Pneumatic And Hydraulic Equipment Page 525

G A S T Installation It is important to include a vacuum gauge at the vacuum pump inlet in the air line within a few inches of the unit. Diagnosis of system problems is easier and more accurate with a gauge at this location. In reciprocating units, a "snubber" should be installed in the gauge connection to reduce pulsations which can damage the gauge. The installation of a relief valve is equally important. Unit life is directly related to duty levels and most systems require only a fraction of the pump's advertised capacity to operate efficiently. The Gast relief valve makes it simple to "fine tune" the pump to minimum system needs, reducing electrical consumption and maximizing pump life. Electric Motors All electric motors supplied with Gast vacuum pumps are designed to operate at plus or minus 10% of nameplate voltage. Motors to meet special requirements are available upon request. Lubrication Unless otherwise specified, every lubricated Gast unit is equipped with a standard lubrication system that automatically delivers the correct amount of oil to the pump. To provide correct lubrication, it is important to keep the oil reservoir filled. In general, a reservoir holds enough oil for 25-50 hours of operation. Variables, such as duty level and ambient temperature, can cause significant variation from this range. However, an oil reservoir that needs refilling outside this range may indicate a malfunction in the lubrication system. Too much oil usage seldom does as much harm as insufficient lubrication. The most serious consequences of too fast an oil feed rate are oil fog or heavy oil condensation at the exhaust. A likely consequence of too slow an oil feed rate is complete pump failure. Unit Life Expectancy Many variables determine the life expectancy of a unit. Among them are: 1. Ambient temperature 2. Duty level 3. Operating cycle 4. Operating speed 5. Condition of air handled Cleanliness Humidity Heat Chemical vapors present (corrosive, non-corrosive) 6. Unit maintenance Lubrication Filter maintenance Muffler maintenance Ambient Temperature A not-to-be-forgotten condition in applying compressors and vacuum pumps is ambient temperature. To determine the ambient temperature reading of the air surrounding the unit, readings should be taken around the unit approximately 4 inches away. Gast's guarantee applies only to units operating within a temperature range of 32F to 100F. Low temperature affects the unit's ability to start and high temperatures affect its life. Continuous vs. Intermittent Operation Continuous vs. intermittent duty usually must be considered. Our defini- tion of intermittent duty is 10 minutes or less on and 10 minutes or more off. A better method of determining if the unit is applied properly is to measure temperatures of the metal portion of the unit that surrounds the discharge port and top dead center of the electric motor. Please note that when you refer to performance curves in this catalog, the solid line indicates continuous operation, while the dashed line shows intermittent duty. Starting Under Load Rotary vane units will start under load. The vanes permit the internal chamber of the unit to bleed off during the cycle. At startup, the pump is not subjected to full load until enough centrifugal force has been attained to throw the vanes out against the body. By that time, the motor has gained enough momentum to continue its cycle without stress. In systems where storage of built-up vacuum is important, check valves should be installed between the pump and the system. Blowers start up easily. Adequate internal clearances in Gast blowers make this possible. Oilless piston units will start under load as long as the top of the piston is not subjected to system vacuum. Under more complicated conditions, install a check valve next to the pump. Diaphragm units will not start under load because the surface area of the diaphragm is much larger than that of a piston pump. To start a diaphragm unit under load would require a motor too powerful to be cost effective. Instead, a specific volume of air at zero pressure differential must be provided to start the unit under load. (Specific volumes for different models are available from Gast.) Bleed orifices and dump valves are two common methods of supplying the correct zero-pressure-differential volume of air. ROC-R rocking piston pumps use the same types of motors as diaphragm units and therefore the same conditions apply. Catalog Performance Specifications When looking at a Gast catalog performance chart, please remember that the specifications listed are that of a unit at sea level with an ambient temperature of 70F (21C), operating with normal electrical current conditions. Performance shown in this catalog is the nominal to be expected from these models without accessories. Intake filters and exhaust mufflers, and the accumulation of contaminants in them during operation, will decrease the flow of air as well as the achievable vacuum by the vacuum pump. VACUUM PUMPS & COMPRESSORS IMPORTANT INFORMATION ON GAST VACUUM PUMPS & COMPRESSORS Gast JHF Catalog [ Volume 7 ] (314) 427-0600 800-444-0522 (FAX) 314-427-3502 www. j hf.com 525 Prices Subject to Change Without Notice John Henry Foster pneumatic and hydraulic equipment

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