Finding that the use of an incorrect hose led to an August 2002 chlorine leak near St Louis MO, the Chemical Safety Board (CSB) has issued a safety advisory to chlorine users to verify the materials used in their transfer hoses.
"Chlorine handlers should ensure that any nonmetallic-lined chlorine transfer hoses they use are constructed with the appropriate structural braiding layer, either PVDF monofilament or Hastelloy C-276," said CSB lead investigator John Murphy, citing a recommended safety practice of the Chlorine Institute. "Nondestructive testing methods such as X-ray fluorescence can be used to positively differentiate between Hastelloy C-276, the intended material, and 316 L stainless steel, the use of which can lead to catastrophic hose failure."
The advisory grows out of an August 14, 2002, chlorine release at DPC Enterprises in Festus MO. Sixty-three people, including workers and nearby residents, sought hospital treatment as the result of the leak. In that incident, a transfer hose failed catastrophically during the unloading of a chlorine rail car. Due to the malfunction of an automatic shutdown system, the leak continued unabated for several hours, eventually causing the release of about 48,000 pounds of toxic chlorine gas.
Subsequent analysis showed that the transfer hose was constructed with braided stainless steel--a material that is not recommended for chlorine service--despite documentation from the hose distributor indicating that the hose was made of a chlorine-resistant alloy. The two kinds of braiding are visually indistinguishable. The hose that failed had evidently been degraded by the flow of chlorine, which is a strong corrosive, and had been in service for just 59 days when the failure occurred, according to the CSB.
"The incident at DPC Enterprises underscores the very serious consequences that can ensue from chlorine hose rupture," said CSB Chairman Carolyn W Merritt. "Chlorine users should treat this incident as a wake-up call to verify that their hoses are what they think they are. The board requests that any person who determines that a chlorine transfer hose has been misidentified, or who experiences a related hose failure, to please contact the agency as soon as possible."
To see the safety advisory in its entirety, click here or for more information, telephone Giby Joseph at (202) 261-7633. (Note: Loading the advisory takes a few moments.)