Delivering fuel and Tank Over Pressurization

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ZMiller
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Delivering fuel and Tank Over Pressurization

Post by ZMiller » Tue Oct 29, 2019 6:57 am

We observed 75 bulk deliveries between December 24th, 2018 and January 1st, 2019.

A total of 75 deliveries being 25 in Metro Atlanta, Georgia, 25 in Metro Kansas City, Missouri and 25 in Metro St. Louis, Missouri.

24 out of 25 deliveries observed were being made in a condition considered Out of Compliance due to driver errors in configuring drop and stage 1 vapor recovery connections. During the Out of Compliance bulk fuel delivery and vapor recovery events, open tank scenarios and driver bypassing Stage 1 in order to expedite deliveries were found to be the culprit causing excessive vent VOC releases.

The concerning issue was typically where a driver would vent negative pressure when connecting the Stage 1 vapor recovery hose to the tank before connecting to the delivery truck.

Logically thinking in most cases a receiving tank would ingest when relieving negative pressure pre delivery, extremely large volumes of outside atmosphere.
This mass volume of outside atmosphere ingested caused all kinds of obvious problems that would not normally be seen on a Stage 1 equipment certification test site.
Drivers using poor judgment and a "who cares lack of concern" for escape of massive amounts of VOC's when bypassing Stage 1 in order to expedite the delivery was even more concerning.

Adding to the bypass of Stage 1 problem observed in a number of fuel delivery events was the delivering tanker compartments being intentionally opened to atmosphere allowing increased out of dynamic balance fuel flows (drops). Exceeding vent pressure/vacuum relief valve flow rating during high ( exceeding 1,200 GPM ) speed drops caused extreme dynamic back pressures ( in excess of 10 PSI ) to build in receiving and associated tank(s) empty spaces. For a UL-58 rated tank these over pressurization events would normally be considered by the manufacture to be fatal regarding compartment bulkhead separation and primary tank boundary integrity.


"5.4. Fuel deliveries and accidental vent releases
Based on observations and interpretation of time series of the tank pressure data, it is likely that the peak vent emissions (e.g., Fig. 3b) were partly due to non-compliant bulk fuel drops where the Stage I vapor recovery system either was not correctly hooked up by the delivery driver or to hardware problems with piping and/or valves. This conjecture is consistent with typical US storage tank volumes (~10,000 to 30,000 gal). Assuming that Phase I vapor recovery did not work at all and that 10,000 gal (~38,000 L) of fuel were delivered, the working loss (volume of gasoline vapor/air mixture released to the atmosphere through the vent pipe) is 38,000 L. It is also reasonable to assume that delivery lasted less than 1 h. According to Table 2, the maximum hourly flow rate through the vent pipe was 250 L/min at GS-MW, which would result in a maximum cumulative vapor release of 15,000 L within this hour. The measured maximum cumulative release underestimates the assumed working loss of 38,000 L. This could be due to a fuel delivery, which involved dropping fuel from multiple compartments of a tanker truck, with the vapor return hose not being correctly hooked up for only some of the emptied compartments.

At GS-MW, UST pressure decreased after fuel delivery (causing vent emissions to cease for several hours) during the climatic conditions prevalent during the observation period, behavior not observed at GS-NW. In practice, it is possible to observe both positive and negative pressure excursions, even during the same fuel delivery (when multiple fuel compartments of tanker trucks are unloaded), when Stage I vapor recovery is in place"

Interesting about the PV Valve failures here as I'm sure just about every where else as well. Exactly why they are simply and obviously failing probably worth further discussion.
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
"Tact is the ability to tell someone to go to Hell in a way that they will begin looking forward to the trip"

ZMiller
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Re: Delivering fuel and Tank Over Presurization

Post by ZMiller » Tue Oct 29, 2019 7:15 am

One wonders how saturated vapors causing low PH and corrosive atmospheres are migrating from tanks into sumps during such events?

All but an idiot would realize that ullage pressures exceeding 1 or 2 psi during a bulk fuel drop, will force vapor migration to atmosphere through loose or over pressure rated tank top fittings.

Vapors present in a secondarily contained sump means the Tank or tank(s) associated are Quite Possibly LEAKING?

Of course it is and only a moron or McFly would not recognize the problem.
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
"Tact is the ability to tell someone to go to Hell in a way that they will begin looking forward to the trip"

ZMiller
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Re: Delivering fuel and Tank Over Presurization

Post by ZMiller » Thu Oct 31, 2019 8:26 pm

I figured people would read the post on tank Over pressurization and vapor migration during a delivery.
I fear that most still have no idea what I'm tanking about.
What's happening in the tanks empty space during a bulk delivery is not actually something one can see with the human eye.

I can only say from experience that one doesn't want to be standing on top of a creaking and straining to contain ten thousand gallon glass or steel fuel storage tank when there is 10 PSI in the ullage.
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
"Tact is the ability to tell someone to go to Hell in a way that they will begin looking forward to the trip"

Goofy4TheWorld
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Re: Delivering fuel and Tank Over Presurization

Post by Goofy4TheWorld » Thu Oct 31, 2019 11:07 pm

Even though I am only a single-site owner, nothing about these findings surprise me at all. We have a really great fuel supplier, they treat us and their employees great and expect their employees to know better....

But I have seen way too many drivers with screwdrivers in the vapor riser, or even worse no hose OR screwdriver, to be shocked by this. We used to threaten drivers that if we ever saw it again we would see to it that they were fired. Now we don't even bother with the threat, we go straight to the their bosses. Finally we made it clear to the company that if another driver ever dropped without a hose or with a screwdriver, we were turning them in to the Division of UST, even going as far to say we would call and tell that one guy at UST that EVERYONE in the industry hates! This was mostly in the early days of vapor recovery in our area and maybe it isn't as frequent as it used to be, but we made sure we as a store had a reputation for making driver's life miserable if they EVER put our tanks under pressure during a drop, or vented flammable fumes right at ground level 10 feet from customers who, like it or not, might be smoking a cigarette.

We have now gone a VERY long time without a violation that we have seen (and we watch, sometimes checking surveillance video to check up on drivers) so I'm grateful that the message has finally been received. But this post was nothing new to me!
Last edited by Goofy4TheWorld on Fri Nov 01, 2019 9:42 pm, edited 1 time in total.

justinforman
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Re: Delivering fuel and Tank Over Presurization

Post by justinforman » Fri Nov 01, 2019 6:43 pm

In Ca with ISD delivery drivers have caused a lot of alarms caused by not following the correct steps and dropping before the vapor was hooked up. I have a bunch of ullage pressure logs that clearly show a pressure spike but upwards of 8"wc not PSI. With a vent how are they getting to 10 psi?
P/V cap failures are a whole different story of the ones we can use the Husky 5885 and OPW 723v are lucky to pass a yearly test. The franklin PV Zero is good but expensive.


ZMiller
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Re: Delivering fuel and Tank Over Presurization

Post by ZMiller » Sat Nov 02, 2019 6:13 pm

Pressure sensors are span maxing out (signal pegging) and going into alarm. Duration of monitoring of the over pressure event is to long before registering the alarm. Drivers when filling to fast out of compliance for reasons such as being in a hurry will drop at a rate for example where vapor volume and velocity will float (closed) where they still are present cross contamination ball checks and hammer the tank ullage, often to sometimes extreme (as high as 20 PSI) pressures. The hammer and or over pressure event may only last a fraction of or a few seconds, but enough to damage tank and or force vapor migration. Quite often and not to surprisingly one can hear and even feel ball float chatter at 60% full.

On high throughput test sites where pressures are monitored continuously in real time not using algorithm, higher pressures are typically seen near the end of the customers contract ordering of fuel to be delivered (their quota for the ordering cycle). There are several customer and supplier specific reasons these clustered over pressure events happen when they do and better explained not in an open forum.

I love the PV Zero but it has a cold weather fatal problem. That being condensed and accumulated trapped moisture.
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
"Tact is the ability to tell someone to go to Hell in a way that they will begin looking forward to the trip"

justinforman
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Re: Delivering fuel and Tank Over Presurization

Post by justinforman » Mon Nov 04, 2019 9:39 am

I'm lucky that I dont have to worry about freezing here in San Diego. I did just see a new defender PV that can come with a box so that the PV in installed down low on the vent rack. No CARB approval though.

jjames
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Re: Delivering fuel and Tank Over Presurization

Post by jjames » Tue Nov 05, 2019 11:50 am

Thank you - this is great information.

ZMiller
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Re: Delivering fuel and Tank Over Presurization

Post by ZMiller » Wed Mar 04, 2020 7:03 am

For What it's Worth

Abstract
At gas stations, fuel vapors are released into the atmosphere from storage tanks through vent pipes. Little is known about when releases occur, their magnitude, and their potential health consequences. Our goals were to quantify vent pipe releases and examine exceedance of short-term exposure limits to benzene around gas stations. At two US gas stations, we measured volumetric vent pipe flow rates and pressure in the storage tank headspace at high temporal resolution for approximately three weeks. Based on the measured vent emission and meteorological data, we performed air dispersion modeling to obtain hourly atmospheric benzene levels. For the two gas stations, average vent emission factors were 0.17 and 0.21 kg of gasoline per 1000 L dispensed. Modeling suggests that at one gas station, a 1-hour Reference Exposure Level (REL) for benzene for the general population (8 ppb) was exceeded only closer than 50 m from the station's center. At the other gas station, the REL was exceeded on two different days and up to 160 m from the center, likely due to non-compliant bulk fuel deliveries. A minimum risk level for intermediate duration (>14–364 days) benzene exposure (6 ppb) was exceeded at the elevation of the vent pipe opening up to 7 and 8 m from the two gas stations. Recorded vent emission factors were >10 times higher than estimates used to derive setback distances for gas stations. Setback distances should be revisited to address temporal variability and pollution controlsin vent emissions.

Graphical abstract
5.4. Fuel deliveries and accidental vent releases
Based on observations and interpretation of time series of the tank pressure data, it is likely that the peak vent emissions (e.g., Fig. 3b) were partly due to non-compliant bulk fuel drops where the Stage I vapor recovery system either was not correctly hooked up by the delivery driver or to hardware problems with piping and/or valves.

This conjecture is consistent with typical US storage tank volumes (~10,000 to 30,000 gal). Assuming that Phase I vapor recovery did not work at all and that 10,000 gal (~38,000 L) of fuel were delivered, the working loss (volume of gasoline vapor/air mixture released to the atmosphere through the vent pipe) is 38,000 L. It is also reasonable to assume that delivery lasted less than 1 h. According to Table 2, the maximum hourly flow rate through the vent pipe was 250 L/min at GS-MW, which would result in a maximum cumulative vapor release of 15,000 L within this hour. The measured maximum cumulative release underestimates the assumed working loss of 38,000 L. This could be due to a fuel delivery, which involved dropping fuel from multiple compartments of a tanker truck, with the vapor return hose not being correctly hooked up for only some of the emptied compartments.

2.1. Introduction
In the US, approximately 143 billion gal (541 billion L) of gasoline were dispensed in 2016 at gas stations (EIA, 2017) resulting in release of unburned fuel to the environment in the form of vapor or liquid (Hilpert et al., 2015). This is a public health concern, as unburned fuel chemicals such as benzene, toluene, ethyl-benzene, and xylenes (BTEX) are harmful to humans (ATSDR, 2004). Benzene is of special concern because it is causally associated with different types of cancer (IARC, 2012). Truck drivers delivering gasoline and workers dispensing fuel have among the highest exposures to fuel releases (IARC, 2012). However, people living near or working in retail at gas stations, and children in schools and on playgrounds can also be exposed, with distance to the gas stations significantly affecting exposure levels (Terres et al., 2010; Jo & Oh, 2001; Jo & Moon, 1999; Hajizadeh et al., 2018). A meta-analysis (Infante, 2017) of three case-control studies (Steffen et al., 2004; Brosselin et al., 2009; Harrison et al., 1999) suggests that childhood leukemia is associated with residential proximity to gas stations.

Sources of unburned fuel releases at gas stations include leaks from storage tanks, accidental spills from the nozzles of gas dispensers (Hilpert & Breysse, 2014; Adria-Mora & Hilpert, 2017; Morgester et al., 1992), fugitive vapor emissions through leaky pipes and fittings, vehicle tank vapor releases when refueling, and leaky hoses, all of which can contribute to subsurface and air pollution (Hilpert et al., 2015). Routine fuel releases also occur through vent pipes of fuel storage tanks but are less noticeable because the pipes are typically tall, e.g., 4 m. These vent pipes are put in place to equilibrate pressures in the tanks and can be located as close as a few meters from residential buildings in dense urban settings (Fig. 1).

Fig. 1.
The three vent pipes (enclosed by the red ellipse) on the right side of the convenience store of a gas station are <10 m away from the residential building.

Unburned fuel can be released from storage tanks into the environment through “working” and “breathing” losses (Yerushalmi & Rastan, 2014). A working loss occurs when liquid is pumped into or out of a tank. For a storage tank, this can happen when it is refilled from a tanker truck or when fuel is dispensed to refuel vehicles (Statistics Canada, 2009) if the pressure in the storage tank exceeds the relief pressure of the pressure/vacuum (P/V) valve (EPA, 2008). P/V valve threshold pressures are typically set to around +3 and −8 in. of water column (iwc) (7.5 and −20 hPa). However, P/V valves are not always used, particularly in cold climates, as valves may fail under cold weather conditions (Statistics Canada, 2009).

Breathing losses occur when no liquid is pumped into or out of a tank because of vapor expansion and contraction due to temperature and barometric pressure changes or because pressure in the storage tank may increase when fuel in the tank evaporates (Yerushalmi & Rastan, 2014; EPA, 2008). Although delayed or redirected by the P/V valve, breathing emissions can be significant and represent an environmental and health concern (Yerushalmi & Rastan, 2014).

Stage I vapor recovery systems, put in place to prevent working losses while delivering fuel to a station, collect the vapors displaced while loading a storage tank, redirecting them into the delivery truck. Stage II vapor recovery systems minimize working losses while delivering gas from the storage tank to the customer's car. During Stage II vapor recovery, gasoline vapors can be released through the vent pipe, if the sum of the flow rates of the returned volume and of the fuel evaporating within the storage tank is greater than the volume of liquid gasoline dispensed (Statistics Canada, 2009). We refer to this scenario as pressure while dispensing (PWD). In theory, a properly designed Stage II vapor recovery system should not have working losses, although in practice this is not typically the case (McEntire, 2000).

Regulations on setback distances for gas stations are based on lifetime cancer risk estimates. Several studies have assessed benzene cancer risk near gas stations (Atabi & Mirzahosseini, 2013; Correa et al., 2012; Cruz et al., 2007; Edokpolo et al., 2015; Edokpolo et al., 2014; Karakitsios et al., 2007). Based on cancer risk estimations, the California Air Resources Board (CARB) recommended that schools, day cares, and other sensitive land uses should not be located within 300 ft. (91 m) of a large gas station (defined as a facility with an annual sales volume of 3.6 million gal = 13.6 million L or greater) (CalEPA/CARB, 2005). This CARB recommendation has not been adopted by all US states, and within states setback distances can depend on local government. Notably, CARB regulations do not account for short term exposure limits and health effects. An important limitation of existing regulations is the use of average gasoline emission rates estimated in the 90s that do not consider excursions (CAPCOA, 1997).

2.1. Sites
Data for this study were obtained from vent release measurements conducted at two gas stations as part of technical assistance to the gas stations to quantify fuel vapor losses through the vent pipes of their storage tanks. A motivation for conducting the measurements was to perform a cost-benefit analysis to compare the economic losses due to the lost fuel versus the cost of technologies that reduce the emissions. The exact location of the two gas stations is not revealed for confidentiality reasons. The gas station managers and staff who authorized the collection and analysis of these data have not been involved in the current manuscript.

The first gas station, “GS-MW,” was located in the US Midwest and is a 24-hour operation. The study was conducted from December 2014 to January 2015 for 20 full days, and fuel sales V̇sales were about 450,000 gal (1.7 million L) per month. Fuel deliveries to the gas station usually took place during the nighttime. The second gas station, “GS-NW,” was located on the US Northwest coast and closed at night. Hours of operation were between 6:00 am and 9:30 pm on weekdays and between 7 am and 7 pm on weekends. That study was conducted in October 2009 for 18 full days, and fuel sales were V̇sales ~700,000 gal (2.6 million L) per month.

Both gas stations are considered to be high-volume, because they dispense >3.6 million gal of gasoline (both regular and premium) per year (CalEPA/CARB, 2005), and fuel was stored in underground storage tanks (USTs), which is typical in the US. Both gas stations had Stage II vapor recovery installed using the vacuum-assist method. In that method, gasoline vapors, which would be ejected into the atmosphere as a working loss during refueling of customer vehicle tanks, are collected at the vehicle/nozzle interface by a vacuum pump. The recovered vapors are then directed via a coaxial hose back into the combined storage tank ullage (head space) of the gas station. Stage I vapor recovery was also used at both gas stations during fuel deliveries. Both sites had a 3-inch diameter (7.5 cm) single above-grade vent pipe with below-grade manifold that connected the vent lines from several USTs; the cracking pressures of the P/V valves were set to +3 and −8 iwc (+7.5 and −20 hPa).
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
"Tact is the ability to tell someone to go to Hell in a way that they will begin looking forward to the trip"

glop6868
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Re: Delivering fuel and Tank Over Presurization

Post by glop6868 » Tue Mar 17, 2020 10:48 am

As always, I really enjoy the insight of Zmiller. always informative and his writing is easy to understand. I often dream of someday having the honor to meet such a truly magnificent individual that Zmiller must be!

I've heard through the grapevine that there is this company in Arizona that has designed a state of the art tank pressure monitoring system that alerts the driver by way of an audible/visual alarm (horn and light) when an over-pressurization event occurs. The device even logs the events so that the site owner can track them! This device is also rumored to have wireless communication to a satellite unit that can be placed inside the store! OMG! Could this miracle device really exist?

I was wondering if Zmiller has heard of such a wonderful device? And, if he knows who manufactures it?

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