Mine shaft lifting safety technology
shaft lifting is the lifting and transportation work carried out through the equipment and devices installed at the shaft mouth, shaft and bottom. The main equipment and devices used in the shaft lifting system include hoist, derrick, crown wheel, steel wire rope, connecting device, lifting container, shaft guide device, bearing device at the wellhead and bottom of the shaft, car stopper, safety door, signal device, etc. These equipment and devices are not only an indispensable part of shaft lifting, but also an important link that must be paid attention to in the safety work of lifting
according to different hoists, shaft hoisting is divided into shaft single rope winding hoisting, double barrel double rope winding hoisting and multi rope friction hoisting. Generally, single rope winding hoisting is mostly used in mines with a depth of less than 600m, and double barrel double rope and multi rope friction hoisting are mostly used in mines with a depth of more than 300m
according to different lifting containers, shaft lifting can be divided into cage lifting, skip lifting and bucket lifting. Cage hoisting is widely used in small mines. Generally, double cage hoisting is adopted in mines with large shaft section, large hoisting capacity and low hoisting level; Single cage with counterweight can be used for hoisting in pingduo coal mine with small shaft section and the third stage of hoisting water from 2026 to 2030; The mine with small wellhead section and less lifting capacity can be lifted by single cage. During shaft excavation and extension, bucket lifting is generally used
(I) safety technical requirements for hoists
hoists, also known as winches or hoists, are used to complete the task of lifting or lowering loads by winding steel wire ropes. They are the main equipment for mine hoisting. There are mainly three series of hoists used in non coal mines, namely, single simple rope and then hypocritical and submissive image winding series, double barrel double rope winding series and multi rope friction series.
1. Requirements for winding rope of drum
the steel experimental data can be arbitrarily processed into the data format corresponding to any processing method in the data modules such as tension, contraction and twists. After the wire rope is wound on the drum, it will produce winding stress on the drum. Excessive winding stress will cause too fast damage to the steel rope and deformation and damage to the drum shell. In order to make the stress distribution of the cylinder shell uniform, the lining wood is installed outside the cylinder shell, and the rope groove is carved on it, so that the steel ropes are arranged neatly. In order to limit the winding stress and avoid rope skipping and rope biting, the safety regulations stipulate the number of layers of wire rope winding. It is specified that when the number of winding layers is more than two, the height of the drum edge above the outermost layer of steel wire rope shall not be less than 2.5 times the diameter of the steel wire rope; The critical section of the steel wire rope from the lower layer to the upper layer (equivalent to one quarter of the rope loop length) must be checked frequently, and the critical section of the steel wire rope should be moved in series at the position of one quarter of the rope loop every quarter
the rope head of the steel wire rope must be firmly fixed on the drum, and there must be a special rope clamping device, which must not be tied to the drum shaft; The threading hole shall be free of sharp edges and burrs, and the bending of twists and turns shall not form sharp angles to prevent the deformation of the steel wire rope; Three rings of rope must always be wound on the drum as a friction ring to reduce the tension at the connection between the steel wire rope and the drum.
2. Hoist safety device
the safety device of hoist mainly includes braking device, anti roll device, depth indicator, speed limiting device and emergency foot switch
(1) braking device
braking device is the main safety device of the hoist. It not only meets the working braking of the hoist during normal operation, but also can carry out safety braking in time in case of accidents (also known as emergency braking). The braking device of the hoist should enable the hoisting system to brake quickly and smoothly, and its braking torque should be appropriate, not too small or too large. Too small will make the braking distance too large, and even fail to stop the car when it is overloaded; Too large will cause excessive deceleration and impact, and even cause accidents such as rope breakage. For this reason, the safety regulations stipulate that the braking torque of the working brake and safety brake shall not be less than 3 times of the maximum static torque of the actual lifting; The deceleration of safety braking when lowering heavy objects shall not be less than 1.5 m/S2, and the deceleration when lifting heavy objects shall not be more than 5 m/S2.
the action of the braking device must be flexible and reliable; All transmission rods shall be free of deformation and cracks, and fasteners shall not be loose; Each pin shaft shall not be loose or lack of oil, and the cotter pins shall be complete. The brake shoe is in good contact with the brake wheel or brake disc; The clearance between brake shoe and brake wheel or brake disc shall meet the requirements of safety regulations. In order to ensure that the braking device can work safely and reliably, it must be inspected and maintained frequently.
(2) overwind protection device
when the lifting container is lifted to the wellhead without stopping, and continues to lift upward over the wellhead, the accident is called overwind accident. Such accidents often lead to serious consequences, such as pulling down the derrick, or breaking the steel wire rope and causing the lifting container to fall to the bottom of the well. When the lifting container is lowered to the bottom of the well without slowing down and stopping, the accident caused by collision with the bottom receiving device or well socket is called pier tank accident. In fact, the stress at the time of yielding is actually the lowering overwind accident
the over roll protection device is a device that can automatically cut off the power and make the safety brake act when the lifting container exceeds the normal unloading position (or the departure platform) by 0.5 meters to avoid the over roll accident. In addition to installing reliable over roll protection devices, the derrick must also have a certain over roll height, which is required as follows:
when the lifting speed is less than 3 M/s, the over roll height shall not be less than 4 m;
when the lifting speed is 3 ~ 6 m/s, the overwind height shall not be less than 6 m
when the lifting speed is 6 ~ 10 m/S (excluding 6 m/s), the overwinding height is not less than the lifting height running for 1 second at the maximum lifting speed; During shaft sinking, the hoisting with bucket shall not be less than 4 meters
(3) depth indicator
the depth indicator can indicate the position of the lifting container in the wellbore. When the lifting container is close to the wellhead, it can send a deceleration warning signal to remind the driver to pay attention. At the same time, the depth indicator is equipped with over winding protection switch, automatic deceleration switch, speed limit, cam plate and other devices. At present, there are two types of depth indicators: arch type and disc type.
(4) speed limit protection device
speed limit protection device is a device that can automatically stop the hoist and realize safe braking when the lifting speed exceeds 15% of the normal maximum speed. The speed limit protection device has two functions: one is to prevent the hoist from overspeed; The second is to limit the speed of the lifting container when it reaches the wellhead, so as to prevent accidents caused by excessive braking distance due to high speed after the action of the overwind protection device. Therefore, the safety regulations require that when the maximum lifting speed of the cage lifting system exceeds 4 m/s and the maximum speed of the skip lifting system exceeds 6 m/s, the speed limit protection device can control the speed of the lifting container when it approaches the wellhead to not exceed 2 m/s
(5) emergency foot switch
in order to quickly cut off the power supply, realize emergency braking and prevent accidents in case of emergency such as the failure of the working brake or main controller of the hoist, an emergency foot switch is installed in front of the driver's desk. As long as the driver steps on it, he can realize emergency braking and cut off the power supply
in addition to the above safety protection devices, the hoist also has over-current, under voltage, loose rope, brake shoe wear and other protection devices, as well as many electrical locking devices. Generally speaking, large hoists with large lifting capacity and high speed have complete safety protection devices and high requirements. The safety protection device of small hoists is relatively simple. However, the existing safety protection devices must be used well, and attention should be paid to daily maintenance and testing to ensure the normal play of their protection performance as far as possible.
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