Cicadas Can Overwelm Your Cooling Towers and Evaporative Condensers
Did you ever wonder what insects make that very loud buzzing sound in trees during the daytime in summer? Well, it’s a widely heard but rarely seen kind of insect called a cicada. The ones you hear every summer are non-periodical, some of them appearing as adults every year despite requiring several years to develop to adulthood; but the ones appearing as adults in the next few years that can overwhelm your cooling towers, evaporative condensers and air handling units emerge as adults in 17 year intervals in large and generally non-overlapping geographic regions of the northeastern United States. Because of this separation in time and place, these species are called periodical cicadas, and their various widespread populations are called broods. A total of a dozen such broods are recognized. The single largest 17-year brood, known as “Brood X” [ten] is expected to appear in sixteen states in 2004 (see figures 1 and 2 below for state and county distribution), while another 17-year brood should appear in four states in 2007, and yet another in 12 states in 2008 (many the same as for Brood X). One can identify periodical cicadas by the combination of largely black bodies, reddish eyes, and reddish veins in their wings. If your company is in a region affected by Brood X this year, you need to begin planning how you will deal with the potential problem because it can have a devastating impact on your operation if you wait until it is too late.
So What’s The Big Deal?
When Periodic Cicadas emerge, their population density is enormous and can exceed 1million per square acre (several hundreds of thousand is usual). If your facility is in a brood infested region and your cooling towers, evaporative condensers and air handling units are in or near naturally forested areas or, surrounded by trees your system may be vulnerable. Please note that this otherwise harmless insect can be sucked into your equipment while flying past the draft zone of the intake opening as they make their way to the nearest tree.
Location Of Your Equipment Can Help Determine If Your System Is At Risk.
Units located on rooftops and away from trees or, in the middle of a paved area are less likely to encounter cicada related problems then those that are near the ground or surrounded by trees or woody plants. If your facility is immediately adjacent to or, nestled away in affected wooded areas, your systems are likely to be at risk.
How Big Are They And When Will They Emerge?
These insects are about the size of your little finger, measuring about 0.5 inches wide and 1.5 inches long. There are three species or kinds that usually emerge mixed together in the same area. Their songs are quite different, and they vary in average size. They are expected to emerge from the soil in early May and June, and are active as adults (only males sing) for 30-50 days. During their short time above ground, they feed both day and night by sucking the sap of trees and other woody plants. They do not chew or bite leaves or people. The songs of males promote mating. After mating, females lay hundreds of eggs in woody tissue, by making slits in the bark of pencil-sized twigs. Shortly after mating and laying eggs, the adult cicadas die, leaving massive numbers of carcasses everywhere. In about nine weeks the eggs hatch and pale ant-sized baby cicadas drop from the twigs to the ground where they burrow underground and remain there for 17 years, sucking sap from the roots of plants.
Here’s What Can Happen
As one Stationary Steam Engineer, working at a major consumer products manufacturer in the Cincinnati, OH area puts it, “The last time the Periodic Cicadas emerged, we had to clean our cooling tower strainers and flume several times per day. If we didn’t clean the strainers, we would lose our chiller due to high-pressure conditions and it would shutdown our cooling system. We had to maintain our cooling towers around the clock just to keep our systems operational”.
If your facility is in an affected area and you don’t anticipate emergence of the Cicadas, it can impact your annual maintenance budget and have an economic impact on your business. Here’s how:
Cooling Towers & Evaporative Condensers:
* Clog Cooling Tower Fill - reducing airflow.
* Overwhelm sump water increasing organic content and increasing bacteria count.
* Increase water treatment chemical consumption and associated cost.
* Clog strainers, reduce flow rate and impact chiller efficiency.
* Clog solenoid blow-down valves in the open position, resulting in increased make-up water and water treatment chemical consumption
* Clog heat exchangers reducing flow rate and heat transfer efficiency
* Can cause production downtime, lost productivity and missed shipments.
* Increase maintenance cost.
Air Handling Units
* Clog Internal Filters
* Load Intake Air Pathways with insect debris
* Increase Filter Changes
* Reduce Internal Air Quality
* Cause Excessive Service & Maintenance Cost
In short, Periodic Cicadas can cause real havoc to companies that are not prepared.
How You Can Prevent Trouble
1. First of all you need to determine if you are located in an affected region - If you had a problem the last time they emerged and there has been little construction or disruption to the soil or forested area around your operation, then you are likely to have trouble again (See Fig. 2).
2. If you are in an affected region, It is recommend that you identify your most critical systems and set extra maintenance dollars aside specifically for protecting and maintaining those systems (systems that support production or other revenue generating operations are key) - anticipate extra maintenance, service, increased water treatment chemical consumption, frequent filter changes on air handlers, overtime or investment in preventative technology such as Air Intake Filters that stop the insects and debris from entering your systems).
3. Research your alternatives. Water filtration and air intake filtration are two good options. Depending upon the level of protection you are seeking, each provide varying degrees of protection - Water filtration will help you to manage the insects and other airborne debris after it has entered the cooling tower and will protect down stream systems including chiller and heat exchanger; however, water filtration does little to protect the cooling tower where most of the maintenance will be required. Air Intake Filtration Systems that mount to the outside of the cooling tower or other air intake openings (as in chillers and air handling units) will filter the air as it is entering the system stopping the debris at the point of entry and protecting your entire system. Long after the Cicadas have come and gone, use of Air Intake Filters will provide long term protection against annual airborne debris (including: cottonwood seed, small & large insects (e.g., May Flies / Fish Flies, Lady Bugs, Cicadas), leaves, pine needles, paper and wrappers, harvest chaff, construction debris, birds and more).
Anticipation and Prevention is Key Knowing if you will be affected and developing a plan of action is the first step in avoiding impact to your operation. Taking a preventative approach is usually more cost effective than simply reacting when the problem occurs and can literally save you thousands of dollars while keeping your operation running smoothly.
What Not To Do
When airborne debris becomes a serious problem, the natural tendency is to look for something to cover the intake opening to prevent entry of the debris. Never use window screen, roll filter media or mesh purchased from a hardware store to cover air intake openings on cooling towers or, evaporative condenser units; these materials are not designed to allow proper airflow and can drastically increase static pressure, increase energy cost and impede cooling efficiency. When using air intake filtration it should provide less than 1/10inch drop in static pressure (as measured in inches H2O). Air intake filtration specifically designed for use on cooling towers and evaporative condensers and chillers is highly recommended.
Air Conditioning - Advantages of a Heat Pump
What is a Heat pump?
A heat pump is a home appliance (similar to a fridge freezer) that heats and cools the atmosphere in the home. It offers home owners comfort that is normally reserved for high-rise office buildings, five-star hotels and executive apartments. It heats, cools, dehumidifies and continuously filters the air of dust and other impurities. It also circulates the air - without heating or cooling - to eliminate stuffiness. A typical heat pump is two units - an indoor unit, and an outdoor unit. For this reason, they are often called “split systems”. Many have remote controls for maximum convenience.
How does it work?
A fridge transfers heat from its food compartment to the coil at the back. Like a fridge, it can be reversed so that the heat flow goes the other way. Heat pumps transfer heat from outside air into the home in winter, and transfers heat from inside the home to outside air in summer.
But how can it heat the home and winter when it is freezing outside?
A home freezer can take the temperature of its food compartment below 0°, in fact as low as -6°C. If it can remove heat from inside a freezer to below 0°, the same process - used in the heat pumps - can extract enough heat from cold outside air to warm the home. Although our body’s feel cold at these low temperatures, there is still a lot of heat energy in the outside air at 0°C.
What size will I need for my home?
Every home is as individual as its owner. The key to selecting the right size heat pump for your home is an accurate estimate of the heat that will need to be transferred into your home in winter for heating, and out of your home in summer for cooling. This needs to be carried out by an experienced and qualified specialist like Excel Refrigeration and Air Conditioning Ltd.
What factors will affect the size of heat pump I need?
The amount of heating needed will depend on the heat loss through walls, windows and roofs. To minimise heat loss and before you invest in the heat pump, it is always a good idea to properly insulate walls and roofs first. In particularly cold climates double glazing windows will insulate them and keep heat loss to a minimum. By insulating first, the size of heat pump selected will generally be smaller and therefore be cheaper to install and run.
The northern aspect of the home is also an important factor. North facing rooms will catch the sun better and more generally need less heating. Conversely, South facing rooms tend to be colder and will need more heating.
Do heat pumps take up a lot of room?
No. Heat pumps are designed to be unobtrusive in size, neutral decor and low noise levels. There are also different types of heat pumps, from a stylish through the wall packaged unit to different varieties of split systems. The least obtrusive is a ducted split system. This can be hidden in the ceiling or under floor and only the grilles for distributing the air are visible.
How much does cost to buy and install a pump?
As stated before, every home is as unique as its owner. The installed cost of the heat pump will therefore be unique for each home and will depend on the size and type of heat pump installed. As an example, a standard three-bedroom 100 m2 timber framed New Zealand home may use a 5.5 KW hi-wall split system heat pump to warm the lounge, dining and kitchen as one open plan area. This type of installation would currently cost just over $3000 plus gst to install. A very broad guide to heat pump installed cost is $60-$100/m2 plus gst of served area. Served area is the area being heated and excludes laundries, garages, toilets and other utility areas in the home.
How much does cost to heat my home with a heat pump?
To answer this question the amount of heating that is currently necessary will need to be known. For the purpose of explanation, assume 5KW of heating is needed. Electrical heating appliances are normally 100% efficient so for 5 KW of heating one will need to pay for 5 KW of electric energy. Gas heating appliances are less than 100% efficient. For discussion, let’s assume that they are 90% efficient. This means, to gain 5KW of heating, one has to pay for 5.6 KW of gas energy. Although gas may be cheaper per KW, one has to use more of it to produce the same heating effect. Heat pumps transfer heat from outside air and in this way produces two to three times more heat. Its efficiency - if it can be called that - is 200% to 300%. This means for 5 KW of heating, one will only pay for around 2 KW of electric energy. Heat pump heating is roughly a third of the cost of electric heating and about half the cost of gas heating.
How can a heat pump be cheaper to run when it has more moving parts?
A heat pump uses electricity to transfer heat. Electric heaters convert electric energy to heat energy and are thereby limited by the amount of electricity used. A heat pump has no such limitation and can transfer twice to three times the heat from outside air than can be converted from the electricity at uses.
Are heat pumps noisy?
No, they are generally not noisy. The source of the noise in a typical heat pump is air impinging on the grille as it is forced out of the unit. Air noise is marginally higher than ambient background noise and is usually not distracting.
Do they dry the air: like on an airplane?
Heating or cooling air changes its characteristics. Heating air increases its ability to carry moisture and suspension by reducing its relative humidity content. This is the same process used in clothes dryers. Cooling air causes the moisture in the air to condense out of suspension. This reduces the absolute humidity content of the air and is the process used in the humidifiers. Either way, reducing moisture in the home is beneficial by discouraging mould and mildew by producing a healthier living environment.
Are they reliable?
Yes. Heat pumps are reliable. They use the same process as the home fridge or freezer and have the same level of dependability and useful life expectancy.
How easy are they to repair?
Provided the service person is experienced and qualified, repairing heat pumps is as straightforward as repairing the fridge or freezer. For repairs, talk to Excel and Refrigeration and Air Conditioning Ltd.
Do they need servicing?
Like cars, heat pumps should be regularly serviced for optimum operation. This involves cleaning the air filter and perhaps checking that the refrigeration charge is correct. It would be a good idea to service the pumps just before the beginning of each extreme season i.e before winter and again before summer.
How are heat pumps better than other forms of heating?
Apart from being cheaper to run, heat pumps offer other benefits that heating only systems cannot.
1) Heat pumps don’t burn oxygen or create stuffiness like open fires do. They are designed for all year round comfort, not just for four months during winter.
2) They produce low-density heat which is safer for children and elderly, unlike fires, oil filled or electric fan heaters.
3) They are unmatched for convenience and ease-of-use.
Showa Denko K.K. Develops New Condenser for Car Air-Conditioners
Tokyo, Japan,- (JCN Newswire) - Showa Denko K.K. (SDK) has developed a new high-performance condenser for car air-conditioners and started selling the product under the trade name of “NRT (new refrigerant tube) III.” NRT III has already been adopted in Suzuki Motor Corp.’s new model Every launched in August this year. In addition, some Japanese and foreign carmakers have decided to install the product in several new models they will launch in and after 2006.
A condenser is a major component of car air-conditioners, consisting of tubes for circulation of refrigerant, headers, and fins for exchange of heat between refrigerant and air. In response to carmakers’ request for smaller, lighter and higher-performance condensers, SDK has developed NRT III by combining good mechanical design, selected aluminum material, and precision fabricating technology to maximize heat exchange efficiency.
In NRT III-, the tubes and inner refrigerant paths are produced by folding and joining high-speed-rolled aluminum sheets . Compared with conventional products based on an extrusion process, the new product has achieved performance improvement of more than 20%. Specifically, NRT III has the following advantages:
1. As the new process enables formation of refrigerant paths with more complexity and precision, the heat transfer area has been maximized, resulting in higher liquefaction efficiency.
2. The thickness of the tube wall has been reduced to 1.1 mm, resulting in the production of a smaller condenser. Under the conventional extrusion process, the thickness has already reached its limit of 1.5 mm.
3. The internal volume of refrigerant paths has been reduced, lowering the required volume of refrigerant.
4. The load of refrigerant compressor has been reduced as fins and headers have become thinner with higher performance. This ultimately contributes to the production of lighter cars with higher fuel efficiency.
SDK has already developed new types of evaporators and heater cores with thinner tubes and fins as well as optimized shapes. This has resulted in performance improvement of 5-10%. Those evaporators and heater cores have been adopted by GM and in the process of being adopted by other carmakers in Japan and abroad.
Garage Heater suits high humidity and dusty areas
With BTU inputs of 30,000, 45,000, 60,000, and 75,000, Hot Dawg[R] Model HDS draws combustion air from outside, optimizing seasonal heating efficiency and minimizing concerns about dusty, dirty, or humid applications. Operating with natural gas or propane, unit features tubular heat-exchanger design and is certified for residential and commercial use. Applications include greenhouses, tool sheds, wet garages, and hostile environments.
With cold weather and snow pounding the Midwest and winter officially beginning soon, Modine Manufacturing Company (NYSE:MOD), a world leader in heat transfer, is launching a new product from its Commercial HVAC&R Division, the Hot Dawg(R) separated combustion garage heater. The Hot Dawg Model HDS is an extension of the successful Hot Dawg garage heater product line that has sold more than 100,000 units in the last five years. This new design will offer improved efficiency, greater durability and less maintenance.
“This is a much anticipated product because it gives users a choice that can withstand more humid environments, more dust and dirt, and has lower maintenance than our current best selling Hot Dawg garage heater,” said Wayne Canfield, Modine’s General Manager of Commercial HVAC&R. “Some of our customers told us they needed a unit heater that could pull air from the outside and work in the wettest of environments. So we’ve spent the last year perfecting our Hot Dawg heater technology to produce another option. This is a product we think will become the leader of the pack.”
The big difference in the new Hot Dawg separated combustion heater is that it draws its combustion air from the outside. This ensures the unit always has plenty of fresh, clean air to breathe, and will reduce concerns about dusty, dirty or humid applications. In addition, by drawing the combustion air from the outside, the overall seasonal heating efficiency is increased. This is especially useful for well insulated buildings where city ordinances or building codes require heaters to use outside air. It could also be used in greenhouses, tool sheds, wet garages, and hostile environments which have high humidity, and lots of dust and dirt, including commercial and industrial areas.
The new HDS is based on the existing Hot Dawg heater platform, with BTU inputs of 30,000, 45,000, 60,000 and 75,000. As with the original Hot Dawg heater, the new HDS is certified for residential and commercial use and features Modine’s field-proven tubular heat-exchanger design. Both the HD and the new HDS are designed for use with natural gas or propane with fast, easy installation. The products are easy to service and trouble-shoot, and are backed by a 10-year heat-exchanger warranty.
From bacteria to biogas
Using an anaerobic reactor, Boise Cascade in Jackson, Ala., has transformed an environmental cost into an energy resource
Sometimes, dollars spent on environmental compliance seem to disappear into a black hole, never to return. But for the Boise Cascade mill in Jackson, Ala., an anaerobic reactor has offered “an innovative way to comply with MACT I foul condensate treatment requirements,” says Richard Garber, Boise’s environmental manager for the paper division.
Boise’s anaerobic reactor is innovative not only due to its technology and the relative rarity of its application within the North American pulp and paper industry, but also because “it is about a zero net cost to operate,” according to Trey Wilson, engineering/ environmental manager for Boise’s Jackson mill. This is especially significant when compared with other EPA-approved methods for foul condensate removal, such as hard piping and steam stripping.
The anaerobic reactor’s low operational costs stem from its ability to convert methanol into a methane-rich biogas that is burned in the mill’s combination burner, offsetting overall fossil fuel consumption. Adding to its appeal is the fact that the reactor has been extremely effective from an environmental standpoint, as well as easy to operate and maintain. However, the industry was not quick to embrace the technology when exploring foul condensate removal options in the mid-to late 1990s.
“Most mills considered the anaerobic reactor too risky,” says Wilson. “The technology isn’t applicable in every situation, but extensive trials showed it was a good option for us. It has exceeded expectations and is one piece in the large puzzle that makes us a low-cost facility.”
Foul condensate treatment options
Boise’s Jackson, Ala., mill produces 512,000 tpy of uncoated freesheet on two paper machines, as well as 82,000 tpy of bleached softwood kraft pulp and 190,000 tpy of bleached hardwood kraft pulp. Six 6,500-ft^sup 3^ batch digesters are used to produce the 680 tpd of bleached softwood and hardwood kraft pulp used by the paper machines.
The EPA released a preliminary draft of MACT I regulations as part of the Cluster Rules in late 1993, although the final regulations were not issued until April 1998. Among other things, these regulations require mills to collect and treat foul condensates as a means of reducing hazardous air pollutants (HAPs), primarily methanol, in mill emissions.
The condensate streams for treatment at kraft pulp mills are: blow heat accumulator, turpentine underflow, evaporator (from the first liquor feed stage), and low volume high concentration (LVHC) and high volume low concentration (HVLC) gases. Specifically, the mills are required collect and treat these condensates for a minimum 92% removal or a total mass removal of 10.2 lb/ bone dry ton (bdt) of pulp. The EPA stipulated three options for treatment:
1. Recycle of condensates to process equipment
2. Hard pipe condensates directly to the wastewater treatment system
3. Treat to reduce HAPs in condensates by use of a steam stripper or other technology
In anticipation of the final MACT I regulations, Boise began a research and development project in 1995 to assess the use of an anaerobic plant for treating HAPs. Though uncommon in the pulp and paper industry (see sidebar, p. 31), the technology had seen widespread application in municipal and industrial wastewater treatment, especially the food and beverage industries. Boise, however, recognized the technology offered the potential benefits shown in Table 1.
Backed by a “strong research and development group,” says Wilson, the company decided these benefits warranted installation of a pilot-scale anaerobic reactor at Jackson in June 1996, which operated for three months. Other pilot programs were conducted at Boise’s Wallula, Wash., and St. Helens, Ore., mills. These and other supporting trials offered insight on black liquor and turpentine toxicity, biogas composition, and micronutrient formulation that were integral to the design of the Jackson mill’s full-scale system.
According to Wilson, the cost for the anaerobic treatment plant was “comparable to a steam stripper system.”
Anaerobic reactor basics
Anaerobic biological treatment is a wastewater treatment process that removes organic constituents from a waste stream. Anaerobic degradation is a multi-step biological process involving two basic groups of bacteria. One group consists of bacteria that hydrolyze and ferment complex organic compounds into simple organic acids. The other group converts the organic acids produced by the acid formers into methane gas and carbon dioxide gas, the combination of which is biogas.
Figure 1 shows the main components and flow of the anaerobic treatment plant at Jackson. Foul condensates from an in-mill collection tank are pumped to a 260-m^sup 3^ buffer tank and travel through a non-contact evaporative cooling system before entering the mix tank that feeds the anaerobic reactor. In the mix tank, condensates are combined with treated condensates. The pH is controlled with magnesium hydroxide, and micronutrients - mostly trace metals - are mixed in to facilitate the methanol-to-methane conversion.
“Most mills considered the anaerobic reactor too risky,” says Wilson. “The technology isn’t applicable in every situation, but extensive trials showed it was a good option for us. It has exceeded expectations and is one piece in the large puzzle that makes us a low-cost facility.”
Foul condensate treatment options
Boise’s Jackson, Ala., mill produces 512,000 tpy of uncoated freesheet on two paper machines, as well as 82,000 tpy of bleached softwood kraft pulp and 190,000 tpy of bleached hardwood kraft pulp. Six 6,500-ft^sup 3^ batch digesters are used to produce the 680 tpd of bleached softwood and hardwood kraft pulp used by the paper machines.
The EPA released a preliminary draft of MACT I regulations as part of the Cluster Rules in late 1993, although the final regulations were not issued until April 1998. Among other things, these regulations require mills to collect and treat foul condensates as a means of reducing hazardous air pollutants (HAPs), primarily methanol, in mill emissions.
The condensate streams for treatment at kraft pulp mills are: blow heat accumulator, turpentine underflow, evaporator (from the first liquor feed stage), and low volume high concentration (LVHC) and high volume low concentration (HVLC) gases. Specifically, the mills are required collect and treat these condensates for a minimum 92% removal or a total mass removal of 10.2 lb/ bone dry ton (bdt) of pulp. The EPA stipulated three options for treatment:
1. Recycle of condensates to process equipment
2. Hard pipe condensates directly to the wastewater treatment system
3. Treat to reduce HAPs in condensates by use of a steam stripper or other technology
In anticipation of the final MACT I regulations, Boise began a research and development project in 1995 to assess the use of an anaerobic plant for treating HAPs. Though uncommon in the pulp and paper industry (see sidebar, p. 31), the technology had seen widespread application in municipal and industrial wastewater treatment, especially the food and beverage industries. Boise, however, recognized the technology offered the potential benefits shown in Table 1.
Backed by a “strong research and development group,” says Wilson, the company decided these benefits warranted installation of a pilot-scale anaerobic reactor at Jackson in June 1996, which operated for three months. Other pilot programs were conducted at Boise’s Wallula, Wash., and St. Helens, Ore., mills. These and other supporting trials offered insight on black liquor and turpentine toxicity, biogas composition, and micronutrient formulation that were integral to the design of the Jackson mill’s full-scale system.
According to Wilson, the cost for the anaerobic treatment plant was “comparable to a steam stripper system.”
Anaerobic reactor basics
Anaerobic biological treatment is a wastewater treatment process that removes organic constituents from a waste stream. Anaerobic degradation is a multi-step biological process involving two basic groups of bacteria. One group consists of bacteria that hydrolyze and ferment complex organic compounds into simple organic acids. The other group converts the organic acids produced by the acid formers into methane gas and carbon dioxide gas, the combination of which is biogas.
The main components and flow of the anaerobic treatment plant at Jackson. Foul condensates from an in-mill collection tank are pumped to a 260-m^sup 3^ buffer tank and travel through a non-contact evaporative cooling system before entering the mix tank that feeds the anaerobic reactor. In the mix tank, condensates are combined with treated condensates. The pH is controlled with magnesium hydroxide, and micronutrients - mostly trace metals - are mixed in to facilitate the methanol-to-methane conversion.
The water/sludge mixture is directed downwards to the bottom of the reactor via the concentric “downer” pipe (8), resulting in the internal circulation flow. The effluent from the first compartment is post-treated in the second, low-loaded compartment (9), where remaining biodegradable COD is removed. The biogas produced in the upper compartment is collected in the top 3-phase separator (10), while the final effluent leaves the reactor via overflow weirs .
(11).Biogas from the reactor is passed through a sediment trap and is compressed for transfer to the combination boiler.
Researchers Advance MANUFACTURING TECHNOLOGY
The annual gathering of North America’s manufacturing research community, highlighted work done by manufacturing’s academic elite
The annual meeting of the North American Manufacturing Research Institute of the Society of Manufacturing Engineers, NAMRC 34, was held in Milwaukee May 23-26 at Marquette University. An international forum on manufacturing research, NAMRC is described by SME as “an annual conference of the international community of researchers whose works contribute to the furthering of manufacturing technology.”
The keynote speaker at NAMRC 34, John Gurda, presented the talk Made in Milwaukee: Our Manufacturing Heritage. Gurda is the author of 15 books on Milwaukee, and in his presentation he discussed the rise and decline of manufacturing in the Milwaukee area. Among the talk’s highlights:
Transportation was the earliest industry because of the city’s deep natural harbor on Lake Michigan. Beginning in the early 180Os, Milwaukee was a major shipping point, because water travel was the dominant way of moving products and basic materials.
The first major change was the switch from just shipping to manufacturing, a trend that would last for decades. It was the era of the entrepreneur and small-shop operator who could cultivate and develop new ideas for a growing country. At the same time there was a strong immigration into the area, chiefly by Germans, many of whom were trained craftsmen. The result was the manufacture of products tied to area resources. In all cases, the engineering content of products was beginning to emerge.
At the same time, small specialty machine shops with one or several ambitious craftsmen began a number of America’s well-known companies. They included Harnischfeger cranes, Chain Belt, Alien Bradley, Allis Chalmers, Kearney and Trecker, and, of course, Harley-Davidson. Despite the linking of Milwaukee to beer, during that time, it was more a matter of gears than beer production.
Manufacturing the material for WWII increased Milwaukee’s manufacturing base even more, with some plants working 10-hr shifts, seven days a week.
However, the manufacturing scene began to change in the ‘5Os. The day of the small enterprise was fading. As foreign competition grew and new industries became dominant in other areas, Milwaukee’s manufacturing base began to contract.
Today, this manufacturing center, as many other former manufacturing giants in the US, has embraced service industries such as health care, data processing, finance, and insurance. In its peak manufacturing years, 57% of the Milwaukee area workforce was in manufacturing, Today it’s around 7%.
In his opening remarks, NAMRI/SME President Ralph A. Resnick commented on the sobering message from Gurda that manufacturing matters in the success of a city or a nation, and further that science is critical to manufacturing. He noted that to survive in a global economy it is necessary not only to be inventive, but to be able to transfer that information to stimulate the economy. It’s important that our nation should not only provide leading-edge discoveries, but have industrial champions that will get new technology onto the factory floor. NAMRC has the task of recognizing those developments during the time of research and overseeing the transition.
The Founder’s Lecture is designed to recognize members of the original group of NAMRC founders. For the 34th session, the talk was delivered by Betzalel Avitzur of Lehigh University (Bethlehem, PA) on the subject, Road Map for Tube Making: from Tube Sinking to Tube Drawing with Floating Plugs.
In his talk, Avitzur, who is an expert on tube manufacture, reviewed the history of tube making beginning with the Egyptians, who manufactured simple tubes chiefly for jewelry.
Almost 200 researchers saw 80 papers presented during NAMRC 34 in Milwaukee. The following excerpts from selected papers illustrate the nature and depth of the research work now being done on the science and technology of manufacturing.
The performance of a binderless CBN tool in interrupted or continuous hard turning has not been reported in scientific literature, according to the researchers. They set out to study this performance, and developed two new parameters to be used to characterize interruptions in machining. The first, interruption ratio (IR) equals uncut distance/cut distance. When a tool enters a sudden cut (e.g. a weld bead), the IR ratio is small. Zero IR means the tool is never out of cut. The second parameter, interruptions per unit length of cut (IL) is defined as the number of interruptions/length of cut. In longitudinal turning, the length of cut is the circumference of the cylindrical material being cut. Parameters IR and IL are used by the research team to characterize the severity of interruptions in hard turning.
Workplaces were prepared with interruptions of different shapes and frequencies. Binderless CBN performed better than the high-CBN insert in only one test-the case where IR is low and IL is high. Research demonstrates that IL affects flank wear in both binderless CBN and PCBN. Flank wear is characterized by groove formation by three-body-type abrasion caused by plucked-out CBN particles. At 120 m/min cutting speed binderless CBN offers no noticeable advantage over conventional CBN in tool life and surface finish. At a speed of 180 m/min, however the performance of the binderless CBN does not seem to deteriorate, unlike the PCBN tool.
Binderless CBN was found to produce thinner white layer than the high CBN tool at a cutting speed of 120 m/min. The binderless material has higher conductivity than the PCBN tool. Assuming that thermal mechanisms play a major role in white layer formation, then more of the frictional heat caused by flank wear is conducted into the binderless CBN and less enters the workpiece, reducing white layer formation. Because binderless CBN has higher thermal stability than PCBN, the heat may not damage the tool.
Researchers from three institutions, RM Arunachalam of the Mechanical Engineering Department, Sona College of Technology, Salem, Tamilnadu, India, M.A. Mannan, Mechanical Engineering Department, National University of Singapore, and Andrew Christopher Spowage, Precision Measurement Group, Singapore Institute of Manufacturing Technology, collaborated on Comparison of Surface Roughness and Residual Stresses Induced by Coated Carbide, Ceramic, and CBN Cutting Tools in High-Speed Facing of Inconel 718. Among the nickel-based heat-resistant superalloys (HSRAs), Inconel 718 is the most important and frequently used for the manufacture of aerospace gas turbine components. It’s a difficult material to machine, however, because of work hardening, lower thermal conductivity, and a tendency to adhere to the cutting tool. High-speed machining using coated carbide, ceramic, and CBN cutting tools is one approach to improving productivity, when machining Inconel 718. Considerable research has been done on turning and milling of this alloy with such tools; facing operations have not attracted much attention.
The surface roughness of the machined surface was measured after each test using a contact-type profilometer. Residual stress distribution was measured using the X-ray diffraction technique.
Cloaking the Arc with a Coat of Many Colors
Despite all the attention being paid to tank flammability reduction via inerting, we shouldn’t forget that TWA800 was a wiring initiated fuel-tank explosion. Could there be a simpler and more cost effective method of preventing aircraft electrical fires and fuel-tank explosions?
TWA800 and Swissair have both focused the attention of aviation authorities, airlines, crew and passengers on serious electrical malfunctions emanating from wiring with a record of in-service deterioration. In the case of the earlier ValuJet Flight 592 crash, the NTSB found that “jostled oxygen canisters” ignited. There’s also been persuasive anecdotal evidence that the fire was caused by faulty wiring. If VJ592 had happened after TWA800, would a finding against wiring have been more likely?
It all begs the question: why this abiding concern over aircraft wiring? What are the causes of the fires, and how do they propagate to cause such horrific accidents? Without delving too deeply into the technical specifications of different aircraft wiring types, because it is a very intricate and technical field, we can generalize. There are complex criteria that dictate the optimum wiring insulation for different applications–e.g., insulation resistance, dielectric strength, vibration resistance, fluid resistance, chemical inertness, smoke generation , weight, manufacturing and installation requirements, ease of handling, min. radius, topcoat flaking, etc.). Environmental conditions differ in certain areas of an aircraft and so wire- types with differing characteristics are required. At this stage of wiring technology no unique wire type meets all the necessary criteria. However, the high frequency vibration of flight can cause wiring to “strum” like a guitar string and so chafing is a major concern for all types. This aspect and insulation cracking are of paramount importance.
After TWA800, all parties agreed that high time aircraft, especially pre- 1992 constructs, were more likely to have a fire due to their aging wire (most 737s and 757s, post-1992, are fitted with Boeing’s designedly safer TKT wiring). Aging wire is susceptible to nicks, cracks and the chafing of its insulations, all of which generate daily smoke emergencies. Aromatic polyimide (DuPont’s Kapton, BMS13-51) and X-linked ETFE Polymers (Tefzel BMS 13-48, Raychem’s wire) were two wire-types that had exhibited age degradation. Cuts, nicks, cracks and chafing could cause the insulation to be breached (cracked into the conductor), raising the possibility of electrical arcs (short circuits) and arc-tracking.
Arcs And Arc-Tracking
An arc will occur when a powered conductor contacts a ground potential. This happens if the insulation has been compromised by rubbing against the airframe (chafing), or by wire-to-wire abrasion. Arcing will result in a high current flow which should actuate the applicable circuit-breaker (CB) or fuse. However, arc-tracking is a phenomenon whereby an electrical arc between two or more damaged wires sustains itself through a conductive path provided by degradation of the insulation for a measurable length. It is produced by leakage current, and the associated heat effect of the arc, which locally decomposes the wire insulation material into carbon residues and gasses. If simultaneous conditions are present , the low resistance carbon path may allow the current to flow between the conductors, sustaining the arcing along the wire . Because the current is flowing and not going to ground, the CB may not trip.
Conditions For Arc-Tracking
To initiate arc-tracking:
* At least two wires separated by a small distance with insulation at least cracked to the bare metal.
* An initial short circuit-condition.
* A high voltage through the wire.
* A current sufficient to sustain an arc. The presence of an electrolyte or conductive fluid on or in the immediate vicinity of the damaged wires can accelerate the carbonization and cause the more explosive flashover of wet arc- tracking.
Arc-Tracking Limitations
A laboratory can easily reproduce the phenomenon. When concurrent conditions are met along a measurable length, the arc will move along the concerned wires towards the power source, until it is stopped–i.e., when one of the concurrent conditions disappears. Or,
*The current value sustaining the arc reaches circuit-breaker tripping threshold.
* The conductors (core) of the wires come into direct contact.
*It encounters a connection ; a bundle attachment; or a bulkhead pressure seal.
* There is a divergence of the affected wires within the bundle layout.
It is not just the actual electrical arc and the possibility of arc- tracking that is the only risk. The insulation can also ignite and while still burning, drip onto thermal-acoustic blankets, leaked hydraulic fluid, dust, etc., and set them alight. This is also true in the case of the actual conductor. Beads of molten metal are an indication that arcing has occurred. In 1999, Tim Dobbyn of Reuters wrote, “All aircraft wiring ages, and it is not uncommon to find five to 10 insulation cracks per 1,000 feet of wire in active aircraft, a congressional subcommittee heard Wednesday”. A Boeing 747 features approximately 140 miles of wiring, which translates into 7,390 wire cracks.
pH control nerves of steel
Software overcomes common process industry temperature and acid problem areas
A steel caster is the most critical operating unit in a modern steel plant.
The caster transforms the liquid steel into solid slabs, ready for the rolling mill to produce the final product, steel sheets.
The liquid steel cools to form a molded shell, with the shape, thickness, and width established by the mold. The mold consists of water-cooled copper plates attached to steel water boxes, forming a rectangle.
Several thousand gallons of caster cooling water pump in per minute at high pressure through the mold to cool the steel. Since the water temperature affects the condition of the steel slabs, it is one of the most critical quality related process variables, and it needs to be tightly controlled.
Let’s look at what it takes to control effectively the caster cooling water temperature and pickle-line rinse water pH value. This feature will also discuss model-free adaptive (MFA) control technology, which is helping Nucor Steel to improve product quality and plant efficiency.
The mold water process
Nucor Steel’s Decatur, Ala., plant has a caster cooling water system that supplies non-contact cooling water to two 90mm medium thickness continuous slab casters.
During normal operations, two of the three pumps run and supply water flow at 3000-4000 gallons per minute, depending on casting machine status. Since the mold water leaving the casters so hot, it passes through three heat exchangers for cooling.
Controlling of the mold water temperature takes place by manipulating the cooling water flow to the heat-changers. Previously, three PID controllers regulated each of the three cooling water valves.
The goal is to control the temperature of the supply mold water to the casters at 95 or 96°F with no deviation of more than +/- 2°F during any system transients.
During the steady state, the PID based control system could maintain the mold water temperature well. However, during a caster start-up or tail-out, there could be up to eight degrees Fahrenheit deviation, which could cause product quality problems.
In addition, the system is sensitive to the ambient temperature change from winter to summer. PID controllers need retuning seasonally to make up for the fluctuations in the cooling tower operating conditions.
Challenge and analysis
1. During system-transients when a caster is starting up or shutting down, the temperature disturbance to the mold water leaving the casters can be quite large. The PID controllers controlling the temperature for the mold water leaving the heat exchangers cannot react fast enough to compensate for the disturbance.
2. The temperature that needs to be controlled is not necessarily the temperature of the water leaving the heat exchanger, but the temperature of the supply mold water leaving the expansion tank. Therefore, it is better to add a controller to directly control the supply-mold water temperature.
3. The challenge is the supply-mold water temperature loop will have a large time delay of about five minutes. It is difficult to use a PID to control this loop.
4. The ambient temperature variations due to seasonal changes cause the cooling water temperature and other operating conditions to change. The elimination of the manual tuning of PID controllers would be best and is desirable.
We learned about MFA control at ISA EXPO. MFA control is attractive to us because:
* MFA does not require the user to build a mathematical model for the process.
* It can adapt to fit new operating conditions.
* MFA can control complex systems.
* It is easy to use and maintain.
Unlike PID, which is just one controller, there are actually many different types of MFA controllers available, and each one solves a specific control problem.
Some MFA controllers can solve the type of control problems commonly seen in a large process plant.
This means, we can simply select the appropriate controller, do some straightforward parameter configurations having to do with entering the sample interval, process-acting type, and estimated process time constant, and then we are ready to launch the MFA controller.
Single signal control water
In February, we launched a MFA control system with two controllers. We selected a single in single out (SISO) controller to control the caster mold water temperature by manipulating all three cooling water valves at the same time.
We also selected an anti-delay controller to handle the actual supply-mold water temperature, which has a large time delay. A feedforward controller as part of the SISO controller can produce quick control actions to compensate for the large disturbances occurring during process transient conditions.
The system works as a cascade control system with Cl and C2 as primary and secondary controllers, respectively. C3 is the Feedforward controller. Processes 2 to 4 represent the sub-processes of the cascade system. The inner loop consists of C2 and P2, and the outer loop consists of C1 and P1, where Pl consists of C2, C3, P2, P3, and P4. Notice Pl as shown by the dotted line represents the process for Cl to control, where the process variable is the supply-mold water temperature. Since controller C2 is an MFA controller, the closed-loop dynamics of the inner loop will not change much, even though the process dynamics of P2 may change a lot. This means the interconnection of the outer loop and the inner loop becomes much weaker. A more stable inner loop contributes to a more stable outer loop, and vice versa.
Kanban Can Cut Inventory
Luvata, a manufacturer of stainless steel and copper products headquartered in London, faced two bottlenecks in its manufacturing process: knowing what to build and ensuring materials were on hand. The company established an electronic inventory control system, or e-kanban, to form a loop between its customer in Mexico and the actual production cell that makes the copper product. Within seconds of customers consuming product, the production cell manager now knows exactly what he needs to build and when to buy.
Kanban is a visual cue to manufacturers to replenish, said Tom Cutler, president and chief executive of TR Cutler, Inc., a manufacturing marketing firm in Fort Lauderdale, Fla. When a relationship begins between a manufacturer and a supplier, they define a service level agreement. This includes “items such as negotiated lead times, packaged quantities, order receipt confirmations, and advanced shipment notices,” which they need to spell out specifically. “An e-kanban system monitors to make sure each of these service level agreements is being met by the supplier in real time,” he said. “If they’re not, a series of alerts and notifications goes out to all parties. This gives everyone a chance to adjust their behavior to bring performance back in line in real time.”
E-kanban also makes all this real-time information available for historical analysis, Cutler said. It’s available over the internet 24 hours a day, so all parties can see trends in performance. Everyone is aware of late shipments, short shipments, and other supply chain performances, and “these visuals give everyone in the supply chain information about how to focus their energies.”
The old system at Luvata required personnel to send monthly Excel forecasts to the customer service representative, who entered it into the ERP system and re-entered data into the shop floor control system. Daily telephone calls changing order requirements meant the process had to start all over again, sabotaging efficiency in the manufacturing process.
The e-kanban system helps Scott Stringer, operations manager at Luvata’s Franklin, Ky., plant, link the customer’s demand with production efforts. The key is “trying to produce what they really need and streamlining the whole communication effort,” he said. Since it is Web-based, any computer that has access to the Internet can look at the e-kanban levels. So Stringer’s daily routine is, “get my cereal and bring up the Web site to see where the card levels are on the kanban. We’ll link up with customers via a third-party Web site kanban system. A large manufacturing firm will call the third-party company and say it wants the supply base delivered from kanban. Then the large manufacturer brings on one of its suppliers one by one,” he said.
The Luvata product (copper tube for condenser and evaporator coils) deals with microfins pressed inside a tube to increase turbulence and surface area for better heat transfer. “There’s a lot of effort and expense of capacity put in place to manufacture this tube,” Stringer said. That’s where the e-kanban helps. Copper prices three years ago were at 80 cents a pound; now they’re at $3 a pound, he said. With prices like that, “we need to bring inventory down and utilize capacity better.”
Firewall challenges
Firewalls can be a challenge in the e-kanban process, Stringer said, because manufacturers need a trusted port number with which to communicate. “Another challenge for us is we were going to our customers with this, and we had to combine benefits so they win too,” he said. “This brings down their inventory levels. It seemed with the old system “we would always be building the wrong part. The expediting going on was horrendous,” he said. If the customer was out of inventory, they’d call and request break down of the setup or overnight shipments.
The old process was to use SAP, an ERP system, which would try to generate a list of parts that were needed for the manufacturing plan. Customers would send a list, but they’d have to exactly execute the plan. So demand was constantly changing and elicited a round of e-mails. With the e-kanban system on the computer, “it linked our customer shop floor with our shop floor. We bypassed all the other management involved,” he said. “As they use a box of our parts on our shop floor, they go and scan the barcode, and that tells us through the Web site they used a box of these parts, so we build one box for them. That keeps happening 24/7.”
Anybody can use e-kanban, Stringer said, because you can plug in part numbers, give lead time and daily usage part information, and the system does the rest. “So basically it doesn’t care what it is, as long as it knows how much the supply pull or how much the tack time is,” Stringer said. It then calculates the number of cards in the system. “As long as each party is telling what’s being consumed, and the other party is telling what’s being built and shipped, we’ve linked that into our shop floor system, so that’s automated.”
Solutions Come In Many Forms
Technological advancements in thread mills, taps and tapholders, and CNC machine tools are enabling manufacturers to meet many of their production objectives for quality threading. These include reducing cycle time, increasing production, and eliminating costly scrap and associated downtime that result from broken tools.
Modern CNC machine tools feature synchronous rigid tapping and helical interpolation capabilities that are needed to control processes, which by their very nature are regarded as more complicated than traditional milling and drilling.
The most dog-eared pages in your shop copy of Machinery’s Handbook (Industrial Press, New York) are likely to be those dealing with the complexity of threading, including such technical aspects as ANSI and ISO standards, types and sizes of thread forms, and how and to what purpose threads are produced.
“Tapping is a process that goes back a long way, but the reality today is that it is much faster than ever before,” says Alan Shepherd, technical director, Emuge Corp. (West Boylston, MA). “CNCs that have synchronous tapping cycles, coolant through, and high-pressure coolant capability have provided significant advantages to the cutting process,” he adds.
“The basic perishable tool, the tap itself, has been developed to a point where tapping can be done at speeds formerly not practical, in large measure due to improvements in CNC controllers and machine tools, as well as new coatings, like our GLT-1, which enables us to run 20-30% faster in stainless and alloyed steels.
“What is high speed? If you were tapping cast iron at 70-80 fpm, or even 100 fpm, we can now bring that up to 200-250 fpm. We can double speed and sometimes quadruple it. Stainless steel that would normally be run at 15-20 fpm can be run at 60-90 fpm,” says Shepherd.
When tapping, the productivity of the operation is governed by the cutting speed (sfm) and feed per revolution is fixed to the pitch (thread per inch) of the thread being produced. Unlike drilling and milling tools, tapping feed rates cannot be increased unless the rpm is increased accordingly, to match the required thread pitch.
For high-speed tapping, Shepherd recommends quality tool holders and application-specific coated tools. “Years ago, when I conducted training seminars on tapping, the first thing I talked about was tap breakage. It always topped my list. Today it’s on the bottom of my list of topics. At the top is cutting oversized threads because modern taps have high rates of relief and require rigid collet-type holders to be able to run at high speeds,” he says.
The ability of the tap to follow the same cutting path as closely as possible is essential to extending tool life by minimizing tool wear. Coatings on taps and coolant-through capabilities are important to reduce the heat-generating friction that limits tap life. Tap holding and machine feed control are critical to minimize the effects of backlash and thrust that all modern machine tools will have to some degree, says Shepherd.
Emuge, which is a manufacturer of both taps and thread mills, as well as end mills, thrillers, and holders, recently moved into a new HQ and technology center in West Boylston, MA, where its customers can see machining demonstrations, receive training, and benefit from applications engineering.
At IMTS, Tapmatic Corp. (Post Falls, ID) demonstrated on a Haas VFl machining center how its selfreversing RDT and RCT tapping attachments produced a steady rpm, compared with fluctuating rpms when running a rigid tap driver. Tapmatic has designed its tapping attachments to compensate both axially and radially for the unavoidable discrepancies between the machine’s programmed rpm, feed, and traverse to produce exact thread pitch and precise hole locations.
In the demonstration, a machine load monitor showed spiking during machine reversal for rigid tapping. However, there was very little loadabout one-fourth as much-when the Tapmatic self-reversing tapping attachment was used. Less load translates into reduced machine wear and energy costs. In addition to CNC machining centers, Tapmatic self-reversing tapping attachments are also available for conventional drill presses and milling machines, manual or automated equipment, as well as for CNC machining centers or CNC lathes with nonsynchronous tap cycles.
An increasingly popular alternative to tapping is thread milling, which traces its use back to aerospace applications in the Gemini Space Program. The drawback at the time was that engineers had to write programming manually, in the absence of helical interpolation routines now commonly available on CNC machining centers.
The basic distinction between tapping and thread milling suggests applications where each is likely to be preferred. As holes get larger and deeper, tapping takes more spindle power. There is always the danger of broken taps that lead to scrapped workpieces, downtime to remove broken taps from high value workpieces, and the recutting of chips.
Thread mills can be of a singlepoint (tooth) design or a multi-point design. Thread mills generate the thread profile by helical interpolation. To generate the thread, a single-point cutter requires the same number of interpolations as there are pitches, i.e. an 8-pitch thread, 1″ (25.4-mm) long would require eight circular interpolations around the workpiece threaded diam. A multipoint cutter, which is essentially a series of single cutters on one body/flute, can normally complete a screw thread in one revolution of the work.
Advent Tool and Mfg (Lake Bluff, IL), a supplier of thread and form milling products in solid carbide, carbide-tipped, and indexable tools, describes helical interpolation: “Thread milling requires the use of a machining center capable of helical interpolation. This means that the machine must be capable of three-axis simultaneous movement. Two of the axes perform a circular movement around the center of a plane while the third axis moves perpendicular (axially) to the circle’s plane the equivalent of one pitch in a 360° circle. For the most part this is achieved by using standard G-code commands.”
“When asked what we do,” says Advent’s Ross Wegryn-Jones, “my standard answer-my ‘pitch,’ if you will-is that at root we are a formmilling company that specializes in thread forms. Thread forms are predefined ANSI and ISO standards. We duplicate that form and put it on the shelf, ready to go. If someone orders a 3-mm pitch thread mill, we have it. We have a good milling platform that is a very good ground tool body and insert-locking and locating system.”
Thread mills are selected based on the application, considering the number of parts or holes that are being produced. In the case of larger lot sizes, cycle time may be an issue along with tooling cost. This is where a single or multiple-flute replaceable insert thread mill would be the best choice.
The main advantage of an indexable thread mill is the ability to change out inserts quickly and inexpensively while utilizing the benefits of increased wear resistance and tool life inherent in carbide. In the case of smaller holes, where replaceable indexable tooling is not available, solid carbide or carbidetipped tooling should be considered.
For selecting the right thread mill, Advent advises having ready access to the following application parameters:
* Major and minor diam of the thread to be milled
* Length of the thread form
* Pitch (number of threads per mm or inch)
* Material to be thread milled and its inherent machining properties
* Relative quality of fixturing and rigidity of machining center
* Amount of tool extension; the shorter, the better
“Due to the cutting action of a thread mill, the forces acting on the tool and the workpiece differ greatly from those that occur with traditional tapping. The more rigidly the part is fastened to the fixture, the faster you can thread mill. The speeds and feeds are maximized when vibration of the part and fixtures is minimized,” says Wegryn-Jones.
“There’s a lot of interest in thread milling among customers and engineers as well as a lot of intimidation about it, but once they have seen it in action and try it, they love it,” says Don Halas of seco Tools Inc. (Warren, MI). “Thread milling works in many key areas, especially in hightemperature alloys like Inconel, Waspaloy, stainless steel, and titanium, where taps are more likely to break. Another common application is tapered NPT threads for pipe where you eliminate the need for taper reaming prior to tapping, getting rid of an entire step.”
Halas points to the quality of thread produced by thread milling. “Thread milling produces a superior thread because thread milling is free cutting. Chips are very small and recutting chips as in tapping is not a problem. Thread milling can be done with the lightest duty machine in the shop, as long as it has helical interpolation,” he adds.
“A rule of thumb for cycle times in typical material is that in 1/2” [12.7-mm] diam holes and smaller, tapping is quicker. In larger diam holes, thread milling is quicker,” says Halas. “Although you also need to consider that if a tap breaks and you scrap the part, this can still blow your cycle time.”
The consequences of breaking a tap when threading a small hole in high-temperature alloys, however, is far more serious. “In this instance, it’ll take time to get that broken tap out, because these are intrinsically expensive parts that cannot be readily scrapped,” says Halas. “So, with high-temp alloys, you should really look at thread milling as a first machining choice.”