What is Steam Tracing?
Steam tracing has long been an accepted means of maintaining temperatures of pipes and vessels under insulation. Steam trace systems consist of metal tubing called traces that are ⅜” to ½” in diameter, with lengths are typically 50 to 150 feet for each run. Tracers are attached to pipe or vessel surfaces via wire, heat transfer compounds or specialty aluminum heat transfer strips.
How Does Steam Tracing Work?
Steam from a plant boiler is piped up to the site where the steam trace is installed and a distribution manifold is used to take steam to each tracer. Steam is then applied to the tracer circuit, effectively transferring heat from its warm surface to the pipe or vessel surface. Once the steam hits the end of its run it will begin to change from water back to steam. This product created is called condensate. Key components in this system are steam traps and the condensate return system.
These two key components provide two key functions: the steam trap provides back pressure to the steam trace circuit so the steam does not escape the tracer, and the condensate return system provides a way for the collected water to either return to the boiler for re-use or out to the sewer once it’s cooled down. Together with the tubing system and boiler, they provide a very effective heat trace system.
Why is Steam Tracing Still Used?
Steam locomotives were all the rage back in the day. Even by today’s train standards, the horsepower created by steam is still impressive. But behold the maintenance! Steam is very hard as far as wear and tear, and after a very short time, many things begin to break down. When water is turned to steam, it can expand up to 1600 times its original size depending on the pressure required. Steam can tax even the most robustly designed equipment, and thus the end of steam locomotives in place of diesel units after the 1950s.
Steam remains the main source of energy for many power plants today, including coal, lignite and natural gas. Until the mid 1960s, steam trace was the primary means of maintaining temperatures under insulation in industrial facilities. They all had boilers, and understood how to work with it. A great deal of maintenance is required for these systems, from water treatment going into the boiler, to routine steam trap inspections, corrosion and pipe integrity inspections as well as control and monitoring of NOx emissions on some of the larger systems.
In the decade that followed, drastic improvements in electric heat allowed many users to begin the switch over to electric heat trace for that same pipe and vessel maintenance application.
Pros and Cons
Pros of steam trace
- Good use for excess plant steam
- Offsets heating costs for some applications
- Much more effective heat transfer: heats up much more quickly
- Recycle condensation through water recapture (closed loop system)
- Steam trace is safer in areas rated as electrically hazardous
Cons of steam trace
- Can effectively only run a max of 150 feet before steam begins to condense out (depending on tracer size)
- Cannot get enough heat on valves and pumps
- Hard to do maintenance on valves and pumps, costs 70% more than piping to maintain
- Requires dedicated crew time for maintaining steam trace
- Steam at high pressure is dangerous
- Boiler maintenance is costly
- Steam temperatures don’t vary much (if you have 250 F steam, that’s what every application gets)
- Costly steam trap audits and maintenance
What is Electric Heat Trace
Electric trace is a matrix with heating properties that looks like flat wire or cable. As voltage is applied, heat is produced at a stated rate. For example, a user might have 120V rated 8 watt heating cable. When 120 Volts is applied, 8 watts is produced. This wattage output is designed to offset losses through insulation into the ambient air. In this application, a customer’s losses at temperature must be less than 8 watts per foot in order for the cable to perform correctly.
Pros and Cons
Pros of electrical trace
- Much longer runs than steam trace, with some as long as 700 feet in one run
- A linear output of heat along its entire length: 8 watts at the start, 8 watts at the end
- Cut to length capability for most heat trace allows the user to keep extra on hand for quick jobs
- Smaller runs of heat traced pipe can be used for drains that would be impossible to do with steam: put the heat right where you want it
- Simple electrical maintenance, easy for any electrician to work with
Cons of electrical trace
- Improperly installed can cause issues in a Class 1 Div 1 or Div 2 area
- Can only produce enough heat to maintain a temperature,and rarely has enough heat to thaw out a line
- Specific GFEP breakers are required
Heat Trace from Powerblanket
Advances in heating technology as well as insulation have greatly improved the desirability of electric trace versus steam. Learn more about including heat trace in your freeze prevention plan by contacting Powerblanket today.