Development of a Single Mechanical Seal equipped with a High-Pressure Containment Seal for Multiple Fluid Pipeline Pumps

Abstract

This paper discusses the critical design aspects, calculations, laboratory verification testing and field experience of a mechanical seal arrangement for multiple fluid Pipeline Pumps. The seal cartridge consists of a single wet lubricated mechanical seal on the product side in combination with a high-pressure containment seal on the atmospheric side. The single mechanical seal has been designed to operate in a product range from the flashing hydrocarbons ethane, propane, butane all the way up to non-flashing hydrocarbons like Natural Gasoline. Basically the single seal runs product lubricated in the media with a specific gravity range of 0,35 up to 0,65 and is designed for a pressure window up to 100bar, respecting the Pipeline Pressure. To assure this, a lift off of the mechanical seal faces at all media and at all operation conditions was targeted. To achieve this the functional components of the mechanical seal were subject of an extensive performance calculation and optimization with FEM (Finite Element Method. The mechanical seal concept includes a containment seal which withstands the full pipeline pressure in the unexpected event of a catastrophic mechanical seal failure of the single product side seal. This means massive leakage cannot leave the seal gland in an uncontrolled way under any case. To achieve similar safety and environment protection with a mechanical seal in a multiple fluid pipeline pump, conventionally a double pressurized mechanical seal with a pressurized supply system was needed. The proposed mechanical seal design provides a reliable pump sealing solution for these critical applications with a “single mechanical seal” in combination with a “high-pressure containment seal”. It provides the performance advantage and the safety philosophy of a double pressurized seal arrangement with the more costefficient single seal arrangement.