To prevent the creation of a danger zone for the operation of a tower crane in cramped conditions outside the boundaries of the construction site or when placing on the site premises in which people can be or are, or other obstacles, a restriction on the site of its maintenance should be provided. It consists in automatically turning off the mechanisms operating in the given modes. This is ensured by limit switches mounted on the crane, as well as turning off the rulers. Let’s further consider how to determine the crane’s danger zone .
General information
To prevent the creation of a danger zone for the crane , the following are forcibly limited:
- Moving crane.
- Lifting height.
- Departure
- Turn the arrow.
Jib cranes to prevent collisions with obstacles in cramped conditions should be equipped with coordinate protection.
Restriction system
It allows you to artificially determine the maximum size and configuration of the hazardous areas of the crane.
The system allows you to limit the area of ​​movement of the load, the boom and the crane itself in horizontal and vertical projections within specified limits. Limitation of the crane’s hazardous areas due to automatic shutdown (blocking) of the respective drives when the cargo enters the restricted area, in case of danger of cargo or boom collision with other objects.
Using the system provides control:
- By turning the arrow.
- Moving the crane on rails.
- Departure and lifting of cargo.
Based on the signals received from the sensors, the system determines the location of the equipment, its components, the height of the suspension at the construction site. By comparing the data obtained with the data set in the parameter block, control signals are transmitted to the corresponding drives.
Service areas
The system provides automatic drive control in the crane operating zones , in which:
- The load should not be moved, but boom elements are allowed if the distance to them exceeds the reach of the load.
- No boom point and load can hit.
In addition, automatic control of the drives in areas in which the height of the load of cargo is limited is provided. There can be no more than 4 such sites.
On the construction plan, hazardous areas of the crane operation are indicated without fail. For areas where the suspension height is limited, the maximum parameter must be set.
Regulatory requirements
When the crane’s danger zone exits the fence, by agreement with the authorized organizations and bodies (traffic police, architecture, fire department, etc.), an additional signal fence must be set in accordance with GOST 23407-78. It must have warning signs.
It is forbidden to use limit switches as working devices to turn off electric motors.
Angle of restriction
It must be tied to the axis of the rail track or crane tower (depending on the type of special equipment).
In the working draft (PPR), coordinates and degrees are used to indicate the angle of the forced restriction. In the course of the rays, prohibition signs are indicated, and warning signs are in front of them. The distance between the lines should be at least 7 meters.
The crane operator must reduce the speed of the cargo to a minimum of not less than a meter before the warning sign. Further, he is obliged to move objects at this speed by repeated short inclusions.
Scheme of operation of the restriction system
The boundaries are indicated on it :
- Hazardous areas of the crane (determination is carried out according to the formula). The boundaries of zones dangerous for finding people when installing, moving, securing structures and elements, sections of a building under construction are indicated.
- Special machinery services.
The diagram also indicates:
- Line of restriction of a site of service.
- A platform for receiving concrete mix, mortar.
- The location of the test load.
- The storage area of ​​containers, removable lifting devices.
- Parking place at unloading.
- Site for the collection of construction waste.
- A place for a folding of columns.
- Special equipment power supply cabinet.
- A stand with printed slings and a weight table.
- Rail grounding.
- Walking paths.
- Connecting conductors.
- Entry / exit.
- Temporary road.
- The direction of traffic.
- Temporary road
- A platform for storing structures and materials.
- Temporary fence (wooden), fencing.
- Restrictive and warning signs.
- Point for washing wheels of vehicles.
Crane Hazardous Area Formula
The danger zone of the crane can be determined by the following formula:
0.5Vgr + L (g) + X - the boundary of the hazardous area.
In this equation, the indicators of the smallest - Vgr and maximum L (g) of the cargo dimension are used. When calculating the danger zone of the crane, the formula includes the value of the minimum distance of departure of the cargo in the event of its fall - X.
Placing characters
Designations must be installed so that the crane operator can see the boundary of the service area. At the same time, at least 2 characters must fall on one corner or line of the restrictive zone. In some cases, the installation of signs on racks is not possible. For example, on the roadway or in the area of ​​rail tracks. In such situations, it is allowed:
- Hang signs on a special bracket or tensioned rope.
- Place signs horizontally so that they cannot be moved. However, they should not interfere with movement.
There must be at least 4.5 m between the suspended sign and the road. The horizontally placed signs are periodically cleaned and updated.
Height limiter
It is used to reduce the size of a hazardous area. During the construction of the structure, the limiter can move to a new level.
To reduce the size of the hazardous area in cramped conditions, it is allowed to limit the distance of lifting of the cargo during loading and unloading, laying underground engineering systems, erecting the underground part of the building with the development of organizational and technical measures.
Nuances
When limiting the height to which the load will rise to 4 Ă· 6 meters, according to the plan of organizational and technical measures, objects should not rise higher than indicated in the PPR. This site on the terrain along the entire perimeter is indicated by signs on which an explanatory inscription should be present.
Visual control of the height of the cargo is carried out by a specially designated signalman from the slinging team. You must choose the most experienced employee. The location of the specialist should be indicated on the drawings. There should be a radio link between the slinger and the crane operator.
Activities related to the visual restriction of the height of cargo movement should be coordinated with the territorial division of the Gosgortekhnadzor.
Additionally
The work, the implementation of which is supposed to be in cramped conditions with the compulsory restriction of the service area or the height of the cargo, is carried out in accordance with the work permit for the implementation of activities in the area of ​​hazardous production factors.
On the activities carried out, entries are made in the relevant journals. The execution time for a specific limitation of the crane service area is recorded in the crane operator’s log. Each time before changing the zone restriction, the implementation of the relevant measures must be confirmed. When changing the boundaries of the service site , safety signs move at the same time .
Conclusion
The requirements established by regulatory enactments, including the provisions enshrined in GOSTs, must be strictly observed. The correct definition of the boundaries of the service site and hazardous areas will prevent property damage and harm to the health and life of citizens.