Progressive cavity pumps, also recognized as single screw pumps, have a single shaft consisting of a steel helical rotor (also available in different materials and with different surface coatings with strong seal water) mounted on a vulcanized rubber steel stator. These pumps are composed of various rubber compounds to be used with viscous and high-density fluids, abrasives, and liquids containing suspended solids. In a progressive cavity pump, the rotor and the stator are the primary components that are responsible for the pump's functionality in a progressive cavity pump. The rotor is shaped like a round screw and consists of a single beginning portion that has a very large pitch. Inside of a steel tube is where the vulcanization process takes place for the stator, which is typically comprised of rubber. The stator has a hollow core that is shaped like a beginning screw (or three starting screws), and it has the same circular section as the rotor but has twice the pitch of the rotor. While the cavities between the rotor and stator move in a helical motion, fluid is moved from the suction end to the discharge end as the rotor rotates within the stator in a semicircular motion.
This allows the fluid to be transferred from the suction end to the discharge end. The accompanying photograph provides a diagrammatic representation of the mechanism. It demonstrates the longitudinal profiles of the rotor and stator as well as the significant cross-sections for a particular point in time during the course of their relative motion. When the direction of rotation is altered, the suction and discharge processes are also switched. Progressing Cavity Pumps (PCP), which have their origins in the treatment of wastewater, deviate typically from the API 676 standard for petrochemical pumps because of the way they work and their background in this field. There is a possibility that some of these aberrations can be fixed, while others cannot be prevented. Understanding and determining which of these deviations are significant, critical, or acceptable for their project is a headache and a conversation starter for project engineers since it is a preventative headache. Pumps that handle fluids smoothly and with low shear or agitation, turbulence, and emulsification are called progressing cavity pumps. These pumps are positive displacement pumps. They are able to handle liquids that have the highest viscosity as well as the largest solid concentration, which may include abrasive or large particles.
They are able to generate tremendous pressure, up to and over 48 bar. In addition to being excellent for multiphase fluids, it also works well with fluids that have a high vapor pressure (low NPSH). It is suitable for use in metering applications as a result of its linear performance curves and low pulsation levels. Simply switching the direction in which the motor is turning will cause the flow to move in the opposite direction. PCP is frequently put to use in the oil and gas industry for the transfer of oily slurries or water, as well as in circumstances in which mild hydrocarbons raise the vapor pressure to a point at which other kinds of pumps are susceptible to cavitation. The PC pumps excel when used in a semi-submerged vertical placement on a cylinder. O pen/closed drain drums or lit drain drums are examples of frequent applications for these pumps. In the following table, some of the fundamental requirements for API 676 and petrochemical applications, on the one hand, and normal wastewater applications, on the other hand, are compared and contrasted. Positive displacement pumps, also known as progressive solenoid pumps, are able to move fluids in a smooth manner with very little shear or turbulence.
Regardless of the particle size or abrasiveness, it is appropriate for use with liquids that have a very high viscosity and contain solid ingredients. It is capable of delivering a high pressure of at least 48 bar. Even a high vapor pressure (the NPSH is quite low), as well as multiphase fluids, provide no difficulty. Counting applications are another good fit for this component due to its linear curve and low pulse. Since progressive cavity pumps were first put to use in wastewater treatment plants (WWTP), the manufacturing process and design of these pumps have been refined so that they are more suitable for usage in this sector. Although they are also generally suitable for use in petrochemical applications, the much-increased pressures and temperatures that these applications inflict on pumps can be a challenge. In addition, the standards utilized in the petrochemical industry were developed in the United States, but the majority of PCP producers are situated in European countries. The intricate measurements that are necessary to modify your regular pumps so that they may be used in the petrochemical industry have a considerable bearing on both the cost and the amount of time it takes to deliver the product. The PCP concept itself necessitates the existence of exceptions as well as additional exceptions, which cannot be avoided.
For instance, the boron lumen principle relies on the persistent sealing contact (clamping) of a steel rotor and an elastomer stator in order to function. There is not a void here. Elastomers, on the other hand, cannot be manufactured with the same level of precision as steel. Because of this, the performance tolerances end up being higher than what is allowed by API 676, which is +3/-0% of the characteristic capacity. PCPs often achieve +10/-5%, with the tolerance being larger for smaller pumps or pumps that operate at higher pressures. The fact that the stator has a contact side makes it a wear part, which means that it needs to be replaced at regular intervals depending on the application, which is difficult to anticipate. This is another one of the problems. PCP makes no assurances whatsoever regarding the continuity of business operations throughout the course of the next three years. The vibrations are altered as a result of the eccentric movement of the rotor. PCP pumps have vibration levels that are significantly higher than those of other types of API 676 concentric motion pumps, assuming a fixed amplitude. The maximum speed of 3.8 mm/s can be exceeded using standard PCP. This low frequency vibration is intended to occur and does not imply that there is a problem. Due to the fact that the shaft length of vertical and semi-submersible PC pumps can reach several meters, vibration is a concern that must be taken into consideration.