Crude Oil Storage Tank Instruments

What ones are in use elsewhere on the facility? It wouldn't do for a non-standard instrument to appear, for maintenance, spares and reliability reasons.

You can use contacting or non-contacting radar technology. Using contacting technology can present a problem because crude oil sometimes can be very viscous and the problem is more prevalent during cold winters. Furthermore, the contacting element will need some maintenance. Non-contacting radar technology if preferable and it has been proven to work well in this application.

Please keep in mind that some tanks have the process connection or mounting nozzle too close to the tank wall and this can cause the instrument to lock on an unwanted obstruction instead of the true level.

A 25 GHZ radar instrument with a 3 or 4 inch horn is the most suited for this application. Either of this horn sizes have a narrow signal spread (the larger horn has a narrower signal spread) and the problem of being too close to the wall is minimum especially if you use an instrument that has a high signal to noise ratio. Please search on auto false echo suppression or radar process intelligence to learn more about these radar instruments.

Standards depend on the location.

My old (1993) copy of API RP (recommended practice) 551 Process Measurement Instrumentation (1993) has 70 pages of instrumentation, however high accuracy tank gauging is another API document. Page 10 lists dozens of other standards that 551 references.

3.7 Tank Gauging
The level transmitters discussed in this section can be used for in-plant noninventory storage tanks. For inventory or other high-accuracy gauging, refer to API Standard 2545.

Hi,

I don't know what the standard is. Some of our tanks use a combination of varec float local level indicators and direct mounted D/P cells, with their diaphragm extended into the nozzle to minimize plugging, for indication on DCS. Some other tanks use an electronic float transmitter.At one time we were considering "upgrading" to radar type transmitters but the instruments we have now are very reliable so is hard to justify spending money for radar transmitters.

Best you can use is a radar type level transmitter or an ultrasonic type since their principle in measuring level are the same. Its up to your budget which will you prefer, radar transmitters are more expensive than ultrasonic but concluded very reliable.

For inventory control purposes, multipoint temperature measurements are also taken for density correction.

Enraf has been doing this for years, they're now Honeywell

http://hpsweb.honeywell.com/Cultures/en-US/Products/TerminalAutomationProducts/default.htm