, safety attachments or anchor points.
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Steel Erector’s Responsibility The steel erector shall be responsible for: Ensuring workers are adequately qualified, suitably trained, and with sufficient experience to safely perform the assigned work. Inform the company about access needs to the site specific work areas. Pre-planning work activities to ensure that workers are not required to work under unsafe or suspended loads. Developing site-specific work instructions and procedures that identify access and area needs Ensuring that requirements for moving loads over working areas are met. The erector must comply with the general and specific requirements of lifting and handling loads. Structural Steel Assembly Installing Columns Columns should be set on levelling plates, levelling nuts, shim packs, or level finished floors for adequate transfer of construction loads. Attach the column rigging through a bolt hole in the top of the column in the web or a beam clip. If the column rigging cannot be attached to the column due to the shape of the column, then a choker may be used provided that a way to prevent the choker from sliding up the column is in place. Signal the crane to lift column. Adjust the crane’s line (by signalling the operator) to remain above the column rigging (pick point) of the lift as column is being raised. Once the column is lifted off the ground and the crane has the complete weight, stop the lift until the load settles (if required). Once the load settles, proceed to signal the crane operator to move the column into position. Lower the column: o Placing columns on anchor bolts. Watch for pinch points. Once the base plate of the shims touches the connection point, put the washer and nuts on the anchor bolts. Plumb the column by tightening the anchor bolts. OR o Placing columns onto a steel column or beam. Watch for pinch points. Once the base plate of the column touches the connection point, bolt down. Plumb the column by tightening the connection bolts. Use spud wrench/sleaver bars to guide the column into position. Use a minimum of 4 bolts to secure the column. Release the weight of the column from the crane. Before releasing the rigging, make sure column is secure on the anchor bolts. Unstable columns must be guyed or braced as necessary. Installation of Beams on Columns During the final placing of solid web structural members, the load shall not be released from the hoisting line until the members are secured with at least two bolts per connection (of the same size and strength as shown in the erection drawings) drawn up wrench-tight or the equivalent as specified by the project structural engineer record. A competent person shall determine if more than two bolts are necessary to ensure the stability of cantilevered members; if additional bolts are needed, they shall be installed. 11
Solid web structural members used as diagonal bracing shall be secured by at least one bolt per connection drawn up wrench-tight or equivalent as specified by the project structural engineer of record.
Double Connections When two structural members on opposite sides of a column web, or a beam web over a column, are connected sharing common connection holes, at least one bolt with its wrench-tight nut shall remain connected to the first member unless a shop –attached seat or equivalent connection devices is supplied with the member to secure the first member and prevent the column from being displaced. If a seat or equivalent devices is used, the seat (or devices) shall be designed to support the load during the double connection process. It shall be adequately bolted or welded to both a supporting member and the first member before the nuts on the shared bolts are removed to make the double connection. Structural Stability Ensure that structural stability is maintained at all times. Construction loads must not be placed on any structural steel unless such framework is safely bolted, welded, or otherwise adequately secured. When used, temporary bracing must be in place and properly installed in conjunction with the steel erection plan to ensure the stability of the structure. Temporary bracing can be removed only with approval of competent person. Rigging Careful consideration must be given to the ground conditions and the soil compaction in areas in which cranes are to be moved and operated. If work is to be done or equipment is to be operated in the area of an energized overhead power line, the employer must contact the power line operator to determine the voltage of the power line, which determines the safe approach distance. Until the power line operator verifies the voltage, the employer must maintain a safe clearance distance. On cranes operating with outriggers, the beams must be extended with the pads down according to manufacturer’s recommendations. The ground should be checked periodically for settling, and the outriggers reset if necessary. The maximum load rating is not the breaking strength of the piece of rigging. An erector must ensure that the load rating of the piece of rigging is appropriate (5 to 1 for all below-the-hook lifting devices; 10 to 1 for hoisting of personnel). The maximum load rating must be marked on the rigging. If making the rigging is not possible the load rating should be available to workers on site. Slings must be checked before each use by workers. Damaged slings must be permanently removed from service. Fall Protection Workers must use a fall protection system if they may fall 3m or more, or if there is an unusual possibility of injury if a worker falls less than 3m (e.g., falling unto exposed rebar pointing upward). 12
Workers working on flat roofs and workers engaged in connecting structural members of a skeleton structure are not exempted from using a fall protection. A fall protection plan must specify the: - Fall hazards at the work site. - Fall protection system to be used at the work site. - Procedures used to assemble, maintain, inspect, use, and dismantle the fall protection system. - Rescue procedures to be used if a worker fall or is suspended by a personal fall arrest system or safety net and needs to be rescued. Review fall protection plan, including the rescue plan, with workers.
Working at Heights Foreman can exercise judgement and shut down all work at his or her discretion due to wind, rain or any other unusual weather condition. Materials must be hoisted using material lifts or ropes and must be secured to prevent falling off steel. Do not carry materials up ladders. Tools must be hoisted using material lifts or ropes and, when the tools are not in use, they must be secured to prevent falling off steel or from being removed. Do not carry tools up ladders unless the tools are part of a tool belt. Secure and mark covers over open holes. Install handrails and kick-plates in conjunction with stair and grating erection, where required. All materials, equipment, and tools that are not in use while aloft must be contained, restrained, or protected from falling. Erectors must protect workers from being struck by falling objects (e.g., an overhead safeguard strong enough to withstand the shock load of falling objects), or if workers enter into the danger area, then barricades, warning or signs can warn workers of the hazards. Construction processes below steel erection must be prohibited unless overhead protection for workers below is provided. Safety net can be used to protect workers from falling objects. Tools Use of Hand Tools Use all hand tools for the purpose intended by the manufacturer. Use the right tool for the right job. Inspect all tools for defects prior to use. Prevent all hand tools from falling (where applicable) by using items such as lanyards, netting, and chains. Use of Power Tools Power tools must be used in accordance with manufacturer’s specifications. Inspect all power tools prior to use. Ensure all guards are in place. Take damaged tools out of service and tag them for repair 13
Use proper personal protective equipment (PPE) while operating power tools Ensure portable magnetic drills are tied off and equipped with lock-tight cord ends. Prevent all power tool from falling (where applicable) by using items such as lanyards, netting, and chains.
Cutting/Burning/Welding Operations Secure compressed gas cylinders in an upright position and protect them or locate them away from falling objects. Oxygen fuel systems required a flashback arrestor and a back-flow prevention devices A back-flow prevention devices is unnecessary in the fuel line of single-line torch systems operating on fuel gas and aspirated ambient air, since the potential for creating an explosive or flammable gas mixture in the hose does not exist (e.g., tiger torch). Remove combustible material from area, if possible. Use fire blankets where required. Assign fire watch where required. Workers exposed to an airborne contaminant or mixture of contaminants must wear appropriate respiratory protective equipment. Equipment The following are some of the equipment available in our company for the convenient erection of our steel components Main Erection Equipment Mobile crane Scissor lift Slings Ladders Electrical Equipment and Tools Generator Grinder Hole cutter Electric shear Measuring and Survey Equipment Plumb Bo Automatic level Measuring tape and square Safety Equipment Welding hood Gloves Safety harness Ear Protection
Forklift Lifting beam Clamps, shackles and clips
Nibbler Hammer drill Impact wrench Stapple applicator Theodolite Spirit level
Googles Safety boots First aid box Fire extinguisher
Other Equipment Welding machine 14
Oxy-acetylene
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