The Karratha Gas Plant has multiple propane vessels which are used for chilling process gases. To ensure optimal process control, the liquid level over the heat exchanger tubes needs to be precisely regulated. Previously liquid levels were calculated by two differential pressure sensors. However, this method is less accurate than direct measurement and has a complex relationship with temperature of the fluid and cannot measure below the lower sensor. The Woodside Technology Team tasked AEC with designing a manhole cover replacement that could be used to support an Endress-Hauser guided wave radar probe (GWR or dip stick) without any modifications to the existing pressure vessel walls. AEC proposed a “dip stick” be inserted through the vessel’s manhole cover with a “welling tube” to support the dip stick.