Caustic (Sodium Hydroxide)

Caustic (Sodium Hydroxide)

Industrial scale pipes and drums

Sodium hydroxide is a strong base (pH 13–14) widely used in petroleum refining, chemical manufacturing, rayon and film production, pulp and paper, aluminum processing, vegetable oil, detergents, soaps, textiles, water treatment, rubber reclamation, and as an alkali in foods. It is primarily produced through the chloralkali process, initially as a 32% solution and then concentrated to 50%. Solid sodium hydroxide is also available in flakes, prills, and cast blocks.

Caustic soda’s viscosity ranges from water-thin at low concentrations to about 78 cP at 50%. It is denser than water, with a specific gravity of 1.5 at 50% and up to 2.0 at 72%, which must be considered in NPSHa calculations. Positive displacement pumps are ideal for transferring moderately viscous liquids like sodium hydroxide because they handle a wide range of viscosities and provide consistent, controlled flow. These pumps trap a fixed amount of fluid and force it through the system, ensuring steady flow even under varying pressures. Their excellent NPSHr characteristics make them suitable for difficult suction conditions, even with high specific gravity fluids.

Because caustic soda is highly corrosive, consult Viking for material recommendations, especially for higher concentrations or temperatures. To prevent severe chemical burns, mechanical seals or sealless magnetic drives are recommended.

Viking in the Process

Viking pumps are found wherever caustic is used, especially in chemical manufacturing and saponification processes in soap and detergent manufacturing. Tank and railcar unloading is commonly performed via top of tank to prevent unintended spills that could come from tank bottom ports. Due to high specific gravity, this requires both the self-priming ability and excellent NPSHr provided by Viking pumps. Transfer pumps may be constant speed, controlled by level controls or load cells. Metering applications typically require variable speed drives.

Applications

  • Tank/railcar unloading
  • Transfer from tank farm to day tank
  • Metering into process
     

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