Mechanical seal leakage
Thread Content
Today I encountered a rather strange issue. The pump inlet has a diameter of DN32 mm, while the pipeline has a diameter of 50 mm. The material level in the storage tank is 5 meters high, and the outlet flange has a diameter of 100 mm. The horizontal distance between the pump and the storage tank is 2 meters. With the inlet valve fully open, leakage of material occurred into the seal cooling water as soon as the pump was started, even before the outlet valve could be opened. The leakage stopped once the inlet valve was closed. I’m not sure what’s causing this phenomenon; I hope experts can provide some guidance.
If negative pressure is created on the inlet side, the sealing chamber will also be under negative pressure, so of course there will be no leakage outside
Are there any pictures or videos of the leak at the scene? Send one to take a look! Let me help you analyze it! There are many reasons for seal leakage!
It wasn’t filmed; after the pump was started, the material came out from the seal cooling water. By reducing the size of the inlet, the leakage stopped – it was quite a remarkable sight.
It seems that the problem lies in the compression amount of the seal; in other words, the spring parameters of the seal you are using are not suitable for your actual application requirements! If that’s the case, we’ll have to find a manufacturer that provides sealed products to solve this issue! It is essential to ensure that both sealing surfaces are clean. Before installation, apply some clean lubricant or butter to them. The area where the rubber seal is located must be smooth, without any burrs or similar imperfections. When installing the stationary ring into the gland, it must be pressed evenly. The amount of compression required varies depending on the type of seal: for seals with large springs, 2-3 mm of compression from the free state to the fully compressed state is sufficient; for seals with small springs, 1.5-2 mm of compression is adequate. These values are merely for reference – the actual requirements depend on the type of seal being used. If the compression is too loose, the spring’s strength will not be sufficient, leading to leaks; on the other hand, too much compression can reduce the seal’s service life That’s basically it; you can refer to these for details: handshake
It’s not possible to determine whether there is a leak before starting the pump. If a leak occurs once the inlet valve has been opened, it indicates that the end faces of the mechanical seal’s stationary and rotating rings are not properly pressed together, or that the sealing ring of the rotating ring has failed. Turning down the inlet valve might result in a decrease in outlet pressure, preventing any signs of leakage from becoming apparent.
After installation, clean lubricant (such as engine oil, butter, silicone oil, etc.) can be applied to the sealing surfaces of the rotating and stationary rings (first wipe these surfaces gently with a clean cloth). Of course, this is not necessary if a pre-sealed assembly is used; some manufacturers apply lubricant before shipping the product. Before starting the pump, it is advisable to turn the shaft by hand (by rotating the coupling or drive shaft a few times), as this helps to ensure better lubrication of the two sealing surfaces But the prerequisite is that it must be clean, with no impurities at all! That’s roughly what it means!
By the way. The original poster can also give it a try and check whether there is any leakage under static pressure conditions before turning on the pump! If there is a leak, then it’s basically a problem with the sealing!
Is no airtightness test performed on the seal? Should oil be applied to the end faces during the airtightness test?