Crane

About Overhead crane

Ceiling crane (Overhead crane) or bridge crane is a type of crane in an industrial environment that is used to move and transport heavy objects in the industry. Ceiling cranes generally consist of: trolley, porter, bridge, stroller and a hook whose task is to lift the objects and move them to the other side. The main part of the crane is the bridge, which provides movement at altitude. Therefore, the number of bridges has led to the classification of these machines into two sections, « Jaft Bridge » and « Single Bridge ». The use of roof cranes, in addition to making it easier to move, takes up less space. It makes it easier to navigate the main space and covers the costs of heavy machinery. In large environments where precise displacements are required, the roof crane is introduced as the best option.


Innovative steel Over-head crane design

Foolad Machine Company has taken a new step in the machine manufacturing industry and heavy equipment production through innovative design for overhead cranes. The main structure of our innovative crane is manufactured with Hollow Structural Sections (HSS) which are our products too.

 Changes in the mechanism are as follows:

  • Structure
  1. Use of Hollow Structural Section (HSS) with High Strength Low Alloy Steel (HSLA)
  2. Ease of crane construction
  • End truck
  1. Wheels and impressing location of force
  2. The connection of the end truck and the main structure (bridge)

Innovative Overhead Crane Components

Structure

Use of HSS with full-strength steel

Integrated production of the main structure is not possible for conventional cranes since steel plates are used in their structures and the maximum dimension of existing plates is 6×1.5 meters. For example, for steel structures with a 20-meter span, it is necessary to use four plates and weld them through a built-up method for constructing a web or flange of the box with related dimensions. It means that structures made of plates as a box have disadvantages such as too much welding volume, twisting, and wrapping resulting from welding and being non-integrated. But the section used in overhead cranes made by Foolad Machine Company is Hollow Structural Section (HSS). These sections are semi-prefabricated and have less welding volume rather than the common ones. In addition, they have shorter construction times. Due to the continuous production process of these sections and in the absence of restrictions in transportation, these longitudinal sections can be produced and integrated to the desired length. Also, the steel which is used in this structure is full-strength and this feature causes less weight and better control (due to inertia and crane motor power along the industrial shed). It can also be affordable because of the structure weight.

Ease of constructing overhead crane structure

The unique mechanism, innovation in the mechanical part of this crane, and consequently use of simple and available instruments and equipment with a fair price and procurement of these sections from reputable manufacturers lead to ease of construction and lower anticipated final cost compare to common cranes.

Wheels and power position

The porter

Common system

Another difference between this crane compare to common ones is about end trucks.

Common cranes usually have two axes in each end truck and because crane beams with H sections are used in these cranes with one web in the middle of the beam, one wheel can be embedded in each axis. The wheel is placed on the crane beam axis on a 5 cm cross rail and can move along the industrial shed using a related gearbox.

Machine steel innovation

In the truss model crane made by Foolad Machine Company, two wheels can be embedded in each axis because of using HSS which has two webs.

These wheels are placed in the corner of the crane beam with a rectangular cross-section which is the strongest spot, so a separate rail is not necessary. Also, they are more accurate and elegant due to manufacturing by machine. In addition, it is anticipated the final cost will be cheaper than common crane beams (with H sections).

As the number of wheels increases from 2 to 4, the load per wheel is halved, so the wheels are operating at half their design capacity. Equipment that works with less capacity will have a longer useful life.

The effect of crane bridge upheavals on high beams

The porter

Common system

Another point in the different mechanisms of these two cranes is the type of end trucks connected to the structure. This connection in the common model is rigid and is connected by a flange to the main structure.

Impressing of F load to the main structure will cause deflection in its axis and a circular or moment force in end trucks of both sides. The deflection of the main structure is always changing due to the variability of the gravity load. So wheels are separated from their rails which leads to crushing, abrasion, and deformation of them and a long time causes structural depreciation.

Machine steel innovation

But in the new mechanism presented by Foolad Machine Company, the end truck connection to the bridge is the pin. Consequently, wheels are constantly stable and can place on HSS (crane beam) uniformly.

The other noteworthy point which resulted from using the new system is about noise and vibration volume of the crane. Because of the lower weight and self-alignment mechanism, the movement of the crane is very soft and without any noise or vibration.

This mechanism can be applied to both single and double girders. Also, these cranes can be designed and manufactured in any span with various capacities and without any limitations. Another advantage of this crane (truss model) is being more affordable in longer spans.

Self-alignment System

Another advantage of this crane is having a self-alignment system. If there was any error or roughness in the crane beams or lack of straightness in the axes, end trucks will adapt themselves to the existing error because of the pin connection of the end truck and bridge. It leads to the uniformly distributed live and dead load of the crane, the impression same pressure on the wheels, and eventually an increase in longevity of wheels, axles, and crane beams.

In cranes with rigid connection and lack of self-alignment system if the crane beam were not aligned completely, it will result in severe tensions in the structure. Repetition of these tensions will eventually cause fatigue and twist in the main structure and will appear in two ways:

If the crane is without load or is not rigid enough, it won’t twist. So in this case one or two wheels will be separated from the crane beam and stay in the air. By entering force, load distribution between wheels will become non-uniform. Therefore, due to the lower crane beam, the force on the opposite side wheel will be reduced and the extra force will be imposed on the under-pressure wheel. 

If the force imposes up to the maximum capacity or even more than 30-40 percent of the capacity, therefore suspended or separated wheels (from the crane beam), will inevitably place on the crane beam, under the imposed pressure. Subsequently, the whole structure will twist around its longitudinal axis which will cause very noticeable tensions in most elements and the connection place of the structure.

Trolley lift

Because the main structure is the box (built-up) and since the lack of web in the middle of the trolley of conventional cranes, rails should be placed on the inner web of the box inevitably, so in this case by impressing F load force, a torque (Rotation) will occur in the box.

But the innovative project of Foolad Machine Company, by using HSS with two webs in their trolley, can add two other wheels as in end trucks which leads to eliminating the torque (Rotation) of the box around the longitudinal axis resulting from impressing asymmetric force to the structure. The trolley has this additional advantage moreover the end trucks.

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