Why does the stainless steel alkali pump always leak fluid from the seal cooling water pipe?
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We use stainless steel alkali pumps (304) with mechanical seals of type 171-35; the model of these alkali pumps is IJ80-50-160. During operation, these pumps often experience leakage at the cooling water inlet for the mechanical seals. I replaced it with a new mechanical seal, but it started leaking again after not long – I don’t know what the reason is How to solve it?
May I ask about the alkali concentration, temperature, and salt content? If the alkali concentration is high, the temperature is low, or the salt content is high, the mechanical seal will be worn due to the precipitation of crystalline substances.
The crystallization-induced wear of the mechanical seal in the alkali pump is the cause of medium leakage; reducing the standby time of the spare pump can slow down the crystallization rate of the alkali solution. If the concentration of the alkaline solution is not very high, and cleaning is required as well as low delivery pressure, a magnetic pump can be used.
If crystallization occurs easily, using a magnetic pump won’t work either. Is it possible that the pressure of your cooling water is too low, causing the fluid to leak out?
May I ask about the alkali concentration, temperature, and salt content? If the alkali concentration is high, the temperature is low, or the salt content is high, the mechanical seal will be worn due to the precipitation of crystalline substances. The concentration is 30%, the temperature is room temperature, the salt content is low, but it contains a small amount of activated carbon, about 0.3%.
If crystallization occurs easily, using a magnetic pump won’t work either. Is it possible that the pressure of your cooling water is too low, causing the fluid to leak out? Thank you, moderator! Our materials don’t crystallize very often. Magnetic pumps cannot be used for crystalline materials. The moderator is right. Our cooling water isn’t working. I wonder if this is the main reason?
The cleanliness of the cooling water and its tendency to form scale also affect the sealing. Water with high hardness that tends to form scale can result in poor rinsing performance, affecting sealing and heat dissipation.
You are using a double-end face mechanical seal; the sealing chamber must be filled with a sealing fluid, and the pressure of this fluid must be higher than the pressure at the pump outlet.
Double-surface fluoroplastic centrifugal pumps can do without it
The medium transported by alkali pumps tends to crystallize, which can cause the sealing surface to separate or lead to the failure of elastic components. Generally, a PLAN62 unit is required for cold water flushing; or in the event of a medium leak, using steam or water to purge away the crystalline substances can help reduce the amount of leakage.
Characteristics of a poorly designed alkali pump: the mechanical seal needs to be replaced frequently; even after it has been replaced, leakage occurs again after just a few days, and the leakage is quite severe. The reason is simple: it’s not used continuously, but intermittently. For example, for loading and unloading. A tank truck arrived today; the pump ran for a while, filling the tank, or once the loading/unloading was complete, the pump stopped again. When liquid caustic comes into contact with air and the pump stops, the residual liquid caustic inside tends to crystallize very easily. These crystals are the main cause of seal leakage. It can be tried: before starting the pump, connect the steam pipeline, and have the operator blow air at the seal area for about 0.5 hour to warm up the pump, thereby heating the crystals inside and turning them into a liquid state; this helps to extend the lifespan of the seal significantly. As a complete solution, I’ve seen some factories replace the pumps with diaphragm pumps or magnetic drive pumps, and others add steam heating pipelines