Traditional heat transfer fluids and systems have been around for many decades. Although much has been learned and written about the safe operation of these flange systems, less has been shared about the proper approach to making trouble-free repairs.
The safe execution of repairs depends on effective planning to protect against possible risks. This article focuses on mitigating potential risks associated with HTF that can be encountered when repairing high-temperature organic HTF systems (those that typically operate above 500 F). It is not intended to replace any manufacturer-specific fluid-specific risk information or process-specific risk information or equipment associated with individual processes involved.
Each process has unique risks associated with the manipulated chemicals. Effective work planning and execution takes into account the dangers of both the processes and the HTFs involved. The risks associated with HTFs can be divided into three primary areas: fire, human exposure and environmental exposure. The single best source of fluid safety information is the Material Safety Data Sheet (MSDS) provided by the manufacturer.
Fire potential is typically assessed using flash point, fire point, and auto ignition temperature (AIT) data. Most commonly used HTFs running from 500 F to 750 F, including diphenyl / diphenyl eutectic fluid (DP / DPO) and the others listed in the table, have hydrocarbon chemistry. Thus, they are typically classified as Class III B combustible liquids capable of being ignited under the appropriate conditions (fuel / heat / oxygen).
Depending on the system design, operating environment, and age and fluid maintenance, some fire properties may be depressed below the values shown, which may increase the risk of fire. Aware of these conditions, proper work planning can disrupt hazard mechanisms and greatly reduce or eliminate the risk of fire. A safe approach to fire prevention should include minimizing the potential for spark, inert, work while the equipment is near ambient temperature, and ensuring that the area is clear of hydrocarbon waste before hot work begins.
Limiting the potential for human exposure to chemicals should be at the forefront of work planning considerations. The specific chemistry of HTFs will help define certain requirements for personal protective equipment (PPE), material handling fluid handling, etc. The review of the MSDS and the technical literature will assist in the proper selection of EPP to prevent glove permeation or protective aprons. prevent failure of polymer and other equipment components causing loss of containment.
The most common injury related to HTF is heat burns. Whenever possible, the system should be allowed to cool enough to prevent hot liquids from burning or contact with the equipment when manual work begins. An added benefit of cooling the fluids is reduced vapor pressure, thus reducing potential exposure to fluid vapors.
Should non-routine material transfers be required, the selection of hose materials, gaskets, containers and rings or seals should conform to all manufacturer’s guidelines to prevent leakage, leakage and unexpected physical contact. Ideally, work plans incorporate these considerations, in addition to knowledge of industrial hygiene surveillance, to determine the best combination of splash, face, eye, thermal burn, and / or respiratory protection required for each situation.
Exposure to the environment can also be managed safely through proper planning. Chemicals must be handled responsibly, but certain fluids may have regulatory restrictions that place a stricter emphasis on environmental protection. This information should be provided in the MSDS.
During repairs, most of the fluid should be properly insulated within the system designed for containment, if possible. Any fluid that requires disposal by pumping, draining, striking or other means must be transferred using equipment and materials fully compatible with fluid chemistry. All questions regarding the compatibility of the materials should be resolved first by discussion with a competent person who is fluent.
Additional preventative measures to protect the environment may include temporary dikes / curbs, drain plugs, and absorbent media / pigs / socks. For fluids with high crystallization points (for example, DP / DPO), make sure that the pipe is clean of standing liquid to prevent possible failure due to expansion effects when freezing. It can be done by draining low points, blowing the lines with inert gas and carefully opening the low point flange if necessary. Successful management of this component of the work will help prevent unnecessary work of cleaning, removing fluids and recovery materials, and will allow faster termination of work, thus reducing downtime.