Accidents arising out of working on height or on the roofs are always severe in nature and often fatal. Therefore it is necessary to provide facilities to work at height safely as well as means to reach there (the work place at height) safely. It is also essential to ensure that the persons intending to work at height are sound in health and do not suffer from vertigo or any other phobia of working at height. All these things require planning and preparation in advance. In the absence of proper facilities for working at height the workers may resort to unsafe practices which may result in an accident.
Facilities provided to work at height
Stairways are provided as means of access and egress at elevated places and basements.
These are permanent structures made up of masonry,wood,or steel.
1) The tread or step width should be about 20 cm. And preferably provided with a nonslip strip of about 2.5 cm. this strip should be firmly fixed throughout the length at each step.
2) The tread or step should be horizontal and not slanted outside. The treads slanted outside will put some one out of balance while climbing down.
3) Rise between each tread or step should not be more than 20 cm or less than 12.5 cm and it should be uniform for all the steps. If steps are uneven then it will affect the judgement of the user, may loose his balance and result in a fall .
4) Handrail at height of about 75 cm. should be provided many time the persons are required to carry material in their hand or on their head and hence a handhold for support is essential.
5) After every after flight 10-12 steps a landing must be provided. The landing in between will offer relif while climbing. Also, if someone falls while climbing, the fall can be restricted at the landing.
6) All construction should be sturdy and if it is made from steel or wood is structural members should be firm in there position and should not be loose.
7) The slope for stairways should preferably be 30 degree with the horizontal. If slope is too stiff then it will cause strain and fatigue.
Precaution and care:
1)Attempting to climb too many steps at one streted should be avoided since it will cause exertion.
2) Heavy material should not be dragged along the stairs. It will damage step nose.
3) The handrail should be kept clean and free from oil, chemicals, dust, etc.
4) The steps should be kept clean and free from loose material. While climbing down if someone steps on loose material may cause him slip. There is also a chance that such loose material get kicked and hurt someone bellow.
Ramps are of two types one is permanent and the other temporary.
a) permanent ramps : permanent ramps is ‘a structure usually made of a cement, concrete, masonry or steel frame with wooden top. If consists of a-platform and an inclined plane attached to it. Ramps are used for loading or unloading the material from trucks conveniently and safely. There also used to join two horizontal floor surfaces at different levels.
Construction features :
1) The height of platform should match with the height of trucks.
2) The ramp platform may be provided with railing.
3) Ramp should not be too steep. Preferably slope should be 15 degree it 20 degree. it will be difficult to control handcart movement on steep ramps. If also causes one to slip or strain in its use.
4) The ramps when used for the handcarts it likely that surface may get damage by its wheels. Therefore, at centre there should be anti-skid strip provided for use of workmen when they are pushing the cart.
5) If there is regular pedestrian traffic, then along outer side separate portion should be kept reserved for its use with anti-skid surface and railings.
Precaution and care
While pushing material along slope care should be taken that the material does not fall.
Good housekeeping is necessary to keep surface free from oil, dirt or any other loose material.
Temporary ramp is a makeshift arrangement made for a one-time or limited use. The purpose is to serve the immediate need. Ramp-like temporary structure may be set from the material available at site. If may be wooden planks, angles, bars, etc.
Precaution and care:
1) Since the arrangement is made from available material, its strength and sturdiness is doubtful.
2) The load is likely to be supported by individual members rather than the structure as a whole. As such there is a possibility of a structural member may slide down or dislodged. It may break also.
3) When it is used for pedestrian traffic, any loose or unstable structural member may disturb the balance of person and result in a fall.
4) It may get overloaded due to over crowing or carriage of heavy materials and collapse.
These are usually provided at height for manual movement. The provision can be a permanent structure or a temporary arrangement. In chemical plants to reach the equipment and accessorises such as reactors, pressure vessels, storage tanks walkways are provided as means of access.
Permanent walkways or gangways
Design features: Its design and material of construction depends upon the requirement i.e. in chemical plants structure should have anticorrosive coatings, in fabrications shops and foundries structure should be study to withstand vibrations of crane movements, etc. The walkways provided for crane tracks or conveyor line are for a limited use. These are normally used by maintenance persons for repair or inspection and also by crane operators in emergency. It is laid on cabin side to crane operator. The gap between crane cabin landing and walkways should be kept short. In an emergency, the operator should be able to cross over the gap without difficulty and risk. The top surface of walkway should be neatly in level and it should be without any gaps or holes. It is provided with a toe-guard and handrail. When installed inside the shed, sufficient head room should be provided. The structural members of shed over the walkway obstructing the movement should be distinctly painted.
Precaution and care: The walkway along the crane track when used by maintenance personnel, the crane movement should be suspended. Crane operator should be informed and suitable warning signs displayed to that effect.
The surface should be free from any loose materials and oily substance.
Temporary walkways or gangways
Temporary walkways or gangways are erected for boiler cleaning, chemical vessel or tank repair, civil constriction, etc.
Design features: These structures are supported from ground or adjacent structure. The strength of structural members and its fittings should be adequate to support men and material movement over it. The material me be steel angles or bars, wooden planks, etc. The height of walkway whether temporary or permanent should be provided with adequate head-room below it. Its structural members should not obstructed movement of men and material on the floor.
Precaution and care: The gangways should not be overcrowded. These are likely to get overcrowded at the end of the days work when people are in hurry to leave the site. The structure is usually erected for a specific purpose and should be dismantled one it is over.
The ladders are mainly of three types
- Permanent or fixed type
- Sliding or movable type
- Portable type
Permanent or fixed type ladders or erected when there is space limitation and stairway structure cannot be installed. At some locations the frequency of use is seldom or very limited, then in such cases stairway installation is not economical and hence not preferred. In such situation, the ladders of suitable design are fixed. These ladders are usually made of steel and painted to protect from corrosion.
They had preferably inclination of 75 degree at its base with horizontal. The step or rung width is kept about 40 centimetre and spaced 30-40 CM apart. When ladders are more then 6 metre long then in between the platforms should be provided. The side rails are extended by about 1 metre above the top landing. This is to provided hand hold after reaching at the top.
The tall structure like chimney, stacks, storage tank, watchmen cabin etc. The ladders provided are vertical. For vertical ladders the cage guard provided from climbing side. The ladder structure is fixed a little away from to allow toe gap to about 18 cm.
Sliding or movable ladders
Sliding or movable ladders is similar to a fixed ladder. It is usually made of steel and is usually inclined. The top end of the ladder is held in a fixed horizontal metal guide, bar or grove. The ladder can slide sideways along the guide without getting detached from it. Lower end of the ladder may be directly on the floor or in a metal guide or grove. Usually the horizontal traversing distance is not large. One of such ladder is on a large multiple-burner furnace. The ladder is provided on both sides of a rectangular furnace with its several rows of burnes on its sides. The sliding or moving ladder is fixed permanently to the furnace to facilitate easy access to each burner. It has application in storerooms also. These are installed in rows of tall cup-boards.
The design features of portable ladders are similar to that of permanent ladders. The only difference is that these are of suitable length and made from light-weight materials.
These are usually made of aluminium, wood or bamboo, etc. The wooden ladders are firm but these are heavier then the aluminium ladders. The aluminium ladders are light in weight, easier to carry. Use of aluminium ladders near electrically live installation is dangerous.
The base of metal ladders is provided with non-skid shoes to prevent sliding or slipping. The portable ladders are frequently shifted and set on the floor or ground. If needed the wedges should be used at its base to adjust ground slope or unevenness.
Two separate roe or wire loop pieces are usually provided at top for lashing to hold the ladder. One piece rope loop may hinder while crossing over it. This area is at top and at crossing point between ladder and platform. In particular this portion of ladder is potentially hazardous part of the journey. After tying the rope at fixed structure the ladder will not slip sideways while someone is climbing up or performing light task with its support. Similarly fastening ladder at top will not allow the ladder to twist, disturbed or dislodge from its position by external force.
Precautions during use:
- The portable ladder should be placed in such a way that its base is kept at ¼ of the length of the ladder (measured from base of the part touching the vertical part or wall) away from the supporting wall or structure. When placed this way. The ladder will make an angle of about 75 degree with the floor level, which will make the ladder stable and safe use.
- One of the upper rugs should be tied to the structure. Its upper end is extended above the platform by about 1 metre.
- The ladders should not be used horizontally as a bridge, as they are not designed to withstand load in this position.
- These should not be set near the open door or a passage. The door movement or traffic may disturb ladder base.
- The base should be supported on firm and fairly levelled surface. It should never support on barrel or any movable object.
- Care should be taken of electric fittings, live wires and pipelines.
- Use of ladders outdoors during stormy or windy period should be avoided.
- Before using ladder it is necessary to ensure that the shoes are free from mud, oil, grease or chemical substances.
- While climbing up or coming down the body should be faced towards the ladder. This will ensure a firm handgrip, proper foothold and a good body balance.
- As far as possible, the ladders should not be used as platform for doing continuous or heavy work. The ladder is safe to carry out light jobs such as inspection, changing electric bulb or fuses, painting jobs, cleaning work etc.