Letters to the Editor May 2015

April 28, 2015
Readers sound off regarding water. worker shortages, reference materials and more.

Consider A Location With Abundant Water

Your editorial on “water worries” (see: Water Worries Aren’t Dampening) highlights the importance of water, and the problems resulting from neglecting it. Engineers often assume there will be an abundant supply of suitable water, but this is simply not true for much of the world, and even for much of the U.S.

However, let me say, on behalf of everyone from Chicago to Buffalo and from Detroit to Duluth, “If you need lots of good quality water, come back to the great lakes! We’ve got plenty!” There’s no excuse to waste it, or pollute it, but water is the region’s greatest natural advantage.

Paul R. Young, research chemist
St. Michael, Minn.

Take a Closer Look At Ammonium Nitrate

The article titled "Learn from the West Fertilizer Plant Explosion" in the October 2014 issue of Chemical Processing attracted my attention as a chemical engineer with chemical process plant and military explosives experience. Expecting insight into the disaster at West, Texas, on April 17, 2013, however, I found mostly a litany of trite chemical process safety principles and no practical insight into ammonium nitrate process and storage safety. Only from another source did I learn that the West Fertilizer Company fire started in a seed room and spread to the ammonium nitrate (AN) storage area.

A survey of AN incidents revealed a long list of deflagration-to-detonation events. The Monsanto AN plant detonation near Mt. Vernon, Mo., in 1966 is strikingly similar. A fire of undetermined origin occurred in the packaged AN warehouse at the plant. The Mt. Vernon and area volunteer fire units tried to extinguish the fire but made no headway in suppressing it. One of the fire chiefs determined that AN detonation was possible and ordered his unit from the site. The other volunteer units and Monsanto personnel followed suit. When the AN detonated, no one was injured; there was some plate glass breakage at businesses in Mt. Vernon about one mile away and minor damage to the roof of a farmhouse a half-mile distant.

At above 200°C, AN decomposes exothermally to nitrous oxide and water. Burning packaging material, wooden pallets and other warehouse flammables can trigger this decomposition reaction. Nitrous oxide is an "oxidizer" that can cause the fire to progress to a deflagration condition. If the packaged AN is fairly closely or tightly stacked deflagration can trigger detonation. It appears that this was the underlying cause of the West, Texas explosion.

The author mentions closer oversight by state and federal agencies as beneficial in preventing such disasters. However, my experience with multiple OSHA inspections is that they can verify adherence to documentation requirements (e.g., training, management of change, etc.) but OSHA processing plant inspections are almost totally worthless due to the inspectors having no real knowledge of chemical processes and the chemistry involved. When the OSHA Process Safety Management (PSM) rule was implemented, the large chemical companies (e.g., DuPont, Dow, Eastman, etc.) already had 90+% of this excellent safety model in place. It was the small chemical plants that were most deficient.

There were two general suggestions by the author that have merit:
a) "Properly designed automatic fire alarm and suppression systems can minimize damage from all but the worst conflagrations."
b) "Safer storage practices and less ammonium nitrate at West Fertilizer could have helped prevent disaster."
The large, reputable chemical companies mentioned above normally have deluge sprinkler systems which can extinguish insipient or beginning fires, but small, less-competent facilities usually do not have them because they add to the capital cost of the unit.

My bottom-line recommendation for the many AN production and storage units scattered around the nation is that they a) be located at least one mile from towns or communities, relocating if necessary to attain this distance, and b) that their packaged goods storage facilities have deluge sprinkler systems to immediately suppress any accidental fires.

J. Dale West, PE
Longview, Texas

The Maintenance Engineer Is Right

I’m sure I am not the first to comment on the Field Notes article by Dirk Willard in the May 2014 issue of Chemical Processing (see: "Check Standard Conditions”), where he states that the maintenance engineer was wrong to say that ”the pump discharge pressure will change depending on the liquid”.

Pump manufacturers typically supply pump curves in head rather than pressure specifically because pump discharge pressure does change depending on the liquid being pumped.

A pump that deadheads when pumping water to a height of 50 ft will also deadhead when pumping liquid mercury to a height of 50 ft — but the pressure gauge on the discharge of the pump will be reading 13.6 times as much pressure when pumping the mercury. Of course you will require 13.6 times as much power.

I can only conclude that the maintenance engineer knows more about pumping than Mr. Willard is giving him credit in this article.
I must live in a different world than Mr. Willard. I have never met anyone who would size a pump so close that a difference in specific gravity of 0.002 would make a difference. I have, however, on multiple occasions seen engineering firms add 20% to a calculated head requirement to ensure the pump met real-life flow requirements.

Bill Akers, maintenance engineer
Saraland, Ala.

Is There Really A Workforce Shortage?

I have been hearing that there is shortage of chemical engineers, but most companies are not prepared to hire experienced engineers who can provide vision and leadership, can innovate, and have designed before the days of just putting things into the computer. These experienced personnel can see the results and tell an engineer where he is going wrong and guide these engineers in simulation, e.g., what and how to use the thermo packages and what else to do to put reaction kinetics in the reactor and other areas.

So, employers should take advantage of this pool of engineers who are accomplished and can deliver what it takes to be productive, save time and meet budget schedules — which they have proven in their career. Many of these older engineers have gone from bottom to executive level management and know how things work and have the experience.

Anyway, this approach will fill a lot of the shortage. Some of the shortage is self-created: jobs still open after a year either are not real, or hiring managers are not capable of or interested in hiring people; other jobs are cancelled, which is poor judgment on the part of the organization, wasting their time, as well as that of recruiters and candidates.

So in short, some of this shortage is self-created and that goes for other parts of world as well where they retire experienced personnel at a certain age (which is age discrimination in the United States). Yet, in the United States, despite laws, age discrimination still exists.

Dr. Amarjit Bakshi, president
Katy, Texas

Add Solid-Liquid Filtration To Your Library

I always enjoy Dirk Willard’s column but his March 2015 column (see: “Establish a Good Reference Library”), did not include “Solid-Liquid Filtration” as a key book.

I have just published "Practical Guides In Chemical Engineering: Solid-Liquid Filtration"; this book is part of the series of “Practical Guides of Chemical Engineering” published by Elsevier, Oxford, U.K.

“Solid-Liquid Filtration” covers the basic principles and mechanisms of filtration, filtration testing, including filter aids and filter media, types of filtration systems, selection of filtration systems and typical operating and troubleshooting approaches. This guide also discusses general applications and tips for process filtration and can be utilized by process engineers as a framework for “idea generation” when analyzing filtration for an operating bottleneck issue or a new process development problem.


Finally, BHS, over the past several years, has been asked by the marketplace for technical and hands-on training for solid-liquid filtration. BHS is meeting the needs by organizing the initial Solid-Liquid Filtration Workshop (www.bhs-filtration.com/workshop). We think this will be an important benefit to the industrial community.

Barry A. Perlmutter, president & managing director
Filtration, Mixing & Recycling Divisions
BHS-Sonthofen Inc.
Charlotte, N.C.

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