Inspection methods, procedures and precautions for rotary drilling rigs
The rotary drilling rig is the core equipment for constructing bridge piles, foundation of high-rise buildings, and railway and highway piles. It integrates mechanical, electrical, hydraulic, and soil mechanics technologies and completes vertical drilling and rock penetration in different strata through the drive head of the drill pipe and drill tools. Then, the main winch lifts the drill and rotates to discharge the soil, and the process repeats to form the hole. The working conditions of the rotary drilling rig are extremely harsh - the drive head continuously withstands huge torque and impact, the drill mast bears alternating bending moments, the main winch steel wire rope repeatedly bends under heavy load, and the hydraulic system operates at full load for a long time. Once the weld seam of the drill mast cracks, the drill pipe breaks, the main winch steel wire rope breaks, or the entire machine topples, not only will it cause millions of dollars in equipment damage, but it may also lead to hole collapse and casualties. In scenarios such as new machine delivery, second-hand transactions, major overhaul factory delivery, and annual asset evaluation, a comprehensive inspection covering the drill mast and variable amplitude mechanism, the drive head and drill pipe, the main and auxiliary winch systems, the hydraulic and electrical control, and the walking chassis is essential for accurately determining the drilling capacity and safety status of the equipment.
I. Overview of Inspection Methods
Based on the chassis type (track-mounted/wheel-type), drive type (electric/hydraulic), maximum drilling diameter and depth, drill pipe type (friction type/locking type/composite type), and commissioning requirements, the inspection comprehensively utilizes the following methods:
Static Full Inspection: The equipment is stationary, and the chassis walking system, rotation platform, drill mast structure and variable amplitude cylinder, drive head assembly, drill pipe, main and auxiliary winches, steel wire rope, counterweight, hydraulic and electrical control systems are inspected item by item, measured with measuring tools, and subjected to non-destructive testing.
Dynamic Function Testing: In a safe area, verify the chassis walking and rotation, drill mast lifting and pitch adjustment, drive head operation, main winch lifting, pressure cylinder actions, auxiliary winch and auxiliary crane functions.
Special Inspection of Drill Mast Verticality and Structural Integrity: Use a theodolite or total station to verify the accuracy of the drill mast's automatic pitch adjustment system, and conduct non-destructive testing on key weld seams of the drill mast.
Deep Test of Hydraulic System: Conduct rated pressure, overflow pressure and pressure retention tests on the drive head rotation circuit, main winch circuit, pressure circuit, and variable amplitude circuit.
File and Nameplate Traceability: Verify the consistency of the entire machine nameplate, engine/motor nameplate, drive head nameplate, main winch nameplate, drill pipe model serial number and factory documents, and major overhaul records.
Third-party inspection is a complete execution package of "static full inspection + dynamic function testing + drill mast verticality and structural inspection + deep test of hydraulic system". For major transactions or accident repair inspections, additional weld seam flaw detection and oil sample spectral analysis must be added.
II. Inspection Process
1. Data Collection and Inspection Preparation
The client provides a list of the drill rigs to be inspected, clearly specifying the manufacturer, model, maximum drilling diameter/depth, torque/rotation speed of the drive head, length of the drill pipe, type and length of the drill pipe, power form, working hours, applicable standards (such as GB/T 21682, JGJ 106, etc.). The inspection party prepares: theodolite/total station, laser rangefinder, ultrasonic thickness gauge, magnetic particle/penetrant testing equipment, steel wire rope diameter gauge, hydraulic pressure gauge set, infrared thermal imager, vibration analyzer, oil sample bottle, etc.
2. Site and Safety Status Confirmation
The inspection site is a solid and flat hard surface, with no obstacles within the radius of the drill mast lifting. The inspection area is isolated and guarded. Inspectors wear safety helmets, reflective vests, and anti-crush shoes. When checking below the drill mast, inside the drive head, or in the pile stacking area, confirm that the equipment has been turned off and disconnected, the drill mast has been reliably supported or locked.
3. Identity and Nameplate Verification
Whole Machine Nameplate: Verify the manufacturer, model, factory serial number, manufacturing date, maximum drilling diameter/depth, working weight, etc.
Engine/Motor Nameplate: Verify the model, serial number, power, and match with the whole machine nameplate.
Drive Head Nameplate: Record the model, maximum torque, speed range, factory serial number.
Main hoist nameplate: Records the model, rated lifting capacity, wire rope specification, and factory serial number.
Drill pipe serial number: The unique serial number engraved on the drill pipe body, which is compared with the factory documents. Any missing nameplate, mismatched serial number, or scratched serial number must be immediately upgraded to a serious non-conformity item.
4. Inspection of chassis and slewing system
Track行走 system： Chain rail pitch measurement， wear of drive wheel surface， flexibility of supporting wheel and supporting chain wheel rotation， and leakage inspection of floating oil seal. Track tension meets the standard.
Slewing platform： Comprehensive inspection of main structural steel plate weld seams， with key areas being the connection earplate of the drill mast at the base of the slewing platform， the support point of the amplitude oil cylinder， the main hoist frame， the support seat of the power head， and the installation area of the counterweight suspension. Any missing nameplate， mismatched serial number， or scratched serial number must be immediately upgraded to a serious non-conformity item.
4. Inspection of slewing bearing: Inspection of the entire slewing system
Upper and lower connecting bolts torque sampling inspection. No broken teeth on the tooth surface, and severe pitting. Sealing strips are intact. Listen for periodic abnormal sounds during slewing operation.
Slewing drive： No oil leakage in the slewing motor/moderator， effective braking function， no inertia slip after slewing stops.
5. Inspection of drill mast structure and amplitude system - The lifeline of the entire machine's safety
Drill mast is the core structural component of the rotary drilling rig. If the weld seam cracks or the structure becomes unstable， the consequences will be catastrophic.
Drill mast box structure： The drill mast is usually a large-section box-type welded structure. Use a strong flashlight to inspect the weld seams of the main tension rods and diagonal rods section by section. Key areas include： the weld seam of the connection earplate between the drill mast and the slewing platform， the hinge point area of the amplitude oil cylinder， the installation area of the pressurizing oil cylinder/slewing pulley group， the support seat of the power head， and the welding area of the power head guiding slide rail. Any suspected cracks should be cleaned and undergo PT or MT inspection for confirmation.
Drill mast straightness： When the drill mast is upright， use an instrumentor or total station to detect the straightness of the drill mast in two perpendicular directions. Excessive deviation indicates that the drill mast has previously endured abnormal lateral loads (such as stuck drill due to hole collapse)， and there is residual deformation and reduced structural strength.
Drill mast guiding slide rail： The guiding slide rail for the power head to move up and down. Check for surface wear and scratches on the slide rail. Severe wear of the slide rail will cause the power head to shake up and down， affecting the verticality of the drilling.
Amplitude system： No leakage during the full stroke of the amplitude oil cylinder， and the balance valve function - after the operating valve returns to the middle position， the drill mast should be able to reliably stop at any position without obvious self-sinking. The gap between the ear seat pin shaft and the bushing of the amplitude cylinder ear seat is measured.
Automatic leveling system： After the drill mast is upright， use an instrumentor to check the verticality of the drill mast， and compare it with the verticality value displayed on the driver's console. The deviation should be within the manufacturer's specified range. Failure of the leveling function will cause the pile hole to tilt， which is a serious quality hazard.
6. Inspection of power head and drilling system - The core of drilling capacity
Power head appearance： The power head shell has no cracks or oil leakage. The gap between the wear plates/sleeves of the power head and the guiding slide rail of the drill mast is measured using a feeler gauge at multiple points. A large gap will transfer the torque shock to the drill mast.
Power head drive： Hydraulic motor or motor drive， no leakage in the shell， no abnormal noise during operation. The speed adjustment range of the power head should be within the nominal value.
Power head reducer： Check the oil level and quality. Use an infrared thermal imager to detect the temperature distribution after operation， and abnormal high temperature indicates damage to the internal bearings or gears.
Pressurizing oil cylinder/pressurizing hoist： No damage to the piston rod of the pressurizing oil cylinder， no sinking during the pressure holding test. Check the condition of the pressurizing hoist wire rope.
7. Inspection of drill pipe and drill tools - Hidden risks in the borehole
The drill pipe is subjected to huge torque and pressure in the borehole. If it breaks， it will cause the drill tools to fall to the bottom of the hole， resulting in huge recovery costs and serious delay of the construction schedule.
Drill pipe appearance： Inspect the scratches， pits， and rust on the inner and outer surfaces of each section of the drill pipe. Key areas include： the thread of the drill pipe joint - for any reverse teeth， cracks， or severe rust. Check the keyway of the drill pipe/bushing wear， and for any cracks on the edge of the keyway.
Drill pipe straightness： Support the drill pipe horizontally， rotate it， and use a dial indicator to measure the runout at the middle position to determine if the drill pipe is bent. When the bent drill pipe rotates at high speed inside the hole, it will cause violent oscillation, resulting in the collapse of the hole wall and additional loads on the drill mast.
Drilling tools: Statistics on the wear and loss of the teeth of the drill bucket/drill bit and the cutting teeth. The opening and closing mechanism of the drill cover is flexible and reliable, with effective locking. There are no cracks on the connecting heads or shafts of the drilling tools.
8. Inspection of the main and auxiliary winches and steel wire ropes - the final line of defense for lifting safety
Main winch: Random inspection of the torque of the anchor bolts of the frame. The reducer of the winch has no oil leakage and no abnormal noise during operation. The brake is sensitive and the wear of the friction plates is measured with a caliper.
Auxiliary winch/auxiliary crane: Function is normal. The condition of the steel wire rope is inspected.
Steel wire rope: Use a diameter gauge to measure multiple points along the full length from the winch to the top pulley of the drill mast. If the wear exceeds the standard or the number of broken wires reaches the standard, it is judged as scrap. The rope end fixation - the alloy casting of the wedge joint has no cracks, and the number and direction of the rope clips are compliant. The steel wire rope is neatly arranged on the drum without random rope compression.
9. Depth inspection of the hydraulic system
Hydraulic oil tank: The liquid level is normal, and the respirator is clean. The color of the oil - dark brown and black indicates oxidation and deterioration, milky white indicates water ingress, and metallic flash indicates abnormal wear. If possible, take samples for testing.
Hydraulic main pump set: The main pump shells have no leakage, and there is no abnormal noise during operation. The connection pipelines and joints have no leakage.
Multi-way control valve set: The valve bodies have no oil leakage, and the actions of each valve core are flexible. The functions of the return rotation of the power head, the lifting of the main winch, the pressure increase, and the extension of the boom are all normal.
Depth test:
Main overflow pressure: Install pressure gauge groups at the pressure measurement ports at the outlets of each main pump to measure the overflow pressure at the rated speed and compare it with the manufacturer's standards.
Pressure of the power head circuit: The pressure should reach the rated value when the power head is blocked. Insufficient pressure indicates wear of the main pump or leakage in the motor.
Pressure of the main winch circuit and pressure retention: Raise the rated load and hover, and leave it stationary for 10 minutes to measure the sinking amount of the heavy object. Excessive sinking indicates leakage of the winch motor or failure of the balance valve.
Pressure retention of the pressure increase circuit: Increase the pressure of the pressure increase cylinder to the rated value, leave it stationary for 10 minutes, and record the pressure drop value.
Piping: Check the aging and cracking of the rubber hoses one by one. The top of the drill mast, the traveling pipe of the power head, and the piping in the winch area are high-risk areas for vibration and friction, and must be inspected by hand touch in segments.
10. Inspection of electrical and control systems
Instrumentation and monitoring: Engine/motor parameters, torque/rotation speed of the power head, display of drilling depth, display of the verticality of the drill mast, etc. are normal, with no fault codes.
Control devices: The handles, buttons, and pedals function normally.
Safety devices: The emergency stop button is effective. The lift and descent limiters of the drill mast, the up and down limiters of the power head, and the over-rotation and over-release protection of the main winch are triggered and tested one by one. The walking alarm and rotation warning lights are effective.
11. Dynamic function test
On a safe ground, start the equipment to the working temperature:
Walking and rotation: Forward and backward movement, left and right turning, and idling rotation functions are normal.
Drill mast lifting: The drill mast is lifted from the horizontal transportation state to the vertical working state, then lowered back to the horizontal, and the entire process is smooth. The extension cylinder of the boom has no crawling or abnormal noise.
Power head operation: The low, medium, and high-speed rotations are smooth, without abnormal vibration. The infrared thermometer monitors the temperature of the power head reducer and hydraulic motor.
Main winch lifting: Full-speed lifting is smooth, and the braking is effective. The steel wire rope is neatly arranged.
Automatic leveling: After the drill mast is upright, start the automatic leveling, and observe the automatic centering and verticality of the drill mast. The readings on the display are consistent with the calibration values of the theodolite.
12. Sampling and analysis of oil products (strongly recommended)
Extract samples of engine oil, hydraulic oil, gear oil of the power head reducer, walking reducer gear oil, and main winch reducer gear oil and send them to the laboratory for spectral analysis. The cleanliness of the hydraulic oil is crucial for the lifespan of the precision proportional valve; abnormal iron and copper elements in the gear oil of the power head indicate early damage to the bearings or gears.
13. Report output Summarize all inspection items, measurement data (such as the straightness of the drill mast, rotation clearance, steel wire rope diameter, pressure-holding data, oil analysis results, etc.), and dynamic test records. Mark the qualified items, observation items, general defects, and serious defects. Form the "Third-Party Rotary Drilling Rig Inspection Report" which includes photos of the entire machine's nameplate, weld inspection photos of the drill mast, photos of the drill mast's verticality verification, and photos of the main hoist steel wire rope detection. Deliver this report to the client.
III. Notes
Drill mast structure integrity - "the first risk item" of the rotary drilling rig inspection
The drill mast bears the reverse torque of the power head drilling, the pulling force of the main hoist during drilling, the supporting force of the luffing cylinder, and the abnormal lateral loads during ground collapse. The weld cracks of the drill mast are the most fatal defect of the rotary drilling rig. During the inspection, 100% close-up inspection with strong light must be conducted on the key welds such as the root of the drill mast, the hinge points of the luffing cylinder, and the guiding slide rails. Any suspected cracks must undergo non-destructive testing.
The straightness of the drill mast is an important indicator for judging whether it has experienced a collapse accident and strong lifting of the drill tool. A drill mast with excessive straightness has already suffered structural damage and continues to use it has a risk of fracture. It must be clearly warned and recommended to downgrade use or replace in the report.
Drill pipe - Hidden safety hazard in the hole
The wear between the inner and outer tubes of the drill pipe, the wear of the keyway, and the fatigue cracks of the joint are difficult to detect in daily use. Once the drill pipe breaks at the bottom of a hole that is tens of meters deep, the salvage and repair costs are extremely high and seriously delay the project schedule. During the inspection, the drill pipe must be lowered under certain conditions and the joint threads and keyway status must be inspected section by section.
The bending of the drill pipe will cause severe oscillation in the hole, not only reducing the drilling quality but also generating additional alternating loads on the drill mast. The bent drill pipe can be detected by the rotation gauge method, and any exceeding the standard must be scrapped.
Main hoist steel wire rope - The last line of defense for drill rig lifting safety
The main hoist steel wire rope of the rotary drilling rig is long, under high tension, and has a high working frequency. The steel wire rope bears impact loads during the lifting moment. It is necessary to use a steel wire rope flaw detector or conduct section-by-section visual inspection. Any excessive wear or broken wires will be judged as scrap, and it is not affected by subjective factors such as "it can still be used for a while".
Hydraulic system oil temperature and cleanliness
The power density of the hydraulic system of the rotary drilling rig is extremely high, and the hydraulic oil temperature is high during continuous drilling. The oil runs in a high-temperature environment for a long time, accelerating oxidation and reducing cleanliness. The cleanliness level (ISO 4406) of the hydraulic oil must be included in the oil analysis.
Drill mast lifting and high-altitude operation safety
During the inspection, the drill mast lifts, and the top height can reach tens of meters. It is necessary to confirm that there are no overhead cables above. Drilling mast lifting operations are strictly prohibited in windy weather.
When entering the top of the drill mast for inspection of pulleys and steel wires, a safety belt must be worn and hung at a reliable anchoring point. Use an aerial work platform or a dedicated ladder.
Key points of photo archives
The entire machine's nameplate is independently archived. Close-up photos of the welds at the root of the drill mast and the inspection results. Photos of the measurement process of the straightness of the drill mast (with the theodolite/total station and the drill mast in the same frame). Close-up photos of the joint threads of the drill pipe. Photos of the gap measurement with a feeler gauge between the power head and the drill mast's guiding slide rails. Close-up photos of the diameter measurement of the main hoist steel wire rope and the defect areas. Photos of the pressure gauge reading during the hydraulic pressure holding test. Data displayed by the instrument during the load (stall) test.
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Inspection methods, procedures and precautions for rotary drilling rig
The rotary drilling rig is the core equipment for constructing bridge piles, foundation of high-rise buildings, and railway and highway piles.