Common faults and solutions of vacuum degassers

Vacuum degasser is the second level of solid control equipment in the drilling mud solid control system, and it is a special equipment used to deal with gas-immersed drilling fluid. Its working principle is the use of vacuum pump suction, in the vacuum tank to create a negative pressure area, the mud in the role of air pressure, through the suction pipe into the hollow shaft of the rotor, and then by the hollow shaft around the window, the jet thrown to the wall of the tank, due to the collision and the role of the foam separator, immersed in the mud in the bubble crushed, the gas escapes, through the vacuum pump suction is discharged to the safety zone. Mud is due to self-weight into the empty cavity, the rotor discharged out of the tank, in addition, due to the vacuum pump and the main motor started at the same time, the rotor connected to the motor was also a high-speed rotation, the mud can only enter the tank from the suction pipe, will not be sucked in from the discharge pipe.

The vacuum degasser is installed in the mud solids control system to prevent gases carried by the drilling fluid from the well from affecting mud performance and safety hazards during drilling operations. To ensure optimum performance and efficiency of the vacuum degasser, it must be mounted in an area where there is sufficient space for the operator and maintenance personnel to connect the various attachments, as described in the following table.

Typical operation and maintenance of the vacuum degasser includes the following:

1. opening the inspection panel

2. removing, replacing, and adjusting vacuum pump drive belts

3. connecting and disconnecting suction and discharge lines

4. servicing the electrical junction box

5. servicing the vacuum pump air lines and oil reservoirs, placed horizontally.

The sequence of vacuum degasser installation procedures will vary depending on the user’s resources, experience, and choice of equipment.

1. install the degasser downstream of the slurry shaker or upstream of any secondary solids control equipment such as desanders, desludgers, cleaners, and centrifuges.

2. Ensure that the unit is mounted securely and horizontally.

3. place the inhalation tube from the degasser in the first interval downstream of the grit separator. Install the 8″ suction pipe, at least 3 feet below the regular operating mud scale of the mud tank. It is best to install the inhaler pipe 6″ above the bottom of the slurry tank, the shorter the inhaler pipe end the better when operating.

4. install the ejector in another interval immediately downstream of the grit separator, a maximum of 25 feet from the outlet of the degasser to the inlet of the ejector. Install an 8″ discharge pipe horizontally or at a slight angle.

5. install the ejector outlet pipe at least 1 foot below the regular operating slurry level of the slurry tank.

6. feed the ejector with a centrifugal pump providing 75 feet of pressure head to the ejector inlet. Install a centrifugal pump suction pipe as recommended by the centrifugal pump manufacturer. Attach a 6-inch feed tube, not to exceed 20 feet in length, to the ejector nozzle, keeping the tube bend at a minimum.

7. connect a 1.5″ discharge line from the vacuum pump outlet manifold to a safe area.

8. Apply power to the unit.

Vacuum Degasser (Vacuum Degasser) is a new type of special equipment used to deal with gas-invasive drilling fluids, also called negative pressure degasser, which can quickly remove all kinds of gases intruded into the drilling fluids, and it has an important role in restoring the specific gravity of mud and stabilising the mud performance. At the same time, it can be used as a high-power mixer, and is suitable for all kinds of mud circulation purification system. The equipment belongs to negative pressure type degasser, scientific and reasonable design structure, can achieve effective separation of gas and liquid, filter out impurities, to ensure that the exhaust pipe is always smooth.1, vacuum type degasser: its working principle is, with a vacuum pump to inhale the drilling fluid, the film flocculation after the separation of the gas, and then pumped away by the vacuum pump. This type of degasser has good effect, but it is bulky and heavy.

2、Normal pressure type degasser: the main parts are centrifugal pump and jetting tank. Gas intrusion drilling fluid from the centrifugal pump to the jetting tank, the formation of a high-speed layer in the tank and thrown to the inner wall of the tank to promote gas rupture, separation, discharge. Smaller volume, good results.

3、Centrifugal degasser: It is composed of motor, pump and gearbox. The use of drilling fluid centrifuge separation principle to separate the gas out, is a relatively new device.

Structure advantages

1、Using the vacuum pump’s suction to make the slurry enter into the vacuum tank, and using it to make the gas be pumped out of the vacuum tank, the vacuum pump plays two different roles here.

2、Water ring vacuum pump is always in isothermal state during the working process, which is suitable for pumping flammable and explosive gases with reliable safety performance.

3、Mud is shot to the four walls at high speed through the window of the rotor, and the air bubbles in the mud are broken thoroughly, with good degassing effect.

4、The main motor is offset, and the centre of gravity of the whole machine is lowered.

5、Adopting belt drive, avoiding the complication of deceleration mechanism.

6、The application of vapour separator will not cause water and gas to be discharged at the same time, so that the exhaust pipe is always free. In addition, water can be circulated into the vacuum pump, saving water.

7、The suction pipe is inserted into the mud tank, which can be used as a high-power agitator when the mud is not air-soaked.

Failure one, vacuum degasser vacuum degree is not high

Vacuum degasser operation if you find that the vacuum is not high may be water ring vacuum pump no water or water is not enough to lead to, can be appropriate to the water ring vacuum pump water; vacuum degasser operation need to ensure that the suction pipe and the discharge pipe must be in the drilling mud below the liquid surface, you can check whether the inlet and outlet pipe are immersed in the liquid surface below; vacuum degasser vacuum tank to maintain good sealing, you can also check the vacuum tank Connection or exhaust pipe line leakage, if the leakage of timely repair; there is also a possibility that the impeller clearance at both ends is relatively large, you need to adjust the clearance at both ends of the impeller.

Failure two, vacuum degasser start abnormal

Vacuum pump startup strong vibration or abnormal sound, you can check whether the vacuum pump internal damage, if there is damage need timely repair, there may be a vacuum tank into the debris caused by timely cleaning up the tank debris.

Failure three, vacuum degasser shaft horsepower is too large

If the equipment is found to be too large shaft horsepower during operation, it may be caused by too much water inside the pump, and it is necessary to adjust the ball valve to control the water level in a reasonable position; it may also be caused by the impeller of the degasser not being able to automatically adjust the gap, and at this time, it is necessary to remove the cover of the pump and adjust the impeller gap to ensure that the impeller is able to move freely on the shaft.

The vacuum degasser uses the suction effect of the vacuum pump to create a negative pressure area in the vacuum tank, the mud, under the action of atmospheric pressure, enters the hollow shaft of the rotor through the suction pipe, and then by the window around the hollow shaft, it is thrown to the wall of the tank in the form of a jet, and due to the collision and the action of the separation wheel, it separates the drilling fluid into a thin layer, and the bubbles that have been immersed into the mud are crushed, and the gas escapes, and through the vacuum pump’s suction and the gas-water separator, the gas is exhausted to a safe place by the separator exhaust pipe, and the mud is discharged from the impeller to the outside of the tank. The gas is discharged to safety by the exhaust pipe of the separator and the mud is discharged out of the tank by the impeller. As the main motor starts first, the impeller connected with the motor is rotating at high speed, so the slurry can only enter the tank from the suction pipe and will not be sucked in from the discharge pipe.

Before installing the vacuum pump, turn the coupling by hand to confirm whether there is any jamming and other damages in the pump, if not, install the pump on the pump base. Before the motor is fixed on the pump seat, the concentricity of the motor shaft and pump shaft should be corrected. This is because even a very small tilt of the motor shaft and the pump shaft can cause consequences such as heating of the bearings and severe wear of the parts. The required concentricity is achieved when a straightedge is placed parallel to the coupling, and any position in the entire circumference fits closely with the circumference of the coupling without clearance, and the axial clearances of the coupling are equal.