Read the passage below:
High-pressure industrial steam boilers require dissolved oxygen levels in feedwater to remain below five parts per billion to prevent severe pitting corrosion inside carbon steel piping. Thermal deaerators achieve this by spraying incoming feedwater through steam-heated trays, raising the water to its saturation temperature and scrubbing out non-condensable gases. The liberated oxygen and carbon dioxide are continuously vented to the atmosphere through a calibrated orifice at the top of the vessel. While mechanical deaeration removes the vast majority of entrained oxygen, chemical oxygen scavengers must still be injected into the storage tank downstream to neutralize residual traces.
Match each statement derived from the passage with its corresponding inference evaluation.
- Mechanical scrubbing alone leaves dissolved oxygen above the safe five parts per billion threshold.Supported inference because chemical scavengers are explicitly required to neutralize remaining traces that mechanical scrubbing cannot fully eliminate.
- Dissolved carbon dioxide causes more rapid pipe degradation than dissolved oxygen in carbon steel piping.Unsupported assumption because the passage identifies both gases as non-condensable but provides no comparative data regarding their corrosion rates.
- Obstructing the atmospheric vent orifice will ultimately compromise the corrosion protection of the boiler system.Supported inference because preventing the exhaust of liberated gases allows oxygen to remain trapped in the system, threatening pipe integrity.
- Feedwater must be brought to its saturation temperature before entering the deaerator vessel.Unsupported assumption because the text indicates that water reaches saturation temperature while flowing through the internal steam-heated trays, not prior to entry.