New SILConforming Safety Switch from Drexelbrook

Jan. 12, 2009

Tank Farms Have Problems with Environmental Safety

Not only are they prone to fugitive emissions, but they are also subject to tank overfills and spills when moving petroleum products from tank to tank, and out of the tank farm. Overfills and spills are major sources of product releases which cause fugitive emissions, and they create soil and water and groundwater pollution issues. Spills are expensive to clean up and bad for the environment. Overfills, especially large ones, can cause fires—huge catastrophic fires that can result in millions of dollars of damage, not to mention lost product and the inability to deliver to contract on time.

Overfill protection for above-ground bulk storage tanks is being recommended by API 2350, a standard produced by the American Petroleum Institute. API 2350 is a recommended practice for high-high level alarms for tank farms.

To help users ameliorate this problem, Ametek Drexelbrook has announced the first safety switch in the IntelliPoint RF Series.

“This switch is designed for high reliability applications in difficult environments,” says Bob Irving, VP of Marketing from Ametek Drexelbrook, “like overfill protection for bulk storage tanks in the petroleum industry. We have produced an industry-leading, SIL-certified point level switch—standard is SIL1. SIL2 is an option, and with a redundant switch, the IntelliPointRF can achieve SIL3 ratings.”

The Safety IntelliPoint RF Switch is based on Drexelbrook’s proven RF Admittance technology, which is designed to shield the sensor from the effects of coatings. The Cote-Shield technology ignores coating buildup on the sensing element, preventing false alarms. It can detect the presence or absence of liquids, slurries, interfaces or granular media.

The IntelliPoint RF software continuously monitors the application for changes in composition, dielectric or conductivity, and maintains a repeatable trip point on the probe, with a repeatability of 2 mm (0.08 inch) in conductive liquids and a response time of less than one second. Repeatability in other media is somewhat different, but similar.

The unit is FM- and CSA-approved for use in all hazardous areas, is ATEX Ex II 1G T5 approved from -30 ˚C to +75 ˚C and II 1D T90 ˚C. The electronics can be remote- mounted to a location that is either safer or more convenient than the probe location. The IntelliPoint RF Safety Switch has an independently tested mean time to failure (MTTF) of 110 years.

Exida has certified the switch for use in safety-related systems with requirements for functional safety for SIL2, with SIL3 available using a redundant switch, in keeping with IEC 61508-2.

Like other IntelliPoint RF devices, there are no calibrations to perform on the Safety Switch. The unit’s Auto-Verify self-testing function monitors the entire system continuously to ensure proper operation, even in changing conditions of conductivity, composition or material dielectric, making the switch useful for non-dedicated tanks in which a wide variety of products are stored. An Auto-Certify mode checks the function of the system via an operator-initiated electronic self-test. This test enables the level switch to perform as if it actually were in a real-life situation with the fluid or granular media touching it.

The safety switch can be supplied with a variety of sensing elements, including one for floating roof tanks, with cable attachment and brass bottom weight. Elements for corrosive liquids, sanitary service, agitated tanks or granular media are available, as is a miniature sensor for use in pilot plants. The sensors can be mounted with threaded (NPT), sanitary TriClamp, or DIN or ANSI flanged connections.

The IntelliPoint RF Safety Switch comes with a 36-month warranty.

For more information, contact Ametek Drexelbrook.