Common Fault Analysis and Maintenance of Hydraulic Rock Drill
| The structure of hydraulic rock drill is complex, and there are many reasons for the damage of its parts. Hydraulic rock drills are widely used in rock drilling rigs. The common faults of rock drills, such as rotation, impact, waterway, gas path and sealing are introduced in this article, and the solutions will be showed in the following. The precautions for the use of hydraulic rock drills will be summarized .
The hydraulic rock drill is a rock drilling construction tool with multiple functions, including impact, rotation, propulsion and flushing, mainly used in blast hole or anchor hole construction. |
1. Rock Drill Composition
The rock drill is a low-pressure and high-flow impact part of the drill rig. The middle part of the rock drill is mainly a centering and straightening part, the hydraulic stop part has the functions of rotation and striking, and the front part mainly provides straightening support for the rotary impact of the drill tail.
2. Common fault classification and solutions
2.1 Rotation problems
2.1.1 Rock drill rotation jam
(1) The logic sequence valve spool of rotary oil inlet of rock drill is blocked due to hydraulic oil contamination, which will lead to poor flow of rotary oil and stuck, as shown in Figure 2 (a). The solution to this problem is to remove the valve core and clean it with diesel.
(2) Damage to components in the rotating part of the rock drill, such as the rotary bearing and gear damage, as shown in Figure 2 (b), (c), and (d). The cause of damage is generally insufficient lubrication or fatigue. Sufficient lubrication is a necessary condition for the rotary bushing to maintain good performance. High propulsive force and large bore hole making should improve the lubrication requirements in time. Insufficient lubrication can cause high-temperature discoloration around the bushing end face. In severe cases, it can even cause the rotary bushing to break into two parts in severe cases, and even cause expensive secondary damage to the rock drill. The rotary bushing is a wear-resistant part and should generally be replaced after 300-400 impact hours of operation to prevent damage caused by part fatigue.
2.1.2 Rock drill rotation half a circle
After the rock drill rotates a certain angle, it stops rotating. Similar phenomena also occur in the reverse rotation. The reason for this phenomenon is that the torque of the rock drill body fixing bolts is inconsistent, resulting in the rock drill rotating stuck.
2.2 Impact problems
2.2.1 Rock drilling is weak and rock drilling efficiency is reduced
The rock drill is weak and the rock drilling efficiency is reduced, which is mainly manifested by the severe shaking of the impact pressure gauge and the propeller boom oil pipe on the cab panel. The main reason is that the high-pressure or low-pressure nitrogen area of the rock drill is insufficient or the nitrogen diaphragm is damaged. The nitrogen diaphragm needs to be replaced or filled with nitrogen, as shown in Figure 3. When this type of fault is serious, the accumulator end cover may crack, causing nitrogen leakage. |
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2.2.2 No impact in drilling
The drilling rotation is normal, the impact pressure gauge is normal, but there is no impact, the reasons are as follows:
(1) The impact reversing valve of the rear end cover of the rock drill is stuck due to hydraulic oil contamination, and can be used after cleaning.
(2) The impact stop valve of the rear end cover of the rock drill is broken, The main reason is that the hysteresis pressure is large after stuck and lead to the damage. At this time, the impact stop valve needs to be replaced.
2.2.3 There is sound at the time of drilling impact
The rotary motion of the rock drill is normal, the impact pressure gauge is normal, but there is no impact, and there is a rattling sound when impacting. Most of these problems are due to the failure of the impact piston, such as the impact piston break, stuck, or the impact guide piston stuck. Inconsistent torque of the rock drill will lead to eccentric impact piston, the rock drill is not maintained in time (the copper sleeve at the front end of the rock drill and the copper spline sleeve in the head of the rock drill are seriously worn and not replaced in time), or insufficient gas lubrication will lead to foreign matter entering the impact piston, causing the impact piston to be partially scratched.
2.2.4 Rock drilling is difficult to find holes with low punch and almost no advance
The main reason why the rock drill is difficult to find holes with low punch and almost no advance is that the shank damage, as shown in Figure 6 (a), resulting in difficulty in holes opening. If the shank ring damages too frequently, it is because the low impact pressure is too high and the copper sleeve is seriously worn, resulting in a large gap. The shank is not in center. At this time, the copper sleeve size needs to be measured and verified for replacement.
| 2.3 Waterway problems 2.3.1 The flushing head of the rock drill is broken
The main cause of water leakage caused by the rupture of the flushing head is mostly the back beating or impact without propulsion. Two other reasons are as follows:
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(1) The flushing head is corroded. This is because the material to make the flushing head not be fully strong and corrosion-resistant at the same time. If the flushing water is acid-alkali corrosive, the flushing head may be corroded, which will cause cracking (see Figure 7 (a)) and eventually fatigue failure. The only way to improve this situation is to keep the shank and flushing head seal, and to keep connection plate in good condition.
(2) Front end is corroded. If the front end is corroded, the flushing head will move forward and the impact force from the stop ring will be transmitted to the connecting plate instead of the connecting thread of the front end bolt as expected, which will cause an adverse stress distribution around the orifice at the front end connecting plate, resulting in a rupture. The shank, water seal ring and connecting plate are in good condition to effectively avoid front end corrosion. In the actual drilling, try to eliminate the use of low or no propulsion impact, especially high impact, this is one of the effective measures to improve the service life of the flushing head.
2.3.2 The impact piston has obvious spider pattern
The internal rust of the rock drill is serious, and the crack source of the end face of the rock drill impact piston is clear. This phenomenon will cause the end face of the rock drill impact piston damage in advance, and the service life couldn’t reach the predetermined design value. The main reason is that the water seal of the rock drill is not replaced in time, and the water inside the rock drill is repeatedly quenched in the impact area, resulting in the crack source.
2.4 Gas Path problems
The damage of rock drill gas path problemsZ: There is no lubricating oil on the shank, the shank is dry, and the internal components frequently damage, for the following reasons:
(1) The failure of the gas lubrication system of the rock drill may be due to the damage of the pulse relay, which can be replaced after inspection.
(2) The front end of the rock drill side airway plug failure, disassemble it to clean the internal, take necessary protective measures on the springs and steel balls.
(3) Air leakage at the rear of the rock drill, the following 2 of the 4 bolts at the back end can be removed, and the feed strip is added at the tail of the bolt to block the air leakage.
2.5 Sealing problems
2.5.1 The rear end cover crack of the rock drill
The rock drill seal damage is shown in Figure 10. The cracking of the rear end cover of the rock drill is mainly caused by the impact of the rock drill in the case of long time low propulsion, no propulsion or reverse propulsion (reverse punching), and the impact force from the impact piston is transmitted and the peak pressure is generated on the end cover, which will lead to the end cover cracking. Therefore, it is necessary to reduce empty and anti-hit, and eliminate the full impact of the working situation.
2.5.2 Serious oil leakage at the rear, middle and front of the rock drill
Most of the oil leakage in the rock drill joint is because the seal damage, resulting in the rock drill impact high pressure oil leakage.
3. The use of hydraulic rock drill precautions (1) The accumulator pressure should be checked frequently before the test drilling, and the high pressure accumulator is required to be less than 8MPa; Low pressure accumulator 1MPa. (2) Reduce empty and reverse punching, eliminate full impact, and try to eliminate the use of low or no propulsion impact in the actual drilling, and high impact is not allowed. (3) Frequently check the damage degree of the shank, flushing head seal and connecting plate, and timely replace water seals and other wearing parts. (4) Often check the side bolts and rear end cover bolts damaged tightening force. (5) Regularly (generally every 300-400 impact hours) replace seals, copper sleeves, bearings, spline copper sleeves, shank rings (washers), back punching washers and other vulnerable and consumable parts, regularly check the outer clearance of copper sleeves, spline copper sleeves and other parts, and regularly check the preload force of bearings and other parts. (6) Ensure smooth and sufficient gas lubrication, and ensure that the gas lubricating oil model is correct. Adequate lubrication is the necessary condition for the rotary contact parts (rotary bushing, copper bushing, shank ring (washer), splined copper bushing and impact piston, etc.). |
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4. Hydraulic rock drill maintenance and assembly precautions
Assembly of medium cylinder block
Installation of the plug
When installing the plug, the surface of the O-ring on the plug must be coated with hydraulic oil.
The following table lists the specifications and tightening torque of plugs on the RD18 rock drill
5. Maintenance and replacement of cylinder block bushing
Repair of bushing: If there are slight wear and tear on the lining of the middle block, polish them with a pneumatic tool to repair them.
Replacement of bushing: (a) If the bushing is still unable to remove the damage after repair, a new part needs to be replaced; (b) Remove all joints and plugs on the middle cylinder block.
Take out the inner parts of the middle cylinder block.
Replace the parts.
