Epichlorohydrin Factory Audit Checklist: 22 Points for an ECH & Epoxy Resin Plant

An integrated epichlorohydrin (ECH) and epoxy resin plant is audited as a single reactive-hazards system, not as two separate production departments. The initial inspection pass starts at the storage and utility interfaces because ECH is a Class IC flammable liquid with a closed-cup flash point of 31°C under NFPA 30 and an OSHA 8-hour time-weighted average permissible exposure limit of 5 ppm (19 mg/m³) under 29 CFR 1910.1000. The current ACGIH Threshold Limit Value is 0.5 ppm as an 8-hour TWA with skin notation. Feedstock quality is then compared against batch-to-batch variance for either the glycerin-to-dichloropropanol route or the allyl chloride chlorohydrin route. The checklist below is organized by process node rather than by department and treats the 22 points as a closed verification matrix: storage, chlorohydrin reaction, dehydrochlorination, distillation, brine treatment, epoxy resin advancement, and safety instrumented functions.

Points 5 through 8 are treated as one coupled process audit because sodium hydroxide demand, pH loop stability, and column vacuum integrity cannot be verified independently. The chlorohydrin reactor recirculation pump discharge pressure and heat exchanger return temperature are reviewed for short-loop variation. A drop in circulation velocity reduces chlorine absorption and increases high-boiling chlorinated byproducts, particularly 1,2,3-trichloropropane, which is difficult to separate and becomes a waste brine organic load. The audit compares the pH control valve position with the recirculation flow to identify control valve stiction or pH electrode fouling. In the dehydrochlorination reactor, the NaOH/dichloropropanol molar ratio is expected to remain within 1.05–1.15. Lower values drive unreacted dichloropropanol into the crude ECH stream; higher values raise brine pH and accelerate hydrolysis losses. At the distillation battery, vacuum decay testing is reviewed as a leading indicator of air ingress. The reboiler is inspected for steam-side fouling and tube-skin temperature above the resinous fouling onset range. An increase of pressure drop greater than 15% over the clean baseline, or a decline in heat-transfer coefficient below the design minimum, should trigger API 570 external inspection of the shell-and-tube reboiler. The same pass checks column absolute pressure below 10 kPa and the overhead condenser outlet temperature because dry-running vacuum pumps and high bottom temperature are the two most common causes of polymer formation in ECH distillation. Published data for this specific configuration is limited; therefore, the audit uses the site’s own pressure-rise test baseline and tube-skin thermocouple signatures.

Why Does the Epoxy Resin Stage Demand a Separate Set of Reaction-Kinetic Checks?

Liquid epoxy resin production introduces a polycondensation hazard that is not present in ECH distillation. The reactor is charged with excess epichlorohydrin and bisphenol A, followed by controlled caustic soda addition. The audit verifies that the ECH/bisphenol A molar ratio is set to deliver the target epoxide equivalent weight, typically 182–192 g/eq for standard liquid DGEBA, measured by ASTM D1652. Batch records from production-scale reactors show two recurring failure modes: caustic slugging due to pH probe fouling, and emulsion layer carryover into the aqueous brine cut. The audit therefore checks the caustic charging pump minimum flow and the phase-cut logic against the reactor conductivity probe. The addition profile of caustic is reviewed against the phase-cut timer and conductivity probe because an early cut can leave hydrolyzable chloride above the grade limit. Standard liquid epoxy resin viscosities are commonly 12,000–16,000 mPa·s at 25°C under ASTM D445, and hydrolysable chloride is controlled below 300 mg/kg for many standard LER grades under ASTM D1726. Residual ECH after vacuum stripping is checked by headspace gas chromatography because even small residuals create volatile organic compound load in downstream storage and exposure risk in handling. Reactor emergency relief sizing is reviewed under DIERS methodology, with relief device capacity against the maximum self-heating rate. The audit also compares batch records against the caustic addition rate design basis; a slow addition rate reduces gel risk but increases cycle time, while a fast addition rate can exceed the condenser load and lift the relief device.

Leak Detection, Wetted Materials, and Safety Instrumented Function Verification

Epichlorohydrin service requires mechanical integrity checks that are stricter than general chemical service. ECH area detectors are evaluated for alarm set points aligned to the ACGIH TLV of 0.5 ppm and the OSHA PEL of 5 ppm; detector placement is checked around pump seal cavities, sample points, and flange rows. Mechanical seals in ECH service are reviewed under API 682, with API Plan 53A or 54 flush systems and seal cooler outlet temperature trending. Wetted materials are limited to glass-lined vessels, PTFE envelope gaskets, and tantalum or PTFE trim; zinc, copper, and magnesium-based alloys are excluded from ECH contact because they can promote exothermic polymerization or chloride salt formation. Fire protection is reviewed under NFPA 30 and NFPA 11, with alcohol-resistant foam application density verified against tank diameter and dike area. The final audit pass verifies the safety instrumented function proof test intervals and on-line analyzer calibration records under IEC 61511; a GC or IR analyzer that has missed a proof test is logged as a compliance gap rather than a calibration nonconformity.

If the Plant Uses a Glycerin-Based Route, What Additional Mass-Balance Checks Close the Audit?

Glycerin-based ECH trains convert crude glycerin with hydrogen chloride to dichloropropanol, discharging methanol and salt-laden water before dehydrochlorination. The audit checks the methanol recovery column pressure drop because methanol carryover into the chlorination reactor consumes HCl and disturbs the water balance. Crude glycerin chloride and ash content are trended across supplier batches; a chloride spike can increase the brine load and aggravate salt deposition in the downstream vacuum system. Waste brine total organic carbon is reviewed against the activated sludge respiration rate using OECD 209 or ISO 8192. Nitrification inhibition is the operational boundary: if the site cannot demonstrate stable ammonia oxidation at the current brine discharge rate, the audit records the gap against ISO 14001:2015, 8.1. The glycerin route also requires verification that the dehydrochlorination caustic stoichiometry is adjusted for dichloropropanol isomer distribution. The audit is closed only after the brine treatment system backflow prevention and the ECH storage tank secondary containment are confirmed.