ndustrial Pump Materials: Selection & Use（I）

The selection of materials for water pumps in industrial production is critical, as it directly impacts equipment service life, operational efficiency, maintenance costs, and even the safety and stability of the entire production process. Material selection is not about choosing the most expensive option, but rather a comprehensive trade-off based on the chemical properties, physical characteristics, operating conditions of the fluid being handled, and cost-effectiveness.

Below is a systematic explanation of the material requirements for various water pumps in industrial production.

I. Core Selection Principles

Before selecting pump materials, the following key factors must be defined:

Corrosiveness of the Medium: This is the primary consideration. The pH, chloride ion content, oxidizability, etc., of the medium determine the required corrosion-resistant material.

Abrasiveness: Whether the medium contains solid particles (e.g., sand, slurry, catalyst particles). This requires materials with high hardness and wear resistance.

Operating Temperature and Pressure: High temperatures accelerate corrosion and reduce material strength; high pressure demands higher mechanical strength from materials.

Medium Purity and Special Requirements: For industries like food and pharmaceuticals, non-toxic, non-contaminating, and easy-to-clean materials (e.g., stainless steel) are required. For pure or ultrapure water, materials that do not leach ions and contaminate the medium are essential.

Cost Considerations: Select the most economical material that meets the process requirements.

II. Common Pump Body Materials and Their Applications

1. Cast Iron

Characteristics: Low cost, good castability, moderate mechanical strength. Poor corrosion resistance.

Applications:

Water Pumps: Transporting ambient temperature, non-corrosive industrial water, cooling water.

Some circulating water pumps, HVAC pumps.

Limitations: Not suitable for acids, alkalis, salt water, seawater, or media containing a large amount of abrasive particles. In tap water, long-term operation can lead to rust, causing "yellow water."

2. Stainless Steel

This is the most widely used corrosion-resistant material in industrial pumps, but "stainless steel" is a category containing various grades.

304 Stainless Steel:

Characteristics: General-purpose austenitic stainless steel, resistant to general corrosion (e.g., dilute nitric acid, organic acids).

Applications: Food, beverage, pharmaceutical industries (meets sanitary standards); transporting mildly corrosive chemicals in chemical industry; alkaline solutions at ambient temperatures.

316/316L Stainless Steel:

Characteristics: Contains Molybdenum (Mo), providing better resistance to chloride pitting and crevice corrosion than 304.

Applications: The most widely used material for chemical pumps. Used for conveying seawater, brine, chloride solutions, dilute sulfuric acid, phosphoric acid, etc. 316L has lower carbon content, offering better resistance to intergranular corrosion, suitable for welded components.

304L/316L Stainless Steel:

Characteristics: Low-carbon versions, primarily used where heat treatment after welding is not possible, to prevent intergranular corrosion.

Applications: Large pump casings or pumps with complex structures that require extensive welding.

Duplex Stainless Steel (e.g., 2205):

Characteristics: Combines austenitic and ferritic structures, strength is twice that of 304/316, excellent resistance to chloride stress corrosion cracking, and good pitting resistance.

Applications: High-concentration brine, seawater, harsh conditions containing chloride ions, oil & gas, offshore platforms, flue gas desulfurization (FGD).