Lifting crane is a machine equipped with fixed lifting devices designed to move heavy and dimensional objects in space both in height and in a horizontal plane. They are used on construction sites, in production workshops, for other industrial purposes.
Types of cranes
Since these machines are used in various industries, they must perform special tasks and operate under certain conditions. Therefore, there are several types of construction:
1. Arrowheads. Such cranes can be seen on construction sites. The load-lifting mechanism of such machines is suspended from a moving cart or to the boom itself.
2. Overhead cranes are equipped with a trolley moving on a fixed structure. Such work in shops, on cargo areas in ports, etc.
3. Cable have a gripping mechanism suspended from a cart moving along fixed ropes on stationary supports. They participate in the construction of bridges, are used in quarry and mountain areas.
These are the main types of crane structures. Each of them works with different in size and mass objects, the movement is made by various gripping mechanisms.
Types of portable devices
There are several ways to attach objects to a crane:
- Hook. It is attached slings, which, in turn, grab the assembly loops of structures or other elements intended for transportation and lifting.
- Ticks are used to move objects that do not have special devices (pipes, barrels, logs).
- The magnet attaches metal objects and containers to itself.
- Grapple captures bulk goods.
Depending on the specific application of the crane, gripping devices may vary.
Types of chassis
Cranes are delivered to working objects in different ways: some arrive by themselves, others require delivery, others serve permanently in one place without the need for movement.
Stationary cranes are used in large industrial and manufacturing plants, where there is a need for carrying the goods from place to place, but there is no need to move the mechanism itself. Representative - a crane pavement. It is a lifting mechanism moving along a certain path. Trajectory of motion is determined by hanging constructions on a fixed support.
Crane on the road (pneumowires). It is installed on the car platform, which it transports, from it it is controlled. Such mechanisms have an average load-carrying capacity, are applied on small construction objects, at a lining of communications.
The crane on its own way is an installation that can move independently on the platform to which it is mounted. An example is a tower crane on a construction site, highly specialized devices on railway platforms, etc.
Also used various running gear: caterpillar, railway, rail, walking, floating.
All kinds can have different drive:
All of the above features describe the variety of designs and differences of cranes. The use of each species depends on the specific conditions and tasks. But the choice of the machine is not determined only by its constructive feature. Next, consider the functionality that must be considered when selecting a crane.
All mechanisms have different performance indicators. Basic:
- Lifting capacity is the maximum weight of cargo that the crane can move (Q, t).
- Hook radius - horizontal distance from the rotation axis of the turning part to the suspension axis of the load (Lcr. m).
- The length of the boom is the distance from the axis of rotation of the turning part of the crane to the end of the working part of the boom (Lpage. m).
- The height of the hook lift is the vertical distance from the floor to the load-handling device located at the highest point (N, m).
There are also other highly specialized parameters that are calculated when choosing cranes of high power or special purpose (load torque, depth of lowering the load, speed of movement and lifting, etc.).
All these factors in different combinations are considered when choosing a device. Because of errors in determining the technical parameters of the crane, necessary for work, the consequences can be different: from overpaying for renting a more powerful machine to its failure or the inability to take action when there is a lack of functional characteristics.
Calculation of basic parameters
The choice of the type and brand of the crane is made by calculating its characteristics, which are controlled by SNiP 3.03.01-87; SNiP 12-02-2001; SNiP 12-04-2002 and PB 10-382-00.
The power of the crane is determined by the formula:
Me - the mass of the heaviest lifted element, t;
Lcr тр - required length of the hook outlet, m;
Mfrom - weight of lifting and gripping devices, t;
Mbase - weight of the mounting hardware, installed on the load, t.
The height of the crane is calculated as follows:
h0 - the height of the mounting horizon or the previously mounted element, m;
hz - gap between the installed and previously mounted element, m;
he - height / thickness of the element, m;
hfrom - height of the lifting structure, m;
hthe - the level of the crane parking from the zero mark, m.
The radius of the hook and the length of the boom depend on the most remote structure and the maximum weight of the load.
Other features of the choice and organization of the workspace
The crane lifts the load to a certain height. As a rule, moving objects have a large mass. There is always a risk for people on the site, so it is absolutely necessary to comply with security requirements. Do not put other objects near the operating mechanism at risk. Therefore, before starting production, it is necessary to think about the location of the goods and objects in such a way that the use of the crane is as effective as possible and the risks of damage to other materials are minimized. For construction sites develop master plans with detailed schemes of movement and movement, in production departments there are requirements for the layout and location of goods.
The crane must comply with the requirements of technical safety, be completely serviceable. Regular examinations by specialists should be carried out.