Crane operation area: dangerous zones - calculation. Construction site. Safety precautions
Reliability and trouble-free operation during constructionbuildings and structures - a task that requires a serious approach. It's no secret that the construction site is a territory of increased danger. And one of the most unfavorable of its places is the space on which the crane is operated and moved. Prior to the beginning of all work related to the lifting of goods, when the crane's working area has already been determined, hazardous areas must be correctly calculated. It is there that potentially have emergency factors that can be either directly related to the operations performed, or exist independently of the work process.
Installed crane operation area. Dangerous zones - what does it concern them?
Let's look at how you can calculate the boundariesthis potential emergency area. The boundary of the dangerous zone of operation of the crane passes through those places over which it moves the building cargo. What does it concern? This is directly the zone that the crane serves, but not only. To it it is necessary to add the distance equal to half from the least external dimensions of that cargo which it will move.
Then - add here the minimum distance that the falling cargo can fly off, and, in addition, increase the size of the danger zone to the largest of the overall dimensions of this cargo.
The boundary of the zone that is serviced,depends on the maximum reach of its boom (denoted as P (max)). To determine the smallest distance that a load can fly off when it falls, (we will denote this value as P (ex)), we must take into account the height of its ascent.
To find out the height of a possible drop in cargo,take the distance from the surface of the construction site to the bottom of the cargo, which is suspended to the boom of the crane. Stroepovka cargoes is made with the help of special devices, called traverses, slings, etc.
Calculation by formula
For clarity, we give the formula. Calculation of the hazardous area of the crane, according to it, looks like this:
Pcr (o.s.) = P (max.) Art. + 0.5 * P (min.) Gr. + Р (отл.) + Р (макс.) Гр.,
where: Рcр (о.з.) - calculated radius of dangerous zone of crane operation;
P (max.) Art. - the maximum reach of his arrow in meters;
0.5 P (min.) Gr. - half the distance from the minimum of the cargo dimensions in meters;
P (ex) - the minimum distance to which the load to be moved is able to fly off, (in meters);
P (max.) Gr. - the maximum of its dimensions in meters.
How to designate hazardous areas at the construction site
At the boundaries of those zones where the hazardsproduction operate in a constant mode, it is necessary to install safety fences. Those areas that are potentially dangerous should be surrounded by signal fences and marked with safety signs.
Thus, when the work area is definedcrane, dangerous zones on the terrain are marked with the help of GOST signs, which have a warning function. They should be placed so that the borders are clearly visible. During the dark hours of the day they are required to be illuminated.
Install them on special racks thatmust be securely secured in order to avoid falling from walking people and passing vehicles. Where the crane operation area ends, hazardous areas can be closely adjacent to people's access areas (roads and footpaths). In such areas, there are also mandatory warning signs.
It is inadmissible to place sanitary facilities, rest areas, passages for people, that is, any zones of permanent or temporary stay working in a dangerous territory.
Other necessary conditions
If in the danger zone any work should be carried out, the nature of which is not related to the planned, this action must necessarily be accompanied by the issuance of a work permit.
If the construction site is organized so thatfrom the side where the erected building is located, there are no railings of the crane railways, any of the doorways facing it must be closed tightly.
If there is a crane equipped with a magnet or a grab, the zone of its operation must be indicated with the appropriate warning signs in accordance with GOST and be fenced off with signal boundaries.
Wherever such a crane works, be peopleforbidden. Maintenance of it in technical terms by ancillary personnel is allowed only in the intervals between work intervals, when the magnet or grab takes a stable position on the ground.
All crane operators and auxiliary workers must beare instructed in the safety precautions in carrying out such work. The crane operator is supposed to know not only the definition of the dangerous zone of the crane's operation and be able to establish its boundaries, but also to understand the routes of moving the magnet and the grab.
What should cranes be equipped with?
If there is no ring collector between the individual parts of the crane - rotary and non-rotating - there must be a stop limiter.
It is necessary to provide a safety device, the function of which is to automatically stop the truck when the trolley rope breaks.
The crane must be equipped with a sound signal, the tonality of which does not coincide with the car.
There must be a voltmeter, as well as a time counter that is worked out by a cargo winch or the crane itself, and, in addition, a cable drum.
What determines the safety of the crane
Much here solves the correct slinging of goods andrope sealing. It is attached to the metal parts of the crane using various types of loops, couplings, knots, wedge clamps. Hinges at its ends are made by braiding, preventing flattening and rubbing.
Cramping ropes of a tower crane is strictly prohibited. The cargo is attached with its help to the lifting mechanism thanks to special devices in the form of blocks, drums, pulleys.
With the help of blocks, the load is raised and lowered,The pulley block is a system of interconnected moving and stationary blocks. Drums in lifting mechanisms look like hollow cylinders with screw grooves on the surface for easy routing and reducing wear.
Tower cranes - why frequent accidents?
Unlike other types of lifting mechanismsTower cranes are relatively often collapsed. The reason for this is in their design features. The track along which it moves, as a rule, has a width (i.e., an inter-ridge distance) of not more than six meters. The base of the crane (it is a question of the gap between the axes of its running trolleys, which are located on the same rail) is also insignificant and, as a rule, does not exceed this distance.
The height of it is quite large, and from thisThe tower crane is very sensitive to wind loads. The same applies to other conditions of its operation. With strong gusts of wind, the crane can fall even in the idle state. To prevent this, anti-theft clamps are used.
On the fall of cranes, the frequency of which is prettygreat, practically do not have the influence of carefully observed safety requirements. Statistics found that most often this happens with those of them that use rail to move.
What does it depend on?
Practitioners have long suspected thatthe cause of high accidents is the imperfection of the foundations of the track. Its main factor was the uneven compaction of the soil under each of the rails. Back in the 70s of the last century, experiments were conducted to control the density of rail underfill, but they had no serious effect on the actual state of affairs - the incidence of crane failure continued.
Experienced crane operators believe that the fall canbe caused by a sway. The compliance of the ground mass under one of the rails is capable of increasing in connection with tectonic disturbances with increasing seismic load. As a result, the valve loses its reliable support and can tip over at any shift of the center of gravity.