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Analysis and troubleshooting of common problems in drilling operation of rock drilling jumbo
Release time:
2019-10-21
Author:
Source:
During the drilling process, the setting and adjustment of impact pressure, propulsion pressure, anti-card protection pressure and rotation speed of the rock drilling rig in advance according to the rock conditions are the necessary conditions to ensure the normal excavation of the rock drilling rig.
In the process of drilling jumbo tunneling, even if the various pressure parameters are set correctly, sometimes there will be drilling deviation and sticking problems, which not only affect the blasting effect, but also sometimes have a great impact on the service life of drill bits, drill rods and rock drills. For this reason, it is necessary to analyze the reasons and eliminate them in time to ensure the quality of drilling and the safety of the drilling rig.
1. Cause analysis and elimination method of drilling deviation of rock drilling jumbo
(1) Causes of drilling deviation
There are two obvious reasons for the deviation of drilling: one is that the positioning of the drilling is not accurate, the other is that there is an error when drilling holes, and the third is not easy to control the drilling deviation, which is generated in the hole during the drilling process. It is usually caused by the geological conditions of the rock body being drilled. For example, the rock condition of drilling consists of a layer of soft rock and a layer of harder rock. If the hole is not drilled in the vertical direction of the layer, a large drilling deviation will occur.
The magnitude of the deviation depends on the angle between the drilling direction and the rock layer, and large drilling deviations can result from slow or slippery drilling of hard rock and fast drilling of soft rock. Only when the operator is clear about the boundary between soft rock and hard rock, can the deviation be reduced or avoided by taking appropriate measures. In order to achieve the expected blasting effect, a prerequisite is that the actual drilled rock hole is consistent with the pre-designed rock hole.
This means that the hole position is completely correct, the drilling direction is correct, and the drilling depth is consistent with the drilling plan. The feed device is installed with a corner indicator and a drilling depth indicator. By measuring and calculating the location, depth and quantity of the required drilling, drilling in strict accordance with the predetermined location and the specified depth drilling can obtain a rock hole with high drilling accuracy. This also provides a good working perspective for the operator operating in the cab.
(2) Main factors affecting drilling deviation
1) Influence of geological conditions of rock mass
The most influential factor on drilling deviation is the actual drilling process, especially when drilling in rock formations with complex geological conditions (e. g. large variation in crystal particle size and severe fracture of layer foliation). The actual drilling direction is at right angles to the joint of the rock layers, but the drilling process deviates from the intended direction.
Obviously, the longer the drilling length, the greater the resulting drilling deviation. It is generally considered that the drilling deviation is proportional to the drilling depth value. Experience has shown that the drilling angle between the bit and the rock layer is very important. When this angle is less than 15 degrees, the drilling direction of the bit is inclined to an angle parallel to the plane of the rock layer. On the contrary, if the rock with uniform texture is drilled, such as granite with uniform texture, the deviation of drilling will be small or no deviation.
2) Drill factor
The drill bit structure and shape will also have an impact on the drilling deviation. Practice has shown that drilling with a drill bit with a flat front end or a concave front end center is straighter than drilling with a convex front end. Drilling with a variety of drill bits, for the best drilling accuracy, the drill bit must be reground to restore the drill button shape and diamond sharpness. Grind the shape of the button to restore the raised height of the button from the flat surface of the drill body.
When grinding the drill bit, it is important not only to restore the original shape of the button (or inlaid alloy), but also to restore the raised height of the button from the plane of the drill body. This means that the entire end face of the drill must be ground down, not just near the root of the button. If this is not done, the space required for debris flow in front of the bit will be reduced, forcing the debris flow rate to increase. If necessary, the slag hole and slag groove on the bit body must be ground to restore its correct size.
Therefore, if the drill bit is frequently ground, the feed force will be fully applied to the periphery of the drill bit, and even if the drill pipe is bent, the entire drill bit plane will fully contact the rock for drilling. But in any case, due to the drilling process will produce rock slag, in the role of rock slag, the drill bit by the feed force will still be uneven, sooner or later will cause drilling deviation.
3) Drill pipe factor
When drilling, if other drilling conditions are the same, the larger the diameter of the drill pipe, the straighter the hole will be obtained. In addition, the large diameter drill pipe increases the safety and stability against swinging during drilling. Before the swing of the drill bit occurs, the rock slag is carefully ground and removed. Therefore, the guide tube is much larger than the diameter of the drill pipe, so that more straight holes can be drilled.
It is necessary to obtain sufficient flushing capacity when drilling a complete drill pipe with conduit in the ground. Generally, the guide pipe is connected to the drill bit to make full use of the large diameter of the guide rod. Compared with the ordinary drill rod, this can reduce the amplitude of the drill bit shaking. At the same time, the connection of the guide pipe and the drill bit is integrated, and the swing angle of the drill bit is reduced as much as possible by extending the length of the guide rod. Another way to reduce bit wobble is to use an intermediate flute annular skirt bit. The skirt diameter is consistent with the drill head diameter, maximizing the guide rod diameter while the guide rod length is short and effective. The middle groove annular skirt drill bit is mainly aimed at drilling rock with complex drilling conditions and easily disturbed drilling direction. The resulting debris and impurities are washed out of the rock hole by flushing water through the drill skirt groove, and the tail of the skirt has a cutting edge between each groove to cut the rock. Although the middle groove annular skirt drill bit and the standard drill bit whose skirt is much smaller than the diameter of the drill bit will not swing when drilling, the middle groove annular skirt drill bit is improved on the basis of the standard drill bit and can drill straighter holes. Even so, working with a conduit is still more straight than drilling with an intermediate groove annular skirt drill.
4) Other factors
In addition to the geological conditions of the rock mass, the influence of other factors on the drilling deviation is not obvious, such as the specifications and conditions of the impactor and the design and conditions of the drill bit and drill pipe, as shown in the table: various factors affecting the drilling deviation.
(3) Methods to avoid drilling deviation
In fact, there are many ways and means to avoid the deviation of drilling, which can be seen from the above:
1) Use a hard and straight drill pipe and ensure that the diameter of the drill hole is as close as possible to the diameter of the drill pipe;
2) Use a new type of TDS catheter behind the drill bit to improve the flushing effect and reduce the risk of broken rods;
3) Use ITH rock drilling equipment with more accurate drilling to reduce drilling deviation;
4) Reduce the feed force and increase the rotation speed to reduce the drilling deviation;
5) The drilling equipment operator can reduce the deviation of drilling by drilling shallower holes in sections.
2, rock drilling jumbo drilling stuck drilling reason analysis and troubleshooting methods
(1) Causes of sticking
In the process of rock drilling jumbo driving, the most common failure phenomenon is sticking. The main reasons for the sticking of rock drilling jumbo are as follows:
1) The setting value of anti-sticking pressure is wrong
If the anti-sticking pressure setting value of the anti-sticking device is too high, sticking will occur frequently. Only when the sticking pressure is greater than the pressure set value of the anti-sticking device, the anti-sticking device will respond when the sticking occurs, so that the rock drill can realize reverse feed, pull out the drill bit, and release the sticking.
2) Bit damage
Damage to the drill bit can also cause sticking. Generally, new drill bits or newly ground drill bits are tapered from head to tail. When drilling holes in abrasive rocks (with high quartz content), the wear around the drill bit gradually causes the positive cone to become an inverted cone, the drill bit is seriously damaged, and the barb cannot be retracted in the rock hole, resulting in drill sticking.
3) Cracks in rock
Cracks in rocks are also more likely to cause sticking. Once the drill bit is drilled into the rock crack, it is easy to be caught, and the rotation resistance rises, causing the drill to be stuck.
4) Poor drilling and flushing
If the flushing water pressure is too low, it may cause poor flushing effect of the rock hole, retain a large amount of rock slag, increase the friction force when the drill bit is drilling, thus causing the rotation resistance to rise, and the drill bit may be stuck in the rock hole.
5) improper selection of hydraulic oil
Improper selection of hydraulic oil can also cause sticking. By the hydraulic oil viscosity temperature: the higher the temperature, the smaller the hydraulic oil viscosity; the lower the temperature, the greater the hydraulic oil viscosity. In the case of low ambient temperature, the hydraulic oil temperature will be lower, at this time the hydraulic oil viscosity increases, it may make the rotary resistance more than the normal drilling rotary pressure, resulting in sticking.
(2) Elimination method of sticking drill
The following methods are mainly adopted to eliminate the sticking problem:
1) If the phenomenon of sticking occurs frequently during drilling, first consider adjusting the pressure setting value of the anti-card device. The rotary pressure of the anti-card device action (switch the advancing direction at this time) should be set to 15 standard atmospheres higher than the normal drilling advancing rotary pressure value. The setting of anti-sticking pressure must be accurate. It cannot be too high or too low. If it is too high, sticking will occur frequently. If it is too low, the rock drilling rig cannot work normally (at this time, the anti-sticking pressure is less than the normal working pressure of the rock drilling rig. Before the rig reaches the normal working pressure, the anti-sticking device has already operated, making the rock drill reverse feed and the rock drilling rig cannot drill normally).
2) In unfractured rock mass, sticking occurs frequently. If it is not the problem of anti-sticking pressure setting value, it is the signal of grinding the drill bit, with special emphasis on peripheral grinding to restore taper. The drill bit becomes blunt due to wear, which will inevitably affect the drilling efficiency and increase the rotary resistance during drilling. If the rotary resistance exceeds the normal drilling rotary pressure, the drill will be stuck. In addition, under the condition of maximum pushing pressure, the reduction of rotary pressure is also a sign that the drill bit needs to be ground. The shape of the button should be ground to restore the convex height of the button from the plane of the drill bit body. Therefore, it is very important to grind the drill bit regularly and restore the taper of the drill bit.
3) If the drill bit is stuck in the rock gap, the anti-sticking device cannot eliminate the drill bit. The rotary pressure can be increased, the push handle can be placed in the reverse feed position, and the drill rod and drill bit can be pulled out.
4) If the rock slag in the rock hole is not washed well, the flushing water pressure should be checked first, and the flushing water pressure should be appropriately increased to improve the slag flushing effect.
5) If the anti-sticking pressure is set correctly, the rock has no cracks, the drill bit taper is appropriate, and the flushing effect is good, but there is still a sticking phenomenon, it is necessary to consider whether the viscosity of the hydraulic oil is correct. If the oil temperature is too low, take appropriate measures to increase the oil temperature, and replace the hydraulic oil with appropriate viscosity when necessary.
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