Text For Citation: 01 Item/Group: 001 Hazard: CHEMICAL

T.C.A. 50-3-105(1): The employer did not furnish employment and a place of employment which were free from recognized hazards that were likely to cause death or serious physical harm to employees in that employees were potentially exposed to explosions, fires, and resultant reaction products (such as phosphorous pentoxide and phosphoric acid) that could result from uncontrolled and unintended heating of hypophosphorous acid in an evaporator in the Hypo Plant. Such heating could cause the hypophosphorous acid to be concentrated to the point of essentially 100acid, and subsequently cause the acid's thermal decomposition into explosive gases such as phosphine and possibly hydrogen (which was stated on the company's material safety data sheet, MSDS, for hypophosphorous acid). The phosphine could then spontaneously ignite with contact with oxygen in air to cause explosions and fires, such as those that were experienced during an incident involving the hypophosphorous acid evaporator at the Hypo Plant on 5/2/2000 between approximately 8:48 PM and 10:15 PM. During that incident, the company felt that pressurized steam had leaked through a steam flow control valve and caused unintended heating of 600 gallons of (initially) 10hypophosphorous acid in an evaporator to the point of thermal decomposition. The evaporator part of the process was not intended to be in operation at the time. Such uncontrolled and unintended heating of the hypophosphorous acid was not prohibited through adequate process design and/or work practice (such as operating procedure) controls and/or other controls. Employees potentially exposed to serious burns and death from such explosions and fires before and/or on 5/2/2000 were a Hypo Helper, a Hypo Crystallizer Operator, a Hypo Reactor Operator, a Production Foreman, and Hazardous Materials Technicians (Hazmat Techs, who were members of the CAERS [the company's Communications and Emergency Response System] Team or the Emergency Control Team) who responded to the fires to assist in controlling them and putting them out, while wearing personal protective equipment including self contained breathing apparatus (SCBAs). The Hazmat Techs were also potentially exposed to unknown airborne concentrations of phosphoric acid aerosol, fume, or mist. Among other methods, one feasible and acceptable abatement method to correct this hazard was to follow one of the company's stated (in a 6/12/00 letter) "Normal operating procedure[s]" and "transfer the entire contents of the evaporator to the product storage tank." Other methods of control, which would be present in an effective safety and health program for such a chemical process facility, would be: 1.Effective process design controls, such as having an instrumentation system with established absolute parameters, for instance on temperature of the evaporator when it was not intended to be used for acid concentration, and that would shut down the heat supply if the critical parameters were exceeded. Effective application of heat sensing alarms could be such a control method. Heat sensing alarms were said bythe company to be present (in their 9/1/00 correspondence), but they did not control the unintended application of heat. Effective alarms could be programmed in the control system to automatically shut down the steam flow to, and heating of, the evaporator; 2.Redundant levels of automatic control, which would be important to ensure control; 3.Effective operating procedures for any possible control reliant upon manually operated valves or other equipment or procedures, such as a "block valve" that "was physically open (i.e., not manually isolated) prior to the event of 5/2/00" (quote from the company's 9/1/00 correspondence). Such procedural controls would be less effective than automatic controls, and must be accompanied by strict operating procedures with adequate Operator training, adequate verification checklists, and strict enforcement of such procedures, with a system applied to safely manage any proposed changes to the procedures; 4.Effective preventive maintenance of process equipment, such as the steam flow control valve that was believed to have leaked pressurized steam to the evaporator on 5/2/2000, through application of a replacement schedule, and/or inspection schedule, and/or testing schedule. The company's "Preventative and Predictive Programs to maintain all plant equipment in good repair...[where] Employees are trained to spot and trouble shoot problems with equipment and routinely originate work orders for repair" (quote from the company's 6/12/2000 correspondence) did not effectively prevent the leaking steam flow control valve feeding heat to the evaporator on 5/2/00; and 5.Effective hazard analysis of the process, which would address the potential for unintended potential heat application to the evaporator, and recommend and cause to be implemented adequate safeguards and controls to prohibit such an event. The company's "Risk Assessment - Hypophosphorus Acid Plant," of 5/17/93, and its "Hypophosphorus Acid Process Hazards Analysis Revalidation," of 12/12/98, did not address the potential for unintended potential heat application to the evaporator. NOTE: this hazard was corrected during the course of the inspection with the shut down of the hypophosphorous acid process after the 5/2/00 accident. The company stated on 9/1/00 that "There are no plans to restart the unit at this time." In the company's "Analysis of May 02, 2000 Incident," they stated that "If it is decided to operate the [Hypophosphorous Acid] unit, a HAZOP [hazard and operability study, which is a form of process hazard analysis] study will be conducted, and any necessary mitigation steps identified will be taken before startup."