Installation requirements for hydraulic pipelines of extrusion blow molding machines

Hydraulic Pipeline Installation Requirements for Extrusion Blow Molding Machines

Basic Principles and Layout Considerations

The installation of hydraulic pipelines for extrusion blow molding machines is a critical process that directly impacts the operational efficiency and safety of the equipment. Before starting the installation, it is essential to have a comprehensive understanding of the hydraulic system's working principle diagram and pipeline connection diagram. This ensures that the layout of the pipelines is logical, with a focus on minimizing the length of the pipelines, reducing the number of bends, and avoiding crossovers as much as possible.

When designing the pipeline layout, prioritize ease of installation, maintenance, and operation. The pipelines should be arranged in a parallel or perpendicular manner, with a clear hierarchy. For horizontal pipelines, the parallelism should not exceed 2/1000, while for vertical pipelines, the perpendicularity should not exceed 2/400. These standards can be verified using a level. Additionally, ensure that there is a minimum gap of 10mm between parallel or intersecting pipelines to facilitate disassembly and maintenance without causing interference.

Pipeline Selection and Cutting

The selection of pipeline materials is crucial for ensuring the reliability and durability of the hydraulic system. Only pipelines with clear material specifications should be used, and those with unknown materials should be strictly prohibited. The diameter of the pipelines should be chosen based on the flow rate and pressure requirements of the system, avoiding overly thin pipelines that may cause excessive pressure drops.

When cutting the pipelines, different methods should be employed depending on the diameter. For pipelines with a diameter of less than 50mm, a sand wheel cutting machine can be used. For larger diameters, mechanical processing methods are preferred. If gas cutting is used, mechanical processing must be carried out afterward to remove the heat-affected zone and create a welding bevel. The cutting surface of the pipelines should be smooth, free of burrs, oxide scales, and slag, and perpendicular to the pipeline axis.

Bending and Support of Pipelines

The bending of pipelines should be done using professional bending equipment to ensure that the bending radius meets the requirements. For pipelines with an outer diameter of less than 30mm, cold bending can be used, while for those between 30mm and 50mm, both cold and hot bending methods are acceptable. For pipelines with an outer diameter greater than 50mm, hot bending is generally recommended. The minimum bending radius should be at least 2.5 times the pipeline diameter to prevent excessive thinning of the pipeline wall or the formation of wrinkles on the inner wall.

Proper support of the pipelines is essential to prevent vibration and noise. Pipeline supports and clamps should be installed at appropriate intervals to ensure that the pipelines have sufficient rigidity and anti-vibration capabilities. For bent pipelines, supports or clamps should be installed near the bending points. It is important to note that pipelines should not be directly welded to supports or clamps. Additionally, the weight of the pipelines should not be borne by valves, pumps, or other hydraulic components, nor should they support the weight of heavier components.

Installation of Flexible Hoses

Flexible hoses are commonly used in hydraulic systems to connect components with relative motion or to absorb vibrations. When installing flexible hoses, several key points should be considered. First, avoid sharp bends, and ensure that the bending radius is at least 8-10 times the outer diameter of the hose. The ends of the hose should have a straight section of at least 6 times the outer diameter before bending to prevent stress concentration.

Second, flexible hoses should not be installed in a stretched state and should have a certain amount of slack (approximately 4% length change) to accommodate pressure variations and movement. If the hose is too long or subjected to severe vibrations, it can be secured with clamps, but the use of clamps should be minimized for high-pressure hoses to avoid friction energy loss.

Third, flexible hoses should be installed away from heat sources as much as possible. If this is not possible, insulation plates or sleeves should be used to protect the hoses. It is also important to ensure that the hoses, connectors, and the surrounding environment are compatible to prevent chemical degradation.

Welding and Assembly of Pipelines

The welding of hydraulic pipelines requires skilled personnel with appropriate certifications. For carbon steel pipelines with a wall thickness of less than or equal to 2mm, oxyacetylene gas welding can be used, while for those with a wall thickness greater than 2mm, arc welding is preferred. Argon arc welding is the best method for welding pipelines, and for wall thicknesses greater than 5mm, argon arc welding should be used for the root pass followed by arc welding for filling.

During welding, it is important to prevent wind, rain, and snow from affecting the welding quality. After welding, pipelines with a wall thickness of less than or equal to 5mm should be allowed to cool naturally at room temperature and not be forced cooled with strong winds or water. The welds should be fully penetrated and have a uniform and smooth appearance. Pressure pipelines should undergo sampling radiographic inspection to ensure welding quality.

After welding and pre-assembly, the pipelines should be disassembled for acid pickling and phosphating treatment to remove rust and scale. After drying, the pipelines can be reassembled into the system. Before final assembly, each pipeline should be pre-cleaned to remove any contaminants. The entire system should then undergo a circulating purification process until it meets the design cleanliness requirements.

Final Inspection and Testing

After the installation of the hydraulic pipelines is complete, a thorough inspection should be conducted to ensure that all connections are tight and there are no leaks. The system should be pressurized in stages, starting from 1MPa and gradually increasing to the maximum operating pressure, with each stage being held for a sufficient amount of time to check for leaks. If any leaks are found, the pressure should be released, and the connections should be tightened. If there is still slight seepage after tightening, the connectors can be gently tapped with a hammer and then tightened again.

In addition to leak testing, the system should also undergo functional tests to ensure that all hydraulic components are operating correctly. The response time, pressure stability, and flow rate of the system should be verified to ensure that they meet the design requirements. Any abnormalities should be promptly investigated and resolved to ensure the reliable operation of the extrusion blow molding machine.