The mechanical seal is made of 316L with silicon carbide Q2; cracks in the silicon carbide have appeared during use. Please help analyze this situation
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This post was last edited by SecretCover on 2011-6-30 19:13. The pump is of Japanese TO-1506MMS type, and the processing method involves anodic electrolyte NAOH at 32% concentration and at 80 degrees Celsius. It was originally designed to be a double-seal design; I uploaded only the media side. Both the moving and stationary rings of this media are made of 316 steel with silicon carbide inlays. However, the 316 steel of the moving ring has not changed color, while the stationary ring has changed color as can be seen from the images, and the bottom part of the silicon carbide inlay there has cracked. The area from the inside of the insert to the back of the static ring has changed color, and the PTFE O-ring has been deformed. I understand that the mechanical seal itself is not defective; rather, it’s the process medium that is lacking. This leads to friction on the surface, resulting in high temperatures. The different expansion coefficients of silicon carbide and the 316 substrate cause cracks to form. Please help analyze it
Reply to 1# Sealed surface: The main reason is likely dry grinding. Due to the dual-seal structure, when observing the condition at the atmospheric side, it is similar in that this is caused by a lack of sealing fluid. If the atmospheric side is in good condition, it is necessary to analyze the dynamic ring sealing pressure on the medium side or any assembly issues. Personal analysis for reference only
It should have been dry-milled. 0.0.0.0
I have also experienced the issue of seal failure in pump motors. In my opinion, this is caused by dry friction, which leads to high temperatures. On one hand, silicon carbide and 316L have different coefficients of thermal expansion. Additionally, I believe there is an O-ring between the silicon carbide ring of the seal and the 316L ring; it’s possible that the O-ring, under the effects of high temperature or corrosion, could cause the silicon carbide ring to crack.
There should be brief periods when no liquid is applied, which causes the temperature of the friction surface to rise; then, when liquid is applied again suddenly, the rapid change in temperature leads to cracking.
The atmospheric side of the seal water is good. From the images, it appears that the moving ring on the medium side is in good condition, and the rubber O-rings have not undergone any deformation due to high temperatures. However, it seems that the stationary ring on the medium side has been exposed to high temperatures. The people in charge of the manufacturing process say that this is an electrolytic ion membrane system, and the pump for the sodium hydroxide solution used as the anode fluid cannot run out of liquid – such a situation is not allowed by the manufacturing processes; if the liquid runs out, the entire system will stop functioning. But I still doubt his claims; I hope everyone can help analyze it further
The silicon carbide used in machine seals seems to be particularly prone to cracking