To Assure the Safety of Tanks and Vessels – Switch Your Switch

A piping systemSpills are costly, messy and can easily become health, environmental and safety disasters, generating bad publicity. But one petroleum storage and logistics company found a way to easily and continually verify high-level alarm functionality at any time to ensure these kinds of disasters don’t occur.

 Often what stands between a leak from a petroleum vessel and a costly disaster is a high-level alarm switch. However, typical high-level switches offer no real-time certainty of their functionality. Mechanical switches are prone to wear and need frequent rebuilds. Vibration adds to the problem, with floats unscrewing, and levers and arms failing. Small parts in the switches add to the difficulty of rebuilding while lost parts in the vessel add another layer of challenge.

 Few mechanical switches offer a selectable failure mode. Manual testing is highly problematic since remote locations, weather conditions, and lack of easy, safe accessibility all add to the difficulty of verifying the operation of a switch, creating unnecessary risk and personnel exposure to potentially hazardous liquids and vapors. Plus, manual testing only verifies the operation at that specific point in time. One must also trust that the unit was reinstalled correctly after “bucket testing.” Threads can get damaged and seals wear out with repeated use.

 The costs of testing mechanical switches are also considerable:

  • A process may need to be shut down, tanks drained, and production lost during the test period
  • Travel to and from the location, as well as manpower costs for the testing procedure, which can take up to several hours

 These costs can easily add to up hundreds of dollars per unit tested. But the costs of testing are minor compared to the cost of a spill.

 To assure that their high-level alarms will operate when they need to, the logistics company chose to eliminate mechanical switches in favor of the world’s first HART vibrating fork switch – Emerson’s Rosemont 2140. This device can provide: 

  • Self-diagnostics, via HART
  • Ability to set a failure mode
  • Remote or local partial proof testing
  • Ability to see the status of a current device around the clock, via HART
  • Ability to differentiate between liquids

 The company employs the HART switch as the natural gas compressor scrubber bottle high-level alarm. The switch confirms their high-level alarm operation without having to shut in the scrubber bottle or compressor, while remote proof-testing eliminates the need to remove the switch. The simple addition of this unique technology has freed maintenance time and helped protect personnel, significantly lowered testing costs, and reduced safety concerns. It was a very smart switch.

Click here for more information on the Rosemount 2140 vibrating fork level detector.