Turning Operation Before Starting the Hydraulic Lube Oil Pump HSNH660-46

In the hydraulic system of power plant generators, the lube oil pump, as one of the key equipment, undertakes the core function of providing stable oil pressure and lubricating medium for the hydraulic system. Among them, the three-screw lube oil pump HSNH660-46 is widely used in the lubrication system of large generator sets due to its compact structure, stable flow, and adaptability to high-pressure working conditions. However, in actual operation, this type of lube oil pump must be turned before starting, usually requiring more than 2 turns. This operation seems simple, but it is an important part of ensuring the safe operation of the equipment. This article will combine the working principle, operating environment and failure cases of the lube oil pump to deeply analyze the necessity of turning operation and explore its practical significance in power plant maintenance.

1. Operating characteristics and turning requirements of lube oil pumps

The core structure of the three-screw lube oil pump HSNH660-46 consists of a main screw, a driven screw and a pump body, and the medium is sucked and discharged through the rotation of the screw. Its working principle is based on the precise meshing between the screws, and the oil is transported through volume changes. Due to the extremely small gap between the screw and the pump body, the equipment is highly sensitive to the mechanical state. If the cranking is not performed sufficiently before starting, the following risks may occur:

Risk of mechanical jamming: During long-term shutdown or high-temperature environment, the oil inside the lube oil pump HSNH660-46 may cause the rotor parts to jam due to viscosity changes or impurity deposition. For example, during shutdown, high temperature causes local carbonization of the oil, forming hard deposits that adhere to the surface of the screw or the inner wall of the pump body, hindering the free rotation of the rotor. If the motor is started directly, the rotor may not be able to rotate due to excessive resistance, which may cause the motor to overload or even burn out.

Hidden danger of insufficient lubrication: Lube oil pumps need to rely on pre-lubrication to establish an oil film and reduce friction loss in the early stage of operation. If the cranking is not performed in advance, the pump body may cause local dry friction due to uneven oil distribution or residual air. For example, after shutdown, the oil flows back to the oil storage tank, and the amount of oil remaining in the pump cavity is not enough to cover the surface of the screw. At this time, direct starting is likely to cause metal contact, accelerate wear and even damage precision parts.

Thermal deformation and stress concentration: Under high temperature conditions, the metal parts of the lube oil pump HSNH660-46 may produce slight deformation due to thermal expansion and contraction. For example, the clearance between the main screw and the pump body may be reduced due to a sudden drop in temperature after shutdown. If the stress is not released by turning, the screw may break or the pump body may crack due to rigid collision during startup. In addition, the rotor may be slightly bent due to gravity during long-term shutdown. Turning can effectively correct its geometric center to avoid increased vibration during startup.

2. The practical significance and technical details of the turning operation

The core goal of the turning operation is to rotate the rotor of the lube oil pump HSNH660-46 manually or with auxiliary devices to check its operating flexibility and create favorable conditions for subsequent startup. Specifically, the requirement of turning 2 turns is not set arbitrarily, but is based on the following technical considerations:

Comprehensive detection of mechanical status: During the turning process, the operator can judge whether the rotor is stuck, has abnormal noise or abnormal resistance by hand. For example, if the resistance of the cranking is uniform and there is no obvious setback, it means that the screw and the pump body cooperate normally; if a sudden increase in local resistance is found, it is necessary to further investigate the problem of impurity blockage or component wear.

Promote oil circulation: The cranking action can promote the flow of residual oil in the pump cavity, cover the surface of the screw and fill the sealing gap. For example, before restarting after shutdown, the cranking can deliver lubricating oil to key parts such as bearings and shaft seals to form a preliminary lubricating film and reduce the risk of dry friction.

Release thermal stress and correct deformation: For lube oil pumps that have been shut down for a long time, the cranking can release the stress caused by thermal deformation of the rotor by slow rotation. For example, after some power plants are shut down in high temperature environments in summer, the metal parts of the lube oil pump may produce slight deformation due to thermal expansion. The cranking can gradually adjust its geometric state to avoid component breakage due to stress concentration during startup.

In actual operation, failures of lube oil pumps due to failure to crank are common. Especially during shutdown, the oil in the pump body is oxidized by high temperature to form colloidal deposits, which adhere to the surface of the screw to form hard lumps. The operator did not perform the cranking operation, and directly started the motor. The rotor could not rotate due to excessive resistance, causing the motor to overload and trip. After disassembly, it was found that there were many scratches on the surface of the screw, and the entire set of rotor components needed to be replaced.

3. Specifications and precautions for cranking the lube oil pump

To ensure the effectiveness of the cranking operation, the following technical specifications must be followed:

Operation timing: The lube oil pump HSNH660-46 must be cranked after being shut down for more than 8 hours or encountering abnormal working conditions. In addition, the newly installed or overhauled equipment also needs to verify the mechanical state through cranking.

Operation method: The cranking is usually done manually, and the rotor is rotated slowly through a coupling or special tools. Keep a constant speed during operation to avoid violent impact. If the resistance is too large, stop immediately and check the cause. Do not force the cranking.

Environmental preparation: Before cranking, make sure that the inlet and outlet valves of the lube oil pump are in the open state to avoid rotor jamming due to pressure difference. At the same time, check whether the oil temperature is within the recommended range. In low temperature environments, a heating device is required to improve the fluidity of the oil.

Record and feedback: After each cranking, the operator needs to record the smoothness of the rotor rotation, whether there is any abnormal noise and the change of oil state. If any abnormality is found, it must be reported in time and special maintenance must be arranged.

In the hydraulic system of the power plant generator, the cranking operation of the three-screw lube oil pump HSNH660-46 seems simple, but it is actually an important part of ensuring the safe operation of the equipment. Through cranking, not only can potential risks such as mechanical jamming and insufficient lubrication be discovered in advance, but it can also effectively release thermal stress, correct component deformation, and extend the service life of the lube oil pump.

When looking for high-quality, reliable lube oil pumps, YOYIK is undoubtedly a choice worth considering. The company specializes in providing a variety of power equipment including steam turbine accessories, and has won wide acclaim for its high-quality products and services. For more information or inquiries, please contact the customer service below:
E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

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