How to test the sealing performance of the top drive plug?

The top drive plug is a key component of the drilling fluid circulation system in the top drive device. It is closely coordinated with components such as the top drive motor and gearbox. When the top drive motor drives the drill rod to rotate for drilling operations, the top drive plug controls the supply of drilling fluid to ensure that the drilling fluid can flow steadily into the drill rod, providing necessary cooling and chip removal functions for the drill bit. For example, during the drilling process, changes in the speed and torque of the top drive motor may affect the circulation requirements of the drilling fluid. The top drive plug can adjust the flow rate of the drilling fluid in a timely manner according to these changes, maintaining the balance of the entire drilling system.

The top drive plug is usually installed on the drilling fluid circulation channel of the top drive device, ensuring that its installation position is easy to operate and maintain. Generally installed at a higher position near the wellhead, this can better control the flow of drilling fluid using gravity, and also facilitate quick access and operation in emergency situations.

How to test the sealing performance of the top drive plug?

Appearance inspection

First, a preliminary visual inspection can be conducted. Check if there are any traces of drilling fluid leakage at the sealing part of the top drive plug, such as whether there is liquid leakage or scaling at the connection between the valve body and the valve core, the sealing part of the valve stem, etc. This is a simple but effective preliminary detection method that can quickly identify obvious sealing issues.

Stress testing

Static pressure test:

Install the top drive plug in a specialized testing device, close the plug, and gradually inject liquid with a certain pressure (usually water or simulated drilling fluid) into one side of the pipeline. Then observe whether there is liquid leakage on the other side of the plug under the set pressure (which should be determined based on the working pressure range of the top drive plug, generally reaching or exceeding its rated working pressure). It is possible to detect pressure changes or liquid outflow by connecting a transparent observation tube or pressure sensor at the outlet on the other side. For example, if the rated working pressure of the top drive plug is 35MPa, the test pressure can be set to 40-45MPa and observed continuously for a period of time, such as 15-30 minutes. If there is no liquid leakage or pressure drop, it indicates that the sealing performance is basically qualified in terms of static pressure.

Dynamic pressure test:

Simulate the flow state of actual drilling fluid and conduct tests at a certain flow rate and pressure. Turn on the liquid supply system to allow the liquid to pass through the top drive plug at the flow rate and pressure during operation, and observe whether there is any leakage around the plug. This type of test can better reflect the sealing performance of the plug in actual working environments, as the flow of liquid may have additional effects on the seal under dynamic conditions, such as flushing. The sealing performance of the plug under different working conditions can be tested by changing the parameters of flow rate and pressure.

Helium detection

For some top drive plugs that require high sealing performance, helium detection method can be used. Fill the inside of the plug with helium gas, and then use a helium gas detector to check for any helium gas leakage outside the plug. Helium molecules are small and highly diffusive, capable of detecting tiny leakage channels. This method has high accuracy, but the equipment and operation are relatively complex, and the cost is also high. Usually used in the manufacturing of high-precision top drive plugs or in post maintenance inspections with strict requirements for sealing performance.

Ultrasonic testing

Use ultrasonic flaw detectors to detect sealed areas. When there is a small leak at the seal, the ultrasonic signal generated by liquid leakage can be detected. This method can detect some small leakage points that are difficult to detect by conventional methods, and can be detected without disassembling the top drive plug, with high efficiency. However, it requires professional equipment and technicians to operate, and for complex on-site environments, it may be subject to external ultrasonic interference.

The top drive plug needs to withstand high pressure during the drilling process. Its pressure level is generally divided into multiple levels, such as 15MPa, 35MPa, 70MPa, etc. When selecting, the appropriate pressure level of the plug should be chosen based on the maximum expected pressure of the drilling operation. If the pressure level is not selected properly, it may cause damage to the plug under high pressure, leading to safety accidents such as drilling fluid leakage.

The hydraulic top drive plug uses a hydraulic system to drive the valve stem movement, thereby controlling the opening and closing of the plug. It can quickly respond to control signals and achieve automated operations. Widely used on large and efficient drilling platforms, it can be integrated with drilling control systems to automatically adjust the status of the plug according to preset parameters or real-time monitoring of downhole conditions.