Chlorine and sodium hypochlorite (bleach) are powerful oxidizers used in water treatment, chemical manufacturing, and disinfection. Pumps must handle corrosive chlorine gas/liquid, oxidizing hypochlorite, and safety hazards. This guide covers pump selection for chlorine and sodium hypochlorite handling.
Chlorine / Hypochlorite Pump Services
| Service | Fluid | Concentration | Key Characteristic | Pump Type |
|---|---|---|---|---|
| Liquid chlorine transfer | Liquid chlorine (Cl2) | 100% | Very corrosive (dry chlorine passivates steel, wet chlorine = explosive corrosion), toxic, high vapor pressure (~7 bar at 20°C), safety-critical | Fluoroplastic pump (PTFE/PFA — only for wet chlorine) or specialized chlorine pump (dry chlorine = carbon steel, but zero moisture critical) |
| Chlorine dosing (to water) | Chlorine gas or liquid (injected) | 100% | Toxic, corrosive, precise (dosing), small flow, safety-critical, vacuum feed system | Chlorine vacuum feeder (ejector, not pump) or diaphragm metering (PTFE, for liquid chlorine solution) |
| Sodium hypochlorite (bleach) transfer | NaOCl solution (bleach) | 5–15% (household 5%, industrial 12–15%) | Corrosive (oxidizer), decomposes (heat/light/metal → O2 + NaCl), viscous (1–10 cP), precise, large flow, off-gassing (O2) | Fluoroplastic pump or 316SS centrifugal (corrosion, zero leakage, off-gas handling) |
| Hypochlorite dosing (to water) | NaOCl solution | 5–15% | Corrosive, precise (disinfection dose), small flow, continuous, off-gassing, safety | Diaphragm metering (PTFE, precise, zero leakage, off-gas tolerant) — standard for bleach dosing |
| Hypochlorite production (chlor-alkali) | Cl2 + NaOH → NaOCl (in reactor) | Variable | Corrosive (Cl2 + NaOH), exothermic, precise (ratio control), large flow, continuous, critical | Fluoroplastic pump or 316SS centrifugal (corrosion, large flow, zero leakage) |
| Caustic (NaOH) feed (for hypochlorite) | Sodium hydroxide (NaOH) | 20–50% | Corrosive (caustic), viscous (50% ~80 cP at 20°C), hot (exothermic with Cl2), precise, large flow, crystallizes (50% below 12°C) | 316SS centrifugal or screw pump (viscous, jacketed, corrosion-resistant, EPDM/PTFE seals) |
| Brine feed (chlor-alkali cell) | Saturated NaCl brine | ~26% (saturated) | Corrosive (chloride pitting), abrasive (salt crystals), large flow, continuous, critical (cell feed), high purity | 316SS/duplex centrifugal (chloride-resistant, large flow) or fluoroplastic (severe corrosion) |
| Cell liquor (from electrolyzer) | NaOH + NaCl + hypochlorite (cell liquor) | NaOH 10–12%, NaCl ~15% | Very corrosive (chloride + caustic + hypochlorite), hot (80–90°C), large flow, continuous, critical | 316SS/duplex centrifugal or fluoroplastic (corrosion, high temp, zero leakage) |
| Hydrochloric acid (HCl, byproduct/use) | HCl solution | 30–37% | Very corrosive (HCl attacks 316SS above ambient), fuming, toxic, precise, small/moderate flow | Fluoroplastic pump (PTFE — only for HCl) or PTFE metering (zero leakage) |
| Sodium chlorate (byproduct) | NaClO3 solution | Variable | Corrosive (oxidizer), viscous, moderate flow, byproduct | 316SS centrifugal or fluoroplastic (corrosion) |
| Demineralized water (for dilution) | DM water (low conductivity) | 0% | Very clean, corrosive (low conductivity attacks carbon steel), large flow, continuous | 316SS centrifugal (corrosion, clean, large flow) — NOT carbon steel |
| CIP / flush | Water + dilute NaOH (flush bleach residue) | 1–2% NaOH | Corrosive, intermittent, large flow, bleach decomposition | 316SS centrifugal (corrosion, large flow, CIP-compatible) |
| Wastewater (bleach plant) | Alkaline wastewater (hypochlorite + chloride + caustic) | Variable | Corrosive (oxidizer + chloride), toxic (residual chlorine), environmental, large flow | 316SS/duplex centrifugal or fluoroplastic (corrosion, zero leakage) |
| Scrubber liquor (chlorine scrubber) | NaOH + NaOCl (scrubbing Cl2 gas) | NaOH 5–20%, NaOCl 1–5% | Corrosive (caustic + oxidizer), exothermic, large flow, continuous, safety (emergency scrubber) | 316SS centrifugal or fluoroplastic (corrosion, large flow, reliable — safety critical) |
Critical: Chlorine Safety (Toxic + Corrosive + High Vapor Pressure)
Chlorine is one of the most hazardous industrial chemicals — safety is paramount:
- Dry vs wet chlorine: Dry chlorine (＜150 ppm water) is compatible with carbon steel (passivates). Wet chlorine (＞150 ppm water) is EXTREMELY corrosive — attacks carbon steel, 316SS, most metals. Use PTFE/PFA-lined pump (fluoroplastic) for wet chlorine or chlorine solutions. Moisture control is critical — dry chlorine systems must be kept dry. Chlorine + water = HCl + HOCl (corrosive + oxidizing).
- Toxic: Chlorine gas is toxic (IDLH 10 ppm, TLV 0.5 ppm). Zero leakage required. Use magnetic drive or canned motor pump (no shaft seal) or double mechanical seal with barrier fluid. Gas detection (Cl2 sensor). Emergency scrubber (NaOH). PPE (respirator, chemical suit). Ventilation. Secondary containment. Our zero-leakage range prevents chlorine exposure.
- High vapor pressure: Liquid chlorine ~7 bar at 20°C, ~10 bar at 30°C. Pump must handle high suction pressure. Low-NPSH design (chlorine vaporizes easily). Flooded suction. Pressure relief. Store below 30°C (pressure increases with temp). Our high-vapor-pressure pumps handle liquid chlorine.
- Chlorine dosing: Water treatment uses vacuum feed system (ejector creates vacuum, chlorine gas drawn into water) — not a conventional pump. For liquid chlorine solution dosing: PTFE diaphragm metering pump (precise, zero leakage).
Critical: Sodium Hypochlorite (Decomposition + Off-Gassing + Corrosion)
- Decomposition: NaOCl decomposes: 2NaOCl → 2NaCl + O2 (heat, light, metal catalysts, pH ＜10 accelerate). Decomposition causes: (1) loss of strength (bleach potency drops), (2) oxygen gas generation (off-gassing), (3) pressure buildup. Use PTFE or 316SS (avoid copper, iron, nickel — catalyze decomposition). Store cool, dark, pH ＞11. Vent pump (off-gas). Our PTFE/316SS range minimizes decomposition.
- Off-gassing: Oxygen gas from decomposition accumulates in pump — gas locking, loss of prime. Use pump with gas handling capability: diaphragm metering (tolerates gas), peristaltic (no valves to gas lock), or centrifugal with vented seal chamber. Vertical pump (gas rises away). Avoid standard centrifugal (gas locks). Our off-gas-tolerant pumps handle bleach.
- Corrosion: NaOCl is an oxidizer — corrosive to carbon steel, copper, aluminum. 316SS is OK for 5–15% at ambient (but check — pitting possible). PTFE/PFA-lined is best for ＞12% or high temp. EPDM or PTFE seals (NOT NBR — oxidizer degrades NBR). Zero leakage (bleach burns skin, damages equipment). Our corrosion-resistant range handles hypochlorite.
Critical: Caustic (NaOH) + Chlorine Reaction (Exothermic)
- Exothermic reaction: Cl2 + 2NaOH → NaOCl + NaCl + H2O is exothermic (heat generation). Caustic feed pump must handle hot fluid (40–80°C). Use 316SS (caustic-resistant) with high-temp seal. Jacketed (cool if needed). Temperature control (reaction heat). 50% NaOH crystallizes below 12°C — use jacketed pump (maintain ＞20°C), heat tracing. Our 316SS/jacketed range handles caustic + exothermic reaction.
- Caustic corrosion: 50% NaOH at ＞80°C causes caustic stress corrosion cracking (CSCC) in carbon steel and even 316SS. Use stress-relieved 316SS or nickel alloy (Alloy 400/600) for high temp/concentration. EPDM or PTFE seals (NOT NBR — caustic attacks NBR). Our alloy range handles severe caustic.
Critical: Brine + Chloride Pitting
- Chloride pitting: Saturated brine (~26% NaCl) and cell liquor (high chloride) cause pitting/crevice corrosion in 316SS. Use duplex or super duplex (PREN ＞40) or PTFE-lined pump. High velocity (＞3 m/s) increases erosion-corrosion. Control velocity. Monitor pitting (UT). Our duplex/PTFE range handles brine/chloride.
- Cell liquor: Hot (80–90°C) caustic + chloride + hypochlorite = very corrosive. Use duplex or PTFE-lined. Zero leakage. High-temp seal. Our corrosion-resistant range handles cell liquor.
Material Compatibility
| Material | Liquid Cl2 (dry, 20°C) | NaOCl 12% (ambient, oxidizer) | 50% NaOH (60°C, caustic) | 37% HCl (ambient) | Saturated brine (ambient, chloride) |
|---|---|---|---|---|---|
| Carbon steel | Good (DRY only, passivated) | NOT (oxidizer corrosion) | Fair (CSCC risk ＞80°C) | NOT (HCl corrosion) | NOT (chloride pitting) |
| 316SS | NOT (wet Cl2 attacks) | Good (5–15%, ambient, check pitting) | Good (stress-relieved, ＜80°C) | NOT (HCl above ambient) | Fair (pitting risk) |
| Duplex SS | Fair | Excellent | Good | Fair | Excellent (PREN ＞40) |
| Alloy 400/600 (Ni) | Good (dry Cl2) | Fair (oxidizer) | Excellent (caustic, high temp) | NOT (HCl) | Good |
| Hastelloy C | Good | Excellent | Excellent | Excellent (HCl) | Excellent |
| PTFE/PFA lined | Excellent (wet Cl2) | Excellent (best for bleach) | Good (up to 100°C) | Excellent (only for HCl) | Excellent |
| Titanium | NOT (dry Cl2 — pyrophoric!) | Good (wet oxidizer) | NOT (hot caustic) | Good (dilute HCl) | Excellent (seawater/brine) |
| EPDM seals | Fair | Good (oxidizer-resistant) | Excellent (caustic) | Good (dilute HCl) | Good |
| PTFE/FFKM seals | Excellent | Excellent | Excellent | Excellent | Excellent |
| NBR seals | NOT | NOT (oxidizer degrades NBR) | NOT (caustic attacks NBR) | Fair | Fair |
| FKM (Viton) | Fair | Fair (oxidizer may affect) | NOT (caustic attacks Viton) | Good | Good |
Critical: Dry chlorine = carbon steel (KEEP DRY) or Alloy 400. Wet chlorine / bleach = PTFE/PFA lined or 316SS + EPDM/PTFE (NOT NBR, NOT copper/iron/nickel catalysts). Caustic 50% = stress-relieved 316SS or Alloy 400 + EPDM/PTFE (NOT NBR, NOT Viton) + jacketed (prevent crystallization). HCl = PTFE/Hastelloy C only. Brine = duplex/PTFE. All = zero leakage (magnetic drive or double seal) + safety (gas detection, scrubber, PPE) + off-gas handling (bleach) + decomposition control (cool, dark, pH ＞11).
Common Problems and Solutions
Problem 1: Chlorine pump leaks (toxic). Seal fails — chlorine gas released. Solution: use magnetic drive pump (zero leakage, no seal) or double mechanical seal. Gas detection. Emergency scrubber. PPE. Our zero-leakage range prevents chlorine exposure.
Problem 2: Bleach pump gas locks (off-gassing). O2 from NaOCl decomposition accumulates — pump loses prime. Solution: use diaphragm metering (gas-tolerant) or peristaltic (no valves). Vented seal chamber. Vertical pump. Store bleach cool/dark/pH ＞11. Our off-gas-tolerant pumps handle bleach.
Problem 3: Bleach decomposes (metal catalyst). Iron/copper in pump catalyzes NaOCl decomposition — potency drops, gas generation. Solution: use PTFE-lined or 316SS pump (avoid copper/iron/nickel). Store cool/dark. pH ＞11. Vent. Our PTFE/316SS range minimizes decomposition.
Problem 4: Caustic pump crystallizes (50% NaOH). 50% NaOH crystallizes below 12°C — clogs pump. Solution: jacketed 316SS pump (maintain ＞20°C). Heat tracing. Insulation. Flush with water before shutdown. Our jacketed range prevents caustic crystallization.
Problem 5: HCl pump corrodes (316SS). 37% HCl corrodes 316SS pump. Solution: use PTFE-lined fluoroplastic pump or Hastelloy C. PTFE diaphragm metering for dosing. Zero leakage. Our PTFE range handles HCl.
Selection Summary
- Liquid chlorine: Fluoroplastic (PTFE/PFA) (wet Cl2) or carbon steel/Alloy 400 (DRY Cl2 — moisture critical) + zero leakage + safety
- Chlorine dosing: Chlorine vacuum feeder (ejector) or PTFE diaphragm metering (liquid solution, precise, zero leakage)
- Bleach transfer: Fluoroplastic or 316SS centrifugal (5–15%, corrosion, off-gas handling, zero leakage, EPDM/PTFE)
- Bleach dosing: Diaphragm metering (PTFE, precise, zero leakage, off-gas tolerant) — standard
- Hypochlorite production: Fluoroplastic or 316SS (Cl2 + NaOH, exothermic, large flow, zero leakage)
- Caustic (NaOH): 316SS centrifugal or screw (20–50%, viscous, jacketed, EPDM/PTFE, stress-relieved for high temp)
- Brine: 316SS/duplex centrifugal or fluoroplastic (saturated NaCl, chloride pitting, large flow, high purity)
- Cell liquor: 316SS/duplex or fluoroplastic (hot 80–90°C, caustic + chloride + hypochlorite, zero leakage)
- HCl: Fluoroplastic (PTFE) or Hastelloy C (30–37%, zero leakage, fuming, toxic)
- Scrubber liquor: 316SS or fluoroplastic (NaOH + NaOCl, exothermic, safety-critical, reliable)
- Critical: chlorine = dry (carbon steel) vs wet (PTFE) + zero leakage + toxic safety + high vapor pressure, bleach = PTFE/316SS + EPDM/PTFE (NOT NBR) + off-gas handling + decomposition control (cool/dark/pH ＞11, avoid Cu/Fe/Ni), caustic = 316SS/Alloy + EPDM (NOT NBR/Viton) + jacketed (crystallization), HCl = PTFE/Hastelloy ONLY, brine = duplex/PTFE (chloride pitting), all = zero leakage + safety + corrosion monitoring
- Our fluoroplastic covers wet chlorine/bleach/HCl; 316SS/duplex centrifugal covers caustic/brine/bleach; diaphragm metering covers dosing; magnetic drive covers zero-leakage chlorine. For chlorine/hypochlorite pump selection, talk to our chemical engineers with your chlorine form (dry/wet/gas), bleach concentration, and safety requirements.