INDUSTRIAL PLANT PROTECTION
SAFETY MEASURES TO BE USED AT GASOLINE REFINING PLANTS
Many Factors to Be Followed in Designing a Plant—Chlorine in Contact with Gasoline Is an Exceedingly Dangerous Hazard
ALTHOUGH the natural-gasoline industry has recently made great strides in reducing accidents, the industry remains a hazardous one, due to the very nature of the raw materials handled, the process of extracting gasoline from natural gas, and the products obtained, according to the United States Bureau of Mines, Department of Commerce. Since gasoline is extracted under pressure and gas and gasoline are highly inflammable, the risk of fire and explosion always attends the recovery of gasoline from natural gas. The serious explosions and fires that have occurred recently demonstrate the need of increased efforts to prevent recurrence of similar disasters.
Decreased height of towers, better design of stills, automatic regulator controls, and proper venting, have improved operating equipment and increased the safety of operation. Improvements in equipment and the introduction of new devices and methods have resulted also in the manufacture of better grades of gasoline than heretofore.
In designing a natural-gasoline plant the following factors bear directly upon its safe operation: Selection of the site; the plan of the plant and equipment with reference to the surface contour; arrangement of the hazardous equipment to reduce, so far as possible, the risk of fire; provision for future construction without congestion; adequate strength of all structures and equipment; and specifications for materials.
In so far as safety is concerned, the advantages offered by selecting a site with reference to topography call for considerable attention. An elevated location is superior to one that is perfectly level, because the buildings and equipment can be arranged so that gasoline or oil from a bad break or spill will flow away from the course of ignition and thus reduce perceptibly the danger of fire.
Judicious Arrangement of Equipment
The next important factor upon which the safety and success of a gasoline plant depend is judicious arrangement of equipment. Spacing equipment at minimum distances that will provide for economy in construction, safe and efficient operation, and the security of the men connected with operations are very important problems. Because of the variety of sites upon which gasoline plants are built and the various types of equipment used it is evident that a set of specifications for arrangement of equipment that will be best for every condition cannot be drafted. Nevertheless, there are certain fundamental considerations on the location of the more hazardous machinery and equipment which must be noted by the designer in making a layout of any installation. Systematic arrangement of the plant equipment facilitates the efficient use of fire-fighting equipment. Moreover, experience has shown that fires are more easily confined to small areas in properly designed plants.
To reduce the fire and explosion hazards of a plant to a minimum, a proper place must be provided for every combustible substance, safely removed from every source of ignition. This is acomplished by progressively arranging the sources of ignition and combustion so that the most dangerous is farthest removed or isolated from the most dangerous combustible, the next dangerous in a correspondingly closer relation and the least dangerous accordingly placed in the closest relation to each other.
Although some designers of gasoline plants still adhere to wood-frame construction for compressor buildings, the trend in design is toward all-steel fireproof buildings. The adoption of fireproof structures is a forward step in plant safety. A building of steel frame construction covered with corrugated-iron sheathing and with a contiguous row of steel sash around it, wide doors in front and back of each compressor unit or opposite the aisles between the units, and a monitor on the ridge which runs the entire length of the building is a type of construction that is commonly adopted in recent compressor-plant design.
The spacing and arrangement of the compressor units with reference to duplicate units and auxiliary equipment are details that affect safe operation. Wide passageways between machinery in motion greatly reduce the danger of accidents.
Few gasoline-plant managements fail to provide safeguards for compressors and auxiliary operating equipment. Moreover, nearly all states have mandatory regulations governing the safeguarding of moving machinery.
Pressure Equipment and Storage Tanks
The construction of absorbers, stills, accumulators and other pressure equipment is rather well defined and standardized. Both riveted and w’elded shells are in common use. Although poor welding and poor materials, coupled with poor design, have resulted in welding failures and disaster and have created a sentiment unfavorable to welded vessels, it is significant that successful welding is being accomplished in building this equipment.
To prevent excessive losses due to vaporization, it is general practice to store natural gasoline in tanks under a low pressure. In the mid-continent area nearly all of the product is shipped in tank cars, and a large storage capacity is therefore required at the plants. Experience has shown that storage should be provided for thirty days’ production to allow for irregularities in shipping. Horizontal tanks ten feet in diameter and forty feet long are the most commonly used and are undoubtedly the best storage for handling large quantities of gasoline. The tanks are designed to withstand an operating pressure of twenty to twenty-five pounds per square inch and are subjected to a hydrostatic test of fifty pounds per square inch.
Statistics show that inadequately and improperly installed illumination causes or helps to cause approximately eighteen per cent of industrial accidents. Improper lighting also impairs vision and decreases efficiency. At gasoline plants safety in a large measure depends upon good illumination.
When free chlorine combines with certain hydrocarbons in gasoline, hydrogen is liberated with explosive violence, especially in the presence of sunlight. To be safe, therefore, it is ncessary that the most rigid precautions and safety provisions be incorporated in the design of hypochlorite treating plants, so that there is no possibility of gasoline coming in contact with the free chlorine used in the process.
Care Required in Choosing; Fire-Fighting Equipment
To provide adequate protection against fire, too great stress cannot be placed upon the need of considering firefighting equipment as a part of the operating equipment and the importance of installing it before the gas is turned into the plant. To accomplish this end, individual plant conditions and hazards must be studied with the view to making the installation of a size and nature compatible with the requirements of the particular hazard. A careful study of conditions results in equipment being properly centralized and distributed, which greatly speeds up fire fighting.
Safety in natural-gasoline plants involves much more than the mechanics of the plant itself. After plants have been constructed according to the best design and have been provided with adequate fire-fighting equipment only a part of the work of accident prevention has been completed. The principal problem in the operation of plants deals largely with the human element. The selection of men who are careful to take charge of operations and proper instruction of the personnel in safe methods of operation are probably of greater importance in preventing accidents than any other single factors. Incorporating safety in the design of equipment and safeguarding mechanical hazards in compressor and absorption plants are comparatively simple matters, but the education of the men to recognize and guard against the inherent risks, whether small or great, requires consistent and persistent effort. Most accidents can be avoided by exercising ordinary skill and prudence, provided the men are thoroughly acquainted with the causes of accidents and the hazards of their occupation.
Importance of Periodic Inspection
Satisfactory and safe operation of natural-gasoline plants is obtained only by adhering strictly to a routine periodic inspection at regular intervals and by keeping an accurate log of operations, such as temperatures, pressures, fuel consumption, gas output, shutdowns, repairs, and any abnormal operating conditions.
Under the most favorable conditions the extraction of gasoline from natural gas is full of hazards, and it is exceedingly important that plants be designed and operated under the supervision of competent and careful engineers and foremen who fully realize their responsibility for the safety of the men and who are able to secure their full ocoperation. The men, in return, should realize the moral significance of thoughtfulness and attention in order that the safeguards which experience has provided are not nullified. A knowledge of the plant and the causes of accidents enables operators to anticipate in some measure the possibility of such accidents and to exercise a greater control over their occurrence.
In this industry accident prevention is inseparably related to fire prevention. Although every accident hazard is not necesasrily a fire hazard, every fire hazard is an accident hazard.