Easy-to-Use Steam Heat Can Push Equipment beyond Safe Design Limits

Easy-to-Use Steam Heat Can Push Equipment Beyond Safe Design Limits 

Loss Prevention Engineers and Safety Professionals have repeated stories in Louisiana about the misapplication of steam on one-ton chlorine cylinders. Two similar stories were discussed at inter-plant loss prevention meetings a couple of decades ago. Naturally, the details are now a little vague but the stories were from companies located over 100 miles apart in two separate petro-chemical sections of the state. 

Process engineers who have requirements for low flow rates of chlorine can purchase chlorine in 150-pound and one-ton cylinders. These containers are very robust and industries have safely used them for decades. The one-ton cylinders are 1 f ft. (0.75 m) in diameter and just under 7 ft. (2.1 m) long with extended cylinder walls to protect the valves. Chlorine ton-cylinders are hydrotested at 500 psig (3450 kPa gauge). 

Chlorine can be provided from the ton cylinders as a liquid or a gas. The discharge rate depends on the pressure within the cylinder and this is a function of the ambient temperature. In order to withdraw gas, you must vaporize liquid chlorine. Withdrawal tends to reduce the temperature and hence the vapor pressure and the surrounding air must supply sufficient heat to boost the vapor pressure. Typical maximum discharge rate for a one ton chlorine cylinder in a 70° F environment is about 15 pounds per hour. 

When chlorine gas is withdrawn from a chlorine cylinder at a rapid rate, the cylinder will cool down. Some companies that need to boost the gaseous chlorine flow rate have placed warm water spray or utility water on the cylinder to add a well-controlled heat input on cool days. However, some individuals were reported to have become more creative and blew live steam via a hose to even further increase the rate of vaporization. That would seem like a good idea—unless you took the time to read the precautions. 

When chlorine gas is withdrawn from a chlorine cylinder at a rapid rate, the cylinder will cool down. Some companies who need to boost the gaseous chlorine flow rate have placed warm water spray or utility water on the cylinder to add a well-controlled heat 

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Easy-to-use steam heat can push equipment beyond safe design limits... 

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