Industrial Valve Grinding Procedure

Industrial Valve Grinding Procedure

Individually Driven Grinding Heads: The Key to Flat Valve Seats

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Are you looking for a valve grinding procedure that is easy to use and yields excellent results?

The goal of valve grinding and lapping is to create a dense and flat surface. The LarsLap system, featuring individually driven grinding heads, successfully achieves this.

In contrast, friction-driven grinding heads often produce a concave surface, which is slightly lower in the center.

Method of Valve Grinding During Maintenance

The valve grinding process involves three main stages: cleaning and inspection, grinding, and final inspection. This article shares valuable insights from the Valve Grinding Machine Supplier.

1. Cleaning and Inspection Process

Begin by cleaning the sealing surface in the oil pan using a professional cleaning agent. During the cleaning, inspect for any damage to the sealing surface. Fine cracks that are not easily visible may require stain flaw detection.

After cleaning, check the tightness of the disc or gate valve along with the sealing surface of the valve seat. Use red chalk for testing. Apply red chalk to assess the sealing surface's integrity and determine its tightness. Alternatively, use a pencil to draw concentric circles on the sealing surfaces, then rotate both the valve disc and valve seat together. Check whether the pencil lines are worn away to confirm the tightness of the sealing surfaces. If tightness is inadequate, use a standard flat plate to inspect the sealing surfaces of the disc and gate, as well as the valve body, to identify where grinding is required.

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2. Grinding Process

The grinding process is fundamentally a cutting operation performed without a lathe. The depth of pits or minor holes on the valve head or valve seat typically does not exceed 0.5mm, making grinding suitable for maintenance. This process can be divided into three stages: coarse grinding, middle grinding, and fine grinding.

Coarse grinding aims to remove defects such as scratches, indentations, and corrosion points on the sealing surface. This stage enhances the flatness and smoothness of the surface, preparing it for middle grinding. Coarse grinding uses grinding heads or grinding seat tools with coarse-grained sandpaper or abrasive paste, typically ranging from 80# to 280#. While this method offers high efficiency, it may leave rough surface patterns and deep cut lines, thus it should primarily focus on eliminating pitting.

In the middle grinding stage, the goal is to remove rough lines from the sealing surface, further improving its flatness and smoothness. Fine-grained sandpaper or abrasive pastes with a particle size of 280# to W5 should be utilized. These finer materials allow for a smaller cutting amount, which results in reduced roughness. Clean and appropriate grinding tools should be used, and after middle grinding, the contact surfaces should appear shiny. You can verify smoothness by applying a few strokes with a pencil on the valve head or seat and then rotating them slightly to see if the pencil lines are erased.

Fine grinding, the final stage, primarily enhances the smoothness of the sealing surface. During this process, lubrication is added using engine oil or kerosene mixed with W5 or finer abrasives. The valve head is then used to grind the valve seat gently, ensuring tightness in the sealing surface. The grinding should be done by turning clockwise at about 60-100°, followed by a counter-clockwise turn at 40-90°. Regular checks should be made to ensure that the surface appears bright and shiny. Any thin black lines should be rubbed gently with engine oil and wiped with clean gauze. After grinding, it is essential to address any remaining defects and assemble the parts quickly to avoid damage to the ground valve head.

Manual grinding, whether coarse or fine, requires a combination of lifting, lowering, rotating, reciprocating, tapping, and reversing operations throughout the grinding process. This technique ensures that the abrasive grain tracks do not repeat, leading to a uniformly ground sealing surface and improved flatness and smoothness.

3. Inspection Stage

During the grinding process, ongoing inspection is crucial to maintain quality. Continuous monitoring allows operators to keep track of grinding conditions, ensuring that the quality meets technical standards. It is vital to use suitable grinding tools for different valve types, which will help enhance grinding efficiency and ensure quality outcomes.

Gate valve grinding is a meticulous task that requires consistent experience, exploration, and improvement. Despite achieving ideal grinding results, leaks may still occur after installation. This can be attributed to deviations that occur during the grinding process, such as misaligned or improperly angled grinding tools.

For more information on our Gate Machine, please contact us for professional assistance.