Description:

Recent incident reports and studies of pipeline equipment indicate that pump seal performance is likely at the root of a significant increase in releases to the environment. Although these releases are small compared to a breach in a pipeline, they are of great concern to pipeline companies. While crude oil and refined fluid pipelines have been around for a long time, the pumping of natural gas liquids (NGLs) such as ethane, propane, butane and various mixtures of these liquids is relatively new and presents demanding challenges for the mechanical seal manufacturer and pump OEM’s. API (American Petroleum Institute) 682, the governing mechanical seal standard for mechanical seals in hydrocarbon services, is a great foundation for the sealing of process plant equipment. However, for pipeline services API 682 is of limited use due to more demanding operating conditions as well as the different operating character of pipeline pumps.

 

Generally, two seal face lubrication technologies can be applied to seal NGL Pipeline Pumps with dual unpressurized seals:

• A contacting wet lubricated mechanical seal (2CW-CS / Arrangement 2 Contacting Wet – Containment Seal)

• A non-contacting Dry Gas Seal (2NC-CS / Arrangement 2 Non Contacting – Containment Seal)

 

Both sealing solutions include a high-pressure non-contacting containment seal to protect the environment.

 

Within this paper we discuss the general design aspects for two different sealing technologies, in particular the leakage and friction behavior in NGL services. The impact of critical operating parameters like vapor pressure and temperature margin, flush flow rates, solids handling, axial shaft shuttling is assessed. In addition, the safety, leakage containment and monitoring related aspects are described, summarized and compared with the mechanical seal recommendations.