Heat Tracing System
Piping systems involve heat sinks such as valves, pipe supports and instruments, which along with residual loss through insulation which accounts for loss of heat in large amounts whenever there is sufficient difference between the pipe and ambient temperatures. Variation in ambient temperatures from freezing winter nights to scorching summer days affect the extent of heat loss . (There can be situations when there can be a heat gain as well.)
Heat tracing is a way of maintaining the temperature variation in a pipe within acceptable limits. Trace heating is used for the purposes of
The combination of trace heating and insulation may be described as the creation of an artificial to surround a process pipeline, container or instrument. Many industrial products and processes environment are prone to a variety of undesirable effects if they are not maintained and pumped at the correct temperatures. Some of the effects our products are listed below
Process materials have different optimum operating temperatures, some of which are required to be maintained at certain temperature band to avoid any of the aforesaid states. Eriman Insulations specialize in providing technically best suited and most economical package integrating a well matched combination of optimum Tracer conductor with correct temperature rating and heat output and correct choice of Insulating material and the thickness. The precise design is carried out to deliver end performance at the lowest first cost of installation and the most economical running cost.
Type of Heat Tracing
Heat tracing can be accomplished by any of the following methods
Steam Heat Tracing
Electric heat tracing
(A) Steam Tracing
Steam tracing can be done using any of the following methods
(a) External Pipe Jacket Method
In this method of tracing, heating or cooling is accomplished by running a small line (Pipe or Tubing) containing the heating medium either parallel or spiral wound around the pipe or vessel.
(b) Internal tracing method.
In this method, the tracer with heating medium is fitted inside the process pipe and runs parallel to it.
This is a very reliable and simple method of heat tracing. The hot spot and over heating problems cannot come up because the maximum temperature is limited by the pressure of the steam. Depending on the temperature requirements the pressure can always be adjusted.
In the past when the cost of energy was low, steam was treated as a free commodity and hence the proliferation of steam tracing systems.
Steam is usually available in most industries and does not require additional arrangements for production. Being produced at the site, the problem of unreliability in quantity and quality does not exist.
Even if the system has steam leaks and faulty traps, it continues to work although at a higher energy cost.
(B) Electric Heat Tracing
In recent years electric tracing has enjoyed increasing applications in the industry. This is mainly due to –
Proliferation of a large number of new types of heat tracing systems.
Increase in cost of steam due to oil price hike.
Very serious housekeeping problem in Steam Tracing including heavy Corrosion in process pipes caused by steam leaks.
As the impedance type and skin effect current type electric tracing systems have limited application, the discussion that follows is focused on the pros and cons of resistance type electric tracing systems.
The resistance type systems could also be classified as ‘Constant wattage type’ and ‘Variable wattage type’. The advantages and disadvantages of the Mineral Insulated Cable (MI) and Zoned Series Resistance Wire type in the constant wattage category are as follows:
Advantage of MI Cable
It can tolerate brief periods of over heating
It can be used for high temperature applications (as high as 800°C)
It has good impact resistance
It has relatively low cost per feet length
Disadvantages of MI Cables
The greatest disadvantage with MI Cable is that it must be factory fabricated to length to deliver exact wattage to the system and cannot be cut or sliced to desired length in the field. This makes design, installation and maintenance more difficult than other types of electric tracers.
It is also not flexible and is therefore, difficult to be installed over complicated shapes.
Because of the series circuit design, failure of the heating element at any point causes the entire circuit to fail.
Generally it uses non standard voltages and a transformer may be necessary to produce required voltages.
It requires skilled personnel and techniques to seal ends and exclude moisture. Additional Advantages of Zoned Series Resistance Type Tracers
The Zoned Series Resistance wire type tracing systems are an improvement over the MI Cable because a few of the problems associated with MI Cable have been overcome in this type and hence it offers the following additional advantages:-
The main advantage of this tracer is that it can be cut to length in the field because of the parallel circuit design.
It operates on standard voltages.
Advantages of Auto-Trace Self Regulating & Self Limiting Type Tracers The most promising electric tracing system is the self-limiting type. Because of the unique principle which is adopted in this type of tracing system for generating heat, almost all the disadvantages of the other type of electric tracing systems have been overcome. In addition it uses energy at very high efficiency levels compared to steam tracing. The salient advantages of the self-limiting type heat tracing systems can be summarized as follows:-
High Energy Efficiency
The energy efficiency of self regulating type heat tracing system is very high because of the unique self-regulating feature built in the tracers. The tracer resistance varies as a function of its temperature. As temperature increases, the resistance of the polymer, constituting the core of tracer, increases which causes a decrease in the power output. The energy output, therefore, always matches the requirements of the system.
Self-regulating type electric tracers are intrinsically safe and can be used in hazardous
areas. In fact, it has been given an unconditional T-rating in several countries. Again, because of the self-regulating feature, at no point can the tracer create high surface temperature and there are no chances of any fire hazard even in the presence of inflammable gases/liquids in and around the pipes. Even if the tracer crosses over itself, as in case of tracing of pipe elbows, valves and fittings, there will not be any local hot surface temperatures.
Ease of installation
It can be installed on any contour such as pipe elbows, valves and different fittings due to its flexibility. The tracer can be cut-to-length in the field and precise measurements at manufacturing stage are not required. The heater strip is very flexible and can be mounted on any shape.
Precise Temperature Control
The tracer maintains uniform temperature profile throughout the pipeline which results in greater energy economy.
The temperature variation in pipe is automatically controlled due to its self regulating feature hence there is n temperature fluctuation in the pipe The temperature at the hot and cold zone in the same pipe can be controlled by the tracer itself hence provision for separate thermostat at different zones is eliminated.
The self regulating type tracers are guaranteed for more than 40 years of working life. This results primarily from the absence of any hot spot at a particular point and also due to the absence of any corrosive material in the tracer. In fact, the tracer once installed, generally does not require any replacement for the entire life of the plant.
The self regulating type electric tracer hardly requires any maintenance work during its entire life period. But for minor circuit defects, which are unavoidable in any electrical system, practically nothing goes wrong with the tracer. It has been the experience of industries using such tracers for a number of years that absolutely no maintenance is called for as far as the tracing system is concerned.
SKIN EFFECT CURRENT HEAT TRACING:
Skin Effect Current Heat Tracing is the most cost effective heat tracing design for long runs of pipe. The design can be furinished as a single end power feed or mid fed power feed design on preinsulated pipe or field insualted pipe applications.
Skin Effect Current Heat Tracing combines the engineering principles of skin effect and proximity effect design that offers an economical solution to heat tracing problems in long pipelines by providing a single or mid-fed power point. ERIMAN INSULATIONS specialize in design, supply and installation of a complete system that includes the engineering, material selection, and insualted pipe system for any application.
ERIMANS have been associated with some of the longest heat traced lines for hot oil featuring Skin Effect current Heat Tracing system even in totally buried lines. Special insulation and external cladding system have been developed and perfected to face the most adverse and aggressive soil and terrain situations.