Zero position can be seen The protection also has the function of voltage loss protection.
At this time, due to the failure of voltage loss protection and zero position protection, the cage continued to rise, leaving a vacancy outside the landing door, and the workers fell from the gap.
At that time, a worker sent mortar upstairs and entered the right cage of the elevator.
The automatic reset handle automatically sets the control handle back to the zero position by the action of spring, which must be firmly applied to the handle during the operation of the elevator; the non automatic reset handle can only manually set the control handle back to the zero position during the operation of the elevator In the process, the operator does not have to keep the force on the handle all the time.
In terms of voltage loss protection, it is preferred to use the same button for the electric bell and starting function, so that the installer is not easy to miss the line; in terms of zero position protection, the electrical zero position protection with high reliability is preferred Type..
At present, there are the following views on the loss of voltage protection setting: the actuator adopts the operating handle and button control (i.e.
If the operation is stopped due to fault or loss of voltage during operation and the power supply is restored, the mechanism shall not act by itself.
After the incident, it was found that the right cage stopped to the trigger upper limit position, the cage door was closed, the top floor door was closed, and the 16th floor door was open.
Therefore, there are still some disputes and blind spots in the setting of voltage loss protection and zero position protection of construction elevator.
An accident led to thoughts on the safety protection of construction elevators.
The mechanism can be restarted only after the controller is manually reset to zero position.
However, considering personnel quality, use safety and other factors, voltage loss protection and zero position protection shall be set at the same time.
Loss of voltage protection – when the power supply of the crane is interrupted, All electrical equipment involving safety or not suitable for automatic opening shall be in the power-off state to avoid the automatic operation of electrical equipment after power supply is restored.
The lifting cage runs to the upper limit position and stops after triggering the upper limit switch.
The control handle in the construction elevator is generally divided into automatic reset handle and non automatic reset handle.
Its main purpose is to avoid unattended monitoring or emergencies Accidents are caused by the automatic operation of the equipment under normal conditions.
Thinking caused by an elevator accident at noon on April 2012, a high-altitude falling accident occurred at a relocated commercial housing construction site in a district of Shanghai.
The standards directly related to construction elevators (gb10055-2007 safety code for construction elevators), GB / t10054-2005 construction elevators, and gb26557-2011 construction elevators with vertically guided cage for both people and goods) do not make any explicit statements on voltage loss protection and zero position protection, but only in 5.2.10.1 of GB / t10054-2005 construction elevators The description of “electrical components and installation shall comply with the provisions of relevant national electrical standards” is given in 5.2.10.2.1 “The following faults in the electrical equipment of the construction elevator shall not be the cause of dangerous action of the construction elevator: a) no power; b) insulation problems of the ground or metal components; c) short circuit or open circuit; d) the movable iron of the contactor or relay does not pull in.” It can be seen that the voltage loss protection and zero position protection of the elevator are not clearly described in the above direct standards, and the requirements are vague.
After a cart of mortar was sent to the 16th floor, a high-altitude falling accident occurred.
In these cases, if the pressure loss protection is not set, there will be great potential safety hazards.
Basically, 40% (12 sets) of elevators are equipped with voltage loss protection, of which about 66% (8 sets) use the same button for electric bell and starting function to realize voltage loss protection, and the others (4 sets) The start button is set separately to realize the loss of voltage protection.
The construction elevator belongs to lifting machinery, and should also comply with the general safety standard for lifting machinery gb6067.1-2010 safety code for lifting machinery part 1: general provisions And 8.4 and 8.5 of the standard gb6067.1-2010 clearly put forward: zero position protection – each transmission mechanism of the crane shall be equipped with zero position protection.
Considering the actual use situation and many falling accidents of construction elevator personnel, the author believes that although the construction elevator is not directly specified in the relevant standards of construction elevator The setting of voltage loss protection and zero position protection shall be specified.
According to the accident statement and on-site investigation, the workers transported mortar at noon on the day of the accident.
From the above accident process, it can be seen that the main reasons for management are the weak safety awareness of workers and the inadequate management of site equipment; The main technical reason is that the equipment voltage loss protection and zero position protection are invalid.
The function and type of voltage loss protection and zero position protection.
The author randomly investigated 29 construction elevators in 20 construction sites, involving 17 manufacturers.
On the issue of zero position protection, some professional technicians believe that the elevator with automatic reset control handle has no zero position protection, because it is different from the standard requirement that “the mechanism can be restarted only after the controller is manually reset to the zero position” No.
here, the author believes that we should grasp the essence, as long as it can realize “when the power supply is restored, the mechanism shall not act by itself” It is considered that the normal operating state for the automatic reset handle means that once the elevator stops running, the handle will no longer be stressed and will automatically return to the zero position, so that the elevator will not act when the power supply is restored.
With the continuous expansion of construction scale in recent years, the use of construction elevators has become more and more frequent, and manufacturers have sprung up rapidly, but the technical strength of each manufacturer is uneven, The safety details of elevators vary greatly, and there are some technical disputes on individual devices, which not only increases the difficulty of safety supervision, but also brings hidden dangers to the on-site use of equipment.
The combination of button and contactor that can automatically reset is generally used on the construction elevator to form voltage loss protection, which is mainly reflected in that the start button must be pressed first every time the equipment runs.
The investigation found that most construction elevators can be set with zero position protection, and nearly 80% of elevators adopt “mechanical zero position” , only a few manufacturers of construction elevators have adopted the “electrical Zero” protection mode; for some equipment, the zero protection is invalid due to improper maintenance.
Elevator voltage loss and zero position protection analysis the standard requirements of voltage loss protection and zero position protection.
mechanical zero position) that can be reset automatically , the loss of voltage protection function can be realized without setting the loss of voltage protection; when the controller with non automatic reset and zero contact is used for control, the electrical Zero protection should be set in order to realize the loss of voltage protection.
Construction elevators are more and more used lifting machinery for carrying goods and people on housing construction sites.
The voltage loss protection of construction elevator is set to prevent the automatic operation of equipment when power supply is interrupted and power supply is restored.
The worker fell into the ground enclosure of the elevator and died on the spot.
During the field investigation, it is found that the mechanical zero spring fails to reset automatically, or the electrical Zero is not set, and some operators will reset their hands automatically The binding of the handle causes zero position failure.
After that, the workers returned to the landing door and closed the inner door of the cage.
Zero position protection is the protection set to prevent the operation mechanism from acting after the power supply of the construction elevator is restored when the control handle is not at zero position.
In this paper, the zero position protection type of the operating handle automatically reset by spring is called “mechanical zero position” , the non automatic reset zero position protection type of the handle is called “electrical zero position” Setting of voltage loss protection and zero position protection on elevators.
Because there was no driver on site, they operated the right hanging cage to the 16th floor, opened the inner door of the hanging cage and the floor door, and sent the mortar to the floor.
The elevator with pressure loss protection is equivalent to double insurance, and this potential hazard is basically eliminated.
