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Melamine Gear Metering Pump Selection
To address the customer's need to transport solutions with two different pH values and high viscosity, and considering the material compatibility, flow matching, and coating enhancement solutions of the gear metering pump, the following are optimized selection suggestions and operating guidelines:
I. Material Selection and Corrosion Protection
1. Solution A (Melamine-Urea-Formaldehyde Condensate, pH 9.5±3)
Base Material: 9Cr18 (Martensitic Stainless Steel)
Advantages: Contains 18% chromium and 0.95% carbon, resistant to neutral to weakly alkaline corrosion (pH 6-12), high hardness (HRC≥58), and strong wear resistance.
Applicability: Suitable for the pH range and density (1.25-1.35 kg/L) of Solution A, but the impact of viscosity (2000-10000 mPa·s) on gear wear needs to be considered.
Coating Enhancement:
Recommended Coating: Ceramic coating (e.g., alumina) or tungsten carbide coating.
Applications:
1. Ceramic coating (HV 1200-1500) resists particle scratches and reduces wear from solid particles in high-viscosity solutions.
Tungsten carbide coating (HV 2000+) resists extreme wear but is more expensive and suitable for long-term high-load conditions.
2. Solution B (Formic acid mixture, pH 1-2)
Base material: Stellite 6B
Advantages: Cobalt-based alloy containing 28% chromium and 5% tungsten, resistant to strong acid corrosion (such as sulfuric acid and hydrochloric acid), especially suitable for extremely acidic environments with pH < 2.
Alternative: If budget is limited, Hastelloy C-276 (nickel-based alloy) can be considered, but the cost is 30%-50% higher than Stellite.
Coating reinforcement:
Recommended coating: Polytetrafluoroethylene (PTFE) lining or tungsten alloy plating.
Applications: PTFE lining is resistant to acid corrosion (pH < 1) and has strong self-lubricating properties, reducing friction between gears and the pump body.
Tungsten alloy coating (W-Co-Cr) has an acid corrosion resistance rate of <0.01mm/year, extending pump life.
II. Flow Rate and Displacement Matching
1. Solution A (High Viscosity 2000-10000 mPa·s)
Selection Principle: High-viscosity fluids require low-speed operation to reduce shear force and avoid solution structure damage.
Recommended Displacement: 12CC
Calculation Example: If the system requires a flow rate of 30L/min and a drive speed of 1500r/min, then the pump displacement must be ≥20mL/r (30×1000÷1500).
A 12CC pump can output 6L/min at low speeds (e.g., 500r/min). High flow rate requirements can be met by parallel operation of multiple pumps or frequency conversion speed regulation.
Advantages: Large displacement pumps operating at low speeds reduce wear by more than 50%, making them suitable for long-term stable delivery.
2. Solution B (Medium viscosity 1500-6000 mPa·s)
Selection Principle: Balance flow rate and efficiency, avoid gear overheating due to high-speed operation.
Recommended Displacement: 6CC
Calculation Example: If the system requires a flow rate of 15 L/min and a drive speed of 2500 r/min, then the pump displacement must be ≥6 mL/r (15 × 1000 ÷ 2500).
A 6CC pump can stably output 6-12 L/min within the range of 1000-2000 r/min, adapting to viscosity fluctuations.
Advantages: Medium displacement pumps operate at medium speeds, balancing flow requirements and equipment lifespan.
III. Structural Optimization and Operational Recommendations
1. Gear Type Selection
Solution A: Circular arc toothed gear
Advantages: Less meshing impact, wear rate reduced by 40% compared to involute toothed gears, suitable for high-viscosity solutions containing solid particles.
Solution B: Involute gear teeth
Advantages: High machining accuracy (tooth surface roughness Ra≤0.4μm), reducing electrochemical corrosion in acidic media.
2. Upgraded Sealing Method
Solution A: Fluororubber (FKM) seal
Temperature resistance: 150℃, resistant to melamine-formaldehyde condensate chemical corrosion.
Solution B: Polytetrafluoroethylene (PTFE) seal
Acid resistance: pH<1, and strong self-lubricating properties, reducing friction.
3. Drive and Filtration System
Drive Matching: The motor speed must be compatible with the pump's rated speed (1000-3000r/min) to avoid accelerated wear due to high speed (>3000r/min).
Filtration System: Install an 80-mesh filter at the suction port and a 10μm filter element at the return port to reduce impurities and reduce pump damage.
4. Temperature Control
Solution A: Maintain temperature <60℃ to avoid sudden viscosity increases that could overload the pump.
Solution B: Maintain temperature > 20℃ to prevent formic acid crystallization and pipe blockage.
IV. Selection Scheme Summary
Solution Type | Recommended Material | Recommended Displacement | Gear Type | Sealing Method | Coating Treatment
Solution A (pH 9.5) | 9Cr18 + Ceramic Coating | 12CC | Circular Tooth | Fluororubber (FKM) | Alumina Ceramic Coating
Solution B (pH 1-2) | Stellite Alloy + PTFE Liner | 6CC | Involute Tooth | Polytetrafluoroethylene (PTFE) | Tungsten Alloy Coating
Email:sales01@cxflowmeter.com
whatsapp:008618049841995
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