Mechanical seals are the most common means of sealing industrial centrifugal pumps. There are a wide variety of seal options including the use of single or dual seal arrangements. While dual seals provide benefits in leakage containment and monitoring, single seals continue to be widely used due to their lower cost and simpler designs. Newer piping plans however offer options to increase leakage detectability and containment in single seals without sacrificing the simplicity of the seal design.
A Plan 65 piping plan was introduced in API 682 Third Edition and ISO 21049. This captured leakage detection practices which were currently in use in the pipeline industry. The upcoming Fourth Edition of API 682 changes the designation of this plan to Plan 65A and adds an alternative version designated as Plan 65B. In addition, the Fourth Edition of API 682 will introduce Plan 66A and 66B which provide additional alternatives for monitoring and containing seal leakage in the seal gland.
The selection of piping plans in any seal application depends not only on the application conditions but also on the expectations of the end user. This includes the design of the pump and also the infrastructure to monitor equipment performance and handle process leakage. With these new options for piping plans, end users can add additional capabilities to their existing Arrangement 1 seal installations and consider single seals for future applications.