This vacuum generation equipment features a simple structure and stable, reliable performance. It is widely used across industries—such as petroleum and petrochemicals, chemicals, pharmaceuticals, metallurgy, light industry, textiles, food processing, sugar refining, and salt production—for processes including vacuum extraction, sublimation, drying, crystallization, concentration, deodorization, decolorization, dehydration, vacuum material transport, chemical absorption, degassing, deoxygenation, and refrigeration. Today, the pump experts at Shanghai Shenyin Pump Manufacturing Co., Ltd. will explain the characteristics, operating principles, installation, and maintenance of these vacuum pumps.
They are generally classified by the number of stages (single-stage through five-stage) and by the type of condensation (direct cooling or indirect cooling).
I. Characteristics: 1. Low-level installation; no barometric leg required. 2. Suitable for systems with large volumes requiring rapid evacuation. 3. Suitable for systems with high levels of non-condensable gases. 4. Can be used with motive steam that has a high moisture content. 5. Can be used when motive steam pressure is unstable or below 0.4 MPa (absolute). II. Operating Principle: The vacuum pump operates at a specific pressure; motive steam passes through a nozzle, undergoing pressure reduction and velocity increase (converting potential energy into kinetic energy) before entering the mixing chamber at supersonic speeds. Here, it mixes with the pumped medium to exchange energy. The mixed gas then enters the diffuser, where it decelerates and increases in pressure (converting kinetic energy into pressure energy). To reduce the pumping load on the downstream pump, a condenser is installed; heat exchange occurs via convection between two media with a temperature difference, condensing the high-temperature medium before discharge to atmospheric pressure.
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III. Installation: 1. The vacuum pump can be installed outdoors. During shutdowns or freezing weather, the entire unit can be drained quickly, as internal piping is installed to facilitate rapid drainage.
2. A check valve should be installed in the pump's discharge line to prevent intermittent or pulsating air backflow. To effectively balance pressure differences between condensers, the piping loop must be of appropriate length; ideally, a drain line should be installed at the lowest point of each loop, which can also serve as a water outlet when cleaning the condenser. 3. When installing steam piping, ensure that the steam delivered to the nozzle is as dry as possible; the section between the steam separator and the ejector pump must be insulated. Keep the steam piping as short as possible and ensure the separator remains dry during operation; to this end, the steam line feeding the ejector pump must be connected to the top of the main steam header. Wet steam not only causes nozzle corrosion and premature expansion but also severely impairs the performance of the small nozzle orifice.
Given the requirement for high vacuum levels—and the small diameter of the nozzle orifice within the pump—it is essential to verify that the piping between the steam filter and the steam nozzle is clean. Installing a small steam inlet chamber on the vacuum pump facilitates easy nozzle removal, allowing for direct visual inspection of the nozzle passage using a probe. Ensure steam gaskets are not installed off-center, as this could restrict the cross-sectional area available for free steam flow.
IV. Maintenance: 1. Periodically tighten the packing; replace it if wear prevents a proper seal. Do not overtighten the packing; under normal conditions, a slight drip of water is permissible, but the leakage rate must not be excessive. Use oil-impregnated asbestos rope for the packing material.
2. The measured operating temperature should not exceed 70°C. The bearing housing should be filled two-thirds full with grease. Bearings in normal operation require regreasing 3–4 times a year; the bearings should be cleaned and the lubricant completely replaced at least once a year.
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