What is used as the benchmark for the length of the extended rod in extended-rod gate valves?
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Generally, gate valves have standard external dimensions, but sometimes the valve stem needs to be lengthened to facilitate opening and closing. I would like to ask fellow sailors: is the dimension reference for the extended rod based on the center line of the flange?
Use the center of the pipeline (which is the same as the centerline of the flange you mentioned) as a reference. In the long-distance pipelines I have worked on, many underground globe valves are used. We only need to provide the distance from the center of the pipeline to the ground level inside the valve room; the client supplies this data to the manufacturer when placing the order, and it is the manufacturer who calculates the total length of the extension rods (the lengths for the above-ground parts may vary among different manufacturers). The same principle applies to valves used in other places if an extended rod is used.
Does anyone have the standards or manuals for long-stem gate valves? Could you share them?
There is no standard length for the extension rod; it should be made as long as needed
That’s right; it’s based on the center line of the flange. My colleague said it’s based on the center line of the channel, but it’s actually on the same line as the flange’s center line.