Discussion thread on accurate data regarding valve torque!
Thread Content
Question: '(,1. According to the valve design manual, isn’t it troublesome to calculate the torque every time? Do I need to calculate both the sealing force and the axial force on the valve stem? Are there also options for the valve stem material and considerations regarding friction? 2. The simple circular formula for calculating torque doesn’t seem reliable! 3. Refer to others’ samples – each one is different! The difference is quite significant; for large-diameter ones, the difference in high pressure is considerable. For example: calculating data? Too small, sample data? Too large, Lu Peiwen’s manual data? Basically inaccurate. Values are now taken from authoritative sample manuals! Newey’s sample. I’m asking about the torque required for ordinary gate stop valves – where can I find accurate data? Especially those with large diameters and high pressure levels! Even with a 1.5 times safety factor, the calculation still seems to fail the requirements! ! ! (Someone will surely say that since these valves are manufactured by different manufacturers, the assembly requirements and techniques vary, which leads to differences in friction, concentricity, and torque. ) We ignore these factors and attribute it to the choice of safety factor! Around 1.25-1.5! Everyone is welcome to discuss this issue!
This is indeed troublesome, especially with electric actuators. Generally, it is the valve manufacturer who specifies the torque required; otherwise, it’s hard to know which type of electric actuator to choose. If the torque is too low, the actuator may not be able to handle the load, while if it’s too high, it results in wasted money.
Yes, it seems that everyone has concerns and doubts about this issue, but there aren’t many solutions available! It seems I still have to use the data from the Newey sample with a *1.2 safety factor!
Thank you! I hope someone will answer the questions!
:) Below, is there any expert who can help clarify this? Doesn’t everyone really know about it either? Refer to the sample design data!
If you really want to find out, first calculate according to the instructions in the design manual, and then use a torque wrench to apply the force. Many bosses in Wenzhou are so stingy that they won’t even bother to buy a set of torque wrenches – they’re extremely shrewd. The width of their sealing surfaces differs from yours; the actual diameter may be smaller in some cases, and there are also differences in the type of filler used. Therefore, the samples provided by any manufacturer aren’t reliable. I’ve seen Neway’s samples, and the values shown there are on the low side, which makes it somewhat difficult to operate the valve under full pressure. If you really don’t want to do the calculations, you should use a coefficient of at least 1.5 times higher
Thank you! That’s how it’s done at the moment! But Newey’s stop valves seem to be designed with a single disc. For our double-valve design, how should the values be determined?
Stop valve? ? ? Double valve leaflets? Large caliber?
Yes, it’s impossible to conduct a practical test! I just don’t know what “accurate” means—values that aren’t too off! Any suggestions or good methods, as well as book data! Could you please provide a reference?
This post was last edited by Ximadi Valve Industry’s Wu Yongsheng on 2019-12-12 at 12:17. It is best to have the manufacturer provide you with this torque value; for the same product, different manufacturers may produce items with varying torque values. For products of good quality, the torque will be lower; for those of average quality, it will naturally be higher. Furthermore, when selecting the safety factor, the pressure and temperature of the medium, as well as the type of medium, must be taken into account. A general safety factor of 1.2–1.5 is used; if the operating conditions have a significant impact on torque, the safety factor should be increased accordingly. If electric actuators are used, it is recommended to use a higher safety factor; this provides some protection for the electric actuators and also prevents an increase in valve torque over time, which could result in insufficient output torque from the electric actuators and thus prevent the valve from opening and closing properly.