To comply with the Energy Efficiency Directive as required by the European Commission and ISO 500001, Levaco Chemicals in Leverkusen, Germany, had to save energy. After evaluating its current systems, the company’s engineering team determined that defective steam traps were causing loss of steam, inefficient heat transfer and wasted energy. Steam trap failures also were causing process shutdowns, and trying to track down problems with manual rounds was not effective.
Levaco installed wireless acoustic monitors to identify failed steam traps as early as possible, allowing them to correct the issues. Because of this project, Levaco complied with the Energy Efficiency Directive, met ISO 500001 requirements, saved a considerable amount of energy and solved its operational and safety problems.
Levaco Chemicals’ products include specialty chemicals such as dispersants, emulsifiers, wetting agents and anti-foaming agents used in agriculture, fiber manufacturing, paints and coatings. Levaco also manufactures specialty chemicals for major chemical companies on a contract basis.
The plant in Leverkusen has 40 batch reactors in a single building (figure 1). The engineering team knew that we had severe problems with failed and leaking steam traps.
The reactors’ heat controllers are highly complex, and we spent a lot of time optimizing the controllers of the plant, never looking at the steam traps — definitely an error. Defective steam traps prolonged the batches because heating and cooling were ineffective. Batch time has a high impact on the batch price.
When a batch started, the engineering team did not know if a steam trap was working properly and if we could run the batch. To check the steam trap manually is expensive and often not easy to reach. Steam traps were viewed as “part of a pipe” — not as an active element. Therefore, we did not know where to locate them. We knew they were there, but we could not find them. They were not documented and identified with pipes.
The pending Energy Efficiency Directive required by the European Commission — along with the need to meet ISO 500001 requirements — brought these issues to a head.
Company leaders decided to conduct a survey of the 250 steam traps in the plant to identify high risk and critical traps. The survey also would allow us to calculate how much failed steam traps were costing the company and determine the best way to approach the problem.
The survey found that a failed steam trap can lose 220 lb/hr of steam, leading us to calculate that we were losing $45,500 per year from only 15 failed steam traps. The survey also identified 98 steam traps and pressure-relief valves that were either high risk (prone to failure) or critical to process operations. If any of the critical steam traps failed, it could cause a process shutdown.
Making Manual Rounds
Until the survey revealed the extent of the problem, the engineering and production team had relied on manual rounds: The maintenance people checked the steam traps periodically using acoustic and temperature-sensing methods. Trained field technicians went from trap to trap performing each analysis individually, comparing actual parameters to ideal parameters.
Some measurement instruments make this comparison in as little as 15 seconds, but a 15-second interval only allows for one or two cycles of condensate removal. This is not enough time to test for proper discharges and steam trap operation.
In addition, with 250 steam traps in the plant, our maintenance team could only check each trap once a year. This made the plant vulnerable to long periods of failures between checks because a steam trap could fail open or closed and be undetected for up to a year.
Further complicating the maintenance screening was the fact that finding and checking steam traps was only possible when the plant was in operation. When the plant was not running, as was sometimes the case with our batch plant operations, we were not able to find any defective traps.
To streamline checking our traps, we installed Rosemount 708 from Emerson. The wireless acoustic monitors monitor the process continuously. This facilitated steam trap screening because if the plant is in operation during the night shift, the engineering team was able to detect defective traps. With this project, we were able to document each steam trap, including its location. Their locations were mapped as a vector from a plant-zero position so the maintenance staff could find them more easily.
Safety also was a major issue. Performing steam trap tests can be dangerous because it exposes personnel to hot and wet process equipment and leaking seals. It often poses issues in reaching hard-to-access steam trap locations.
For example, defective steam traps cause water hammering. The reflux of a heating pipe should be only condensate. A blow-through steam trap will cause severe water hammering in the condensate system, thus stressing the pipes, valves and flange seals. Leaking at steam pipe seals has a high risk of injury.
Valves in the heating system are sturdy and, therefore, expensive, but water hammering destroys even the sturdiest metal-sealed valves. Valves are expensive, and repairing or replacing them requires a process shutdown.
In all, Levaco installed the wireless acoustic monitors on the 98 critical and high risk steam traps and pressure-relief valves. The engineering and production team used SteamLogic software designed by Emerson to quickly identify steam trap failures.
Wireless Steam Trap Monitoring
The wireless acoustic transmitters clamp onto a steam pipe and measure the acoustic signal and temperature (figure 2). Each transmitter sends its wireless signal via WirelessHART to a gateway — either directly or through another wireless transmitter in the wireless mesh system. A smart wireless gateway sends the signals to a base station, which is connected via an Ethernet cable to a PC in the maintenance department. The software analyzes the signals and determines if a steam trap has failed closed or open (figure 3).
When a steam trap fails closed, it no longer passes steam, and it no longer removes water and air from the steam system. This can cause several problems:
- Water hammer.
- Reduced thermodynamic efficiency.
- Water impingement on plant equipment.
- Pressure surges leading to steam line rupture.
When steam traps fail open, they constantly pass steam. Even though steam traps are built with an internal orifice that limits the amount of steam loss, the amount of lost steam can be significant. This results in increased fuel costs and steam boiler load.
The information from the wireless transmitters also could be transmitted to Levaco’s control system, designed by Siemens. In addition, the data can be used to alert our operators because the Emerson software can send this data via OPC, but we have not implemented this function yet. The company plans to add that functionality so the engineering team can monitor steam trap operations from an office PC.
We also plan to visualize the steam trap of a reactor’s heating pipe in the same way as the control valve in its PLC, using the available function blocks in the Siemens PCS7. This will let the team check the heating system before a batch is started and during the process. This will help ensure that all processes reach reaction temperatures. (Failure to reach reaction temperatures can cause poor product quality.)
At Levaco, the building has four floors and a cellar with a concrete ceiling. The engineering team had some concerns about receiving the wireless transmitter signals, but a light well in the middle of the building lets the wireless signals through. Only a single gateway (figure 4) was needed to handle all 98 wireless transmitters — in large part because each wireless transmitter can act as a repeater station in the wireless mesh network.
The installation of 98 steam trap monitors, the single gateway and the software took two days. Levaco technicians installed the steam trap monitors and gateway while engineers from Emerson installed the software.
Failed Steam Traps Found, Steam Heating Optimized
After the initial installation, the Levaco team found that 13 of the 98 traps had failed open. These were repaired, and the company has cut its energy costs considerably. Any steam trap failures are now reported immediately, repairs are made and energy costs are cut right away.
One year after the steam trap monitoring system was installed, Levaco was issued its ISO 500001 certification. It now conforms to the requirements of the Energy Efficiency Directive.
The installation of wireless instruments was so successful, Levaco plans to expand the WirelessHART network with additional measurements to optimize the plant. For example, the engineering and production team plans to replace pressure gauges with wireless transmitters and install new wireless flow transmitters. Levaco has ordered 38 additional wireless transmitters and a gateway, and our technicians will install them upon their arrival.
The engineering team also is discussing using Emerson wireless temperature transmitters in the central cooling system. The heat exchangers tend to lock because of dirt and mussels in cooling water from the river. The heat exchangers do not work properly after a period of time. We want to check temperature progression on the heat exchanger with the wireless transmitters to determine if they still work properly.
In addition, our raw material tanks have Protego floating roofs on top of them. The tanks are filled with nitrogen at a pressure of 30 mbar. If filled or drained, the Protegos control the pressure of the tanks with a small nitrogen control valve. If the roof is broken or stuck and does not close, nitrogen is wasted because the control valve cannot build up the setpoint pressure. We plan to install Emerson wireless pressure transmitters to monitor the pressure.
Finally, our cooling pumps use a lot of current. If they are broken due to cavitation, we do not get enough water pressure for the reactor cooling. We would like to observe those pumps with Emerson wireless pressure transmitters.