Text For Citation: 01 Item/Group: 029 Hazard: BURNS

Section 5(a)(1) of the Occupational Safety and Health Act of 1970: The employer did not furnish employment and a place of employment which were free from recognized hazards that were causing or likely to cause death or serious physical harm to employees in that employees were exposed to: a) Potential toxic vapor cloud or spray of hydrofluoric (HF) acid into the HF alkylation unit exposing employees to serious HF acid burns and absorption due to contact or inhalation of HF acid. The following conditions contributed to the existence of these hazards: (i) Vessels containing HF which can simul- taneously relieve with the isostripper column (A-V7) can result in the subsequent ejection of lime water (and potentially non-neutralized HF acid) through the top hatch of the lime water tank (A-V16). This could likely result in a release of HF acid vapors into the Alky Unit. (ii) The lime water scrubbing system was an older U.O.P. design utilizing lime water to neutralize HF acid reliefs. A small amount of potassium hydroxide is now added to the lime water to increase its neutralization capacity. In light of the 1988 Alky Unit Expansion the adequacy of this system must be evaluated to ascertain its capability to neutralize HF releases from multiple reliefs. (iii) The lime water scrubbing system was subject to flooding the flare knockout drum and the flare line when lime sludge blocks the lime water level sensor (LT-33) on the relief gas scrubber (A-V15). Blockage of the flare line could cause catastrophic line or vessel failure with the release of hazardous HF- containing materials into the unit, i.e. should an HF pressure relieving device lift while relief paths were blocked. One method of abatement is to utilize HF sensor(s) and alarms on the lime water tank (A-V16) to detect HF vapors and to conduct a through engineering design review to ensure the system and safety designs in place are still adequate in light of the 1988 upgrade modifications in the Alky Unit. The HF acid scrubbing system in the HF Alkylation Unit must be throughly evaluated to acertain its capacity and ability to neutralize the HF acid or mixtures which can be vented to the scrubber in both normal and emergency conditions.