Integral Pumping Devices for Dual Mechanical Seals: Hydraulic Performance Generalization Using Dimensional Analysis

Abstract

An experimental study is carried out investigating hydraulic performance for various designs of dual-mechanical-seal cartridges with integral pumping-rings. The tested devices are classified into two main families: radial-flow and axial-flow. The radial-flow family utilizes the modified-paddle-wheel (MPW) pumping ring with either a radial or a tangential oriented cartridge outlet port, while the axial-flow family utilizes the pumping scroll (PS) pumping ring in the following cartridge-geometries: single-pumping-scroll (SS) and double-pumping-scroll (DS); as both types can be of either a radial or a tangential outlet port; and of an internal clearance value complying with American Petroleum Institute (API) 682 standard or smaller clearance. An experimental setup is constructed, and appropriate instrumentation is employed to measure inlet pressure, outlet pressure, rotational speed, and barrier fluid flow rate acquiring flow-head characteristic curves. Moreover, empirical generalized characteristic curves are deduced from experimental observations obtained from the present study and previous companion work. The generalized curves can be employed in estimating pumping ring performance for a different size or other operation conditions such as varying rotational speed or fluid type. They can be also utilized to validate numerical simulations for geometrically similar designs.

Integral pumping rings for dual mechanical seals: hydraulic performance evaluation using numerical simulations

“…The second measure is the slope of the Q − P curve, as it was shown to be directly proportional to ρN/D (Warda et al, 2018b). The relative error in the slope Figure 8.…”

“…Even though one could propose here that a streamlined outlet with the expected incident flow should be used, such as the volute casing of centrifugal pumps, this is not simply the case here since the geometry needs to be symmetrical in both directions of rotation to retain bi-directionality of the cartridge. For instance, another variant of the present seal was experimentally investigated by Warda et al (2018b), wherein the outlet port was tangentially oriented. As expected, a significant increase in the flow rate was observed.…”

“…It is noted, however, that limited published literature is available about the performance evaluation of integral pumping rings for dual seal cartridges, even though this design has been widely applied in the industry. For this reason, the previous companion works (Warda et al, 2016(Warda et al, , 2018bWarda, Wahba, et al, 2018;Warda et al, 2015) and the present one have been conducted in a quest to enrich the available literature investigating various designs of integral pumping rings for dual mechanical seals. In the first companion work (Warda et al, 2015), experimental and numerical setups were constructed to review the hydraulic performance of axial and radial flow integral pumping rings, which was the foundation stone of the following studies.…”

“…After that, in Warda et al (2016), the influence of barrier fluid properties on the hydraulic performance of radial flow pumping rings was investigated experimentally. Moreover, the study was further extended in Warda et al (2018b) to treat the remaining designs of axialflow type. Additionally, generalized empirical correlations were proposed based on the experimental observations replacing the conventional Q − P curves by generalized π 1 − π 2 characteristic curves.…”

“…A major characteristic of this design is its independence of direction of rotation and hence the name 'bi-directional'. Moreover, despite being hydrodynamically inferior to most scroll-type pumping rings (see for example Figure 3) (Bloch, 2017b;Warda et al, 2018b), the MPW design considered in the present study is superior in industrial applications where shaft deflection is anticipated (Bloch, 2017b). This is because the axial-flow family in general relies on tight clearance between the ring and its housing, while, on the other hand, radial-flow types rings can operate with more permissive clearance, as will be illustrated in what follows.…”