Specifications and dimensions of valve packing
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Leakage at the valve gland is one of the common faults in valves. In such cases, it is usually necessary to replace the packing. However, since there are many different valve diameters in use on site, is there a table showing the relationship between valve dimensions and packing sizes? Thank you everyone
This table exists; you can search for it
First, determine what type of filler you need. Graphite? Tetrafluoride? Asbestos? ……? Next, determine the job requirements. Should all valves be regularly inspected and replaced, or only those that are damaged? Third, one must understand. Some valves require the use of packing specifications specified by the manufacturer ； Some specifications of packing can actually meet the requirements of multiple specifications ； Fourth. The valve port diameter and the size of the stuffing box do not correspond exactly; the specifications for the stuffing must be determined based on the thickness of the valve stem, rather than solely on the diameter ； The graphite packing ring shown in the image is made by rolling graphite sheets into a cylindrical shape and then cutting them; several layers of it can be removed from the outside or inside when in use, to suit different stuffing boxes.
In other words, the thickness of the packing can only be determined based on the thickness of the valve stem; does that mean it can only be adjusted on-site? So, one buys a generic packing, measures it, adjusts its thickness and length, and then installs it?
Different manufacturers produce various types of packing, and different sizes are available. We use PTFE packing and graphite packing of different thicknesses, each suited for specific operating conditions. The advantage of using packing is that it is not necessary to disassemble the valve stem connections; simply removing the old packing and inserting the new packing layer by layer is sufficient
It uses more packing material, which is convenient. But these days, basically no one wants to replace them; they just replace the valve directly. They didn’t give me more money for the repairs, and they won’t give me back the money saved on the valves either. Few are willing to do this job, unless it is arranged specifically.
Although it sounds negative, that is indeed the case.
If you change the packing yourself twice, you won’t be so worried about it. Depending on the properties of the packing and the requirements it must meet, in most cases it does not matter if the specifications of the packing are slightly larger or smaller than those shown in the diagram below; this does not affect its performance or functionality. It’s just that operating with the appropriate specifications makes things easier and reduces the likelihood of mistakes. U-shaped or V-shaped packing rings, as shown in the figure below, have strict size requirements; without sufficient experience, it is necessary to refer to the specifications in the valve technical manual to determine the appropriate dimensions. Moreover, replacement is rather troublesome (it is necessary to disassemble parts other than the stuffing box in order to replace it). For routine repairs (fixing whatever is damaged), it is recommended to have three or five different types of packing available, depending on the materials used.
The 9th floor explained it in great detail! Thank you for sharing!