The Questtec LT-440 provides an exclusive means of achieving accuracy with Guided Wave Radar, or any other loop powered instrument, when used in a water column to determine level in a high pressure steam system.
Water density increases as the temperature of steam condensate decreases. This can create a significant error to the actual water level in the water column as compared to the water level in the steam drum. For example, the density of water in a steam drum operating at 650° F is 599.54 kg/m . The sub cooled water in a water column may be only At 615° F, and have a density of 657.49 kg/m . This would result in an error of 8.9% of the water height in the column as compared to the steam drum. A water column with 30″ of water indicated, could be expected to be nearly 3″ lower than what is actually in the drum. Even an accurate measurement of level at the water column would result in a Water Density Error.
The LT-440 utilizes the data collected from at least 4 thermocouples installed on the water column and determines an actual average water temperature. The primary loop is dynamically corrected and a secondary loop is communicated to any device included in the loop.
