Winter is coming: How to prepare for the heating season

October 31st, 2016

Winter is right around the corner – is your facility prepared for the incoming cold weather? Winterizing your plant is an essential task year after year and preparing your unit heaters, tracers and steam traps for use are arguably the biggest steps in that process. Tristian McCallion of Swagelok Energy Providers conducted a webinar in which he discussed the important aspects of winterization.

Follow the written procedure
Any time you winterize your facility, there should be a process in place that is consistent and specific. Your written procedure should address the following items:

  •     Safety: equipment, PPE, incremental pressure system increases
  •     Manpower: How many people are required for a given task?
  •     Communication methods
  •     System start-up steps and confirmation

Tracers
Tracers are a series of small pipes designed to replace heat loss from process fluids in the piping system due to poor insulation or other factors. Additionally, tracers are used to prevent a system from freezing in low ambient temperatures – for example, in northern Canada where temperatures can reach extremes like minus 40 degrees, tracers play a crucial role. By passing steam through these tracers, you can prevent your pipes from freezing, thereby avoiding considerable costs in damage and downtime.

When you start up your tracer system, some of the first things to look for are obvious examples of steam loss. Using an ultrasound probe, it's easy to identify leaks that may not be visible or loud enough for the human ear. These tools are particularly valuable in checking the valves and isolating leaks.

Unit heaters
These items often fly under the radar at your typical plant. Around autumn every year, plant managers go around and start up the unit heaters – flip the switch, open the valve and leave it alone to do its thing. But by paying a little more attention to these heaters, you can prevent early failure, low efficiency and maintenance or replacement costs.

For example, the heat transfer fins should be clean – even a thin layer of dust can reduce the system's efficiency by 20 or 30 percent. A gentle dusting or rinse can make a big difference, just don't use a high-pressure system or you'll risk damaging the components. Additionally, too much steam pressure alone won't make a difference, even though many facility managers simply increase steam pressure to increase temperature. Without adjusting the fan speed, that hot air will simply rise to the ceiling and go to waste. Instead, use the steam pressure for which the unit heater was designed.

Steam leaks are costly problems.Steam leaks are costly problems.

Steam traps
Steam traps perform several essential functions in any plant:

  • Remove condensate as quickly as it forms – condensate backup improves the chances of waterhammer in the system and can act as an insulator
  • Prevent live steam loss – capturing steam accelerates heat transfer and optimizes steam's heat
  • Remove air from the system – there is usually at least some air trapped in your heat unit system when you start it up in the winter

Testing steam traps requires a variety of methods, ranging from visual to temperature measurement to ultrasound. Typically, visual inspection doesn't yield much information. Temperature measurement tools provide some valuable data, but ultrasound tools paint the most complete and holistic picture of steam trap health. That's because it clearly indicates when steam passes through the trap and closely mirrors trap exhaust. In other words, if a trap is stuck open and steam is being lost, there is constant sound. When the trap is stuck shut, preventing condensate flow, there is hardly any sound present.

Infrared analysis is a decent tool as well, but it really only indicates whether or not there is live steam coming to the system, Still, infrared tools can yield some useful data points. Plus, infrared non-contact measurement devices can show an estimate of the steam pressure.

Nevertheless, ultrasound tools should be your go-to when starting up your heat system for the winter. For steam traps, 20 to 25 kHz is the recommended setting. For lower pressure traps, use a higher sensitivity, and vice versa for higher pressure traps.

When you start your steam trap testing, it's helpful to follow a flow chart. First, make sure the steam trap is operating – if the valves are open, that's a good sign. Then, check the trap's temperature. If it's cold, the trap has failed in the closed position or it's plugged. If it's hot, then it's time to start ultrasonic testing.

At that point, it's a good idea to use the comparison method. That means comparing test points along the trap or valve. Usually the loudest point will be on the downstream or discharge side. If it is a trap, compare one point upstream, usually the trap junction with one test point downstream, where the pipe and trap meet. If it's a valve, compare two points upstream with two points downstream (points A and B with points C and D). Point C should be the loudest when testing a steam trap. When testing a valve that should be closed, if your ultrasound is highest downstream from the discharge valve, this indicates a leak. The comparison method allows you to isolate the failure or leak. Remember to record your readings or to use an ultrasound tool that can compile data points for future use.

As you test your traps, remember to look at your overall system in addition to the individual components. Your entire installation needs to function optimally as a whole. You should demand at least 6 years of performance from any steam trap component, and by remembering plant maintenance best practices – and investing in quality steam traps in the first place – that should be possible.

In addition, you should test all your steam traps every 3 to 6 months, depending on the climate. Remember, the need to winterize your plant is a result of temperature changes in the outside world. Any fluctuation might influence how your equipment performs.

Cost of steam trap failure
Finally, remember why you need to undertake this process in the first place: Steam trap malfunctions can be costly.

For example, in a facility where steam value is $4.50 per 1000 pounds, an open trap on a 150 psig line with an eighth-inch diameter can cost $2,988 per year. That's just one bad trap.

Remembering to prepare your plant for winter means avoiding unnecessary costs, improving plant efficiency and providing a more comfortable area for your employees to work. Using ultrasound tools and following the best practices, your facility will be in great shape for this coming season.

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