Pump selection
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This post was last edited by FLYTOINTER on 2010-7-12 at 13:18. The company has started a new project that involves passivating stainless steel pipes using 40% concentrated nitric acid; what type of pump can be used for this purpose? See floor 6; the answer was quite professional. ——by flytointer
A tetrafluoroethylene pneumatic diaphragm pump can be used, but larger models cannot be manufactured domestically; those with high flow rates are not available. I’m not sure if you have any requirements regarding flow rate or continuity – diaphragm pumps generate pulses
Non-metallic pumps can be considered, with all liquid-flowing components having a steel-lined fluoroplastic structure. The fluorine-coated thickness is generally between 3 and 8 mm, and F46 material is currently the best corrosion-resistant material available in China. It completely replaces titanium alloys and Hastelloy. The sealing type is a mechanical seal, with the sealing surface material being pressure-sintered silicon carbide. Actual use shows that this type of pump has advantages such as resistance to severe corrosion, no aging, good sealing performance, and an advanced and rational design. It is the king of corrosion resistance among pumps, and it offers good compatibility and interchangeability with IH-type chemical centrifugal pumps. II: Scope of application: It is widely applicable to industries such as chemicals, pharmaceuticals, metallurgy, power generation, electroplating, and pickling. It can transport highly corrosive media such as sulfuric acid, hydrochloric acid, nitric acid, acetic acid, hydrofluoric acid, strong oxidizers, organic solvents, and reducing agents at any concentration over a long period of time, in temperature ranges from -20°C to +120°C.
It is feasible to use a metal pump; C4 material can be selected. It can be manufactured by ordinary domestic chemical pump manufacturers. If frequent startup is required, it is recommended to choose domestic manufacturers based in areas such as Jingjiang; if stable operation is sufficient, chemical pumps from the Dalian area can be selected. Both of the above have good effects. Make sure the machine seal is properly configured – nitric acid is no good thing.
A nitric acid concentration of 40% is not very high; it also depends on the temperature at which it is used! If the temperature is below 50°C, either 304 or 12%Cr steel will meet the requirements! If the temperature is above 50°C and below 100°C, 316 can also meet the requirements! Generally, for concentrated nitric acid with a concentration of over 70%, only titanium or fluoroplastic pumps can be used! As for whether to use a metal pump or a non-metallic pump, other factors also need to be taken into consideration, such as inlet pressure, price, service life, spare parts, and the ease of maintenance! :)
We recommend that you avoid using pumps with a steel-lined fluoroplastic structure. Our organization has used such pumps, and the results were poor. The main reason is the large difference in thermal expansion coefficients between the steel layer on the inside and the fluoroplastic layer on the outside; as a result, the outer plastic layer cracks after a short time, and even the components crack on their own after being stored in the warehouse for just a few months.