Working Principle of Screw Pump

The main working parts of a progressive cavity pump consist of a liner (stator) with a double-ended helical cavity and a single-ended eccentric screw (rotor) that engages with it in the stator cavity.

When the input shaft drives the rotor around the center of the stator through the universal joint to do planetary rotation, due to the special geometry of the rotor and stator, respectively, to form several individual sealing cavities.

The operation of the rotor will be in each sealed chamber of the medium from the suction end of the continuous, uniform, volume-constant transport to the pressure end.

This pump also relies on the rotation of a screw to push the liquid forward, but its high-pressure and low-pressure chamber is not connected.

The special structure of the screw has an internal helical surface of the specialized bushing (made of elastic material), screw, and bushing to separate the liquid along the axial direction, and at the same time in the radial direction of the liquid flow is divided into two, forming a sealing chamber.

Therefore, in each screw liner vice, the screw is a single helical surface, and the inner surface of the liner is a double helical surface, both of which have the same direction of rotation, that is, the same as the right or left rotation.

Single screw pump because the medium is axial, uniform implementation of the flow, so the internal flow rate is low, stable pressure, will not produce vortex and churning; suitable for conveying high viscosity, containing solid particles or high fiber, the requirements of continuous and stable pressure occasions.

Screw pump common failure

The drive motor burns out because of the large content of gum and asphalt in the downhole and the high viscosity of the oil, causing it to show an emulsified state, and the emulsion is mainly in the form of oil packages. With the rising degree of emulsification, the viscosity of the liquid is increasing, which directly affects the loading capacity of the screw pump, and at the same time, causes the failure of the ground drive device and damages the ball bearings.

The gap between the tooth surface of the power input shaft and the tooth surface of the main hammer body exceeds the design standard range, the bearing capacity is uneven, the load on the equipment is getting bigger and bigger, and the viscosity is increasing, which directly affects the return pressure value of the screw pump well, and if you want to re-exploit it, you have to take the measure of washing the wells, and at the same time, you have to sweep the ground technical pipelines, and you can’t avoid the emulsified oil from being affected by temperature by taking the method of adding warmth, and it is usually necessary to take the measure of backwashing the wells. The pumping rods are disconnected.

Sucker rod disconnection

After shutdown the rods will reverse at high speed due to excessive load and torque on the screw pumps, resulting in sucker rod decoupling. The torque increases as the screw pump jams, generating a large elastic deformation potential energy in the tie rods. Once the screw pump stops, the elastic potential energy is released in the tie rods, resulting in a high degree of counter-rotation of the tie rods, and tie-rod decoupling occurs. The depth of the dynamic liquid level in the oil well will increase with the shutdown of the screw pumping device, and the pump rotor will reverse under the influence of the hydraulic force of the oil healthy column of the screw pump, resulting in the unbuckling of the rods and columns.

Poor sealing of the drive unit

Generally speaking, there are two key points in the sealing of the ground drive unit, one is the oil sealing of the deceleration unit and the other is the packing seal of the wellhead unit. Among them, once the wellhead device packing sealing problem occurs, it will cause oil leakage. The wellhead packing material will produce certain abrasions with the continuous operation of the light rod, resulting in the continuous decline of the light rod outer diameter, affecting the sealing effect between the light rod and the packing device, and oil leakage failure may occur.

The reason why the downhole working condition cannot be judged accurately

The current lack of effective monitoring of the work of the screw pump operation, pump condition detection of the common methods are two, one according to see whether the change in operating current is normal, and the second is to monitor the casing pressure, oil pressure changes, according to the changes in the production of curves, analyze the curve, the curve is complex, the changes in the irregularity can not be accurately judged.

Countermeasures:

1. Continuously optimize the oil recovery screw pump system: to reduce the probability of failure of the screw pump system, it is necessary to continuously optimize and upgrade the system. Make full use of new information technology to develop software that can adjust the parameters of the screw pump system, such as optimizing the screw pump.
2. Ratio of catalyst: The amount of TEAL is reasonably controlled to ensure the catalyst has strong activity and efficiency.

Improve the operation of D201: Effectively improve and perfect the cooling water of D201, such as increasing the flow rate of chilled water, strictly controlling the speed and temperature of the feed of “three agents”, etc., and controlling the operation temperature at about 10℃, meanwhile, ensuring that the materials existed in the D201 can be fully mixed, to enhance the activation of the catalyst and maintain the stability of the activity. Maintain the stability of the activity.

3. Improve the operation of pre-polymerization: The degree of reaction of pre-polymerization can be enhanced by adjusting the temperature of the reaction and prolonging the residence time of the material in R200. It is important to note that in the process of adjusting the temperature of the R200, due consideration should be given to the activity of the catalyst and the degree of reaction. The residence time can be controlled by reducing the amount of propylene feed, and the constraints of Z203 should be emphasized.
4. Strengthen the operation of polymerization: strictly control the slurry density inside the ring tube and the feeding amount of propylene to keep it within a reasonable range, and avoid the reactor from being impacted by the lifting load.
5. Strictly control the pressure of the high-pressure circulation system: strictly control the pressure of the system. If the setting value is high, on the one hand, it will lead to a small pressure difference between the large ring tube reactor and the system, resulting in the reactor not being able to discharge properly; on the other hand, it is very easy to lead to a large pressure at the outlet of PK301. If the setting is too small, the pressure difference between the high-pressure circulation system and the large ring tube reactor will be large, which will lead to the transportation of polypropylene is very prone to fines.
6. Ensure the quality of propylene: effectively monitor the indicators in the production of propylene to ensure that the various reaction towers in the refining section can operate normally, effectively remove the toxic substances in propylene to avoid the quality of the product being greatly affected.

Screw Pump Working Animation – YouTube