fridger:
Thanks for the insight chaps/ladies, it’s the kind of thing that never crossed my mind before, gas that is, and how it all works. Even if it’s not specific to my job still interesting to read about your own experiences uktramp and caladonin.
Diesel dave I would love to say I recognise the UN number but I would just be nodding and smiling.
So if I’m beginning to understand, because a loaded trailer is pressurised, and your using a vapour recapture system, as product is moved from one tank to another the product is expanding in to a gas as your tipping, as well as vapour coming back in to the trailer via recapture system, all while stay above atmospheric pressure untill pretty much empty, save any remaining vapour.
So my original question about what is replacing the gas as you tip a load is redundant, because it’s nothing like tipping a regular liquid tank eg. Milk water or something not requiring vapour recapture.
Unless iv completely missed the point and should have tried harder in school…
Are you one of UKTs mates or a genuine wind up merchant ?
UKtramp:
… I would be interested to know what gas your dealing with and how it is transferred though.
Hi UKtramp,
I was dealing with:
UN 1978 PROPANE, 2.1
UN 2187 CARBON DIOXIDE, REFRIGERATED LIQUID, 2.2
Both of these (and the gas mentioned in the OP now we think we know what it is) are transferred between vessels by the vapour pressure balance method I described above, which is sometimes known as the ‘pendulum’ method.
Propane normally has a vapour pressure of about 120psi (8bar), whilst CO2 is normally at about 300psi (21bar)
The man at the top, original poster said that his new boss would put him through lots of training before getting his fingers burnt.
Uk tramp who carries bales, compressed GRASS or STRAW. talks of compressors
Compressor is an all-encompassing term for many things used in many industries
Wheel Nut:
The man at the top, original poster said that his new boss would put him through lots of training before getting his fingers burnt.
Uk tramp who carries bales, compressed GRASS or STRAW. talks of compressors
Compressor is an all-encompassing term for many things used in many industries
Not in gas transfer it isn’t, there are many industrial uses of compressors and that is different altogether, gas transfer compressors are of two types only and utilise two very different cycles. youtube.com/watch?v=f_8FjWZzzAI this is an example of vapour recovery
dieseldave:
UKtramp:
… I would be interested to know what gas your dealing with and how it is transferred though.
Hi UKtramp,
I was dealing with:
UN 1978 PROPANE, 2.1
UN 2187 CARBON DIOXIDE, REFRIGERATED LIQUID, 2.2
Both of these (and the gas mentioned in the OP now we think we know what it is) are transferred between vessels by the vapour pressure balance method I described above, which is sometimes known as the ‘pendulum’ method.
Propane normally has a vapour pressure of about 120psi (8bar), whilst CO2 is normally at about 300psi (21bar)
Thanks for the clarification Dave, C02 certainly has high pressures and is commonly used in supermarket refrigeration systems.
UKtramp:
The compressor doesn’t introduce air, it compresses the vapour and pumps it as a high pressure gas, no air involved. Its how refrigerant gasses are pumped, they are special compressors not ordinary types, they are sealed units, air in a refrigeration system would cause havoc with both moisture and high discharge pressures. However when we pump cyanide gas we always pump nitrogen through the system to purge all of this gas. Gas turns into liquid at pressure, for example if you keep ammonia under pressure it stays as a liquid, as soon as you get an air leak and it hits atmospheric pressure it comes out of solution and immediately gases. I transfer various gases on a daily basis and by keeping them pure is the only way to do the job properly. You do not cross contaminate or introduce air in any circumstances.
And a compressor is what? … a pump maybe?
m.a.n rules:
when i was on the petrol we called it vapour recovery or is this totally different?
hi dd is there a difference ?
caledoniandream:
And a compressor is what? … a pump maybe?
No a pump utilises an impeller to pump and doesn’t compress the gas, a compressor will compress the gas and discharge that gas in a different way, but having said that, your correct in thinking it is acting as a pump although does not work in the same way a pump does.
UKtramp:
dieseldave:
UKtramp:
… I would be interested to know what gas your dealing with and how it is transferred though.
Hi UKtramp,
I was dealing with:
UN 1978 PROPANE, 2.1
UN 2187 CARBON DIOXIDE, REFRIGERATED LIQUID, 2.2
Both of these (and the gas mentioned in the OP now we think we know what it is) are transferred between vessels by the vapour pressure balance method I described above, which is sometimes known as the ‘pendulum’ method.
Propane normally has a vapour pressure of about 120psi (8bar), whilst CO2 is normally at about 300psi (21bar)
Thanks for the clarification Dave, C02 certainly has high pressures and is commonly used in supermarket refrigeration systems.
Hi UKtramp,
CO2 is also used in other refrigeration/cooling, such as at Wylfa and Heysham power stations, which were two of my regular drops when I was doing that job.
It’s also used in the drinks industry as well to make pop/beer fizzy, Wrehxam Lager and a brewery at Burton-on-Trent (Ind Coop?) and the pop place at Kegworth are some other drops I did quite regularly.
IIRC, we carried that at about -55 deg C, whereas the propane (and the gas in the OP) is a liquid by compression alone at ambient temperatures.
dieseldave:
Hi UKtramp,
CO2 is also used in other refrigeration/cooling, such as at Wylfa and Heysham power stations, which were two of my regular drops when I was doing that job.
It’s also used in the drinks industry as well to make pop/beer fizzy, Wrehxam Lager and a brewery at Burton-on-Trent (Ind Coop?) and the pop place at Kegworth are some other drops I did quite regularly.
IIRC, we carried that at about -55 deg C, whereas the propane (and the gas in the OP) is a liquid by compression alone at ambient temperatures.
I wouldn’t fancy driving the stuff around, I don’t mind transferring gases and liquids but can imagine a bit hair raising to drive. I would be worried of the slightest of leaks or accidents. Hats off to tanker drivers.
UKtramp:
caledoniandream:
And a compressor is what? … a pump maybe?
No a pump utilises an impeller to pump and doesn’t compress the gas, a compressor will compress the gas and discharge that gas in a different way, but having said that, your correct in thinking it is acting as a pump although does not work in the same way a pump does.
Fluids flow from a higher to a lower pressure.
A pump works by creating a pressure differential. The pressure differential doesn`t have to be present in the whole of the vessel being discharged. It may only be within the body of the pump, but it is still there.
No compressor mechanism, no pressure difference.
No pressure difference, no flow.
There are conventions on using different words, compresser/pump, to describe the same basic bit of kit, according to whether you`re moving liquids; or moving gases, and whether those gases move from one one vessel to another of the same-ish pressure, or to one of a higher pressure.
Of course, I could be wrong, again. But I`m sure someone will politely point out the error of my ways. 
the maoster:
Keg worth was Carters Dave, they also had a place at Long Eadton. Just trying to aid your failing memory
Thanks maoster, I was thinking it was Cott, but I wasn’t sure.
Thinking on a bit… IIRC, I think Cott was where I used to load palletised shrink-wrapped pop when I did agency on nights for T&B.
I’m speaking of the late 90s here so I’ll own up to a failing memory.
UKtramp:
I wouldn’t fancy driving the stuff around, I don’t mind transferring gases and liquids but can imagine a bit hair raising to drive. I would be worried of the slightest of leaks or accidents. Hats off to tanker drivers.
It’s not as bad as you might think UKT, and htat’s due to the safety systems.
As a general rule, an ADR liquid tanker usually has to have three independent means of closing each opening that is below the level of the liquid.
1.) Internal valve (aka ‘footvalve.’)
2.) External valve
3.) Blanking cap
Add to that an ADR requirement for baffles (aka ‘surge plates’) which break up longitudinal surge to obey the rule in ADR that you’re not allowed to drive around with your own personal tsunami in the back, and you’ll see that they’ve got the safety features pretty well specified.
As already discussed, there’ll be plenty of on-the-job training when the OP gets properly to work.
dieseldave:
UKtramp:
I wouldn’t fancy driving the stuff around, I don’t mind transferring gases and liquids but can imagine a bit hair raising to drive. I would be worried of the slightest of leaks or accidents. Hats off to tanker drivers.
It’s not as bad as you might think UKT, and htat’s due to the safety systems.
As a general rule, an ADR liquid tanker usually has to have three independent means of closing each opening that is below the level of the liquid.
1.) Internal valve (aka ‘footvalve.’)
2.) External valve
3.) Blanking cap
Add to that an ADR requirement for baffles (aka ‘surge plates’) which break up longitudinal surge to obey the rule in ADR that you’re not allowed to drive around with your own personal tsunami in the back, and you’ll see that they’ve got the safety features pretty well specified.
As already discussed, there’ll be plenty of on-the-job training when the OP gets properly to work.
Is the ADR requirement for baffles a newer one Dave? Ive memories of 33 Inflammable Liquids in ISO tanks with no baffles. At least I think theyre true, not false, memories! Im thinking of the mid to late 90s. Could be confusion on my part as we did both Haz and non-Haz tanks. The baffles were good to stop surging, but a pig to clean when reloading with a different product.
UKtramp:
caledoniandream:
And a compressor is what? … a pump maybe?
No a pump utilises an impeller to pump and doesn’t compress the gas, a compressor will compress the gas and discharge that gas in a different way, but having said that, your correct in thinking it is acting as a pump although does not work in the same way a pump does.
There are so many different pump type, centrifugal, displacement, plunger, membrane, rotary lobe, screw, you name it, and you also have piston pumps.
A compressor is nothing else than a pump, an air pump if you like.
Even you bicycle pump is a pump (and a compressor)
If you ever off loaded a silo tanker with an air pump (HVLP) you know that their are air pumps, however most people will call them a compressor, many of these do Max 2 bar but 1000 cubic meters per hour,
caledoniandream:
There are so many different pump type, centrifugal, displacement, plunger, membrane, rotary lobe, screw, you name it, and you also have piston pumps.
A compressor is nothing else than a pump, an air pump if you like.
Even you bicycle pump is a pump (and a compressor)
If you ever off loaded a silo tanker with an air pump (HVLP) you know that their are air pumps, however most people will call them a compressor, many of these do Max 2 bar but 1000 cubic meters per hour,
Not arguing here btw in case you think I am trying to be clever or something, I am speaking as a refrigeration engineer and a trained licenced toxic gas handler. I refurbish & repair compressors as well as all of the pumps that you mention. You are correct in what your saying so don’t take it the wrong way, I am in no way a tanker driver or have any experience of tankers, I find this thread of interest and am only offering my take on what I know. The types of gas transfers that I undertake are the same as a tank in general principle and am keen to learn on how they are off loaded out of pure interest.
UKtramp:
caledoniandream:
There are so many different pump type, centrifugal, displacement, plunger, membrane, rotary lobe, screw, you name it, and you also have piston pumps.
A compressor is nothing else than a pump, an air pump if you like.
Even you bicycle pump is a pump (and a compressor)
If you ever off loaded a silo tanker with an air pump (HVLP) you know that their are air pumps, however most people will call them a compressor, many of these do Max 2 bar but 1000 cubic meters per hour,
Not arguing here btw in case you think I am trying to be clever or something, I am speaking as a refrigeration engineer and a trained licenced toxic gas handler. I refurbish & repair compressors as well as all of the pumps that you mention. You are correct in what your saying so don’t take it the wrong way, I am in no way a tanker driver or have any experience of tankers, I find this thread of interest and am only offering my take on what I know. The types of gas transfers that I undertake are the same as a tank in general principle and am keen to learn on how they are off loaded out of pure interest.
That’s a fair comment UKT, and very understandable to me.
For my part, I know nothing about the technical side of it because I was a tanker driver, not a technician.
A tanker driver needs specific training for both the vehicle AND the product to be carried.
I was not concerned or had any understanding of what anybody did with the ‘stuff’ once I’d put it in the correct receiving tank because the bit that I do understand is that those people are far cleverer than I on their subject.
Franglais:
dieseldave:
UKtramp:
I wouldn’t fancy driving the stuff around, I don’t mind transferring gases and liquids but can imagine a bit hair raising to drive. I would be worried of the slightest of leaks or accidents. Hats off to tanker drivers.
It’s not as bad as you might think UKT, and htat’s due to the safety systems.
As a general rule, an ADR liquid tanker usually has to have three independent means of closing each opening that is below the level of the liquid.
1.) Internal valve (aka ‘footvalve.’)
2.) External valve
3.) Blanking cap
Add to that an ADR requirement for baffles (aka ‘surge plates’) which break up longitudinal surge to obey the rule in ADR that you’re not allowed to drive around with your own personal tsunami in the back, and you’ll see that they’ve got the safety features pretty well specified.
As already discussed, there’ll be plenty of on-the-job training when the OP gets properly to work.
Is the ADR requirement for baffles a newer one Dave? Ive memories of 33 Inflammable Liquids in ISO tanks with no baffles. At least I think theyre true, not false, memories! Im thinking of the mid to late 90s. Could be confusion on my part as we did both Haz and non-Haz tanks. The baffles were good to stop surging, but a pig to clean when reloading with a different product.
Hi Franglais,
There was a bit of an earthquake that went through the UK road tanker game that came about in as from 10th May 2004.
From then, all new tank vehicles (tankers) had to have baffles, except in some circumstances.
There was also a rule that I call the 80/20 rule to do with the % fill that an unbaffled ‘old’ tank could carry.
ISO tanks have different rules, primarily for the difficulty in cleaning that you mentioned.