August 11, 2022
Analysis and Improvement of the Stability of the Hoisting System of DGZ-150B Jet-grouting Drilling Rig
DGZ-150B multi-tube Omni-directional jet drilling rig ( see Fig. 1 ) is the main construction equipment for the multi-tube rotary jet method. The drilling rig has two main functions in the construction process: power head rotation and power head lifting. The stability of these two functions will affect the construction quality. In the construction process, the lifting mode of the power head is step-by-step lifting, and step-by-step lifting is to increase every time according to the construction parameters. Stepped lifting requires the power head to stay in a certain position for a period of time to keep the position unchanged for high-pressure grouting. Generally in the construction process step distance is 25 or 50mm. Due to the short step distance, high-pressure grouting is not required in the lifting process, and the lifting time is required to be as fast and stable as possible to improve production efficiency and avoid cement slurry waste.
1 Mechanical structure of the hoisting system and hydraulic system design
1.1 Mechanical structure of the hoisting system
As shown in Figure 1, the hoisting system of the drilling rig mainly consists of four main parts: power head, bracket, column, and hoisting cylinder.
1.2 Design of the initial lifting hydraulic system
The hydraulic principle of the initial lifting system of the drilling rig is shown in Figure 2. It consists of oil tank, constant pressure variable pump, three-way four-way reversing valve, descending speed control valve, ascending speed control valve, and lifting hydraulic cylinder. hydraulic cylinder, etc.
The constant pressure variable pump provides power for the whole system, and the three-way four-way directional valve controls the descending and ascending of the power head. The speed of descending and ascending is adjusted by the descending and ascending speed control valves. The three-position four-way directional valve uses an O-shaped valve spool to keep the hydraulic cylinder stopping and not falling.
In the step lifting work, firstly, the three-position four-way reversing valve moves to the right to Make the rodless cavity into oil, the rod cavity back to oil, the power head upward lifting, when the power head lifts the set distance value, the three four-way directional valve back to the middle position, the cylinder stop lifting and keep not falling. The cylinder stops lifting and keeps not falling.
Specific parameters of hydraulic components:
(1) constant pressure variable pump: displacement 22 mL / r, cutting pressure 16MPa, maximum input speed 2000r/min.
(2) three-way directional valve: rated flow 45L/min, maximum pressure 35 MPa, maximum flow 60L/min, pressure drop 1.5 bar (1 bar = 0.1MPa, below) 1bar = 0.1MPa, the same below).
(3) down speed control valve and up speed control valve: rated flow 40L / min, the highest pressure 31.5MPa.
min, the highest pressure 31.5 MPa, pressure drop 2 bar.
(4) Lifting hydraulic cylinder: cylinder diameter 100 mm, piston rod diameter 70mm, stroke 1000mm.
According to the parameters of each component can be derived: the total flow rate of the system is 33L/min, the system pressure is 16 MPa, and the lifting speed of the hydraulic cylinder is 4.2 m/min. The lifting speed of the hydraulic cylinder is 4.2 m/min, and the lifting force of the hydraulic cylinder is 120 kN. Since the self-gravity of the power head is about 20 kN, the actual load of the power head is 100 kN. The actual load of the power head is about 100kN.
In the actual construction process, the lifting speed is fast and the lifting distance is caused the whole rig to vibrate because of the fast lifting speed and short lifting distance, which led to unstable lifting and stopping each time. This will not only causes construction quality not to be guaranteed but also shorten. This will not only cause the construction quality not to be guaranteed but also shorten the service life of the drilling rig. In addition, due to the leakage between the spool of the three-way four-way reversing valve. The hydraulic cylinder cannot keep the load in the same position.
In addition, due to the leakage between the spool of the three-way reversing valve and the valve body, the hydraulic cylinder cannot keep the load in the same position and will fall. When the load is bigger, the displacement of the lifting hydraulic cylinder falls back to a larger displacement, which will lead to a small lifting distance, reducing This will lead to a small lifting distance, reducing construction efficiency and wasting cement material.
1.3 Hydraulic shock
The main reasons for hydraulic shock are:
(1) the sudden stopping of the flow of liquid at high speed and the resulting hydraulic shock;
(2) the sudden braking or reversal of the load in motion, due to inertia causes a sudden increase in pressure and the resulting pressure shock.
1. 4 Design of improved lifting hydraulic system
In order to slow down the hydraulic impact of the lifting system, the reasonable liquid flow rate is selected and the reasonable lifting speed of the power head is designed while meeting the requirements of the system. At the same time, the hydraulic system of the lifting system is improved to prevent the power head from falling during the slurry injection process.
Mainly on the basis of the original hydraulic system, two two-position two-way solenoid valves are added to control the lifting and stopping of the hydraulic cylinder, and the load does not fall when stopping. The internal leakage of the two-way solenoid valve is 1 drop/min ( 0.05 cm3 / min ). The original three-position four-way reversing valve is an O-shaped spool, now changed to a Y-shaped spool. Others remain unchanged. When the step-up lift is improved, the three-position four-way reversing valve is powered to the right, and the two-position two-way solenoid valve is powered to open so that the rod cavity enters oil, the rod cavity returns oil, and the power head rises upward. When the power head rises to the set distance value, the two-position two-way solenoid valve I am powered off and closed, the three-position four-way reversing valve and the two-position two-way solenoid valve II continue to maintain the open state of electricity, and the cylinder stops lifting and does not fall.
At the same time, the displacement of the constant pressure variable pump is changed to 16 mL / r, and the pressure remains unchanged. The rated flow of the down speed control valve and up speed control valve is adjusted to 25 L / min. The parameters of a two-position two-way solenoid valve are: rated flow 45 L / min, rated pressure 35 MPa. The lifting speed of the hydraulic cylinder is 3m / min.
