Heat Transfer Fluids

WHY USE HEAT TRANSFER FLUIDS?

Heat transfer fluids, (HTF) are high-temperature heating fluids that allow operation at lower pressures than comparable water/steam heat exchange systems. In addition to the lower operating pressure, with related cost savings, the use of organic heat transfer fluids can provide more precise process temperature control, lower maintenance and lower total capital cost. Fluids which operate up to 400*C are available. Most heat transfer fluids are rated by the National Fire Protection Association (NFPA) Standard 30, Flammable and Combustible Liquids Code.

TWO GENERAL TYPES, LIQUID AND VAPOUR/LIQUID PHASE
There are two general types of heat transfer fluid systems - liquid phase and vapour/ liquid phase. Liquid phase systems transfer with sensible heat(a change in temperature). Vapour/liquid systems transfer heat with the heat of vaporization via a boiling condensing cycle. Oiltech markets both fluid types.

LIQUID PHASE
The application of heat transfer fluid involving any of the following requirements are particularly well suited for the use of liquid phase heat transfer fluid:

Carefully controlled high-temperature heating
Multiple heat users within a single process or plant
Heating of thermally sensitive materials
Heating and cooling with the same system
Cooling
Operations where minimum operating supervision is available

Heat transfer fluid systems using liquid phase heat transfer fluid offer the designer and the operator the following advantages:
Simple design
Easy to operate
Low maintenance cost
Minimal capital cost
Energy efficient
Eliminates multiple ignition sources
Flexible operation

ORGANIC HEAT TRANSFER FLUID FIRES AND THEIR PREVENTION.
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This article looks at the safety aspects of heat transfer fluid in relation to the following:

Liquid phase versus vapour phase systems
Fire types
Insulation fires
Leak/rupture fires
Flash point fires
Process materials fires, and
Fire prevention

HEAT TRANSFER SYSTEM EXPANSION TANK DESIGN
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The design of the expansion tank in a liquid phase heat transfer system using Oiltech heat transfer fluid or other organic fluids is an important parameter in the total system's successful operation. An expansion tank correctly installed and maintained can contribute to increased fluid life along with lower maintenance associated with the various mechanical components of the system, such as pumps, gaskets, seals and heaters. A properly designed expansion tank can eliminate many problems from the initial startup through everyday operation of the heat transfer system.

This article explores the purpose and design of an expansion tank in a heat transfer system. However, a qualified engineering firm should be consulted in connection with the design of an actual heat transfer system, since considerations outside the scope of this bulletin may be critical.

IN-USE TESTING OF OILTECH HEAT TRANSFER FLUIDS
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When heat transfer fluids are used within suggested temperature limits, they should provide years of service.

To help keep that long-lasting performance optimal, Oiltech provides a heat transfer system fluid testing service. This service helps detect system malfunction, fluid contamination, and moisture and thermal degradation, as well as other areas that impact on system performance. Details of the testing service - how samples should be submitted for testing and guidelines for interpretation of analytical results - are outlined in this article.

HEAT TRANSFER FLUID FILTRATION: HOW AND WHY
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Indirect heating of processes by thermal liquid fluids offer highly reliable operation, and the heat transfer systems are generally treated as low-maintenance utilities. Occasionally the heat transfer fluid can become contaminated, resulting in the formation of sludge particles, or other sources of dirt can infiltrate the system. These solid particulates can cause circulation pump shaft seal leakage problems, valve stem wear, plugging of flow passages and sometimes, fouling of heat exchange surfaces.

After contamination, the fluid can sometimes be cleaned by in-system side stream filtration. For seriously fouled systems requiring chemical cleaning, the heat transfer fluid can sometimes be cold filtered outside of the system. Filtration may also help protect the system from solids problems by being installed before start-up.

ORGANIC HEAT TRANSFER SYSTEM CLEANOUT
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Oiltech heat transfer fluids are used for indirect heating of processes by circulating the heat transfer fluids, HTF, between heat source and heat sinks.

Organic heat transfer fluids generally are stable if operated below their thermal stability limit and not contaminated by agents from outside the system. Occasionally, overheating and contamination occurs, causing formation of insolubles which deposit on system surfaces and foul heat transfer surfaces. Sedimentation of solids can cause plugging of piping in the system. Fouling reduces overall system efficiency, increases wear of dynamic seals, and can even cause burnout or cracking of the heater surface.

This article looks at the following:
Fouling by system contamination
Fouling by thermal overheating
Heat transfer system cleaning methods
Heat transfer system cleaning with the heat transfer fluid in the system
Heat transfer system cleaning with fluid removed from the system
Heat transfer system start-up after cleaning

HEAT TRANSFER FLUID SYSTEM START-UP PROCEDURE
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To help keep that long-lasting performance optimal, Oiltech provides a heat transfer system start-up assistance. This start up check list outlines issues to consider during start-up.

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