Methods for Removing Air Ingestion in LQRY Type Heat Transfer Oil Pumps
The LQRY type heat transfer oil pump by Lishen is widely used in thermal carrier heating systems in China. It has entered various industrial fields such as petroleum, chemical, rubber, plastics, pharmaceuticals, textiles, printing and dyeing, road construction, and food industries. It is mainly used to transport weakly corrosive high-temperature liquids without solid particles, with a usage temperature of up to 370°C, making it an ideal thermal oil circulation pump. The LQRY type heat transfer oil pump is the second generation product developed by Shanghai Lishen Pump based on the digestion and absorption of foreign oil pumps. Its basic structure is a single-stage, single-suction cantilever foot-supported structure, with axial suction at the pump inlet, central vertical upward outlet, and both the pump and motor are mounted on the base.
Below are methods to remove air ingestion issues in the LQRY type heat transfer oil pump:
1. High-temperature heat transfer oil pumps generally use skeleton oil seals for sealing the pump shaft. If the spring that tightens the lip falls off, or if the oil seal is installed incorrectly, or if its lip is damaged or aged, the rear end of the oil seal will often be in a negative pressure state, causing air to be ingested. Generally, replacing the oil seal can solve this issue.
2. If the oil suction filter is clogged with contaminants or has insufficient capacity, it can increase the suction resistance and cause air ingestion; additionally, larger diameters of the inlet and outlet ports may also introduce air. At this point, cleaning the filter or selecting a filter with greater capacity and appropriate inlet and outlet diameters can not only prevent air ingestion but also reduce noise in plastic pumps and high-temperature heat transfer oil pumps.
3. If there is insufficient oil in the tank or the suction pipe opening is not submerged below the oil surface, the pump will ingest air. In this case, oil should be added to the tank until it reaches the oil gauge line; if the return oil pipe opening is exposed above the oil surface, it may also allow air to enter the system due to instantaneous negative pressure within the system. Therefore, the return oil pipe opening is usually also submerged below the oil surface.
4. If the installation position of the heat transfer oil pump is too far from the oil surface, especially when the pump speed decreases, it cannot ensure that the vacuum degree required in the pump suction chamber is met, leading to insufficient oil suction and air ingestion. In this case, the relative height between the pump and the oil surface should be adjusted to meet the specified requirements.
5. For the LQRY type heat transfer oil pump, the direct contact hard seal between the pump body and the two side end covers may easily lead to air ingestion if the flatness of the contact surface does not meet the specified requirements. Similarly, the direct contact between the pump end cover and the pressure cover can also allow air to infiltrate. If the pressure cover is made of plastic, its damage or deformation due to temperature changes can also cause poor sealing and air ingress. To eliminate this fault, if the flatness of the pump body or pump cover does not meet the specified requirements, it can be ground on a flat plate using diamond sand in a figure-eight motion back and forth, or it can be ground on a surface grinder, ensuring that its flatness does not exceed 5μm and maintaining the perpendicularity requirement between the plane and the hole. For leaks between the pump cover and the pressure cover, epoxy resin or other adhesives can be applied for sealing.
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