OSHA does not have any provisions that require the emergency relief devices on PORTABLE TANKS to discharge to the outside of buildings. However, if portable tanks are part of a PSM-covered process, at a minimum, the employer would be required to IDENTIFY, EVALUATE, AND CONTROL [§1910.119(e)(1)] the hazard of discharging flammable and combustible materials through an emergency relief device into the inside of a building.
If this same condition exists for a non-PSM-covered process and employers have NOT properly evaluated and controlled a release inside a building or a room from emergency relief devices on PORTABLE TANKS, the employer may be cited under the General Duty Clause of the OSH Act for not controlling a serious fire/explosion hazard that is likely to cause death or serious physical harm to employees.
Does §1910.106(e)(2)(ii)(c) and §1910.106(h)(4)(i)(b) apply to processing tanks, such as a buffer mix tank (not a storage tank)? If not, is there a requirement for the processing tank to vent outside the building?
OSHA considers that buffer mix tank operations – where a Class IB liquid is poured into buffer mix tank in making a Class IC liquid – as process tanks, and not storage tanks. OSHA standards §1910.106(e)(2)(ii)(c) and §1910.106(h)(4)(i)(b) apply to storage tanks and NOT to process tanks, such as buffer mix tanks, and OSHA's 1910.106 standards do NOT have provisions requiring processing tanks such as mix tanks containing Class I liquids to vent outside the building. This assumes these tanks are NOT pressure vessels (i.e., designed to operate at pressures greater than 15 psig). If these tanks are pressure vessels, good engineering practice according to the ASME (Section VIII, UG-134(g) of the ASME Boiler and Pressure Vessel Code) REQUIRES in part, "Discharge lines from pressure-relieving safety devices shall . . . lead to a safe place of discharge [emphasis added]."
Similar to above, the employer is responsible for controlling the serious hazard of relieving/venting a process tank into a confined area such as a room/building. If a process tank is part of a PSM-covered process, then the employer must control the hazard. If the process tank is not part of a PSM-covered process, and this hazard exists, then OSHA may enforce the General Duty Clause of the Act.
Note that NFPA 30 – 2008, Paragraph 17.11 requires that exhaust ventilation be discharged to a safe location outside of buildings. This provision applies to all types of operations that use and handle flammable and combustible liquids. Additionally, section 17.15.3 of NFPA 30-2008, in part, states that "The extent of fire prevention and control that is provided shall be determined by means of an engineering evaluation of the operation and application of sound fire protection and process engineering principles." OSHA may find that process tanks that do not comply with these requirements violate the General Duty Clause.
A prevalent belief is that if there is adequate ventilation, processing tank vents do not need to go outside the building. This is desirable in the pharmaceutical industry, because of the concern about the cleanliness of air that may enter the vessel through the vent. Is there a code basis for this belief?
As discussed above, OSHA does not have specific standards which prohibit process tanks to vent inside the buildings. However, venting inside a building is PROHIBITED under the OSHA 1910.106 standard for storage tanks containing flammable and/or combustible liquids. 1910.106(b)(4)(ii), which applies to storage tanks inside buildings, in part states that "Vents shall discharge vapors outside the building." In addition, as stated earlier, if process tanks are part of a PSM-covered process, at a minimum, the employer would be required to IDENTIFY, EVALUATE, AND CONTROL [§1910.119(e)(1)] the hazard of discharging flammable and combustible materials through an emergency relief device into the inside of a building. As discussed above, if employers have not properly evaluated and controlled a release inside a building from process tank vents, OSHA may use section 17.15.3 of NFPA 30-2008 as the basis for enforcing the General Duty Clause for process tanks not venting outside the building for not controlling a serious fire/explosion hazard that is likely to cause death or serious physical harm to employees.
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