Tools and Machinery of the Granite Industry
A small number of basic finished dimension stones made up the great majority of granite shed production. For gravestones and private monuments, there were dies (the main stone on which the lettering and ornamentation was cut), bottom bases, second bases, markers (a small stone set either flush to or raised from the ground level), posts (indicating the corners of a cemetery plot), boulders (natural-shaped stones, usually rock face finished), tablets (a die whose lower portion is buried underground), crosses, shafts, and columns. For mausoleums and vaults, there were roof stones and sidewall stones. For buildings and large public monuments, there were ashlars (four- to twelve-inch thick blocks that were carefully dressed on top, bottom, and sides so they could be set in a wall with uniform and tight joints), columns, capitals, steps, foundations, bas-relief panels, and statuary. The finished surfaces applied to these stones were rock face-an irregular natural looking surface produced by chipping out pieces of stone with a chisel; hammered-a powdered or steeled surface produced by hand or pneumatic bush hammer and of varying degrees of smoothness; polished-a mirror-like finish produced by a polishing machine; and carved-a wide variety of surface shapes and textures produced by hand tools, by a small pneumatic carving tool, or by sandblasting.
The finishing of granite involves only two basic processes-shattering and abrasion. Shattering is the crushing and breaking of granite by the impact of a steel tool. The bull set, hand set, hand point, chisel, circular saw, surfacing machine, cutting lathe, and the first two stages of polishing machine use are examples of tools and machines that work by shattering. Abrasion is the wearing away of granite by an abrasive forced under pressure along the stone’s surface. The gang saw, wire saw, Carborundum saw, grinding machine, polishing lathe, and the last stage of polishing machine use are examples of tools and machines that work by abrasion. Sandblasting appears to employ a combination of the two processes.
Much of the progress in granite finishing can be credited to advancements in abrasive technology. Natural abrasive materials were used from ancient times, including beach sand, whetstone dust, red limestone powder (Tripoli), emery powder, tin oxide putty, garnet dust, and iron filings. In the latter part of the nineteenth century, manufactured abrasives began to appear, including flint shot, cast iron shot, chilled cast iron shot, broken iron shot, chilled steel shot (Figure 1), broken steel shot, and emery bricks. During the twentieth century, artificially synthesized abrasive materials entered the market, including artificial diamonds, silicon carbide, aluminum oxide, boron carbide, cubic boron nitride, cerium oxide, tungsten carbide, and contained abrasive bricks. Contained abrasive bricks are molded blocks of abrasive contained in a binding-matrix material such as magnesite and chloride. They are used for the initial stages of polishing and are more economical to use than loose abrasives.
Evolution of Shed Architecture
Many farmers harvested granite boulders from their fields and shaped the stone during the winter slow time in unused spaces in a barn or shed. The earliest commercial stone sheds were designed around the boom derrick-either a round shed with a centrally located inside derrick that could reach any point in the shed or a horseshoe-shaped shed that defined a semi-circular yard with an outside derrick that could reach all the shed doors and any point in the yard (Figure 2). The final form was the straight shed having a rectangular footprint and designed for an inside overhead traveling bridge crane (Figure 3). One or two cranes could run along tracks that ran the full length of the shed and by this means reach any point in the shed. Whereas granite quarries were typically located at higher hilltop elevations where much of the overburden had been glacially removed, granite sheds were usually located in the valleys, often in an existing town, where worker housing and water or electric power were available.
Granite sheds needed to be provided with a variety of supporting services such as compressed air, water, heat, light, and dust removal. Compressed air was usually supplied via 4-inch diameter threaded iron pipes that went down both sides of the shed. Each pipe had a smaller-diameter steam pipe inside to warm the air and lower its relative humidity to prevent freeze up of pneumatic tool exhaust ports. Heating also yielded an added quantity of compressed air at a lower cost compared to that produced by a compressor. Smaller feeder hoses went to each granite cutter’s or carver’s workstation- called a banker-and surfacing machines with a shutoff valve for each (Figure 4). Water pipes, with either well or cityprovided water, went down both sides of the shed. The horizontal and vertical grinders required large quantities of water to keep the dust down. Considerable water was also used in the tool grinding room.
Grinding Gets Flexible
Accuracy and process flexibility drive innovations in today’s abrasive machining equipment
Customers are demanding more flexibility, higher precision, increased throughput, and longer life for grinding machines. Suppliers are meeting these demands with better machines that feature linear motors, improved abrasives, and multiple wheels and spindles.
A continuing positive trend for the abrasive-machining industry is the transfer of operations from aerospace and automotive OEMs to outside suppliers. Those suppliers need new equipment to meet demand from their customers in Asia, Europe, and South America, as well as the US.
Softer materials that were formerly the domain of grinding are now being machined using EDM or hard turning. “Frankly, the continuing trend towards harder materials, such as Inconel, is what is keeping the grinding industry alive,” says Vic Truelsen of Okamoto Machine Tool Works Ltd.
“In the automotive powertrain market, tolerances are 30-50% tighter than they were five years ago,” says Russell Kaiser, vice presidentengineering, Cinetic Landis Grinding Corp. According to Truelsen, tolerance ranges demanded by industry have gotten tighter as well. In both automotive and aerospace, tolerances on parts are being held to a higher C^sub pk^ tolerance than in the past. “Typical industry C^sub pk^ standard tolerances of 2.0, 1.66, and 1.33 are reducing print tolerances to 40-60% of the total tolerance allowed,” observes Truelsen.
For Drake Manufacturing Services Inc. Tighter tolerances are driven by the market need to reduce noise in geared systems, whether it be automotive power steering, industrial gearboxes, or speed reducers. “Gearbox components that were at AGMA 8 requirements [American Gear Manufacturing Association] in the past are now being specified at AGMA 10-11,” says Jim Vosmik, president and CEO of Drake.
There are different ways to offer flexibility, including multiple spindles, multiple grinding wheels, or single spindles with automatic wheel changers.
Russell Kaiser agrees that “our customers need to react to market changes quickly and cheaply.” Michael DiVentura, a Cinetic Landis vice president, explains that “customers are now demanding a part-changeover in minutes, if at all possible.” Some of the company’s customers are running multiple parts on the same line, calling for on-demand setup.
Changes to the design of their machines and accompanying processes have allowed Cinetic Landis to meet this challenge. Old grinding machine designs were dedicated; new designs are built with rapid changeout in mind. In one example, multiple spindles on one machine enable a customer to do multiple crankshafts on the same production line.
Drake Manufacturing also offers multiple operations in a single machine as an answer to the need for both flexibility and minimal capital expenditure, Vosmik says. An example is the Drake Universal External/Internal Thread grinder. It has multiple spindles and multiple wheels for shops with both internal and external thread-grinding requirements. Drake is also introducing a flexible grinder that can do flutes and spiral points in one operation.
Flexibility can also be had from a single-spindle machine equipped with an automatic wheel changer. The new Blohm Prokos machine from UGT offers an optional ATC system for its single spindle, allowing complex part grinding with a single setup by combining grinding, milling, and drilling operations.
Comparison of Three Strategies for Preventing Hypothermia in Critically Injured Casualties during Aeromedical Evacuation
Critically injured patients are at risk for hypothermia. This study determined the efficacy of three hypothermia prevention strategies: the ChillBuster warming blanket, ChillBuster with a reflective blanket, and two wool blankets. A quasi-experimental design was used to compare changes in core temperature. Following resuscitation from hypovolemic shock, 20 swine were assigned to one of the three interventions, placed in an environmental chamber set to reproduce in-flight conditions onboard a military cargo aircraft (50°F/airspeed 0.2 m/s), and monitored for 6 hours. A repeated measures analysis of variance and least-squared difference post hoc were performed. The ChillBuster/reflective blanket group was significantly warmer than the ChillBuster only group and the wool blanket group.
Under operational conditions, military medical personnel provide patient care In a variety of austere settings including deployable field hospitals, nonmedical buildings, and during aeromedical evacuation (AE) in military cargo aircraft. Since the beginning of Operation Enduring Freedom/Iraqi Freedom, the Air Force AE System and Critical Care Air Transport Teams have transported more than 1,000 critically ill/injured patients. AE may involve patient transport from the combat zone to definitive medical care in Europe and the United States. During these medical flights, which may last from 1 to 14 hours, casualties are exposed to nine stresses of flight.1 These nine stresses include decreased barometric pressure, hypoxia, noise, vibration, gravitational forces, dehydration, third spacing, fatigue, and thermal stress. Thermal stress is the particular focus of this article. Onboard the military cargo aircraft, the temperature decreases dramatically during the first 60 to 90 minutes of flight, reaching an average temperature of 59°F (15°C),2 which may place the casualty at risk for developing hypothermia. Exposure to a cold environment can also occur in a variety of combat environments and hypothermia is a common medical condition encountered in recent combat operations.
In addition to the risk of primary hypothermia due to exposure to a cold environment, trauma victims are at further risk for secondary hypothermia due to an inability to produce body heat because of impaired oxygen consumption.5-7 Body heat production is necessary to maintain normothermia if the ambient temperature is less than 28°C.8 Trauma victims are at further risk for hypothermia because resuscitative measures such as mechanical ventilation and the administration of large volumes of room temperature intravenous (FV) fluids independently cause hypothermia.9 In addition, medications used during patient transport such as sedatives, narcotics, and neuromuscular blockade prevent the warming effect of shivering thermogenesls.
To prevent hypothermia in the AE environment or on a cold battlefield, metabolic heat production and conservation must equal heat loss to the environment. Under conditions where the casualty has impaired thermoregulation and the environmental conditions further exacerbate heat loss, interventions to minimize heat loss and to transfer heat to the body are necessary. The austere environment of care associated with AE operations limits the availability and feasibility of resources to keep patients warm. Interventions typically used in a stateside hospital will not work or are not appropriate for this unique care environment due to Issues such as safety, electrical power requirements, and weight. In addition, field expedient methods such as warming FV fluids with the flameless element on the Meals Ready to Eat has limited utility during long distance transport.19 Based on the risk of hypothermia in combat casualties and the limited utility of many standard wanning devices, there was a need to evaluate alternative methods for preventing hypothermia during the initial field and evacuation phases of care for combat causalities.
The purpose of this study was to determine the efficacy of three hypothermia prevention strategies that are suitable for the operational AE environment. Specifically, this study compared the ChillBuster, the ChillBuster plus a reflective blanket, and two standard military wool blankets. Core body temperature was the measure of the efficacy of each strategy in preventing a decrease in body temperature.
Transformer Coolers feature portable design
Installed on transformer, ForZair(TM) HeatSink auxiliary coolers immediately reduce temperature of dielectric cooling oil. Units can be transferred from one overloaded substation to another, providing relief wherever it is needed most. They employ mono-aluminum extruded fin-tubes and Cardinal transformer oil pumps with glandless design that prevents leaks. To augment cooling on 1-60 Mva OA, FA, or FOA transformers, coolers come ready for fully self-contained operations.
Efficient transformer cooling wherever and whenever you need it London, Ontario - Unifin, a world-leading supplier of cooling equipment and transformer oil pumps and valves to the Power Generation and Power Transformer industries, offers ForZair(TM) HeatSink auxiliary transformer cooler. The strong performance of this portable and highly efficient cooler allows increased overload and extends transformer life.
The ForZair(TM) HeatSink cooler can be installed on a transformer quickly to immediately reduce the temperature of the dielectric cooling oil. With its small footprint, low profile and quick-connect hoses, the ForZair(TM) HeatSink cooler can be transferred easily from one overloaded substation to another, providing quick relief wherever it is needed most.
The ForZair(TM) line of coolers feature Unifin’s unique Mono-Aluminum Extruded Fin-Tubes and the industry’s best plate fin technology, both of which provide optimal heat transfer efficiency and exceptional durability. The ForZair(TM) HeatSink coolers employ Cardinal Transformer Oil pumps, with a glandless design that prevents leaks in demanding transformer oil applications.
To augment cooling on 1Mva to 60 Mva OA, FA or FOA transformers these rugged portable coolers come ready for fully self-contained operations. The skid-mounted package is mounted on a durable frame designed for easy lifting by forklift or overhead crane.