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How Medium Properties (Toxicity, Flammability, and Explosiveness) Influence Chemical Pump Selection

Release time：2026-03-23

Impact of Medium Properties on Chemical Pump Selection-The toxicity, flammability, and explosiveness of the medium

The toxicity, flammability, and explosiveness of your medium directly determine the sealing solution and flushing plan.

Get it wrong — and it’s not a minor leak. It’s an accident waiting to happen.

Highly Toxic & Hazardous Media

Typical media

Liquid chlorine, acrylonitrile, benzene

Advantages

Fully enclosed structure
No dynamic seal
Theoretical zero leakage

Disadvantages

Higher initial cost
Complex maintenance

Flammable & Explosive Media

Typical media

Hydrocarbons, methanol, toluene, H₂S-containing fluids

Industry standard solution

Double mechanical seal+flushing system

flushing system

Plan 52 ,53A / B → buffer/barrier fluid system,controlled leakage,online monitoring & alarm.
Plan 54 → external clean fluid supply, high operational safety.

Gas Media

Flammable & Explosive Media

Ethylene, natural gas

Advantages

Near-zero leakage
Low friction
Long service life

Disadvantages

Stable gas supply system
Higher system complexity

Low-Risk Media

Applicable only when

Non-toxic
Non-flammable
Low hazard level

Seal Configuration and Flushing System Selection Table Based on Medium Toxicity, Flammability, and Explosiveness

Type		Structure	Applicable	Advantages	Disadvantages
Leak-free pump	Magnetic drive pump	Magnetic coupling drive, isolation sleeve completely sealed, no dynamic seals, intrinsically safe.	Liquid chlorine, hydrogen cyanide, phosgene, aniline,acrylonitrile, mercury, and highly corrosive media.	Zero leakage, explosion-proof, and environmentally friendly.	High cost, prone to dry running, and complex maintenance.
Leak-free pump	Canned motor pump	The motor rotor and impeller are coaxial, with a totally enclosed structure and no dynamic seals.	Liquefied petroleum gas (LPG), vinyl chloride, benzene, and toxic volatile media.	Zero leakage, low noise, suitable for clean media.	High cost, difficult maintenance.
Double mechanical seal	Plan52, Plan 53A/	Low-pressure buffer liquid/pressurized isolation liquid circulation, with internal leakage but no external leakage.	Moderately / highly hazardous, flammable, explosive, volatile, and highly corrosive media (such as hydrogen sulfide, methanol, toluene, sulfuric acid, caustic soda).	Double protection, leak controllable, and online monitoring available.	Requires a complementary buffer/isolation iquid system.
Double mechanical seal	Plan 54	Externally supplied clean isolation liquid, suitable for high temperatures, prone to crystallization.			Requires a complementary buffer/isolation iquid system.
Dry gas seal		Nitrogen gas used as sealing gas, non-contact, low friction, and long service life.	Liquefied petroleum gas (LPG), ethylene, propylene, easily vaporized toxic gases, and flare gas system.	Zero leakage, high-temperature resistant, suitable for high speed.	Requires nitrogen gas source, high cost.
Single mechanical seal		Single seal face, no external barrier fluid.	Mildly hazardous, non-toxic, non-flammable, and non-volatile (such as dilute acids, dilute alkalis, and general wastewater).	Low cost, simple structure, and easy maintenance.	Strictly prohibited for use with extremely / highly hazardous media, leakage directly into the environment.