Mechanical seals are critical for safe operation in refineries and chemical plants. Ensuring their proper operation requires following established best practices, explains Sean Hunsicker of Swagelok...
Mechanical seals have long been the dominant sealing technology in chemical plants and refineries. The seals and their support systems contribute to safe and repeatable processes, with seal support systems helping to maintain proper seal and pump functionality.
Here are some key best practices that can help your facility enhance the construction and design of your seal support systems so you can improve reliability and safety.
Leak reduction: In hydrocarbon processing applications, leaks on seal support systems near pumps can cause damage, unplanned downtime, environmental issues, and safety risks. Because every connection is a potential leak point, seal manufacturers, end users, and pump OEMs have implemented tubing to reduce the number of connections compared to threaded pipe. By bending tube lines and appropriately using adapter fittings, the only needed connections are those at the seal and the sealing system. Innovative connection technologies further reduce the number of connections from threaded ports on the seal and seal pots by eliminating the need for multiple fittings.
Simplified operation and maintebnance: Seal support systems require regular visual inspection. Making this inspection process simple can help promote overall system reliability and safety. To do so, follow the best practice design principles, such as described in the American Petroleum Institute’s Standard 682 for mechanical seals and support systems (API 682).
Ensure system design enables easy operation and troubleshooting: Mechanical seals are often damaged when pumps are started and stopped, sometimes as the result of improper seal support system operation. If the design of the seal support system facilitates proper operation, common mistakes when commissioning pumps can be avoided. Whereas API 682 lays out a specific piping plan where multiple instruments and components are installed (Plan 32) which, while operationally correct, does not promote appropriate layout for easy system parameter visualisation or maintenance.
A better solution is to arrange these components on a panel (see pic). An appropriate panel design helps the operator easily determine flow path and places all instruments at eye level for easy monitoring. Panels can also include part numbering information, flow path indication, and operator instructions.
Additionally, seal support systems contain commonly serviced instruments. Therefore, preventive maintenance should be simple and safe for operators. One feature that can help is using a block and bleed configuration for all instruments, including gauges, as recommended in API 682. Without this feature, as gauges fail, operators will be left without critical information until the next turnaround when the pump and support system can be decommissioned and the gauge replaced.
Finally, systems should be optimised for ease of component isolation and replacement. For additional safety, locate all controls and as many serviceable items as possible at grade, thereby keeping workers off ladders.
Implementing best practice design principles helps reduce seal failure. Additionally, working with a reliable supplier who can help esign effective seal support systems with high-quality components can help your facility increase reliability and reduce costs.
Sean Hunsicker is market manager, Chemical & Refining Market for Swagelok