Here is a sampling of letters we've received regarding recent articles in PME, but didn't have the space to print.

Engineers and Terrorism

I write this as a professional engineer with a background in helping and training younger people from schoolchildren to mature graduates. The war against terrorism, in my view, should involve richer nations assisting poorer nations in developing their own resources, including water supply, sanitation, electricity, communications, etc. These things we take for granted in "developed" countries. It seems natural to us that we can eat fresh food, grow crops, rear animals, turn on a tap to get hot or cold water, flush a toilet, switch on a light, turn on a TV, heat or cool our houses, keep food fresh in fridges and freezers, pick up a phone, drive to another city, cross a bridge, take a plane ride, and so on. Almost everything that we take for granted comes with engineering. A major exception may be medicine, but that too involves engineering to a great degree.

Science and engineering continue to evolve rapidly, especially in the high technology areas. However, the fundamentals of water supply and disposal, irrigation and power generation are not widespread in many other countries. Hence, the lives of many other peoples are very dissimilar to ours. Poverty and hunger are commonplace in many areas of the world where education in engineering is lacking. Give a man a fish, and he can feed himself for a day; teach him to fish and he can feed his family forever.

We have newspapers, worldwide news coverage and "freedom" that comes with democratically elected governments. We have largely stopped fighting about our varied religions. However, it seems that terrorism feeds on poor people, perhaps from different religious beliefs, but perhaps coming from mostly poor countries. As engineers, technologists, communicators, doctors, maybe we should all contribute from each of our professional societies to a worldwide "engineering fund" to support development of fundamental professional skills in "undeveloped" countries. Once people are not poor, hungry, or sick and have more contact with the rest of the world, they would be much less likely to harbor terrorists and seek to oppose freedom of religion, freedom of the press, freedom to be peaceful and safe, freedom to marry another race, and freedom to allow ethnic differences to be easily accepted.

Without the ability to feed your nation, educate your nation, or inform your nation of worldwide events, you may be naturally breeding a nation that has nothing to lose by harboring terrorists, or worse still, cannot themselves prevent terrorists doing whatever they want, as the nation may have no police, or worse, the police (or military) may be corrupt and pleased to turn a blind eye.

Education breeds civilization. Engineering is the fundamental foundation of the civilization that we take for granted. We who have the education should help give the capabilities we possess to countries who are less privileged. We could start a fund to put engineers into all countries needing our skills. Independent of any nation, any race and any religion, we in our profession could help defeat terrorism by helping develop poor countries. The governments of the countries in which we work could pay our expenses and for some of our time. We could contribute some of our time, meaning some of our money, and truly work for the benefit of mankind.

W.P. Stewart, P.E., president, Stewart Technology Associates; senior partner, Zeta Stewart Associates, Houston, TX

Holohan's Right About Exchange Students

Just read Dan Holohan's article in the April 2002 PM Engineer on the exchange students. TRANE actually makes their engineers go out and work with the technicians for six months before they move them up the food chain a bit.

I do agree with what you say about seeing how the other half works. Sometimes it seems like engineers and contractors are almost adversarial, us against them. As an old tin man, I do know how that industry works so I have been on the other side of the fence. Good article.

David H. Brown, P.E., SmithGroup, Detroit, MI

Avoiding the Pitfalls of Instantaneous Heating

The author of the article, "Tankless Water Heaters," in the December 2001 issue presents several advantages of the instantaneous water heater concept. The obvious advantage is the reduction of standby losses. The article describes small unitary domestic water heaters, although the concept of instantaneous heating, opposed to load shifting to a storage tank, applies to any size heater for many processes. The tankless design, by elimination of the storage tank(s), can be effective in reducing opportunities for Legionella contamination in the potable water supply and can save considerable space requirements of the mechanical heating equipment.

Properly applied, instantaneous or tankless heaters can be very useful. Like most engineering solutions, the tankless technology can solve one problem (energy consumption, in this case) while creating new ones. The purpose of this letter is to help designers and facilities personnel avoid some potential pitfalls of misapplied instantaneous heating systems. By understanding some basic engineering considerations, the benefits of instantaneous heating can be had without the surprises.

A good way to understand instantaneous water heaters is to view them from the opposite side of the coin. The benefit of a storage system is that the tank serves as a thermal flywheel. With the flywheel, the connected load is reduced and simple on-off control of the heating apparatus can be used by the manufacturer. Without the flywheel, the heating apparatus becomes characteristically oversized, and two things change at once: 1) the need for instantaneous response to changes in load require a more complex heating unit, and 2) the connected load will increase causing a greater instantaneous demand upon the utility infrastructure. Discussions follow:

1. (More complex heating unit.) The heater output design must follow the load and its changes, meaning the heater itself (element, burner, control valve, etc.) must be designed to accommodate a much greater load swing, usually resulting in a more complex heater unit. This necessary complexity usually takes the form of modulating controls with high turndown capability. In the case of modulating electrical current, semiconductor high-speed switching devices may be used that are sensitive to electrical disturbances, and so facilities that have a high incidence of electrical surges or spikes may experience higher repair incidence if not properly protected from electrical transients. In the case of modulating gas valves, the draft of the flue may vary with the temperature of the flue stack and may cause operational problems at light loads when the heat rejected to the flue is light, unless a forced draft system is used. In the case of modulating steam, the high turndown valves may be problematic and require increased maintenance due to wire-drawing failure of valve seats, unless exotic valve seat materials or 1/3- to 2/3-valve arrangements are used.

2. (Greater demand on utility infrastructure.) Even though the average energy consumption of an instantaneous unit can be lower than a storage system (saving the standby losses), the instantaneous demand for energy will be higher, because without the tank, the burner output must meet 100% of the demand requirement. For example, if a hot water demand has an average daily consumption of 100 gallons per hour with a short term increased demand of 200 gallons per hour, the burner for the instantaneous system must be sized for the maximum output, or 200 gallons per hour. Consequently, the connected utility service, whether gas, electric, steam or other media, will be larger than it would be for the storage tank application, i.e. a larger electric service, gas pipe, steam pipe, etc., will be needed to carry the higher instantaneous demand. In a new construction project, this can usually be accommodated by simply running a larger electric, gas or steam service to the heater. In the case of a retrofit, care must be taken when converting storage systems to instantaneous systems, since the instantaneous demands will place an increased burden upon the infrastructure that probably was designed and sized using demand diversity benefit of the storage tanks. For any facility with in-place infrastructure, the indiscriminate replacement of storage heaters with instantaneous heaters can have the unfortunate side effect of over-taxing the existing infrastructure. For such facilities, a load profile and infrastructure analysis should be performed to fairly assess the infrastructure to be sure that using instantaneous heaters does not cause infrastructure-related problems.

Steve Doty, P.E., Farnsworth Group, Colorado Springs, CO,

Looking at Composite Failure

I wish to congratulate Julius Ballanco and his staff for their fantastically insightful coverage of the 9/11 Terrorist attack. I was so moved; each author said all of the things that I felt/feel and wished to have a forum to so express--and did so in such a wonderfully personal manner. I plan to make copies of those tomes available to all of my students, both undergraduate as well as graduate students. In that latter group, we have a predominantly high percentage of foreign students, mostly from Asia, the mid-East and the Asian subcontinent (unfortunately, we have a dearth of U.S. students staying around for graduate engineering studies [those few who do stay are generally leaning toward teaching careers, not going to industry]). But, that is another whole story and not why I decided to contact you.

As noted, I wished to thank you for the quality of the PM Engineer publication in the past and the present manner of presenting plumbing engineering to your readers in a real-life manner.

At the time I write this, none of us yet know if the failure of the American Flight 587 Air Bus A300 was the result of sabotage or mechanical failure. My emotional side stays with the terrorists view; my engineering background drives me to the possible failure caused by delamination of the composite rudder. What the NTSB has released so far indicates considerable interest in the failure of the composite rudder. I have a sub-specialty in the field of composites and have proposed some background in this area of failure to the NTSB (composites are proven to be very prone to premature delamination/interlayer separation within the laminate themselves). But I realize that my submission was an "unsolicited" presentation of experience/knowledge with/about the weakness of composites evidenced in service failures of various composite equipment (and many boats, as I have studied failures of some quite expensive high performance speed boats, ranging in cost from $300,000 to over several millions of dollars per boat, down to many much smaller and less expensive pleasure boats). I can cite one truism, i.e. that while not every composite item of equipment or boat that I have studied has failed by interlaminate separation/delamination, every failed item I have studied that had been subjected to some form of biaxial and/or triaxial service loads/stresses failed by delamination!

The similarity of your needing to educate your readers about the root failure cause of the 9/11 building losses has led me to consider asking for your advice. I have written to the nominal heads of the various subsections of the NTSB, though I question if any of them will ever see my communications, and even if they do receive this information, their bias will direct them to ignore my presentation. If you share any of my feeling of a need to introduce some outside-the-government experience and technical input into such a high-profile accident, perhaps you might suggest an alternative method for my tweaking through the government's "system"?

Qualifications? For openers, I designed and handled the fabrication and installation of the first composite process equipment item at Monsanto in 1950. Over the years, I grew with the composite industry. I aided the writing and promulgation of the first (U.S.) national standard on the design and fabrication of composite equipment, i.e. Department of Commerce, Public Standard, PS 15-69 (and several iterations of that standard). In 1979, I instigated the formation of an ASME code committee to prepare a more technically sound standard on composite design and fabrication, now an ASME/ANSI Standard RTP-1; I retired as the committee chair and am now an honorary member (a nice way of saying an 'old salt'). Along the way, my research at Monsanto and at Washington University has taken me into some truisms about composites that have not been utilized by the professionals in the composite field. These materials, as presently designed, fabricated and utilized within the aircraft industry, take advantage of the increased tensile strength-to-weight ratio of composites compared to metals, but essentially ignore their weaknesses under bending and vibration stress loads, etc.--the environment in which these composites are subjected. (As I learned in Economics 101, the economic long-term theory is quite factual, but people live and die in the short run). I have published several landmark research papers covering the limitations of composites when fabricated using a specific kind of fabric for reinforcement, as well as addressing the subject of the mechanical weakness of composites when subjected to biaxial and triaxial service load stresses.

Over a period of several years, I visited the top airframe designers (at Boeing, the old MAC in St. Louis, etc.). I also attended the Gordon Research Conference on composites one year in the early 1980s. (The Gordon Conference is a yearly gathering of the 100 selected experts in their field held at various remote universities during the summer--a unique, unstructured week of mutual interchange where no notes are allowed, nor photographs or recordings. The concept of Dr. Gordon was to relieve the participants of the responsibility of not revealing the technical secrets of their several employers, etc.) This is a great concept; e.g. for over 22 years I attended the Gordon Research Conference on corrosion of metals.

At the Gordon Conference on composites, I tried to get the attendees to listen to my experience and test findings, all to no avail. They do not recognize that composites (which they believe are a near wonder-material) have any limitations in bending; they do not accept that these materials are prone to fail by delamination and/or creep when subjected to bending stresses.

I am a 77-year-old (yet active) materials engineer in the failure analysis consulting business who remains on the engineering staff of Washington University in St. Louis, teaching (now at a greatly reduced level) materials related subjects, e.g. selecting materials of construction, corrosion (both real and theoretical), composites, metallurgy, welding, etc. (on the adjunct faculty staff since 1953). My background is mixed; my undergraduate studies were in electrical engineering (prior to and during the early years of WWII), my B.S. was in mechanical engineering, and my graduate studies were in metallurgical engineering and eventually chemical engineering (I worked for Monsanto Co. from 1950-1985 and soon realized that unless I had formal training in chemistry or chemical engineering, I would never advance). I retired from Monsanto as a senior fellow in materials engineering, specializing in failure analysis. I have held national office in ASME, AIChE, and NACE (and have received the fellowship from all three of these technical organizations). I have been an invited/visiting professor at Princeton; the University of Rochester; the University of Missouri at Rolla (for 11 years); universities in Strasbourg, France, and Kobe, Japan; and a U.N. Distinguished Visiting Scholar at the Technical University of Beijing, PRC, and Technical University of Monterrey, Mexico. I hold three U.S. patents and one EU patent on welding processes. I have published three technical books and authored the chapter on materials of construction in the 1985 sixth and 1997 seventh editions of "Perry's Chemical Engineering Handbook." I have published over 120 technical papers in referred engineering and scientific journals. From 1994 to the present, I have represented the Dept. of Chemical Engineering in the Interdisciplinary Department of Materials Engineering and Science at Washington University. Our graduate students work in two main areas, aging aircraft and composites. I believe that you might agree that I come to the subject of composites with more than incidental background/qualifications. I wish to help the NTSB solve the failure of Flight 587 (for if it is composite failure, I can aid them as probably not too many others could).

I have always felt that your magazine is the best technical magazine that I receive, bar none. It is a poor commentary on we as a people that we are always ready to complain when things do not go our way, but never get around to thanking the nice characters of the world when they do the normal, every-day things that make our lives so great. Therefore, this is an admission of my failure in the past to be nice to the nice people of the world who have done nice things for me.

Again, while I started this letter to thank you, it occurred to me that perhaps your insight might provide some guidance as to how I might better receive an audience in my latest run at the Washington "Windmills"?

Oliver W. Siebert, president, Siebert Materials Engineering, Inc., Ballwin, MO,

Julius Ballanco's response: Thank you for your kind words. After reading your letter, I would think that the NTSB would be more than willing to have your assistance in analyzing the airbus crash.

I used to have access to the NTSB. My older brother has investigated a number of military jet crashes. He is a former fighter pilot with a B.S. and M.S. in mechanical engineering. Unfortunately, he is long removed from that arena. As he says, contacts in Washington disappear quickly.

My past experience with Washington is that you need to persevere. Quite often, the first person you reach is a bureaucrat that thinks they know everything and considers everyone else an idiot. You need to get past that individual.

A past experience I had resulted in total frustration. Finally, I contacted my congressman. It was amazing the doors he opened. All of a sudden, I made sense and people were listening. So, when in doubt, let your elected leaders know of your expertise and willingness to assist.

I hope you are successful.

Chicago's Behind the Times

I just finished reading Mark Bromann's collective bag of fire protection news. I find it interesting that the City of Chicago still does not have a high-rise sprinkler retro-fit requirement. Unfortunately, it seems that each city must first experience a significant high rise fire with multiple fatalities before they are willing to tune out the lobbyists. I guess the Great Chicago Fire doesn't count since it was not a "high-rise" fire.

A clarification on Mr. Bromann's credit to the City of Philadelphia. It appears that the apartment association put up a successful fight in Philadelphia which resulted in their exclusion from the sprinkler retrofit requirements. In high-rise Group R-2 occupancies, sprinklers are only required for basements, storage rooms over 120 sq. ft., and trash chutes/rooms. Instead, the code requires smoke detection in common areas, basements and corridors.

James Peterkin, P.E., fire protection engineer, HLM Design,

FM 200 Versus Inergen

I saw Mark Bromann's question in the October issue of PME regarding FM 200 vs. Inergen. Many things should be considered when deciding on protection for a vault like he mentioned. Depending on whether this is a new or existing building (retrofit), you may run into limitations that may dictate the type of system that makes sense.

For example, Inergen systems require a fairly large tank storage area, which you may or may not have. FM 200 has limitations with regards to how far away the tanks can be from the discharge area. In addition, a good fire detection system may prevent a costly system discharge and minimize damage to the room and contents. In my opinion, your best protection strategy would be to detect a fire early and shunt affected equipment (if applicable), and only depend on the gaseous suppression system as a last resort. Also, the fire detection system is an integral part of a gaseous suppression system and must be matched to the size or incident you are willing to accept. Air-sampling type smoke detection systems will provide a much earlier response than spot type smoke detectors, so these are recommended in critical installations. Glen Saraduke, P.E., registered fire protection engineer, manager, Denver Office, Schirmer Engineering Corporation, Golden, CO