Equipment selection
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The existing equipment has the following problems: frequent leakage of the mechanical seal. The seal is a double-end face seal, and it is flushed with process water at a pressure of 0.4 MPa; the flushing fluid is discharged on-site. The medium consists of calcium stearate (18%) and hexane, with a flow rate of 2.4 m3/h and a head of 63 m. The pump currently in use is an open impeller centrifugal pump, and the medium may contain packaging film from woven bags as well as fragments of those bags, which are introduced along with the calcium stearate. If we need to reselect the pump, what type of pump do you think would be better?
As for miscellaneous items, they generally need to be filtered, right? We have many single-sided machine seals in our factory; let the experts answer!
It tends to get clogged when filtered, as the material is quite viscous. Single-face sealing is more prone to leakage; therefore, we have chosen double-face sealing
Double-end surfaces are flushed with process water, and the water can also be discharged on-site; it doesn’t seem that such a flushing method is specified in API 682 When the solid content of the material is high, a pressure-driven double-seal such as PLAN 53A should be used; with the pressure in the sealing chamber higher than that in the pump chamber, particles are less likely to reach the friction surfaces or the sealing chamber and thus damage the seal.
In this case, the coolant can easily get into the material, and the material should not enter the coolant either; it is necessary to avoid as much as possible the coolant from getting into the material
This post was last edited by A Le on 2016-7-12 at 15:47. There must always be a difference in pressure inside and outside the mechanical seal friction pair; if the pressure in the pump chamber is high, the material is likely to leak out, and the particles can damage the mechanical seal. If the pressure in the sealed chamber is high, the isolation fluid will enter the pumped medium, but isolation fluids that do not affect the quality of the material or can be easily separated can be used. If the material does not crystallize, polymerize, or solidify easily, a dry gas seal can be considered; it should be relatively easy to separate it by introducing nitrogen inside.
Replacing it with a dry gas seal would be too costly. The pump I have on site is quite small, and I’m wondering if it’s possible to change the design of the pump itself.
Magnetic pumps and shielded pumps are both sealless pumps, ensuring no leakage. Both conventional magnetic pumps and shielded pumps are sensitive to particles and crystals, but many manufacturers today have developed new types of shielded pumps and magnetic pumps that can operate in conditions with a small amount of impurities (as far as I know, this applies to some foreign manufacturers; it’s possible that domestic manufacturers also have such products, but I’m not aware of them). So you can consult manufacturers of magnetic pumps and shielded pumps, such as Hydrac.
Our materials are quite viscous; originally we chose centrifugal pumps with open impellers, as we were concerned that magnetic drive pumps and shielded pumps might break more easily. Has anyone used cyclone pumps? We’re not sure how well cyclone pumps perform with viscous chemical materials
It seems that the cyclone pump can be used to transport your material, but it does not solve the seal leakage problem you mentioned at the beginning.
If the viscosity is high, you can try using a diaphragm pump