Before the advent of the present day man equilibrium conditions had been established in many phases of nature. One of the phases which had reached this equilibrium condition was the coal and mineral deposits. As they stand, the stresses acting on coal and mineral deposits are in equilibrium,—any underground mining operation upsets this equilibrium. Shocks due to the unbalancing of stresses often time cause catastrophic roof-falls which kill and injure miners and damage equipment. Attempts are made to control these unbalanced stresses by choosing the proper method of mining and suitable method of roof support. About 20 years ago, the St. Joseph Lead Company in Missouri, in an attempt to get away from the awkward, bulky and expensive method of supporting roof by timber or steel and concrete, tried a new method of roof support.⁽¹⁷⁾ The new method was named “roof-bolting”. As the name implies, the lower exposed strata of the roof are bolted to the stronger less exposed strata above the mine opening. This new method has been used more and more in the past three years. At the present time over 200 companies are using this method of roof support.⁽¹⁶⁾ The roof bolting method of roof support has presented many problems which have to be solved before definite procedure for its use can be established. Some of these problems are: 1. How long should the bolt be. 2. At what angle should the bolt be inserted. 3. What should be the longitudinal and transverse center-to-center distance between the bolts. 4. What stress should be applied to the bolt when installed. 5. How often should the bolt be retightened. This thesis will be an attempt to solve some of these problems. / Master of Science

M.S.

All available information on heat pumps was read and the articles pertaining directly to design, operation, and the overall performance of air-to-air heat pumps were included in the Review of Literature. The advantages and disadvantages of the basic types of systems and their heat sources were explained. A few of the outstanding units as well as small commercial units were discussed, but the data published on these units were very limited as to design and operating values. One of the major problems encountered with air-to-air heat pumps is the defrosting of the outside coil. Several methods were outlined but the best solution for defrosting the coil would depend upon the conditions pertaining to each unit. Several suggestions were outlined where research is needed for the proper utilization of air as a heat source and sink. arter several trial and error solutions the system was designed to give a conditioned air temperature of 100 degrees F for an outside temperature of 30 degrees F and a heat de= Livery of 436.3 Btu/min. The assumed room temperature was 75 degrees F which gave a 25 degree differential across the inside coil, With an 18 degree differential across the outside coil a refrigerating effect of 338.0 Btu/min could be picked up from the outside air. These values appeared to give the best operating conditions, The tubing was sized accordingly and considerations were given to the fact that the vapor lines would be used for both cycles. The stands were constructed and the component parts of the system were mounted on their respected stands. The piping, duct, and electrical work were completed. ‘The design and construction of each of these phases was done with emphasis on clarity, simplicity, and ease in operation and maintenance. The valves numbered 1 through 12 are the control valves. The system is operated on the heating cycle with the even-numbered valves opened and the odd-numbered valves closed. All the control valves, except the expansion valves and their bypasses, are located on the control board. A dehydrator and oil separator were installed in the pining circuits. A two-wattmeter method of power measurement was installed on the unit. This method enables the operators to determine the power supplied to each motor and instantaneous power when the load on the unit is changing. Each of the motors is protected by fusible disconnect boxes. The procedure for starting, operating, and shut down was explained with emphasis on the factors that should be watched for safe and satisfactory operation. The calculations were based upon the conditions of the air, the heat picked up from the outside air, the work supplied to the motors, and the heat gained by the room air. / Master of Science

In this study, job analyses were made of twenty-two individual record keepers working in over two-thirds of the Roanoke businesses employing twenty-five or more office employees. / Master of Science

The Engineering Index was the primary reference for the articles listed in this bibliography. There are a few articles included which have been taken from various engineering experiment station bulletins. In order to determine the extent of coverage of the Engineering Index, several of the articles which appeared as experiment station bulletins were cross-checked and found listed in the Index. While it is possible that some significant articles may have been omitted from the Index, it is hoped that they were of less importance than any of those which have been listed. The first volume of the Engineering Index appeared in 1884, therefore this bibliography will be limited to those articles listed in the issues of 1884 to May 1951 inclusive. All of the articles published in the United States, Canada, and England, and which were found to be on the campus, were read in a cursory manner in order to determine their applicability to the problem. In each case where the article was read, written additions were made to the abstracts in order that they might be more helpful to anyone using the bibliography. The part of the abstract enclosed with quotation marks was taken from the Index, the rest of the information was added. Photographic copies and English translations of all of the articles listed may be obtained from the publishers of the Engineering Index. It is hoped that this compilation of works on the integral action of beams, columns and slabs will prove helpful to anyone interested in this subject. / Master of Science

The operating characteristics of a boiler prove that pressure can usually be maintained by the supply of fuel and air, regardless of the combustion efficiency; however, to achieve the desired efficiency the burning of the fuel must take place with a minimum amount of excess air. Thus the criterion for boiler operation becomes percent co. in the flue gas. With a CO₂ meter on the control board of the Number Six Boiler it became desirable to acquaint the boiler operators with the conditions in the boiler for a corresponding reading on the CO₂ meter. The percent CO₂ in the flue gas of Number Six Boiler has four effects on the operating characteristics of the boiler when operating under a steam demand of 50,000 pounds per hour. First, it effects the energy loss due to dry exit gases; second, it effects the energy loss due to unconsumed carbon in the refuse; third, it effects slagging and possible deterioration of the refractory walls in the combustion space, and last, it effects the temperature of the refuse as it is discharged from the grate. From a survey of the data obtained from the test runs a decrease in the energy loss due to dry flue gas is seen with an increase in the percentage of CO₂ in the exit gases. This indicates the desirability of operating the boiler at as high a CO₂ as possible in regard to losses occurring from dry flue gases. Similarly, the energy loss to unconsumed carbon in the refuse decreased with an increase in CO₂. Though this is contrary to results obtained in most boilers, the low CO₂, indicating a high excess air, resulted in the boiler being cooled below maximum combustion temperature; consequently, a high percentage of carbon in the refuse occurred with the low CO₂ This too indicates the desirability to operate the boiler at a high percent CO₂. The limiting factors on the maximum percent CO₂ at which the boiler can be operated, with a steam demand of 50,000 pounds per hour, occurred at 12.9 percent CO₂. At this condition the walls began to Slag. This can be harmful to the walls, eventually causing their replacement, an economical loss which would outweigh the slight advantage of increased efficiency when operating at this percent CO₂ over a long period of time. The test runs were not long enough to determine the maximum effect slag would have on the boiler walls; nevertheless, it was noted during the test that slag running off the walls caused the fuel bed to become distorted and that the slagging has necessitated replacing parts of the front wall. Another economical loss would result from the increase temperature of the refuse discharged from the grate when operating at a higher CO₂. Since the refuse is manually removed from the ash pit to the vacuum ash removal system, and since there is a limit to the temperature the operator can withstand and still remove the ashes efficiently, the hotter refuse requires a longer time to be pulled from the ash pit. An additional load of 4,000 pounds of steam per hour, therefore, must be carried over the prolonged period. The optimum percentage of CO₂ for a single boiler is that which will minimize the total losses due to dry flue gases and unconsumed carbon in the refuse and yet keep the refractory deterioration and temperature of the refuse as low as possible. The desirable percentage of CO₂ to be maintained in Number Six Boiler for operation at a load of 50,000 pounds of steam per hour is 12 percent. This allows a maximum feasible boiler efficiency of 73 percent and corresponds to an excess air of 39 percent. It is not feasible to operate the boiler above 12 percent CO₂ because of the increase cost of maintenance due to the formation of slag on the walls and the increased time required to remove the refuse. A CO₂ recorder is a desirable method of obtaining combustion efficiency when the same type of fuel is fired, but it requires periodical checks to maintain it in proper adjustment. / Master of Science

Master of Science

Since careful consideration must be given to the catalyst used in catalytic cracking operation in the petroleum industry to assure economic operation, laboratory catalyst activity test units have been developed. These units approximate the conditions in large scale commercial cracking units. It was the purpose of this investigation to determine the amount of cracking that was obtained from catalytic effects in cracking a standard light East Texas gas oil over a Houdry pellet catalyst when compared to the cracking over silica at temperatures from 500 to 1200 °F in a catalyst activity test unit. A catalyst activity test unit was used to determine the percentage conversion of the feed oil to lower molecular weight hydro-carbons using a Houdry pellet catalyst in one series of tests and silica, which is regarded to be noncatalytic, in another series. Fifteen determinations were made at various temperatures from 580 to 1190 °F and a space velocity of 1.0 volume of feed per volume of catalyst per hour. Ten determinations were made at a space velocity of 2.0 volumes of feed per volume of catalyst per hour at temperatures from 595 to 1160 °F. Data were collected on the quantity of liquid and gaseous products produced, as well as the operating conditions employed. After each cracking determination, the packing was regenerated by heating in the presence of air to burn off any carbonaceous deposits. At a space velocity of 1.0. and various temperatures ranging from 580 to 1190 °F the use of Houdry pellet catalyst produced more cracking than silica at like temperatures. The use of the catalyst effectively reduced the temperatures of the cracking reactions approximately 300 °F at a space velocity of 1.0. The effect of the catalyst was lessened by the effect of temperature at approximately 1200 °F and a space velocity of 1.0. When cracking over silica changing the space velocity from 1.0 to 2.0 raised the temperature required 50 °F for a given amount of cracking. / Master of Science

No description available.

No description available.