“Unlike Humpty Dumpty, the Secretary may not give a word whatever meaning she chooses.”  —Judge Richard DeBenedetto

When the Meer Corporation took the bold and relatively unheard-of step of contesting an OSHA citation for violating the Process Safety Management standard (PSM), no one expected them to prevail. The PSM standard includes an exemption for atmospheric storage of flammables, which the Meer Corporation was convinced applied to their process. OSHA, on the other hand, had regretted that exemption almost immediately upon promulgating the standard. OSHA issued several interpretations to say that the flammable storage exemption didn’t apply if the storage tank was connected to anything.

Without connections to put material into the tank and to take material out of the tank, storage tanks serve no purpose. In essence, OSHA intended to negate the flammable storage exemption with its interpretations.

The Meer Decision

The Meer Corporation believed that their alcohol storage tanks were exempt from the PSM standard, per 1910.119(a)(1)(ii), which excludes “Flammable liquids stored in atmospheric tanks or transferred which are kept below their normal boiling point without benefit of chilling or refrigeration.”

OSHA argued that its definition of process in 1910.119(b) excluded the exclusion. “Process means any activity involving a highly hazardous chemical including any use, storage, manufacturing, handling, or the on-site movement of such chemicals, or combination of these activities. For the purposes of this definition, any group of vessels which are interconnected and separate vessels which are located such that a highly hazardous chemical could be involved in a potential release shall be considered a single process.”

Judge DeBenedetto noted that storage and transfer (on-site movement) were processes under the definition of the regulation, whether connected to anything else or not. He also noted that there are no qualifying phrases in the exemption such as “and not connected to a process or process vessel,” or “unless the atmospheric tank is connected to a process.”

Concluding his discussion of OSHA’s interpretations of the PSM standard, Judge DeBenedetto acknowledged that courts should defer to an agency’s interpretation of its own regulations, but that “an agency’s interpretation of a regulation is valid only if that interpretation complies with the actual language of the regulation. An agency is bound by the regulations it promulgates and may not attempt to circumvent the amendment process through changes in interpretation unsupported by the language of the regulation.”

In other words, the atmospheric storage of flammable liquids is exempt from the PSM Standard, as well as transfer into and out of the atmospheric storage tank, as long as the flammable liquid is kept below its normal boiling point without any cooling. It doesn’t matter how the storage tank is connected to other equipment, even if that equipment is covered under the PSM standard.

Atmospheric Storage and RMP

When the EPA promulgated the Risk Management Planning rule (RMP), its version of the PSM standard, they were already aware of OSHA’s difficulties with the exemption for the atmospheric storage of flammable liquids. There is no exemption for atmospheric storage of flammable liquids in the RMP rule.

Applying the Exemption

Flammable liquids are hazardous, even when in storage, but the atmospheric flammable storage exemption still exists for PSM. However, there are four important points to keep in mind before applying it to your process.

The exemption does not apply to Appendix A materials. Any highly hazardous chemical (HHC) listed on Appendix A is there, not for its flammability, but for its toxicity or reactivity. As such, the exemption does not apply to Appendix A HHCs. So, methyl trichlorosilane, with a flash point of 46 F and a boiling point of 151 F, is a flammable liquid that could be stored at atmospheric pressure, but wouldn’t qualify for the exemption because it is listed in Appendix A.

The exemption only applies to atmospheric tanks. OSHA defines an atmospheric tank  as “designed to operate at pressures from atmospheric through 0.5 psig”. So, a low-pressure vessel designed to operate at 2.5 psig would not qualify. Also, it is not enough that the tank be operated at atmospheric pressure; it must be designed to operate at atmospheric pressure, so that its pressure cannot go higher. One way to do this is to leave it open to atmosphere, such as with the installation of a gooseneck vent. Installing a gooseneck vent on a pressure vessel will change its design to that of an atmospheric tank. In many cases, you may want to operate with a conservation vent. That’s fine, so long as the set point is not higher than 0.5 psig, or 13.85 in WC.

The exemption does not apply if any kind of cooling is necessary to keep the flammable liquid below its normal boiling point. This immediately disqualifies any flammable liquid with a boiling point less than normal ambient temperatures. But it also applies to flammable liquids that are hotter than their normal boiling points and depend on cooling to bring the temperature down to less than boiling while being transferred into the tank.

The exemption only applies to storage. If you are doing anything to the flammable liquid while it sits in the atmospheric tank, then it is no longer simply storage. If there is an agitator or eductors, it is not a storage tank, but a blending tank. If the intent of the tank is to provide the opportunity for flammable material to separate into phases, then it is not a storage tank but a separator, settling tank, or decanter. A storage tank is one from which the material transferred out is the same as the material transferred in without any unit operation occurring in the tank.

What Does the Future Hold?

Almost every year since the Meer decision, OSHA has listed addressing the issues raised by the Meer decision as part of its regulatory agenda. It has been over 20 years since the Meer decision, and still, OSHA has not tackled the amendment process to make this change. If they finally get to it, there will be plenty of notice and time to address the changes you need to make to your process or your PSM program.

The PSM standard first went into effect in 1992. We are approaching the 30th anniversary of this regulation and there is much about it that would benefit from revision. That said, it is still a powerful and effective regulation that exerts enormous influence on facilities that produce or use HHCs. No one should be surprised, however, when OSHA finally sets out to update the regulation. One of the things we should expect to see is a clarification of the atmospheric flammable storage exemption to match what OSHA originally intended, or the elimination of the exemption entirely.

Until then, though, it is the law of the land, to be applied where appropriate.