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Maximum Safety in Man-lifting Operations

Lifting people to safely carry-out Works at height is one of the main challenges on the job place. Special equipment applying aircraft technology is what sets the Elevating Platforms WT700 and WT1000 apart in its class, reaching up to 70m (230ft) and 100m (328ft) respectively, perfectly suited to fill this need. Developed specifically to lift people for works at height, they offer the highest safety standards, easy handling and operation versatility.

Accidents continue to happen with Crane-suspended, attached or fitted Man Baskets
 

There are several records of accidents with crane suspended, attached or fitted man baskets, that were provoked simply because the safety commands -needed to work safely on an elevating platform- were not available. In the case of such contraptions, the risk of accidents is very high, because cranes were not built for lifting people. Thus, they do not offer any emergency resources, platform controls by the operator, stability, and the safety layers in case of eventual electrical or hydraulic breakdowns. According to the NR12 (Brazilian Labor Safety Standards) -which defines the minimum requirements for equipment operation-, the option of using man baskets attached or suspended from cranes is classified as a make-do improvisation, justified only when there are no other alternatives. Yet, a series of inspections and factors are required, aiming to shunt those common accidents that still continue to happen. New PTA (elevating platform) technology offers all of that, is versatile and suits the different needs of construction and industrial activities with maximum safety. Low cost of operations, transport and system assembly (compared to any crane with similar reach).


TECHNICAL COMPARATIVE- WT700 & 1000 Lift Platforms vs. Cranes

SBV Cindy Valve ®
This is a Safety and Sway-control valve- with different specifications than common valves. It’s a Proprietary Design item found exclusively in the WT700 e WT1000. The advantages of this system include:
 
  • Precision of movements;
  • Optimized inertial ramp, minimizing platform sway;
  • Proportional Controls for friendly operation;
  • Safe for eventual hose ruptures;
  • Safe for eventual water-hammer impulses• system.
A common double holding valve, normally used in cranes is a simple construction, and its safety features only consider eventual hose ruptures, relevant for load hoisting operations. Its inertial ramp is steep; steering is accomplished by the pressure line and the cylinder, against the pressure line of the hydraulic command.

Safety Redundancy in the Electrical and Mechanical Systems of the Telescopic Boom

For PTAs, as in cranes, boom extension segments are opened and retracted through hydraulic cylinders, steel ropes and chains. On PTAs, there are build–in redundancies within the mechanical and electrical systems of the telescopic boom. For example, whenever a steel cable is needed, two will be installed so if one should fail, the other one will continue operational not compromising safety. Besides this type of mechanical redundancy, there are monitoring systems for each cylinder, cable and chain condition. Thus, before something critical occurs that may affect the operators’ safety, the other safety layers will be activated, and a warning display on the operation panel will inform the operator and instruct him about what action will mitigate possible operational errors, avoiding misinterpretations of any problem.

Redundant Sensors
 
 On the picture at right, we can see two safety sensors (orange and silver) that monitor the outriggers. They are manufactured by different suppliers. If an eventual fabrication defect affects one sensor, the other one analyzing the same parameter will result in a contrasting read-out. Immediately the operator will be warned and any action that could jeopardize the overall safety will be blocked. 

Load Cells
 
All PTAs are fitted with a load cell at the Work-Platform attachment, featuring two safety functions:
 
1° Protection against equipment overload; 
2° protects the equipment and the operator in case of Work-Platform’s collision that generates sudden negative strain.

Emergency Electric Pump
 
It is a resource against an eventual carrier-engine failure or even a problem of the PTO. With this pump, all movements of the PTA can be accomplished in a safe manner.

Operation Console
 
The PTAs’ Operation Console is placed inside the Work- platform. This console features two joysticks with operator programmable movement speeds to select the best application at the moment of use.
 
This Console includes a display that informs real-time following work conditions:
 
  • Graph;
  • Positioning, Radius x Height;
  • Platform loading;
  • % of equipment capacity usage;
  • Fuel available, and residual autonomy;
  • Wind speed;
  • Further relevant information of the operation.
 

Automatic Stabilization
  

The stabilization of the assembly is done automatically ensuring that the PTA’s chassis maintains 0° of tilt, independently of soil grade. Its outriggers adjust themselves to unevenness of the terrain, minimizing operation errors.

Safety Layers
 
Besides all the items mentioned before, the concept for the PTA’s function -to lift people and not loads- drove its mechanical, electrical and hydraulic design to be totally devoted to operational safety. In case of an electric failure, there is a second way around, never compromising safety. If there is a hydraulic failure, there is a second measure to adopt. And even if a failure is hydraulic and electric combined, there is still another way to bring the operator safely back to the ground.
 
Within a PTA, there are three independent computers that dialogue with independent sensors and that process independent calculations. The results of these calculations are compared and if they are consistent, the operation will be allowed.  If the values are different, the operator will be warned, and the operation halted. The equipment will allow only returning to the berth position until the problem is solved. In failure mode, there is no by-pass or over-run, except the actions indicated which do not compromise safety. The principle is the same as used in Aviation.

VS 

A crane project concept aims at lifting loads, and when used to lift people, results a function adaptation. Its’ structure does not minimize boom bending. This isn’t a problem for a crane when lifting loads, but produces insecurity to the operator when lifting people, due to the lack of positioning precision and collision possibilities against structures. All mechanical and hydraulic systems of a crane is designed for heavy loads, thus, its movements are not as sensitive when it is working without load. (600 kg on an attached man basket is a very small load in a typical load chart of a 100 t rated crane.)
  
For the Elevating Platforms WT700 e WT1000 everything was planned and developed for safely lifting people, on a more comfortable way and with zero risk of accidents.




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