What technical parameters should be clarified first?
Before enquiring, it is recommended that engineers sort out the following data:
| Parameters | Contents that need to be explained when selecting the model |
|---|---|
| Media | Normal, minimum and maximum mass concentrations of sulfuric acid; whether it contains water, chloride ions, solids Solid particles or other chemical components |
| Temperature | Normal, maximum and start-up and shutdown temperatures; whether there is local overheating |
| Hydraulic conditions | Minimum, normal and maximum flow rates; corresponding head, inlet pressure and available Use NPSH |
| Operating conditions | Continuous or intermittent operation, start and stop frequency, whether idling is possible |
| Installation conditions | Horizontal or vertical, tank level, relative position of pump and liquid level |
| Sealing requirements | Allowable leakage level, available cooling or isolation system, maintenance conditions |
Among them, minimum concentration and maximum temperature should be checked in combination. For example, cleaning, water inflow or process fluctuations may change the local acid concentration, and "98%" during stable production cannot be used to represent all working conditions.
How to choose materials for flow-passing parts?
The fluid contact conditions of the pump body, impeller, pump cover, bushings and fasteners should be checked one by one. Do not just write "the pump body is made of acid-resistant material". Materials such as 316L, 904L, high-silicon cast iron and nickel-based alloys each have their own application ranges, but they should not be generally labeled as "resistant to all concentrated sulfuric acid". Especially when the temperature rises, the concentration fluctuates, or the medium contains impurities, corrosion data needs to be checked according to specific working conditions. Haynes' sulfuric acid isocorrosion curve shows that the applicable boundaries of different alloys vary with concentration and temperature; laboratory pure acid data cannot directly replace field media verification.
The material comparison and selection is recommended in three steps: first, screen candidate materials based on concentration, temperature and impurities; then check the manufacturability of castings, welds and all wetted parts; finally, determine the allowable corrosion rate and maintenance cycle based on project requirements. If the manufacturer recommends a higher grade alloy, it should be required to explain the basis; if it recommends conventional stainless steel, it should also be required to provide evidence of suitability for the corresponding working conditions. Material costs should be compared with expected life and downtime losses.
How to configure the mechanical seal?
Shaft seals cannot just look at the name of the sealing surface. When selecting, the sealing surface, metal parts, elastic components, sealing chamber temperature and auxiliary systems should be confirmed at the same time. High-temperature working conditions may push conventional elastomers beyond their scope of use; solutions such as metal bellows seals can be evaluated, but the compatibility of all wetted parts with sulfuric acid must still be checked.
If the process has strict requirements for leakage control, the double-end seal and isolation system can be evaluated with the seal manufacturer, and the acceptability of the isolation medium entering the process side, pressure supply, and failure alarm methods can be clarified. Flange gaskets must also be selected separately: even if they are both modified PTFE, different formulas may have different applicable temperatures for concentrated sulfuric acid, and the decision cannot be made solely based on "PTFE acid resistance".
How to choose the pump type for different project locations?
Storage tank transportation, production unit circulation and underground tank liquid lifting have different requirements for pumps. Horizontal process pumps are usually easy to maintain on the ground, but the suction conditions and shaft seal scheme need to be verified; vertical long-shaft pumps can be used in specific tanks or underwater installation conditions, and the underwater length, support and shafting stability must be checked at the same time. Feiyue's official website lists vertical long-axis pump products for transporting media such as sulfuric acid, but the specific materials and applicable temperatures should still be subject to the project working conditions and the configuration confirmed by the manufacturer. Transmitting concentrated sulfuric acid and transporting liquid sulfur belong to different working conditions, and the same selection cannot be applied just because the product name contains "sulfur".
Two common questions when purchasing
Can 316L be directly selected for 98% concentrated sulfuric acid? You cannot judge based on concentration alone. At least it is necessary to clarify the maximum temperature, impurities, flow rate and concentration changes during start and stop, and then check the manufacturer's corrosion data under corresponding working conditions.
Can the leakage problem be solved by using double-end seals? Double-end seals require appropriate isolation systems, monitoring and maintenance; if the sealing material, temperature or pressure conditions do not match, simply adding a seal will not solve the fundamental problem.
Purchasing Suggestions and Leap Product Plans
When sending an inquiry to a supplier, it is recommended that they also submit a material list of flow-passing parts, material selection basis, sealing configuration and auxiliary system description, performance curves and applicable working condition boundaries. For projects with large concentration or temperature fluctuations, the most adverse working conditions should be written into the technical agreement, and the operating restrictions under start-up, shutdown and abnormal working conditions should be confirmed.
Feiyue can evaluate chemical process pump or vertical pump solutions based on the sulfuric acid delivery location, flow head and installation conditions. Only after the purchaser provides complete media analysis and operating parameters, and then determines the wetted materials, shaft seals and auxiliary systems, can a comparable and acceptable technical quotation be formed.
