level measurement

A SINGLE Wireless standard for the process industries? Not a chance!

Well here we go again.  I just read some editorials in the latest issue of CONTROL magazine.  Greed and ego are proving to trump logic and reason once again.  Users need a standard, a single open protocol standard for Wireless communications.  In existence today with products being marketed offering this capability are Wireless HART.... that's it.  The Honeywell wireless is a proprietary protocol that Honeywell is batting to shove down the throats of the ISA100 committee that have been gathered for three years now trying to develop a standard.  While the battle has been quietly, and sometimes not so quietly, been raging in the ISA100 committee, Wireless HART has been working hard and growing its installed base.  By the end of 2008 there will be even more products offering it, including the measurement instrumentation giant Endress & Hauser and Emerson Process.  I'm with them, Wireless HART is the way to go... and so is wireless in general.

For level measurement applications, especially those used for inventory monitoring and management, wireless offers the ability to save money by eliminating the cost of hard wiring and also enabling the connectivity of sensor and system across physical barriers to hard wiring.  But this wireless application is not anything new.  Many vendors have been providing wireless communications using proprietary protocols for years.  The new wireless standards hope to offer interoperability from application to application and vendor to vendor.  This is a good idea.

Joe

Technorati Tags: Wireless Sensor Communications level sensor level measurement bin level indicator level control solids level indicator guided wave radar 

Hydrostatic Level Measurement is still "King" for liquids

In a recent article published in CONTROL magazine author and writer Paul Miller makes the point that hydrostatic head pressure measurement is still a most common method for measuring the level of a fluid in a tank.  He makes other points too, more important in his article than here.  The point I wish to make here is that this technology for the level measurement of fluid in a tank has been around for many years and is a simple and economical way to measure tank levels, while its "flash" is far less than newer technologies like radar.

Let's take a quick look at how pressure or differential pressure transmitters are used to measure the level of a fluid in a tank.  Why type when I can reference you to a perfectly fine tutorial from Wikipedia so follow this link.  Some application issues affecting the use and performance of hydrostatic level measurement include the cleanliness of the fluid, the corrosiveness of the fluid and how stable the specific gravity or density of the fluid is.  Like other technologies used for level measurement of liquids, there are limitations.... which is why so many technologies exist today and they are all viable in their own right.... EXCEPT for using ultrasonic to measure continuous level of powders and other bulk solids... No No No!

Really though... please read Paul's article "Pressure-Based Level Measurements Keep Getting Better and Better" because it is well written and a great short tutorial on this subject (it also keeps me from having to write it for you LOL).  It's great and a reminder how these devices work well and some of their limitations.

I went back and took a look at the most recent market study report I have available.  Hydrostatic pressure based level devices represent about 48% of all continuous level measurement devices bought each year!  That's huge!

Joe

Technorati Tags: liquid level differential pressure level level sensor level control

Level measurement basics ..........

Why do level measurement applications provide some of the most difficult challenges?  Why are there so many technologies available?  It should be easy, right?  Not necessarily.  I have never been one to want to say a whole bunch when a picture can say it better, and I sure don't want to say any more when a video is available.

In this blog post I want to highlight a great little ten minute video that I recommend for any engineer that now or ever has had the need to figure out how to determine the level of a material in a vessel.  The video is titled "Back to Basics: Basics of Level Measurement".  Walt Boyes is the editor of CONTROL magazine and a major asset to the publication, their website and the automation industry in general.  I can't say enough good about him.  He is brilliant in many areas of process measurement, control and automation, yet very down-to-earth and he cares about the industry and the people within the industry.  I am honored to name him a freind, one I don't see hardly enough anymore (Walt, how about lunch?).  Anyway.... take a few minutes and watch the video!

If you need to measure the level of a powder and bulk solid I have another more detailed resource for you.  Download this file for the white paper titled Continuous Level Measurement of Bulk Solids (or something close to that LOL).  Download whitepaper_tech_review_of_cont_level_for_pbs_apps.pdf

Joe Lewis

Technorati Tags: Ethanol level sensor level measurement basics bin level indicator level control solids level indicator guided wave radar 

Ethanol plants use a variety of level controls

Ethanol production is at an all-time high in the United States and around the world.  There is a huge amount of research on-going in the field as well to determine what else we can process to turn into a fuel source besides corn.  With the surge in gasoline prices this year a boost to Ethanol has occurred.  While some critics blame the Ethanol industry on increasing grain and food prices, this industry generates thousands of jobs and billions of dollars in the economy for construction and operation of these facilities.  Let's look at where level measurement and monitoring devices are used:

Corn storage silos: Typically using open-air radar or smart weight & cable systems.  Guided wave radar is also a possibility depending on range required.  High level overfill protection can be handled with self-validating rotary paddle technology.

Corn surge hoppers: Application for guided wave radar technology as range is usually less than 30' and atmosphere is very dusty.

Corn grind silos: These applications can also be handled with guided wave radar technology or even open-air radar.

Dryers:  Best fit with RF capacitance point level sensors for high and low level detection.

Many other applications exist and sensors required for measuring level are varied.  Open-air radar, ultrasonic, RF, rotary paddle and other technologies are used.  The manufacturers and contractors that thrive from the construction and operation of Ethanol facilities also benefit greatly from this industry.  Ethanol is good for the USA.  What to know more?  Click here for a Download WhitePaper_EthanolSolutions.pdf free white paper.

Joe Lewis

Technorati Tags: Ethanol level sensor level measurement bin level indicator level control solids level indicator guided wave radar

Vegetable oil isn't too slipery for guided wave radar

Measuring a wide variety of crude vegetable oils can be a challenge for some continuous level measurement technologies, but it is an ideal application for guided wave radar.  In China crude vegetable oil is brought in by ship and stored in vessels by the Taixing Port Authority.  This port is in Jiangsu Province near Shanghai.  At this facility there are 11 vessels with crude vegetable oil and the port authority needed a reliable way to monitor oil inventories to ensure security and accurate transfer of the oil in and out of the vessels.  Ranges varied from 55 feet and above.

The crude oil is bought by local manufacturers and refined further.  Most oils at the port in this application include palm oil, olive oil and bean oil.  The dielectric constant of these oils are fairly low, around 1.7-1.8 so many technologies will be challenged to work consistently and accurately.  The solution to the measuring challenge came in the way of guided wave radar when a local instrumentation distributor, Conasen, recommended the sensors.  In this application the GWR sensors were outfitted with a RS485 digital communications output and the automation supplier connected this to a PC running inventory management software furnished by a local supplier.  All is working well!  Guided wave radar, good and reliable for liquids and solids as well.

Joe Lewis

Technorati Tags: vegetable oil level sensor level measurement bin level indicator level control solids level indicator guided wave radar