Vector Equipment Sales » Joe Lewis

What a Shocking Experience!

Joe Lewis — Thu, 17 Mar 2011 22:40:32 +0000

Every once in awhile I come across something that is worthwhile repeating and sharing with others. usually some lesson regarding safety or how to improve a process, measurement or material sensing. In this case I ran across a white paper written by Michael O'Brien, Product Manager for Newson Gale, Ltd. with headquarters located in Nottingham, England (I wonder who the sheriff is? - I just couldn't resist that commentary). They have a location in Jackson, NJ as well. This was of interest to me, not just because of the safety aspect to protect against dust explosions (see a dust explosion story by clicking here) but because of the impact static discharge can have on level sensors.

Not all dust explosions are started by static electricity discharges, but it does happen and sometimes the source of ignition is not a certainty. The previously mentioned white paper indicates that "walking across a carpet can generate 35,000 volts on a person". When you combine this type of voltage potential on a highly conductive metal object the energy discharge can be above that which is known to create explosions in the presence of flammable vapors. This has even happened at gas pumps:

Static discharge can occur often during the processing, conveying, handling and storage of bulk solids. Consider a pneumatic conveying system which is used to move or transfer plastic pellet or resin from storage silos to machine hoppers. Since most pipe or tubing, and vessels are made from aluminum or steel the resistance to electric charge transfer is very low (aluminum is 2.82 x 10 to the -8 power; dang how do you make the -8 superscript in TypePad LOL). This means that static will discharge from these metals (your piping, chutes and bins) very easily!

Static discharge not only can create a hazardous explosion, it can also be the source of damage to sensors in contact with the material or the material bins and piping. Those sensors commonly affected are RF Admittance/capacitance units and the Capacitive Proximity Switch, both used often. The later tends to be more sensitive to the effects from static discharge because the former are usually manufactured with adequate protection against some level of static discharge.

So how do we address the problems associated with static discharge in an industrial bulk solid processing operation? The standards all seem to agree, as the aforementioned white paper points out, proper grounding of processing, conveying and storage equipment! The white paper points out that this is the single most important thing you can do to prevent static discharge caused explosions. By the same action you remove a possible threat to your sensors. How good does the ground have to be? Good. Less than 10ohms resistance between the metal components and ground. Static electricity must discharge quickly to the earth ground plane within the facility to protect your facility against hazardous dust explosions and to protect your sensors attached to this equipment.

Joe Lewis

Blue Level Technologies

Is it really "safe"?

Joe Lewis — Wed, 15 Sep 2010 22:46:05 +0000

Having spent the last 35 years of my life immersed in a wide variety of aspects in the process measurement and control industry I was recently asked for a recommendation regarding a level control device that would be able to control a bin filling operation and be "safe". What a soapbox I was handed.

The powder and bulk solids industry seems as though it lags in adopting some technology, at least from an instrumentation standpoint. However, it isn't just the risk averse nature of most powder and bulk processors, but it is that much instrumentation technology developed for use with liquids (80% of the overall measurement business in level measurement) does not cross over directly or seamlessly to powder and granular material level measurement. It takes time to adapt technology for the challenges of bulk solids.

The same exists in the area of instrument "safety". Driven by large legal and financial ramifications in the chemical and petrochemical area, as well as standards writing bodies such as the global IEC (International Electrotechnical Commission), most "safety" related approaches are quickly developed and adopted in liquid oriented industries, such as chemical, petrochemical, pharmaceutical etc. So when asked, I summarize the four levels of basic safety regarding the function or output of a level measurement or monitoring device.

I recently posted to the Just Level Expert blog the following list. You might want to setup an RSS feed from that blog so you don't miss anything.

SAFEST: Material detection sensors certified to SIS and SIL according to IEC 61508 and 61511. Refer to this White Paper to explain more about this safety level. There are level indicators certified at this level, but primarily technology for liquid applications. It's an interesting subject if you are involved with process safety. Check it out.

SAFER: Self-validating level sensor technology that verifies its health and communicates it to you. This is only available with rotary paddle technology for solids and doesn't eliminate moving parts, the drive motor, and comes at quite a hefty price tag. Fail-Safe rotary paddle, RF and vibrating element devices are just as reliable and protect against many sensor failures, those that occur due to power disruptions.

SAFE: Material detection sensors that are FAIL-SAFE so the sensor output indicates an alarm if the power supply to the sensor fails. Rotary paddle units offer the highest value with this capability, but make sure you ask specifically for a unit that has a fail-safe output on power failure. RF and vibrating element sensors commonly provide this capability on a standard basis.

TAKING YOUR CHANCES: This is any material detection sensor that does not offer at least the SAFE level or above. This is common with some brands of rotary paddle bin level indicators, proximity sensors and also with tilt switches and diaphragm switches. Consider switching these out for the "SAFE" kind.

One final point, thinking about relying on your inventory level sensor for control? Don't! And don't take my word, listen to what the accident investigation report said regarding their findings and recommendations regarding the fuel depot explosion and fire late in 2005 that was estimated to cost 1 billion pounds (that's pounds sterling British currency). You can read about that in an editorial column from September 2009.

Got a question? Give us a call at 888-61LEVEL or 815-625-2224. Email us at bluelevel@blueleveltechnologies.com.

Want Better Inventory Accuracy? Know YOUR Stuff

Joe Lewis — Thu, 08 Jul 2010 03:32:10 +0000

Use of continuous level sensor technologies like wight & cable, radar, acoustic and others are almost always for inventory monitoring purposes when used with powders and other bulk solid materials. In these inventor applications the sensor is used to answer the question, "how much stuff do I have?". Using a continuous level sensor will generally make a measurement of the distance from the sensor to a point on the material surface with good accuracy. But this measurement does not really answer the question. Why? Because you bought or produced the material in inventory storage based on volume or weight.

Now you have to convert from distance or perhaps a material level at a single point to volume and then mass. But wait, your material surface isn't flat. Locating the level sensor for measuring distance at the optimum point on the material surface is a key variable to making your volume and mass calculating as accurate and precise as possible. You need to understand your material profile and work with the level sensor manufacturer to determine the best mounting location based on the best level sensing point on the material surface.

What about the material bulk density? Assuming a uniform bulk density throughout the pile of material in your silo may be inaccurate. Your material packs, therefore the bulk density at the top of the pile is somewhat lighter than that at the bottom. In addition, if you are buying this material from an outside source or if you produce the material in batches or lots, the bulk density may vary slightly from batch to batch. This also impacts the accuracy and precision of the calculated weight.

The most practical solution requires you to know your material profile and have a good average bulk density. Other solutions do exist, such as weighing the vessel/contents using a load system or using the latest technology that maps the material surface and accurately determines contents volume.

For additional information check out the below links:

White Paper Continuous Level and Inventory Monitoring of Powders and Bulk Solids

What You Know Can Make All The Difference

Surface Mapping

In addition, you can review an upcoming technical exclusive article in the August issue of Powder Bulk Solids magazine titled "The Problem with Measuring Levels". I'll update this blog with a link when this is available.

Joe Lewis

Essentials of Modern Measurements —- Book Review

Joe Lewis — Wed, 27 Jan 2010 15:27:05 +0000

“Essentials of Modern Measurements and Final Elements in the Process Industry” is a new book assembled by author Gregory K. McMillan, with a host of contributing writers. I first became aware of this new book from a post at ControlGlobal.com, one of the leading industry news and editorial sites on Internet. I was intrigued by the fact that someone took the time to put a new book together that was about process MEASUREMENT and not control automation. I remember GIGO (garbage-in, garbage-out) and still place a strong priority on measurement technologies rather than the control system. In the end, both are necessary but it is my opinion that many within the Measurement, Control and Automation industry seem to have forgotten about the process measurements and their importance.

I have completed much of the Level Measurement section, Section 5, which begins on page 229 and continues through 273. I have a few observations and constructive comments regarding this section of the book:

MEASURING SOLIDS LEVEL IS ABSENT. This book is definitely well written. My hat is off to the writers of this section on Level Measurement. They and the editor(s) did a fine job in writing the material. The illustrations are also well done. Bravo! However, there is a glaring absence of even a mention of level measurement of powders and bulk solids, which can be just as complex or more complex than liquid level measurements. I view this as a deficit in the book and feel a few pages could have and should have been devoted to this topic. A White Paper on the subject of continuous level and inventory measurement of powders and bulk solids may serve to fill the gap.

ABSENCE OF POINT LEVEL SENSING. Well I guess some folks don’t consider point level “level measurement” and in the strictest possible sense of the phrase it is arguable. However, even third-party market research firms such as Venture development Corporation include point level with continuous level when assessing the Process Level market. This subject should have been included, especially given the introduction of several point level products from a variety of companies rated for SIL-2 use, such as this unit from Magnetrol. I also point to the recent recommendation by the board that reviewed and assessed the aftermath of the Buncefield accident late in 2005. One of the conclusions stated that the failure of the inventory measurement sensor system and the absence of a separate overfill detection and prevention system may have been contributing factors to the accident. Point level sensors have a place within the “level measurement” arena.

FOCUS ON DP, RADAR AND ULTRASONIC. I do agree that these are very important technologies. I also concur that Radar, whether in its contact guided wave form or non-contact form, is the fastest growing technology for level measurement. DP and Ultrasonic also are large segments and heavily used. However, the absence of any discussion about Magnetosrtictive technology, Displacers and only a limited discussion on RF Admittance capacitance type sensors was disappointing, and those are for liquid apps. In addition, the category of smart weight & cable inventory systems, like all else for solids, was absent as well.

I definitely recommend this book as one of the better reference books available. However, I do feel and wished the above deficiencies would have been corrected before publishing.

Joe Lewis
BlueLevel Technologies, Inc.
www.bluelevetechnologies.com
joe@blueleveltechnologies.com

Dust Explosions and Fires Analyzed … What You Don’t Know Could Hurt You

Joe Lewis — Tue, 15 Sep 2009 20:01:48 +0000

Many of us work in companies that process bulk solid materials. Often this processing produces dust., lots of dust. That's why there are dust collection systems and many companies that specialize in that area. Unfortunately sometimes there are hazards we don't know about, or at least we may not be aware of them.

In a recent review of the reports coming from the investigation of the accidents in Buncefieeld England and at the BP facility in Texas City where failure of level detections systems contributed to major accidents, I was made aware of a CSB video that is really pretty cool, though scary and horrifying at the same time.

The USA Chemical Safety Board investigates accidents after they occur. They have spent considerable time investigating numerous accidents involving dust explosions and fires. This is well worth the viewing of this 30 minute video.

CLICK HERE TO WATCH VIDEO

Remember, even the seemingly most benign dust can be hazardous. The reason dust hazards could be more serious than those as a result of vapors is because awareness and focus on dust related hazards is relatively low by comparison. Dust can be dangerous, be very respectful of it.

Joe Lewis

Failure of Tank Overfill High Level System

Joe Lewis — Tue, 21 Jul 2009 23:01:00 +0000

What happens when your high level indicator fails without warning? Everyone knows the answer and we have talked about it before. The unknown failure of a high level sensor that is used for overfill protection can result in an overfilled condition that means lost material, clean-up, damage to equipment and even catastrophic events. People can and have died. This is preventable!

Recent conclusions from the review boards looking at the cause of the explosion at an oil depot in Buncefield England and the explosion a couple of years back at the BP facility in Texas City have cited level detection system failure and the need to utilize equipment meeting IEC 61511 requirements as part of a Safety Instrumented System is necessary. Read the full story here.

Level detection devices meeting SIL2 are commonly available for liquid level applications. However, not for powders and bulk solids. While loss of life may not be as high a risk with powders and solids, it remains a costly occurence to overfill a silo, even with plastic pellets.

Six Sigma Works for Alarm Management

Joe Lewis — Wed, 03 Jun 2009 16:08:14 +0000

Managing any process will require continuous improvement, at least if you want to manage it well. Aspects of continuous improvement, lean techniques and six sigma all call for metrics or measurements that are the standard the process needs to adhere to or exceed. A white paper addresses the application of six sigma techniques to alarm management. Click Here.

Promoting Slurry Flows

Joe Lewis — Tue, 24 Feb 2009 17:18:27 +0000

In some applications a bulk powder, granular material and liquids may be combined to produced a thick slurry. One example is the production of concrete, either in a batch plant, precast operation, block plant or other type of facility. Depending on the angle of your discharge, the thickness of the slurry mix and the mixture ratios themselves, there may be a problem getting the mixture to flow readily.

One example where this problem can occur is with the discharge of concrete mix from mix trucks. Here's a quick look at one of my concrete trucks, it's a collectible die-cast of course. The problem associated with bulk material flow, even concrete, is two things, the cohesive strength of the material and the friction between the material and the material of the vessel the material needs to flow down. Check out the bulk solid material flow experts for more resources and information on flow properties.

The solution in most cases is using an industrial vibrator. This is for very good reason. For example, using our concrete truck illustration let's look at an installation of a turbine vibrator on the discharge chute. In this case (shown in photo at top) the vibrator is quietly introducing several hundred pounds of force into the material through the wall of the chute to promote and maintain the concrete flow. In this case the Turbine vibrator replaced a piston type vibrator because of the noise associated with piston vibrators. The Turbine type is very quiet, well within OSHA guidelines.

Need help with a material flow problem? Give me a call at 800-262-2106 or 815-224-1200.

Joe Lewis