What seals are selected for stainless steel gear pumps when transporting food and chemical raw materials

In the selection of seals for stainless steel gear pumps, there is a significant difference in demand between the food and chemical industries, and targeted design should be carried out based on the characteristics of the medium and industry standards

1、 Sealing selection in the food industry**

1.  Material Requirements

Food grade certification must comply with FDA 21 CFR or EU EC 1935/2004 standards to ensure non toxicity and non contamination.

 Mild and Corrosion Resistant : Must withstand acids, alkalis, oils, and high-temperature cleaning in food (such as CIP/SIP processes).

2. * * Recommended sealing solution

Elastic sealing:

EPDM (Ethylene Propylene Diene Monomer Rubber): Suitable for neutral foods (such as juices and dairy products), resistant to high temperature steam sterilization.

Silicone rubber (VMQ): resistant to high and low temperatures (-60 ° C~230 ° C), suitable for high-fat foods, but with low mechanical strength.

 PTFE (Polytetrafluoroethylene) : Strong chemical inertness, used in strong acid/alkaline foods (such as vinegar, cleaning agents), but needs to be matched with elastomers to compensate for elasticity.

 Mechanical seal :

 Material combination : Silicon carbide to silicon carbide (wear-resistant, long-life) or ceramic to PTFE (economical and practical).

Structural design: Single end sealing with flushing system, or double end sealing with food grade isolation liquid (such as glycerin) to prevent leakage and contamination.

Sanitary design: The sealing surface should be smooth and free of dead corners, comply with 3-A or EHEDG standards, and be easy to disassemble and clean.

2、 Sealing selection in the chemical industry

1. Material Requirements

Chemical corrosion resistance: Depending on the medium, strong acids (sulfuric acid, hydrochloric acid), strong bases (sodium hydroxide), solvents (acetone, benzene), etc. can be selected.

High temperature and high pressure resistance: Some processes can reach temperatures above 200 ° C and require materials with high temperature stability.

2.  Recommended sealing solution

Elastic sealing:

FFKM (Perfluororubber): Resistant to strong acids, alkalis, and organic solvents, suitable for extreme chemical environments such as concentrated sulfuric acid transportation.

PTFE coated O-ring: Combining the corrosion resistance of PTFE with the elasticity of metal springs, it is used in highly corrosive media.

 Mechanical seal 

 Material combination :

Silicon carbide (SiC) versus hard alloy (WC): resistant to granular media (such as solid slurries).

Hastelloy sealing ring: used for strongly oxidizing media such as nitric acid.

Structural Design :

Double end mechanical seal+pressurized isolation fluid (such as ethylene glycol) to prevent leakage of toxic media.

Cartridge Seal simplifies installation and improves reliability.

 Auxiliary measures :

Adopt API 682 standard flushing scheme (such as Plan 32 external flushing) to prevent crystallization or polymerization from blocking the sealing surface.

Stainless steel gear pumps use bellows seals under high temperature conditions to avoid aging of auxiliary sealing rings.

3、 Precautions**

 Working condition adaptation * *: The sealing scheme needs to be selected based on specific medium parameters (pH, temperature, viscosity, solid content).

Maintenance cost : Long life seals (such as SiC mechanical seals) are recommended in the chemical industry to reduce downtime losses; The food industry prioritizes designs that are easy to disassemble and clean.

Compliance: The food industry requires regular material certification audits, while the chemical industry should refer to ASME BPE or ISO 2858 standards.

Through the above targeted selection, it can be ensured that stainless steel gear pumps can balance safety, efficiency, and cost-effectiveness in food and chemical applications.