Mud gas separators play an indispensable and key role in many engineering fields such as oil drilling and building foundation construction. In oil drilling operations, as the drill bit goes deeper and deeper into the ground, various gases in the formation, such as natural gas and hydrogen sulphide, may invade into the drilling fluid. The mixing of these gases will not only change the performance of the drilling fluid, such as reducing its density and changing its viscosity, but may also cause serious safety problems, such as well surges and blowouts. Mud gas separator can timely and effectively separate the gas intruded into the drilling fluid, ensure the normal performance of the drilling fluid, and guarantee the safety and stability of drilling operations.
In the construction field, such as large bridge pile foundation construction, diaphragm wall operation and mud-water shield project, mud also plays an important role. It is used to protect the wall, carry slag, etc., to ensure the smooth progress of construction. However, during the construction process, slurry can also be mixed with various gases, which affects its effectiveness. Slurry gas separator can purify these slurries, so that the slurry can be recycled, not only to save costs, but also to reduce the pollution of the environment.
Mud gas separator in the long-term operation process, it is inevitable that there will be a variety of faults. Once the fault occurs, if not diagnosed and eliminated in time, it will lead to the entire project process is blocked, increase construction costs, and may even cause safety accidents. Therefore, an in-depth understanding of the fault diagnosis and elimination methods of the mud gas separator is of vital significance to ensure the smooth progress of the project.
一.Common Failure Inventory and Solutions
1.Inefficient separation
When the mud gas separator has the fault of low separation efficiency, there will be a variety of obvious manifestations. In terms of mud, the mud treated by the separator still contains a large amount of gas, and the presence of these gases will change the density and viscosity of the mud, affecting its normal wall protection, slag-carrying and other functions.
If it is diagnosed that the internal structure of the separator is damaged resulting in low separation efficiency, such as baffle deformation, cyclone device wear, etc., the damaged parts need to be repaired or replaced in time. For slight deformation of the baffle, it can be mechanically corrected to restore its original state; if the baffle is seriously damaged, it needs to be replaced with a new baffle. In an oil drilling project, a mud gas separator had many cracks and deformations due to the internal baffle plate being washed by the high-speed mud for a long time, resulting in a significant decrease in separation efficiency. The technicians replaced the baffle plate, chose high-strength, corrosion-resistant materials to make the new baffle plate, and installed it in strict accordance with the installation requirements to ensure that the baffle plate’s position and angle were accurate. After the replacement, the separation efficiency of the separator was significantly improved.
If the feed liquid volume is too large or the liquid level is not properly controlled, it is necessary to adjust the flow rate of the feed liquid pump to make it conform to the design processing capacity of the separator and optimise the liquid level control system to ensure that the liquid level is stabilised in a suitable range. The liquid feed volume can be controlled by adjusting the speed of the feed pump or by replacing the pump with one of suitable specifications. In a building foundation construction project, the liquid level of the mud gas separator was too high and the separation effect deteriorated due to excessive liquid feed. The technicians reduced the speed of the pump by adjusting the frequency converter of the inlet pump, thus reducing the inlet volume. At the same time, the liquid level control system was calibrated and optimised so that the liquid level could be stably controlled near the set value. After adjustment, the separation efficiency of the separator returned to normal, and the mud and gas were effectively separated.
2.Abnormal vibration of equipment
Equipment in normal operation, although there will be a certain degree of vibration, but when there is abnormal vibration, the phenomenon is very obvious. Abnormal vibration amplitude is usually much larger than the normal vibration, may lead to the overall shaking of the equipment, and even make the fixed equipment foot bolts loose. This abnormal vibration is often accompanied by a large noise, the frequency and tone of the noise and normal operation is very different, may be sharp friction sound, violent impact sound or irregular roar.
When it is found that the abnormal vibration of the equipment is caused by the loosening of the parts, technicians should tighten the loose parts in time. For loose ground bolts, a special spanner should be used to tighten them according to the specified torque to ensure the stability of the equipment. In a large construction site, a slurry gas separator vibrated abnormally during operation, and it was found that the ground bolts were loose after inspection. The technician used a torque spanner to tighten the foot bolt to the specified torque value, and the abnormal vibration of the equipment disappeared immediately. If the level of the equipment changes, it will lead to a shift in the centre of gravity, resulting in abnormal vibration. At this time, it is necessary to use a level to measure the equipment, by adjusting the height of the legs of the equipment, so that the equipment to restore the horizontal state. During the adjustment process, measurements should be repeated to ensure that the level of the equipment meets the requirements.
If the vibration damping device is damaged, such as broken vibration damping spring, aging vibration damping rubber, etc., the vibration damping device should be replaced with a new one in time. When choosing a vibration-damping device, it is necessary to select a product with appropriate specifications and performance according to the model, weight and vibration frequency of the equipment and other parameters. On an oil drilling platform, the vibration-damping rubber of the mud gas separator deteriorated due to long-term use and lost its vibration-damping effect, resulting in abnormal vibration of the equipment. The technicians replaced the vibration-damping rubber with a new one, which has better elasticity and durability, and can effectively absorb the vibration generated during the operation of the equipment, resulting in smoother operation of the equipment.
3.Pipe blockage
Pipe clogging is one of the common failures of the mud gas separator. In the mud conveying pipeline, as the mud contains various solid-phase particles, such as rock chips, sand particles, etc., when these particles are deposited and aggregated in the pipeline, the pipeline will be gradually blocked. Gas discharge pipelines may also become clogged due to impurities and oil carried in the gas adhering to the pipe wall, or due to condensation of certain components in the gas at low temperatures.
For the mud conveying pipeline blockage, high-pressure water flushing method can be used. The nozzle of the high-pressure water gun is inserted into the pipeline, and the impact of the high-pressure water flow is used to disperse and discharge the sediments and impurities in the pipeline. In the flushing process, attention should be paid to controlling the water pressure and flushing time to avoid damage to the pipeline. At a building pile foundation construction site, the mud conveying pipeline was blocked due to the accumulation of rock chips, and the technicians used high-pressure water flushing equipment to flush the pipeline. After a period of flushing, the blockage in the pipeline was completely removed, and the mud was able to circulate smoothly. If the blockage is hard, the effect of high-pressure water flushing is not good, you can use mechanical dredging methods, such as the use of pipe unclogging machine. The drill bit or steel cable of the unclogging machine is inserted into the pipe and the blockage is broken or removed by rotation or propulsion. When using mechanical unclogging, pay attention to the operation method to avoid damaging the inner wall of the pipe.
For gas discharge pipe blockage, if the blockage is oil or impurity, chemical cleaning method can be used. Select the appropriate chemical cleaning agent, inject it into the pipeline, so that it and the clogging material chemical reaction, the clogging material will be dissolved or decomposed, and then rinsed with water. In an oil drilling project, the gas discharge pipe was clogged due to oil and impurity adhesion, and the technicians used a special pipe cleaner to clean it. Firstly, the cleaning agent was injected into the pipeline, soaked for a period of time, and then rinsed with water, and the pipeline was restored to a smooth flow.
4.Seal failure
Seal failure is the mud gas separator can not be ignored failure. When the equipment seals, such as seals, gaskets, etc., due to long-term use, aging, wear and tear or chemical corrosion and other reasons and lose sealing performance, there will be gas leakage or mud leakage.
If the seal failure is due to aging or wear of seals, new seals need to be replaced in time. When replacing seals, choose products with the same specifications and materials as the original seals to ensure sealing performance. When installing seals, pay attention to the installation method and installation position to avoid damage to the seals. At an oil drilling site, the sealing ring of the mud gas separator lost its sealing performance due to aging, resulting in mud leakage. The technicians replaced the seal with a new one. During the installation process, they strictly followed the installation requirements to ensure that the seal was installed flat and without distortion, and the mud leakage problem was solved after the installation was completed.
If there are slight scratches or damages on the sealing surface, it can be repaired by applying sealant. The sealing surface is first cleaned and polished to remove oil and impurities on the surface, then the sealant is evenly applied, and the sealing performance can be restored after the sealant has cured. If the sealing surface is seriously damaged, it is necessary to repair the sealing surface or replace the relevant components. In the mud-water shield construction of a construction project, the sealing surface of the mud gas separator had deep scratches due to the impact of hard objects, resulting in gas leakage. The technicians repaired the sealing surface by firstly using sanding tools to polish the scratches and make the surface flat, and then applying sealant. After treatment, the sealing performance was restored and the gas leakage problem was solved.
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