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Sodium Hypochlorite Dosing Pump: Anti-Gas Locking & Chemical Compatibility Guide
Sodium hypochlorite (NaOCl) is notoriously prone to off-gassing chlorine gas, which causes positive displacement pumps to experience gas locking (vapor lock) and lose prime. The correct pump configuration requires a glandless diaphragm pump with solid PVDF or Polypropylene liquid ends, PTFE diaphragms, and an integrated automatic degassing head that continuously purges gas bubbles.
Corrosion & Dosing Dynamics: Sodium Hypochlorite (NaOCl)
Commercial sodium hypochlorite (10% to 15% available chlorine) is an intense oxidizing agent and is highly alkaline (pH 11–13). Over time, hypochlorite naturally decomposes into salt, oxygen, and chlorine gas—a reaction accelerated by heat, UV sunlight, and metal contaminants (like iron or copper). In a standard closed pump head, gas bubbles accumulate and compress rather than discharge, causing the pump to run dry without moving liquid.
Recommended Engineering Specifications for Sodium Hypochlorite (NaOCl)
| Parameter | JEW Factory Recommendation |
|---|---|
| Recommended Pump Type | Diaphragm Dosing Pump with Integrated Auto-Degassing Head |
| Liquid End Metallurgy | Virgin Polypropylene (PP) / Machined Solid PVDF / Pure PTFE |
| Diaphragm Material | Virgin PTFE (Teflon) composite with rupture alarm sensor option |
| Check Valve Configuration | Double Ceramic Ball Check Valves on Suction & Discharge to prevent backflow |
| Valve Seats & O-Rings | FKM (Viton) / EPDM / Pure PTFE (Zero metal contact) |
| Anti-Siphoning Protection | Spring-loaded diaphragm back pressure valve set at 1.5 bar |
| Motor Options | 0.25 HP to 1.5 HP, 415V 3-Phase / 230V 1-Phase TEFC IP55 |
| Flow Repeatability | ±1% steady-state conforming to API 675 standards |
Piping, Priming & Installation Best Practices
- Flooded Suction is Essential: Always mount the hypochlorite storage tank above pump centerline. Lift suction induces vapor breakdown and causes severe gas locks.
- UV-Shielded Piping: Avoid transparent tubing; sunlight exposure accelerates chemical breakdown and gas production. Use UV-stabilized rigid PVC or PVDF piping.
- Auto-Degassing Discharge Port: Connect the top degassing port of the JEW pump head back to the top of the chemical day tank to continuously recycle separated vapors.
- Periodic Flush Cycle: Crystallized hypochlorite salts can foul check valve seats. Install a three-way valve to periodically flush the pump head with clean water during maintenance.
Frequently Asked Engineering Questions
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