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Environmental Sanitation Program, National Center for Urban and Industrial Health, Public Health Service, Cincinnati, Ohio
ABSTRACT
The single-stem type of flow-diversion valve has been used on large-capacity pasteurizers with 7.6-cm holding tubes, even though the valve is sized for two-inch (outside diameter) stainless steel tubing. This raised the question of whether the greater pressure drop and higher fluid velocities would affect the performance of this type of valve. Response times and pressure drops were measured for three valves of the 39VJ series (Taylor Instrument Companies) for flow rates of 4,700 to 38,000 liters/hour and product pressures of 0 to 7.0 kg/cm2 (gauge). Response time was between 0.42 and 0.76 sec. A quick exhaust, mounted on one valve, reduced response time to the range of 0.07 to 0.16 sec. Pressure drop through one valve was 0.14 kg/cm2 for a flow rate of 14,000 liters/hour and 0.91 kg/cm2 for a flow rate of 38,000 liters/hour. The performance of all three valves satisfied the requirements of the United States Public Health Service's Pasteurized Milk Ordinance for flow rates through 38,000 liters/hour (in spite of the 0.91 kg/cm2 pressure drop) and for product pressures up to and including the manufacturer's rated values. The higher fluid velocities and larger pressure drops did not affect the response time of the flow-diversion valves.
1 This study was conducted under contract no. NCI-VCL-(65)-30 within the Special Virus-Leukemia Program of the National Cancer Institute NIH, PHS.
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