Valve Selection for Chlorine and Bleach Service

Introduction

Chlorine and sodium hypochlorite (bleach) are among the most corrosive and hazardous chemicals encountered in water treatment, chemical manufacturing, and pulp bleaching. Valve material selection is critical to prevent catastrophic corrosion failures and toxic releases.

Dry Chlorine Gas Service

Dry chlorine gas (less than 50 ppm moisture) is compatible with carbon steel, monel, and titaniumHastelloy C-276 and C-22 for wet chlorine or moist conditionsAvoid copper alloys, aluminum, and nickel above 80 degrees C in dry chlorinePTFE is the preferred soft seat material for chlorine isolation valvesCast iron acceptable for dry chlorine at ambient temperatures only

Liquid Chlorine Service

Monel 400 body and trim preferred for liquid chlorine transfer valvesCarbon steel acceptable for liquid chlorine at ambient temperatureAvoid moisture contamination: even small amounts cause highly corrosive hydrochloric acidAll valve components must be thoroughly degreased and dried before serviceStainless steel may be used but requires careful attention to moisture

Sodium Hypochlorite (Bleach) Service

Sodium hypochlorite is particularly aggressive toward stainless steel, causing pitting, crevice corrosion, and stress corrosion cracking. Preferred materials include PVC-lined or PVDF-lined valves, Hastelloy C-276, titanium, or rubber-lined steel for large bore applications.

Sealing and Packing

PTFE-lined ball valves and butterfly valves widely used in bleach serviceAvoid elastomers (NBR, EPDM) that degrade rapidly in hypochlorite solutionsEPDM may be acceptable in dilute solutions below 5% NaOClUse PVDF or PP packing followers and gland components to resist corrosionDiaphragm valves with EPDM or PTFE diaphragms suitable for dilute bleach

Safety Considerations

All valve actuators and accessories in chlorine service must be chlorine-compatible. Electric actuators require sealed, explosion-proof enclosures. Emergency shutdown valves must fail-close with fast response. Leak detection systems and personnel protective equipment protocols are mandatory.