PHMSA Withdraws Vapor Pressure Rule

The DOT’s Pipeline and Hazardous Material Safety Administration (PHMSA) published a notice in today’s Federal Register (85 FR 30673-30680) withdrawing their advanced notice of proposed rulemaking (ANPRM) on “Vapor Pressure of Unrefined Petroleum Products and Class 3 Materials”. That rulemaking was published in January of 2017.

According to the notice summary, based upon test results obtained by Sandia Laboratories:

“PHMSA is providing notice of its determination that the establishment of vapor pressure limits would not improve the safety of rail transportation of crude oil. Therefore, PHMSA is no longer considering vapor pressure limits for the transportation of crude oil by rail or any other mode. Furthermore, PHMSA is also providing notice that, after considering comments received to the ANPRM, it is no longer considering imposing vapor pressure standards for other unrefined petroleum-based products and Class 3 flammable liquid hazardous materials by any mode.”

Federal Preemption

The notice also includes a discussion of PHMSA’s observations about how this withdrawal would affect State and local attempts to regulate the transportation of crude oil based upon the vapor pressure of that material. The notice begins that discussion by stating:

“PHMSA, in issuing this withdrawal, has affirmatively determined that a national vapor pressure limit for unrefined petroleum-based products is not necessary or appropriate. As explained further below, PHMSA believes that Federal law likely preempts any non-Federal law that attempts to set a vapor pressure limit for these materials.”

PHMSA concludes that discussion by stating:

“A person directly affected by a non-Federal requirement may apply to PHMSA for a determination that the requirement is preempted by 49 U.S.C. 5125. See 49 U.S.C. 5125(d); 49 CFR 107.203-107.213. PHMSA is currently considering a preemption application filed by North Dakota and Montana with respect to Washington's vapor pressure limit, and will consider any application filed with respect to other non-Federal vapor pressure limits.”

In fact, PHMSA has already published their response to the North Dakota and Montana preemption application in last Friday’s Federal Register (85 FR 29511-29528). Unsurprisingly, PHMSA determined that the Washington State rules were preempted by the existing lack of vapor pressure standards in the Hazardous Materials Regulations. Both notices were signed on May 11^th, 2019, but the publication review process apparently took longer on this notice.

Commentary

I think that PHMSA erred in the way they looked at the Sandia Labs test results. As I mentioned in my earlier post on those test results, those tests just looked at the comparative effects of a fire resulting from releases of crude oil with various vapor pressures. Any chemist or fire scientist could have easily predicted the results of those tests, a similar mass of linear hydrocarbons will generate the same amount of heat energy when burned. The fireball tests were equally uninformative because of the extremely high pressure the material was subjected to before the gases were released to the atmosphere.

The testing methodology did nothing to evaluate the effect of vapor pressure on the likelihood of a vapor release during a derailment. Determining the temperature at which a crude oil sample reached a vapor pressure of 32 psig (the pressure relief setting for railcars carrying flammable materials) would provide some measure of predictive value of a vapor release (and probable fireball result) for a given material. In a complex mixture of hydrocarbons like crude oil, that might provide important hazard classification information for regulators. Whether or not that was regulatorily feasible would depend on what transportation safety mitigation factors could be applied to materials with a relatively low temperature to achieve 32 psig.

If President Trump loses the election this November, I would suspect that a Biden controlled PHMSA might revisit this rulemaking.

Sandia Labs Crude Oil Fire Report – August 2019

Last month Sandia National Laboratories published a report on a series of experiments done looking at the pool fire characteristics of a variety of crude oil samples with a wide range of vapor pressures. At least one news organization has jumped on the conclusions explicated in the Abstract to express support for the contention that the regulation of crude oil shipping should not take into account differences in oil vapor pressure.

Study Conclusions

The lengthy and very technical report from Sandia, part of the ongoing DOE investigation of the hazards associated with crude oil shipments, makes the following statement in the Abstract (pg 3):

“The results indicate that all the oils tested here have comparable thermal hazard distances and the measured properties are consistent with other alkane-based hydrocarbon liquids. The similarity of pool fire and fireball burn characteristics pertinent to thermal hazard outcomes of the three oils studied indicate that vapor pressure is not a statistically significant factor in affecting these outcomes. Thus, the results from this work do not support creating a distinction for crude oils based on vapor pressure with regards to these combustion events.”

The key phrase in the above quote is found in the last sentence; “with regards to these combustion events.” Pool fires and fireballs were created and analyzed. The study assumed that in a crude oil derailment accident the conditions would exist to cause these two conditions. In the discussion portion of the report it is noted that (pg 75): “Based on the Phase I effort, the premise is that most train accidents

provide enough kinetic energy to exceed the parameter thresholds indicating flammability;

consequently, ignition is highly probable regardless of the crude oil type.”

Vapor Pressure Measurement

This study used an automated vapor pressure measurement system (ASTM D6377) at 100˚F. This is a different method from the ones that I have discussed previously in this blog (see here for instance), but the report authors include an important discussion (Section 1.1, pg 26) about the need for proper sampling techniques and storage of tested samples. Any discussion of vapor pressure testing needs to address these issues.

Fireball Testing

The fireball testing conducted in this study was designed to look at the effects of the ignition of vapor clouds over a derailment event. It is clear from the description of the test methodology (pg 253) that investigators were concerned about vapor releases from intact railcars that were subject to the intense heating associated with direct flame impingement from a pool fire caused by a release of crude oil (or other flammable liquid) from a nearby ruptured railcar.

The test tanks were heated to 300˚C and 280 psi and a rupture disk was then command released via explosives. To ensure ignition of the resulting vapor cloud, a second explosive device was then detonated.

Commentary

The test information presented in the report is very valuable for fire response planning. It is not really surprising that the test concluded that there is little effective difference in the thermal effects of a pool fire from crude oil with wide variations in vapor pressure. Those thermal effects are more closely related to the heat released in the combustion of hydrocarbons and that is directly related to the number of carbon atoms burned, not the physical state of the molecules within which they are contained. Similar masses of carbon atoms in linear chains will produce similar amounts of heat. This is chemistry 101.

The testing of the fireball, similarly restricts the evaluation to the heat effects and the size of the fireball. Again, this is useful information for fire response planning, but it does little to address the underlying concerns about the dangers associated with variations in crude oil vapor pressure; that is the likelihood of a vapor cloud forming in a given accident.

Since DOT mandates that the pressure relief valve (PRV) on crude oil railcars release vapors at 32 psi, the testing at 280 psi is of little value. What would have been more impressive would have been gradually heating the samples in a pressure vessel until a standard 32 psi PRV opened and then igniting the resulting vapor cloud after some preset time limit. The emissivity testing reported in this study would be done on the resulting fireball, but overpressure testing at set distances from the test to evaluate differences in the blast effects from the resulting fireball should also be required.

Vapor pressure testing of crude oil is going to be of only very limited usefulness. For relatively pure substances, calculating vapor pressures at varying temperatures from single temperature testing is a rather simple application of Boyles Law. For complex mixtures like crude oil this is not the case. Each of the hundreds of components of crude oil has its own boiling point, the temperature at which it begins to significantly contribute to the vapor pressure of the mixture.

To be a valuable predictor of fireball formation in a crude oil derailment, we need a new vapor pressure testing method. Instead of measuring vapor pressure at a fixed temperature, it would be more useful to regulators to have a test that measures the temperature at which we would expect safety devices to release a vapor cloud. For rail transportation that would be 32 psi. Unfortunately, such a test would present an interesting set of potential physical hazards in the testing facility. And that would significantly increase the cost of testing.

It would be helpful in Sandia did a test evaluating a similar variety of crude oils as seen in this testing to see what sort of temperature variations were seen in the temperature necessary to reach 32 psi vapor pressure and what variations were seen in the fireball testing conducted at those temperatures. Oh, yes, please include overpressure measurements during the fireball testing. If there were relatively little practical difference in the release temperature, emissivity and/or overpressure, then we could probably conclude that vapor pressure testing was a dead issue.

PHMSA Publishes Crude Oil Volatility ANPRM

Today the DOT’s Pipeline and Hazardous Material Safety Administration (PHMSA) published an advance notice of proposed rulemaking (ANPRM) in the Federal Register (82 FR 5499-5508) concerning a possible rulemaking addressing volatility of unrefined petroleum products

and Class 3 materials.

As mentioned in an earlier post, this ANPRM is based upon a rulemaking petition filed by the Attorney General for the State of New York. According to the summary of the ANPRM that petition asks PHMSA to revise the hazardous materials regulations (HMR) to “implement a Reid Vapor Pressure (RVP) limit less than 9.0 pounds per square inch (psi) for crude oil transported by rail”. In that same summary PHMSA notes that it will use public comments on this ANPRM to “help assess and respond to the petition and to evaluate any other potential regulatory actions related to sampling and testing of crude oil and other Class 3 hazardous materials. PHMSA will also evaluate the potential safety benefits and costs of utilizing vapor pressure thresholds within the hazardous materials classification process for unrefined petroleum-based products and Class 3 hazardous materials”.

Review of Existing Data

The body of the ANPRM provides a discussion of how PHMSA currently regulates how the transportation hazards of crude oil and other flammable (Class 3) liquids are categorized. It then goes on to provide a brief discussion of how PHMSA dealt with the possible issue of adding vapor pressure to the regulatory scheme in the recent highly-hazardous flammable train rulemaking. PHMSA requested input on the potential use vapor pressure, but did not end up including it in that rulemaking.

In 2014 DOE and DOT commissioned the Sandia National Laboratory to conduct a review “of available crude oil chemical and physical property data literature to characterize and define tight crude oils based on their chemical and physical properties, and identify properties that could contribute to increased potential for accidental combustion”. The initial stages of that study concluded that “the wide-ranging variability in crude oil sample type, sampling method, and analytical method, as well as the acknowledgement that this variability limits the adequacy of the available crude oil property data set as the basis for establishing effective and affordable safe transport guidelines.”

The next phase of that Sandia study is specifically designed to determine what methods of sampling and analysis are suitable for characterizing the physical and chemical properties of different crude oils.

Questions to be Answered

While the Sandia study is on-going, PHMSA is looking for input on a wide variety of issues that would have to be considered in any proposed rulemaking on crude oil and flammable liquid vapor pressure regulation in the transportation realm. In asking for that input PHMSA is asking for answers to a specific set of questions that it breaks down into four broad categories; 24 general questions, six safety questions, eight vapor pressure questions; and a single packaging question.

The general questions covers many of the issues that any new regulatory scheme has to address to justify the cost of the regulation. It includes questions about

• How a 9.0 psi Reid Vapor Pressure limit on crude oil would affect the outcome of accidents involving crude oil transportation;

• How to measure the health and environmental effects of the proposed regulations;

• What methods could be used to reduce the vapor pressure of crude oils above the proposed limit;

• Whether the vapor pressure standard should be applied to all modes of transportation;

• Whether other risk factors that should also be addressed;

• The fixed and variable costs of establishing the vapor pressure limit; and

• The transportation of the flammable gasses removed from the crude oil;

The safety questions address the potential implications that the adoption of the vapor pressure limit have on other portions of the HMR. It includes questions about:

• The definition of flammable gasses;

• The possible adoption of a new crude oil listing in the hazardous materials table (HMT) for high vapor pressure crudes; and

• The effect of flammable liquids with high concentrations of dissolved flammable gasses on the response community.

Public Responses

PHMSA is soliciting public comments on this ANPRM. Comments may be submitted via the Federal eRulemaking Portal (www.Regulations.gov; Docket # PHMSA-2016-0077. Comments should be submitted by March 20^th, 2017.

There will almost certainly be a large letter writing campaign (or even possibly multiple campaigns) orchestrated by environmental activist organizations. Federal agencies do not take any special cognizance of the number of comments submitted for or against a rulemaking. They are required, however, to address specific issues raised in comments. When cut-and-paste comments are received, the agency only has to deal with a single response to each of the issues raised in the response. All of the activist organizations clearly understand this, thus it would seem that these campaigns are designed more for internal reasons (most likely fund raising) than to affect the outcome of the regulatory process.