Securing Industrial Chlorine Supplies

Improved fire codes allow use of fail-safe valves, easing storage and use requirements for chlorine gas.

• By Rudolph S. Caparros, Sr.
• Apr 01, 2005

USERS of chlorine now regulated by the newly created 2003 International Fire Code and the 2003 Edition of the Uniform Fire Code are pleased to find they are no longer required to have a scrubber when storing or using 150-lb cylinders or one-ton containers of liquefied chlorine gas.

A scrubbing system usually consists of a scrubbing chemical (typically, caustic soda) and a blower to draw contaminated air through the caustic solution being circulated by use of a pump.

For indoor and outdoor storage, the need for a scrubber is eliminated if . . .

1. Chlorine cylinder valve outlets are equipped with gas-tight outlet plugs or caps.

2. Where approved containment vessels or containment systems capable of fully containing or terminating a release are available or that are capable of being transported to the leaking cylinder, container, or tank.

For indoor and outdoor use, the need for a scrubber is eliminated if . . .

1. An approved, automatic-closing fail-safe valve is located immediately adjacent to and downstream of the active cylinder valves. The fail-safe must close when gas is detected at the permissible exposure limit (PEL) by a gas detection system monitoring the exhaust system at the point of discharge from gas cabinet, exhausted enclosure, ventilated enclosure, or gas room.

2. Where approved containment vessels or containment systems capable of fully containing or terminating a release are available or that are capable of being transported to the leaking cylinder, container, or tank.

Plant operators have found that fail-safe valves and containment vessels require little or no maintenance, repair, or replacement. According to Maui Plant Operator Wayne Fujiwara, "Total containment is easier to use than a scrubber. It does what it says it will do, and we don't have to worry about leaks."

A scrubber system may require extensive maintenance, repair, and replacement, including testing of caustic solution, replacement of caustic, instrument calibration, belt adjustments, sheave alignment, scrubbing chemical feed pump adjustments, exhaust air fan adjustments, fan wheel service, pump seal replacement, and pump rebuilds and replacement. A fail-safe valve is typically described as a 1/4 turn ball valve that is spring loaded, always fails in a closed position, and does not rely on any electrical power or backup emergency power to close the valve. A valve that does not have all these characteristics is unsafe by comparison.

Ensuring Operators' and the Public's Safety
Unmanned sites located in densely populated areas are especially in need of a system to process chlorine from cylinders or ton containers that will release little or no chlorine gas to the surrounding community.

Total containment vessels used for processing chlorine from a cylinder or ton container that is enclosed within the vessel are the only system that reduces the worst-case off-site release of toxic gas by 97 percent, making it by far the safest method for processing chlorine.

" 'Passive' was a selling point to me," said Ellis DeWell, assistant plant superintendent in Springfield, Ohio. "It made a very important difference since we are governed by the EPA rules and regulations."

Scrubbers and fail-safe shutdown valves provide no reduction in the off-site area affected when conducting RMP studies to assess the effects of a release to the surrounding community. Consulting engineer George Clifford White, author of the "Handbook of Chlorination and Alternative Disinfections, Fourth Edition," said total containment is the "safest and most cost-effective" treatment system available today.

Rick Roll of North Little Rock, Arkansas' water treatment plant chose total containment, as well. "Safety for our operators and the surrounding area was the primary concern," he said. "The locking door adds extra security from prying hands. It seems to be a foolproof system. Simplicity is the best ticket."

Sites located within sparsely populated areas may find the cost of installing a scrubber system or total containment system used for the processing of cylinders or ton containers to be out of the question because of budget constraints. The new codes allow these sites to use the less expensive automatic closing fail-safe shutdown valves located immediately adjacent to the cylinder valves. The fail-safe valves must close when a gas detection system detects a release at the permissible exposure limit.

All sites storing cylinders or ton containers must have available to them containment vessels or systems capable of fully containing or terminating a release from a leaking cylinder or container. If the emergency containment vessel is not located at the site, it must be capable of being transported to the site of the leaking cylinder. A trailer mounted emergency containment vessel would typically be transported to the site of the leaking cylinder or container by the emergency responder.

Options for Communities with Multiple Sites
Communities with multiple sites need have only one emergency vessel available to them to handle leaking cylinders or containers. However, locating an emergency vessel at every site will provide added safety.

The emergency vessel must be designed to process the entire contents of the leaking cylinder or container at the treatment site to prevent transporting a leaking cylinder or ton container. Small communities may, by an association with others, share the cost of a containment vessel system, one that is trailer mounted, to allow compliance at a lower cost.

Total containment vessels satisfy the definition of a treatment system in the codes because, once contained within the vessel, the total contents from the leaking cylinder or ton container can be put into process at the site at a safe, controlled rate.

As in all cases related to fire codes, consult the local fire department to determine its requirements.

This article appears in the April 2005 issue of Occupational Health & Safety.

This article originally appeared in the April 2005 issue of Occupational Health & Safety.