Valve unloader
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If the valve plate stroke of the suction valve is 3mm, then is the stroke of the ejector rod of the unloader, Figure 5, relative to the valve plate, between 0 and 3mm, or greater than 3mm? If it is greater than 3mm, will the ejector rod be bent? If it is between 0 and 3mm, if it is pushed open dozens of times or just opened, will the purpose of unloading be failed?
Considering the stroke is only one aspect, it must also be combined with the flow area of the fluid after the valve disc is opened. If you are engaged in design, you should pay attention to selecting the appropriate relief capacity of the valve. For reference.
It depends on the stroke of the ejector rod of your unloader. The gap between the ejector rod and the valve ejector rod is basically 1-1.5mm. The ejector rod will not bend and the wind pressure will not be that great.
What I mean is that the ejector pin needs to press all the valve discs open, or does it only need to be pressed within 3mm?
The unloader ejector stroke is certain, and it must be greater than the sum of the valve plate stroke and the clearance between the unloader ejector and the air valve ejector. Theoretically, as long as the unloader ejector pin can push open the valve plate, it can unload the valve.
The valve plate stroke of the unloader needs to be measured and adjusted when the unit is installed. The valve plate stroke is given by design calculations. Inappropriate situations cannot be ruled out. Unloading will occur when a gap is seen. The opening has a direct impact on the gas volume.
Personally, I think that the stroke of the unloader is greater than the sum of the opening of the suction valve and the gap between the unloader and the suction valve. The pressure of the unloader only needs to balance the force of the return spring and will not bend the valve stem. During actual maintenance, I also checked the stroke of the unloader in this way.
The unloader stroke is generally around 8mm
Taking the compressor of our factory as an example, the valve plate has a stroke of 3mm, and the unloader ejector has a stroke of about 7mm in the free state. When installing, a 1.6-2.0 gap is reserved between the unloader ejector and the valve, so that there is about 5mm left. The unloader stroke has a margin of 5-3 = 2mm. After excluding the resistance loss, the 0.7mm wind pressure of the instrument wind is not enough to bend the ejector.