For mechanical seals, how is the compression amount of the spring determined during installation?

The last edit to this post was made by 3983596_FPPZ on 2018-11-29 at 16:01. The amount of spring compression is not the goal or criterion we aim for during installation; rather, it should be based on the axial installation dimensions specified by the manufacturer, with the appropriate end-face pressure being ensured in terms of performance. Do not adjust it in order to change the compression amount of the spring. Repost: The compression amount of a mechanical seal spring can be measured directly using a caliper – first measure the extension and retraction of the spring in its free state, then measure its length after it has been installed in place; the difference between these two values represents the compression amount. With modular seals, there is no need to determine the compression amount manually, as it is set once the entire seal is installed; whereas non-modular seals require measurement based on the type of pump. The compression degree of a single-spring mechanical seal is 50%–70%; after the seal is compressed, about 3–5 mm of clearance remains. The compression degree of a multi-spring (disc spring) mechanical seal is around 90%, meaning that 1.5–2.5 mm of clearance remains after compression. At the same time, the width of the sealing surface, the strength of the spring, and the stress conditions during operation must also be taken into account. The compression amount of the adjustment spring is adjusted to meet the specific spring pressure, rather than being compressed for the sake of compression itself, whether it is a single spring or multiple springs. Generally, the spring pressure of mechanical seals in pump systems is kept at around 1.3–2.8 kgf/cm2. The optimal value depends on actual operating conditions, the materials used for the friction pair, the design of the compensating ring and auxiliary sealing ring, as well as the load factor K value. Misconceptions in the maintenance of mechanical seals for pumps: (1) The greater the spring compression, the better the sealing effect. In fact, this is not the case; excessive compression of the spring can lead to rapid wear of the friction pair, resulting in instant burnout ； Excessive compression causes the spring to lose its ability to adjust the end face of the moving ring, resulting in seal failure. (2) The tighter the dynamic ring seal, the better. In fact, an overly tight dynamic ring seal is more harmful than beneficial. First, it exacerbates the wear between the sealing ring and the shaft sleeve, leading to premature leakage ； Secondly, it increases the resistance to axial adjustment and movement of the moving ring, making it impossible to make timely adjustments when operating conditions change frequently ； Third, excessive fatigue of the spring can lead to damage ； Fourth, it deforms the rotating ring seal, affecting the sealing performance. The following posts are requests for help and discussions on adjusting the spring compression amount in the forum; it is recommended to read https://bbs.hcbbs.com/thread-361251-1-1.html, https://bbs.hcbbs.com/thread-1115667-1-1.html, https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1523879, https://bbs.hcbbs.com/thread-1331990-1-1.html (this post was also posted by you), https://bbs.hcbbs.com/thread-966342-1-1.html, https://bbs.hcbbs.com/thread-335651-1-1.html, and https://bbs.hcbbs.com/thread-660531-1-1.html

Currently, it is generally done by a compacting machine; the compression amount is calculated and set based on process parameters, so no adjustment is required. There is usually a pressing plate that is used to hold things in place during installation; once it’s in position, the pressing plate can be released.

The compression amount of single-face mechanical seals varies depending on the design, and thus the calculation methods differ as well

Typically, seal manufacturers provide the installation dimensions for the seals; based on these dimensions, the compression amount of the spring is calculated, and then measuring tools are used to position the seal axially!

The position of the assembled mechanical seal has been determined by the manufacturer before leaving the factory； For non-enclosed mechanical seals, most manufacturers will mill positioning grooves or holes on the shaft sleeve, or provide a positioning platform; in cases where there is no such positioning mechanism, the compression degree of the single reed is around 70%, while that of multiple reeds is around 90%