By Johan Sandberg, Safety Expert, Emerson Automation Solutions

As you know, overfills are a major problem to the process industry in general, but especially so for bulk liquid storage tanks where the consequences can be catastrophic. The industry and society in general are currently investing considerable resources to increase the safety at tank farms. Today the basic overfill prevention technology at many facilities with atmospheric bulk liquid storage tanks uses this configuration:

  • Automatic tank gauge (ATG) for continuous hi-accuracy level measurement connected to a DCS or separate tank gauging system and
  • Separate level sensor connected to a manual or automatic overfill prevention system (OPS-Sensor)

This is the recommended minimum configuration for most tank operations according to API 2350.

Two trends – continuous level for the OPS-sensor and Radar technology for the ATG – are now converging and new installations today often consist of two radar level gauges for both level and independent overfill prevention measurements. Two of the main reasons behind this transition is the high reliability of radar technology combined with the efficient proof-testing procedure it offers. Because of the online measurement the latest generation of Radar level gauges can offer remote proof-testing capabilities. However, existing tanks often have practical limitations that make safety upgrades with two separate level gauges cost prohibited:

  • No tank opening available
  • No measurement pipe available
  • Pressurized tank that cannot be opened
  • Hot tank work cannot be accepted
  • Modifications may require tank to be taken out of service
  • Difficult to modify floating roofs
  • Tank’s Custody Transfer Approval may become invalid
  • Restrapping the tank due to modifications
  • Tank may not pass a new pressure test

That’s where a new technology pioneered by Emerson comes in with a solution. Rosemount 5900 2-in-1 Radar Level Gauge is a new technology that allows a single tank opening to be used for both level (ATG) and separate overfill prevention (OPS-Sensor) measurements. This solution offers substantial cost savings compared to using two separate level sensors.

We’d like to offer you a free white paper that walks you through the issues related to overfill protection, the regulatory requirements and the ways in which this novel solution might work for your tank installations. Please click HERE for the white paper.

If you have any questions, just contact Johan Sandberg, Johan.Sandberg@Emerson.com or call +46703740705. What are the issues you face in improving safety in bulk liquid storage?

by Robin Hudson, Rosemount Level Product Manager, Emerson Automation Solutions

An interesting case history from a 600 kW coal fired power plant in China has implications for any safety-critical environment. This application involved drain pot alarms on super critical steam lines.

As you know, any liquid entering a steam turbine will cause damage. This is costly and even more important, can be dangerous to personnel due to the extreme temperatures and pressures involved in the steam turbine. Generally, steam pots (also called condensate traps or steam traps) are used on steam lines to drain off condensate before it can enter the turbine. These drain pots use level sensors to detect high levels of condensate buildup and then open valves to discharge it.

The problem that arises, however, is that the extreme temperatures and pressures in the steam lines can cause many level detection devices to fail. The plant in China had been using float switches but their performance was found to be unstable over 2900psi pressure and 932˚F. Components had to be replaced frequently. In addition, the devices had no self-diagnostics or status outputs so the operators couldn’t detect when the floats might fail or if they were working properly. This high and unpredictable failure rate increased maintenance which added costs and upped the chances of a significant accident.

To resolve the issue, the plant replaced all of their float switches on the supercritical steam lines with Mobrey Hydratect 2462 Water and Steam Detection Systems. Unlike most detection systems, the patented-design Mobrey Hydratect 2462 functions reliably in steam/water detection environments up to 4350psi pressure and 1,040˚F – easily accommodating the requirements of the Chinese plant. In addition, the electronic controller gives a visual indication and relay output to indicate steam, water or a fault condition. Extensive self-monitoring within the system assures that any component failure results in a fail-safe condition.

To sum up the benefits of using this type of detection system, the Mobrey Hydratect 2462 lets you –

  • Reliably detect water or steam in lines, columns, and condensate pots
  • Eliminate the need for routine testing through superior reliability
  • Prevent turbine water damage with Turbine Water Induction Protection (TWIP)
  • Saves time with self-checks that make routine testing unnecessary
  • Configurable steam/water thresholds adjustable according to water quality

The combination can significantly reduce maintenance costs, and even more important, greatly improve protection of people and property.

Do you deal with level measurement in a safety critical environment? What type of system do you use?