Page 14 - CCPS Golden Rules - Chloral Alkali

Golden Rules for Chlor-Alkali

Golden Rule #4: Avoid High Temperatures in Chlorine Systems.

❖ Why:
Carbon steel will burn (spontaneously) in the presence of chlorine at approximately 250 °C (482 °F) [18].
The ignition temperature of steel in chlorine depends on several things including surface area and
impurities. For example, dry steel wool will ignite at approximately 50 °C (122 °F) [18].
Typical steam distribution systems in most industrial plants will have temperatures in excess of 200°C
(392 °F) and can create chlorine / steel fires in vaporizers and reboilers [15] [16].
Mechanical components can be subjected to localized high temperatures in chlorine compressors [21].
Incident History:
Approximately 7,900 pounds of chlorine were released when a new multi-stage centrifugal chlorine
compressor failed undergoing its final checkout prior to being started. The chlorine was released
when a 12 inch hole on the compressor developed as a result of a chlorine-iron reaction. The
investigation concluded the fire was initiated due to design issues (clearances too tight) associated
with the new compressor [10].
Welders had just completed welding a short section of two-inch (5.1 cm) carbon steel pipe attached
to a long insulated carbon steel chlorine line. The weld that joined the new section of piping was
about six inches (15.2 cm) from the adjacent thermal insulation that covered the long chlorine line.
After completion, an operator/loader pressurized the long carbon steel line with dry air and
determined it was leak-free. He then opened the valve connecting the new two inch line to the
chlorine gas line. Within seconds the pipe caught fire and the escaping gases roared like a jet with
a brownish-orange plume of ferric chloride. The operator extinguished the fire by closing the valve
which stopped the chlorine feed. The subsequent accident investigation determined that the fire
started, not at the weld, but under the adjacent insulated pipe which trapped the heat and had not
sufficiently cooled [18].

❖ How — General:
Limit operating temperature to below 149 °C (300 °F) for chlorine / carbon steel systems [8] [18].

❖ How — Operators, Mechanics, and Technicians:
Understand and follow operating procedures and safe operating limits for chlorine operations [8] [14]
[21].
Never weld / grind on live chlorine equipment or piping until it has been completely isolated, purged,
and confirmed free of chlorine [21].
Avoid the use of high temperature steam on chlorine equipment and piping [15].
Avoid bypassing interlocks associated with high temperatures in chlorine systems.

Updated January 2024 Page 11 of 28