February 13, 2024 • 16 mins
Join us in unraveling the mysteries of overfill prevention valves as bulk fuel storage expert Shannon Oelkers addresses a listener request. We learn how to recognize and locate an overfill prevention valve on a tank before diving into how they operate and why they are essential. Our conversation covers the valve's role in SPCC regulation and how those can vary between different states, followed by Shannon's expertise shedding light on maintenance and how to avoid common mistakes when working with these powerful yet delicate machines. Tune in to get answers to your lingering questions regarding overfill prevention valves!
Additional Resources:
Morrison Bros Co. Overfill Prevention Valve Installation Videos
Part I
Part II
40 CFR Appendix H
This podcast is for informational purposes only and should not be considered legal or regulatory advice. We are not responsible for any losses, damages, or liabilities that may occur from using this podcast. This podcast is not intended to replace professional regulatory or legal advice, and the views expressed in this podcast may not be those of the host, which would be me or Integrity Environmental. Thank you very much for listening. We would be happy to provide professional regulatory advice as part of our consulting services if you need professional regulatory advice.
intro/outro created with GarageBand
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Amanda (00:00):
Welcome back to Tank Talk.
We are in season two.
I'm excited to kick off ourseason with a listener request
covering something that I don'treally know much about Shannon.
Shannon (00:11):
Ooh, what is it?
Tell me more.
Amanda (00:15):
We got a listener request to go over overfill
prevention valves.
Shannon (00:20):
Oh, that is a good one.
Amanda (00:22):
Yeah, so what are they and where are they?
On a tank.
Shannon (00:27):
Ooh, it's a mystery.
Overfill prevention valves areusually along the top line of
the horizontal tank and they areon top of a vertical tank.
Technically they're anautomatic flow restrictor or
flow shutoff mechanism.
There can be different ways toachieve this, but most overfill
(00:48):
prevention valves are an inlineflow that turns a valve
component when it's floated.
That effectively shuts off theflow into the tank as the float
rises.
So if you fill a tank up past acertain preset height, the
float rises to, shuts off thevalve and it stops fuel from
going into the tank andoverfilling.
They're a little bit of amystery though, because they can
(01:09):
be very difficult to spot on atank.
They're mostly inside of thetank because there's a float
component and they're in linewith your fill piping, and so
most of what you can see is ahexagonal nut at the bottom of
your fill pipe as it right as itgoes into the tank, and not all
of the overfill preventionvalves have that hexagonal nut.
(01:30):
Many of them do, but not all.
So it's a little tricky, butgenerally if you're looking at
the top of the tank and you seea big old hexagonal nut in your
fill line, it's mostly safe toassume that there's an overfill
prevention valve installed.
The best way is to look at theconstruction documents of the
tank and verify that that waspart of the original tank design
(01:50):
and that it was installed asdirected.
Amanda (01:55):
So why are those important?
Shannon (01:57):
Well, there are two big reasons why they're important.
The first one is reallyimportant.
They prevent overfills, yay.
They save the environment.
They stop fuel from coming outthe top of your tank.
If people are human and makehuman errors, so that's the most
important one.
But they also meet regulatoryrequirements.
They are required by certainregulatory components to be in
(02:20):
place, specifically the spillprevention control encounter
measures, plan SPCC, our oldfriend 40 CFR 112.
If you have a double walledtank outside of containment,
they have to have an overfillprevention device on the tank to
be exempt from having secondarycontainment.
And we can talk about that morelater.
(02:41):
But those are the two bigreasons that people will have an
overfill prevention valve on atank to prevent the overfills
and to meet regulatoryrequirements.
Amanda (02:51):
So how do these overfill prevention valves work?
Shannon (02:54):
Well, I covered a little bit of it earlier.
But specifically, overfillprevention valves are passive
systems in that once they'reinstalled they will work without
manual activation.
You don't have to push a button, you don't have to remember to
turn it on If you make an error,if you dip the tank incorrectly
, if you're trying to fit toomuch fuel into a tank.
If you've installed thatoverfill prevention valve
(03:15):
correctly, it will stop the flowof fuel if the fuel level in
the tank rises above a certainpoint.
And that's sort of the basicsof it.
It's not complicated, it's amechanical system.
There are electrically basedones that sense fuel levels and
shut off solenoid valves, butthe vast majority of overfill
prevention valves that we workwith are simple mechanical
(03:37):
systems with floats.
Amanda (03:38):
You mentioned regulatory requirements previously.
What are those?
Shannon (03:44):
Sure, well, for most of our clients it's going to be
the SPCC, like I mentionedpreviously, and that's tied
directly to secondarycontainment requirements of four
tanks of a certain size,although I do want to do a shout
out.
Some states have their ownoverfill prevention requirements
.
Some states like Californiarequire them in addition to the
(04:05):
SPCC and sometimes they requirethem outside of the SPCC as well
.
California is a special placein the regulatory world but
basically in the SPCC it saysall bulk fuel containers of a
certain size have to havesecondary containment to hold
the volume of the contentsinside of it.
(04:25):
Fair enough, right?
Well, if you have a large tankand it's double walled, way back
in like 1993, when they weredeciding all of these SPCC rules
, somebody set forth that hey,double walled tanks are their
own containment.
It's a second wall all the wayaround the tank and if the main
(04:47):
tank was to leak it would beheld by this impermeable
containment, the second wall ofthe tank.
Therefore it's secondarycontainment.
The EPA agreed, but with somecaveats.
So there's this document calledAppendix H and I will attach it
to the show notes, and it'sreferenced in the guidance and
the EPA regional guidance whichwe've attached many, many times
(05:09):
to many other episodes.
But basically it says that theEPA has determined that a tank
can be exempt from secondarycontainment requirements if
double walled, and it has thefollowing three things.
One of those is an overfillalarm, so something that
notifies a person in control ofthe transfer that the tank
(05:34):
liquid level is above a presetamount.
An automatic flow restrictor orflow shutoff, also known as an
overfill prevention valve one ofthe three.
And then all product transfersare constantly monitored.
If you have those three things,you can have a double walled
tank outside of secondarycontainment.
So that's mostly where we seethe regulatory requirement for
(05:57):
overfill prevention valves isthat they're meeting that
regulatory requirement for thatautomatic flow restriction or
flow shutoff.
There's a couple other thingsthat go with this.
We could maybe talk about thatlater, but like product
transfers, they can be monitoredby a person.
They can also be monitored by atank management system as long
as there is somebody where, ifthe alarm goes off, they are
(06:19):
able to stop or shut down thetransfer if needed.
That's the basics of it.
There may be other things thatcertain states require and you'd
have to go straight to thestate regulations for that.
In Alaska there are certainoverfill prevention requirements
in the 1880 AC 75, but they arespecific to the vertical tanks
(06:45):
and they are more set up.
They're not set up in the sameway that these horizontal tanks
are, and so there's lots ofoptions for overfill prevention.
It's not as cut and dried ashave an alarm, have a shutoff
valve and have a means ofmonitoring the transfer.
There's an infinite variety onthe vertical tanks.
(07:05):
So, for our purposes, for thisdiscussion here generally, when
people are talking about anoverfill prevention valve,
they're talking about anoverfill prevention valve on a
horizontal tank that's doublewalled and they want to have it
outside of secondary containment, and that's one of the things
that they have to maintain andhave in place to have it remain
outside of secondary containment.
Amanda (07:26):
All right, so we definitely want to keep these
maintained.
Would you be able to describeor recommend maintenance
procedures?
Hmm?
Shannon (07:35):
Well, a lot of the maintenance on an overfill
prevention valve rests oninstalling it properly.
They're little workhorses,they're very simple in design.
They work really well.
They work for a long time.
A couple of things that we seepretty frequently is if and they
actually warn you about this inall of the installation
documents that too much threadsealant.
(07:55):
If you use too much threadsealant it'll be forced inside
that valve system and it canreally gunk up the works.
There's also a lot of care thatneeds to be taken when
inserting the overfill valvebecause the float and linkage
arms there's two little arms onthe side that connect the float
to the valve turning mechanism.
If those arms get damaged fromthe float twisting it'll freeze
(08:18):
up and the float won't liftappropriately and get hung up on
the arms.
And then, lastly, we definitelysee that all the connections
can be over tightened and thatcan cause leaks within the
system.
So when you've been in fuels along time, you'll a lot of
people think of leaks asexternal, right Like you have a
leak and fuel is coming out ofthe flange or the valve or the
(08:39):
pipe and it's spilling onto theground.
But there's internal leaks too,where you've got fuel going
through the overfill preventionvalve and if it's been tightened
too much, even if it'sactivated, it'll be leaky and
it'll still be going into thetank and filling it up more,
even though the valve is fullyengaged.
So you want to make sure thatyou don't over tighten the
connectors.
(08:59):
And again, the installationinstructions are full of
warnings like only tighten threefull turns clockwise to ensure
that that doesn't happen.
And then my last thought onmaintenance is that although
overfill prevention valves arelow maintenance, that does not
mean no maintenance.
Ever I have seen 30 and 40 yearold overfill prevention valves
and they are in rough shape.
(09:20):
We recommend that every timeyou're emptying the tank to
clean it, repair it or inspectit, that the overfill prevention
valve be removed and inspectedat the same time.
We've seen a lot of linkagearms that are stiff, seized,
full of some kind of gunk fromwhatever product was in the tank
or maybe greasing of fittings,stuff like that.
Basically, the float becomesvery difficult to operate and
(09:41):
then it's not lifting like itshould and so it's not actually
rising anymore and so there isno shut off capability in that
system anymore.
But it can be hard to inspectthese valves because they're all
internal to the tank.
So that's why we say if you'retaking the tank down to clean it
, go ahead and get up, you know,take the top apart, expect all
your pieces, replace all yourgaskets and then also inspect
(10:01):
this overfill prevention valve,make sure the entire assembly is
operating smoothly and is freeto rise and fall with the level
of the fuel.
Amanda (10:09):
So how do we know when an overfill prevention valve is
working correctly?
How do we test it?
Take us through that process.
Shannon (10:17):
Well, that's an interesting question because
inspectors like to ask thisquestion a lot from state and
federal agencies.
How do you know it's working?
Generally, if fuel continues toflow into your tank, it is
working.
However, we know from what Ijust said and from what I've
observed that the float canbecome frozen in the down
position and not work at all.
(10:38):
And so we hear a lot in thefield that they fill the tank up
to that preset max height andthen it'll shut everything off
and that'll tell you that it'sstill working.
And technically, yes, that is away to determine if the valve
is working.
But I have thoughts on this.
So hold on.
When you test a system likethat in that manner, you're
(11:01):
creating a pressurized segmentof your fill line and when you
disconnect it can spill productwith back spray from that
pressure that you've nowintroduced into the system.
If you're truly filling thetank to the max fill height or
just a little bit beyond, thereisn't a lot of room for that
fill line to drain back into thetank, right, the tank level
itself is gonna keep thepressure up.
(11:22):
Truck drivers call that takinga bath, because they disconnect
after that valve goes and thevalve engages and then the whole
system's pressurized and thenthey go to unhook their hose
after stopping the transfer andit sprays all over them.
My thoughts are that this shouldnot be your main way to test an
overfill alarm.
It's risky.
(11:43):
There are other ways to ensureyou can test it.
You can utilize nearbyappurtenances, like a lot of
them have, empty appurtenanceswith threaded caps.
You can remove the cap.
You can reach a stick-in or atool-in to make sure that it's
still floating freely or movingup and down freely when the tank
is lower in volume.
You can also just remove thevalve assembly at tank cleanings
(12:03):
, like we mentioned.
I think a perfectly legitimateanswer to a regulatory agency
would be we pull it apart,verify it functions and maintain
it at every 10 or 20-yearinterval that we have it
inspected.
That's a valid way of testingand verifying that it's still
working.
So, lastly, these valves workreally well for a really long
(12:24):
time, but nothing lasts foreverand it's wise to have a plan for
making sure it's working, andthe reason is that if this fails
, you will have an overfill.
Humans are human and eventuallythey make a mistake in how much
foliage the tank has, how muchspace is in the tank for filling
it up, or they tell somebody toput 500 gallons in but it gets
(12:45):
written down as 5,000, whateverMistakes get made, because
people are people and so thesepassive systems need to be
maintained and in place andeveryone who operates that tank
needs to understand how theywork so that they can be part of
that maintenance and ongoingunderstanding of what's going on
.
Amanda (13:03):
All right.
So where can we learn moreabout Overfill Prevention Vows?
Shannon (13:08):
There's a couple places , morrison Brothers Company, who
makes a lot of OverfillPrevention Vows.
They're not the only one, butthey do make quite a few.
They have a really great videoseries of their website and I've
linked them both.
There's two parts.
Part one is a lot aboutinstallation, but there's a
whole section there about how toinstall it carefully to avoid
damaging the mechanism from thevery beginning.
(13:29):
And then part two talks a lotabout sort of documenting and
understanding that flow and howit works once it's in place.
So you should definitely watchboth parts.
There's good stuff in there forboth.
And then I also will include alink to 40 CFRs, appendix H and
that sort of explains why doublewalled tanks need those three
things to be exempt fromsecondary containment areas.
(13:51):
It's a little funky becauseit's not part of the main body
of the SPCC regulations, but westill have to consider it and it
still has to be adhered to ifyou are operating a double
walled tank outside of secondarycontainment and you are subject
to the SPCC rules.
So those are the three.
Find out more resources that Ihave for you.
Amanda (14:11):
All right, that sounds great.
Shannon, thank you so much forwalking us through Overfill,
prevention, vows and, for myfavorite part, what are some
stories you might have from thefield about these little
contraptions?
Have you ever witnessed abackspreading?
Shannon (14:26):
I have not witnessed one, but I've definitely
interviewed people who have been, who have taken baths, about
why they were taking a bath andtrying to problem solve which
part of the system was creatingthe pressure, and in one
investigation it was absolutelythe Overfill Prevention Valve
was malfunctioning and it wascausing.
It was engaging during thetransfer and then it would fall
(14:48):
back and then reengage, and sothere was a lot of start and
stop pressurization and so itwas difficult to understand what
was going on.
We also had one on a tank thatwas 23 years old and we took it
out and it was so stiff thateven the biggest burliest guy in
the shop could not get it toengage.
But they cleaned the linkagearms off and had a whole bunch
of either grease or emulsifiedgunk from being in the tank for
(15:10):
23 years.
And they cleaned those littlelinkage arms off and they're
stainless steel and once theygot them going it was actually
right back to full function.
It was pretty amazing, I meanthe 23 year old Overfill
Prevention Valve and it wasworking great.
So that was interesting to mejust to see.
I mean we were kind of liketreating it like an arm
wrestling match, right, like whocan get this to go.
(15:31):
Nobody was strong enough, butonce it went back in the tank,
it was probably fine for another10 years, I mean as long as
everything's working and itlooks like it's in good order
and it's moving freely andflowing.
But what I learned from that,though, is that I don't know how
long that float had been frozenup right, and 23 years was too
(15:51):
long.
There is no way that fuel wasfloating that float if I
couldn't even get the biggest,burliest guy to move it with his
, you know, trying to force it.
So that's where we come in withthe hey.
If you're going to get thistank cleaned and updated and
inspected at the tenure mark,then go in and make sure that
it's clean there, because I havea feeling it was still
(16:12):
operating at 10 years, but itjust was no longer by year 23.
Amanda (16:17):
All right, well, thank you so much for your time,
Shannon, or truly appreciate yousharing your expertise.
Shannon (16:22):
Yeah, I love talking about all these pieces of the
tanks.
This is one that it's a littleharder because it doesn't stick
out of the tank, so it's alwaysa little mysterious and I think
people struggle to identify themand know more about them,
although people who have themthey definitely know that they
have them because they havepassed that preset fill level on
the tank at least once.
Amanda (16:44):
And they know All right Well, until next time.
Shannon (16:48):
Yep Bye.
Welcome back to Tank Talk.
We are in season two.
I'm excited to kick off ourseason with a listener request
covering something that I don'treally know much about Shannon.
Shannon (00:11):
Ooh, what is it?
Tell me more.
Amanda (00:15):
We got a listener request to go over overfill
prevention valves.
Shannon (00:20):
Oh, that is a good one.
Amanda (00:22):
Yeah, so what are they and where are they?
On a tank.
Shannon (00:27):
Ooh, it's a mystery.
Overfill prevention valves areusually along the top line of
the horizontal tank and they areon top of a vertical tank.
Technically they're anautomatic flow restrictor or
flow shutoff mechanism.
There can be different ways toachieve this, but most overfill
(00:48):
prevention valves are an inlineflow that turns a valve
component when it's floated.
That effectively shuts off theflow into the tank as the float
rises.
So if you fill a tank up past acertain preset height, the
float rises to, shuts off thevalve and it stops fuel from
going into the tank andoverfilling.
They're a little bit of amystery though, because they can
(01:09):
be very difficult to spot on atank.
They're mostly inside of thetank because there's a float
component and they're in linewith your fill piping, and so
most of what you can see is ahexagonal nut at the bottom of
your fill pipe as it right as itgoes into the tank, and not all
of the overfill preventionvalves have that hexagonal nut.
(01:30):
Many of them do, but not all.
So it's a little tricky, butgenerally if you're looking at
the top of the tank and you seea big old hexagonal nut in your
fill line, it's mostly safe toassume that there's an overfill
prevention valve installed.
The best way is to look at theconstruction documents of the
tank and verify that that waspart of the original tank design
(01:50):
and that it was installed asdirected.
Amanda (01:55):
So why are those important?
Shannon (01:57):
Well, there are two big reasons why they're important.
The first one is reallyimportant.
They prevent overfills, yay.
They save the environment.
They stop fuel from coming outthe top of your tank.
If people are human and makehuman errors, so that's the most
important one.
But they also meet regulatoryrequirements.
They are required by certainregulatory components to be in
(02:20):
place, specifically the spillprevention control encounter
measures, plan SPCC, our oldfriend 40 CFR 112.
If you have a double walledtank outside of containment,
they have to have an overfillprevention device on the tank to
be exempt from having secondarycontainment.
And we can talk about that morelater.
(02:41):
But those are the two bigreasons that people will have an
overfill prevention valve on atank to prevent the overfills
and to meet regulatoryrequirements.
Amanda (02:51):
So how do these overfill prevention valves work?
Shannon (02:54):
Well, I covered a little bit of it earlier.
But specifically, overfillprevention valves are passive
systems in that once they'reinstalled they will work without
manual activation.
You don't have to push a button, you don't have to remember to
turn it on If you make an error,if you dip the tank incorrectly
, if you're trying to fit toomuch fuel into a tank.
If you've installed thatoverfill prevention valve
(03:15):
correctly, it will stop the flowof fuel if the fuel level in
the tank rises above a certainpoint.
And that's sort of the basicsof it.
It's not complicated, it's amechanical system.
There are electrically basedones that sense fuel levels and
shut off solenoid valves, butthe vast majority of overfill
prevention valves that we workwith are simple mechanical
(03:37):
systems with floats.
Amanda (03:38):
You mentioned regulatory requirements previously.
What are those?
Shannon (03:44):
Sure, well, for most of our clients it's going to be
the SPCC, like I mentionedpreviously, and that's tied
directly to secondarycontainment requirements of four
tanks of a certain size,although I do want to do a shout
out.
Some states have their ownoverfill prevention requirements
.
Some states like Californiarequire them in addition to the
(04:05):
SPCC and sometimes they requirethem outside of the SPCC as well
.
California is a special placein the regulatory world but
basically in the SPCC it saysall bulk fuel containers of a
certain size have to havesecondary containment to hold
the volume of the contentsinside of it.
(04:25):
Fair enough, right?
Well, if you have a large tankand it's double walled, way back
in like 1993, when they weredeciding all of these SPCC rules
, somebody set forth that hey,double walled tanks are their
own containment.
It's a second wall all the wayaround the tank and if the main
(04:47):
tank was to leak it would beheld by this impermeable
containment, the second wall ofthe tank.
Therefore it's secondarycontainment.
The EPA agreed, but with somecaveats.
So there's this document calledAppendix H and I will attach it
to the show notes, and it'sreferenced in the guidance and
the EPA regional guidance whichwe've attached many, many times
(05:09):
to many other episodes.
But basically it says that theEPA has determined that a tank
can be exempt from secondarycontainment requirements if
double walled, and it has thefollowing three things.
One of those is an overfillalarm, so something that
notifies a person in control ofthe transfer that the tank
(05:34):
liquid level is above a presetamount.
An automatic flow restrictor orflow shutoff, also known as an
overfill prevention valve one ofthe three.
And then all product transfersare constantly monitored.
If you have those three things,you can have a double walled
tank outside of secondarycontainment.
So that's mostly where we seethe regulatory requirement for
(05:57):
overfill prevention valves isthat they're meeting that
regulatory requirement for thatautomatic flow restriction or
flow shutoff.
There's a couple other thingsthat go with this.
We could maybe talk about thatlater, but like product
transfers, they can be monitoredby a person.
They can also be monitored by atank management system as long
as there is somebody where, ifthe alarm goes off, they are
(06:19):
able to stop or shut down thetransfer if needed.
That's the basics of it.
There may be other things thatcertain states require and you'd
have to go straight to thestate regulations for that.
In Alaska there are certainoverfill prevention requirements
in the 1880 AC 75, but they arespecific to the vertical tanks
(06:45):
and they are more set up.
They're not set up in the sameway that these horizontal tanks
are, and so there's lots ofoptions for overfill prevention.
It's not as cut and dried ashave an alarm, have a shutoff
valve and have a means ofmonitoring the transfer.
There's an infinite variety onthe vertical tanks.
(07:05):
So, for our purposes, for thisdiscussion here generally, when
people are talking about anoverfill prevention valve,
they're talking about anoverfill prevention valve on a
horizontal tank that's doublewalled and they want to have it
outside of secondary containment, and that's one of the things
that they have to maintain andhave in place to have it remain
outside of secondary containment.
Amanda (07:26):
All right, so we definitely want to keep these
maintained.
Would you be able to describeor recommend maintenance
procedures?
Hmm?
Shannon (07:35):
Well, a lot of the maintenance on an overfill
prevention valve rests oninstalling it properly.
They're little workhorses,they're very simple in design.
They work really well.
They work for a long time.
A couple of things that we seepretty frequently is if and they
actually warn you about this inall of the installation
documents that too much threadsealant.
(07:55):
If you use too much threadsealant it'll be forced inside
that valve system and it canreally gunk up the works.
There's also a lot of care thatneeds to be taken when
inserting the overfill valvebecause the float and linkage
arms there's two little arms onthe side that connect the float
to the valve turning mechanism.
If those arms get damaged fromthe float twisting it'll freeze
(08:18):
up and the float won't liftappropriately and get hung up on
the arms.
And then, lastly, we definitelysee that all the connections
can be over tightened and thatcan cause leaks within the
system.
So when you've been in fuels along time, you'll a lot of
people think of leaks asexternal, right Like you have a
leak and fuel is coming out ofthe flange or the valve or the
(08:39):
pipe and it's spilling onto theground.
But there's internal leaks too,where you've got fuel going
through the overfill preventionvalve and if it's been tightened
too much, even if it'sactivated, it'll be leaky and
it'll still be going into thetank and filling it up more,
even though the valve is fullyengaged.
So you want to make sure thatyou don't over tighten the
connectors.
(08:59):
And again, the installationinstructions are full of
warnings like only tighten threefull turns clockwise to ensure
that that doesn't happen.
And then my last thought onmaintenance is that although
overfill prevention valves arelow maintenance, that does not
mean no maintenance.
Ever I have seen 30 and 40 yearold overfill prevention valves
and they are in rough shape.
(09:20):
We recommend that every timeyou're emptying the tank to
clean it, repair it or inspectit, that the overfill prevention
valve be removed and inspectedat the same time.
We've seen a lot of linkagearms that are stiff, seized,
full of some kind of gunk fromwhatever product was in the tank
or maybe greasing of fittings,stuff like that.
Basically, the float becomesvery difficult to operate and
(09:41):
then it's not lifting like itshould and so it's not actually
rising anymore and so there isno shut off capability in that
system anymore.
But it can be hard to inspectthese valves because they're all
internal to the tank.
So that's why we say if you'retaking the tank down to clean it
, go ahead and get up, you know,take the top apart, expect all
your pieces, replace all yourgaskets and then also inspect
(10:01):
this overfill prevention valve,make sure the entire assembly is
operating smoothly and is freeto rise and fall with the level
of the fuel.
Amanda (10:09):
So how do we know when an overfill prevention valve is
working correctly?
How do we test it?
Take us through that process.
Shannon (10:17):
Well, that's an interesting question because
inspectors like to ask thisquestion a lot from state and
federal agencies.
How do you know it's working?
Generally, if fuel continues toflow into your tank, it is
working.
However, we know from what Ijust said and from what I've
observed that the float canbecome frozen in the down
position and not work at all.
(10:38):
And so we hear a lot in thefield that they fill the tank up
to that preset max height andthen it'll shut everything off
and that'll tell you that it'sstill working.
And technically, yes, that is away to determine if the valve
is working.
But I have thoughts on this.
So hold on.
When you test a system likethat in that manner, you're
(11:01):
creating a pressurized segmentof your fill line and when you
disconnect it can spill productwith back spray from that
pressure that you've nowintroduced into the system.
If you're truly filling thetank to the max fill height or
just a little bit beyond, thereisn't a lot of room for that
fill line to drain back into thetank, right, the tank level
itself is gonna keep thepressure up.
(11:22):
Truck drivers call that takinga bath, because they disconnect
after that valve goes and thevalve engages and then the whole
system's pressurized and thenthey go to unhook their hose
after stopping the transfer andit sprays all over them.
My thoughts are that this shouldnot be your main way to test an
overfill alarm.
It's risky.
(11:43):
There are other ways to ensureyou can test it.
You can utilize nearbyappurtenances, like a lot of
them have, empty appurtenanceswith threaded caps.
You can remove the cap.
You can reach a stick-in or atool-in to make sure that it's
still floating freely or movingup and down freely when the tank
is lower in volume.
You can also just remove thevalve assembly at tank cleanings
(12:03):
, like we mentioned.
I think a perfectly legitimateanswer to a regulatory agency
would be we pull it apart,verify it functions and maintain
it at every 10 or 20-yearinterval that we have it
inspected.
That's a valid way of testingand verifying that it's still
working.
So, lastly, these valves workreally well for a really long
(12:24):
time, but nothing lasts foreverand it's wise to have a plan for
making sure it's working, andthe reason is that if this fails
, you will have an overfill.
Humans are human and eventuallythey make a mistake in how much
foliage the tank has, how muchspace is in the tank for filling
it up, or they tell somebody toput 500 gallons in but it gets
(12:45):
written down as 5,000, whateverMistakes get made, because
people are people and so thesepassive systems need to be
maintained and in place andeveryone who operates that tank
needs to understand how theywork so that they can be part of
that maintenance and ongoingunderstanding of what's going on
.
Amanda (13:03):
All right.
So where can we learn moreabout Overfill Prevention Vows?
Shannon (13:08):
There's a couple places , morrison Brothers Company, who
makes a lot of OverfillPrevention Vows.
They're not the only one, butthey do make quite a few.
They have a really great videoseries of their website and I've
linked them both.
There's two parts.
Part one is a lot aboutinstallation, but there's a
whole section there about how toinstall it carefully to avoid
damaging the mechanism from thevery beginning.
(13:29):
And then part two talks a lotabout sort of documenting and
understanding that flow and howit works once it's in place.
So you should definitely watchboth parts.
There's good stuff in there forboth.
And then I also will include alink to 40 CFRs, appendix H and
that sort of explains why doublewalled tanks need those three
things to be exempt fromsecondary containment areas.
(13:51):
It's a little funky becauseit's not part of the main body
of the SPCC regulations, but westill have to consider it and it
still has to be adhered to ifyou are operating a double
walled tank outside of secondarycontainment and you are subject
to the SPCC rules.
So those are the three.
Find out more resources that Ihave for you.
Amanda (14:11):
All right, that sounds great.
Shannon, thank you so much forwalking us through Overfill,
prevention, vows and, for myfavorite part, what are some
stories you might have from thefield about these little
contraptions?
Have you ever witnessed abackspreading?
Shannon (14:26):
I have not witnessed one, but I've definitely
interviewed people who have been, who have taken baths, about
why they were taking a bath andtrying to problem solve which
part of the system was creatingthe pressure, and in one
investigation it was absolutelythe Overfill Prevention Valve
was malfunctioning and it wascausing.
It was engaging during thetransfer and then it would fall
(14:48):
back and then reengage, and sothere was a lot of start and
stop pressurization and so itwas difficult to understand what
was going on.
We also had one on a tank thatwas 23 years old and we took it
out and it was so stiff thateven the biggest burliest guy in
the shop could not get it toengage.
But they cleaned the linkagearms off and had a whole bunch
of either grease or emulsifiedgunk from being in the tank for
(15:10):
23 years.
And they cleaned those littlelinkage arms off and they're
stainless steel and once theygot them going it was actually
right back to full function.
It was pretty amazing, I meanthe 23 year old Overfill
Prevention Valve and it wasworking great.
So that was interesting to mejust to see.
I mean we were kind of liketreating it like an arm
wrestling match, right, like whocan get this to go.
(15:31):
Nobody was strong enough, butonce it went back in the tank,
it was probably fine for another10 years, I mean as long as
everything's working and itlooks like it's in good order
and it's moving freely andflowing.
But what I learned from that,though, is that I don't know how
long that float had been frozenup right, and 23 years was too
(15:51):
long.
There is no way that fuel wasfloating that float if I
couldn't even get the biggest,burliest guy to move it with his
, you know, trying to force it.
So that's where we come in withthe hey.
If you're going to get thistank cleaned and updated and
inspected at the tenure mark,then go in and make sure that
it's clean there, because I havea feeling it was still
(16:12):
operating at 10 years, but itjust was no longer by year 23.
Amanda (16:17):
All right, well, thank you so much for your time,
Shannon, or truly appreciate yousharing your expertise.
Shannon (16:22):
Yeah, I love talking about all these pieces of the
tanks.
This is one that it's a littleharder because it doesn't stick
out of the tank, so it's alwaysa little mysterious and I think
people struggle to identify themand know more about them,
although people who have themthey definitely know that they
have them because they havepassed that preset fill level on
the tank at least once.
Amanda (16:44):
And they know All right Well, until next time.
Shannon (16:48):
Yep Bye.
Popular Podcasts
Dateline NBC
Current and classic episodes, featuring compelling true-crime mysteries, powerful documentaries and in-depth investigations. Follow now to get the latest episodes of Dateline NBC completely free, or subscribe to Dateline Premium for ad-free listening and exclusive bonus content: DatelinePremium.com
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.
Intentionally Disturbing
Join me on this podcast as I navigate the murky waters of human behavior, current events, and personal anecdotes through in-depth interviews with incredible people—all served with a generous helping of sarcasm and satire. After years as a forensic and clinical psychologist, I offer a unique interview style and a low tolerance for bullshit, quickly steering conversations toward depth and darkness. I honor the seriousness while also appreciating wit. I’m your guide through the twisted labyrinth of the human psyche, armed with dark humor and biting wit.