5 ms·

How a Gas Compressor Station Works

90 points by teleforce 2y ago

londons_explore 2y ago
theoretically, compressing gas is energyless. Ie. you get back exactly the same amount of energy when decompressing as you got when compressing, so you should be able to do it with no loss. Practically, that's fairly far from true for today's technology. Gas is so cheap that we're happy to waste a bunch of energy to make the plant cheaper.
- ce4 2y ago
  The compressor stations are alongside the gas pipeline network. These put in the energy needed to keep the gas flowing over long distances through the network. Without those it would be just like a very very long garden watering hose that has a trickle of flow compared to a short one.
  - londons_explore 2y ago
    I don't believe this to be the case. The differential pressure from one end of a gas pipeline to the other is not 1800 psi - it is more like 20 psi. You don't repeatedly recompress along the pipeline length - you compress once at the start, and decompress once at the end. The reason to use high pressures is because for a given pipe diameter (and therefore cost), you get far more gas transported at high pressures than you do at low pressures.
    - djaychela 2y ago
      It also means large storage tanks (known as gasometers in the UK) aren't needed. A couple of hundred meters of pipe at high pressure holds the same amount of gas as one of them.
      - squigg 2y ago
        As someone else who grew up seeing these across the UK, it was never clear to me why they disappeared - this explains it perfectly, thank you
    - formerly_proven 2y ago
      Most of the energy in pipelines is lost through friction inside the medium and friction between the medium and the inner wall. These are very much not reversible processes. Also the pressure differential is much bigger than you suggest. E.g. the pressure differential across NS1 was nominally around 110 bar (1600 psi) with an inlet pressure of 220 bar (3200 psi) and an outlet pressure of half that. > You don't repeatedly recompress along the pipeline length - you compress once at the start, and decompress once at the end. There are often recompression stations in pipelines precisely because pressure drops across the length, and on land it's cheaper to have those along the length of the pipeline than one really big one like NS1 had.
    - sveng 2y ago
      Interstate or longer intrastate pipelines require compressor stations every 75-100 miles. The parent article mentions this under "Compressors". As another comment states, friction is the main reason.
    - w1 2y ago
      >> You don't repeatedly recompress along the pipeline length Yes, you do. That is the primary purpose of transmission compressor stations. You may just lose a few psi per mile or something, but over the course of 100s of miles..
    - tantalor 2y ago
      Companies construct these stations along natural gas pipelines and use them to compress gas so it can continue flowing downstream to its final destination
    - tomas789 2y ago
      I don’t think that is the case. Surface roughness and directional changes are big losses. For example a single valve on a high pressure line can have a bigger pressure drop than 2 bars. So 160 km of a pipeline will drop a lot more.
- happyopossum 2y ago
  > theoretically, compressing gas is energyless. Ie. you get back exactly the same amount of energy when decompressing as you got when compressing That's only true in a word with incomplete physics. Friction and drag exist, there's no sense pretending a process is imperfect because of them.
- HPsquared 2y ago
  Expansion could only recover the "compression work done" if the pipeline between the two was perfectly insulated so no heat was lost.
DebtDeflation 2y ago
The reliability aspect of this self-contained system is quite impressive. Over the course of my life, I've personally experience many power outages, water outages, cell service outages, internet outages, etc. but never a natural gas outage.
- BasilPH 2y ago
  It's definitely impressive. However, natural gas outages do happen. For example Winter Storm Uri in Texas led to gas outages. Sadly, the outages and possible the loss of life connected to it could have been prevented if the gas companies hadn't fought back against stricter weatherization rules[^0]. > they made recommendations to the Railroad Commission to implement weatherization rules on the natural gas supply chain because there had been water coming up from the formations — it's called produced water, it's naturally occurring — and it was freezing at the top of the wellheads and restricting gas flow both at the wellheads and in pipelines. And yes, the Railroad Commission is not in charge of trains, but oil and gas in Texas. [^0]: https://www.volts.wtf/p/whats-the-deal-with-the-texas-railroad https://www.volts.wtf/p/whats-the-deal-with-the-texas-railro...
  - toomuchtodo 2y ago
    Also, a contributing factor to gas compressor station outages in Texas during Winter Storm Uri was ERCOT (Texas' electric grid operator) load shedding without knowing they were shedding gas compressor loads. This led to reduced gas supply available for generation. > When load is being shed involuntarily, customers designated as “critical load” can be exempted. Critical load is typically demand from entities, such as hospitals, for whom a power interruption could be extremely costly. To be deemed as critical, the customer must first file paperwork. The winter storm revealed that certain parts of the natural gas supply chain – such as natural gas compressor stations – were not designated as critical load. In consequence, their power was cut, thereby reducing flows of natural gas along the state’s pipeline network and contributing to partial and complete derates at multiple natural gas power generation units. The loss of their output in turn necessitated further load shedding, potentially creating an unstable feedback loop. This represented a single point of failure in the energy supply system. https://www.bakerinstitute.org/sites/default/files/2022-02/import/ces-ercot-wp-020222_cnO6uiA.pdf https://www.bakerinstitute.org/sites/default/files/2022-02/i... (pages 13-17) https://engineering.cmu.edu/news-events/news/2023/04/25-gas-electric-interdependence.html https://engineering.cmu.edu/news-events/news/2023/04/25-gas-... ("U.S. natural gas pipelines vulnerable to electric outages") https://www.sciencedirect.com/science/article/pii/S1040619023000180 https://www.sciencedirect.com/science/article/pii/S104061902... | https://doi.org/10.1016/j.tej.2023.107251 https://doi.org/10.1016/j.tej.2023.107251 ("How vulnerable are US natural gas pipelines to electric outages?")
morninglight 2y ago
I think most people would agree with you. Electrical power outages are somewhat common, but gas delivery seems very solid. Yet when selecting a home backup generator, most people opt for a gasoline powered generator and NOT one powered by natural gas.
- zrail 2y ago
  Gasoline generators are significantly cheaper. There are some tri-fuel generators that can run on gasoline, propane, or natural gas, but again they're more expensive. A natural gas powered permanent standby generator is amazing for peace of mind but they're a significant investment.
  - bob1029 2y ago
    I have more faith in my 2200 watt inverter generator than a typical residential standby unit. If something goes wrong with a generac, you likely need a service tech to come out. If my portable unit acts up I have a 2nd new one in a box just in case. They're so cheap you can basically afford to keep one fresh for each disaster.
    - zrail 2y ago
      Inverter units are nice, those Honda engines run forever. I've had my 26kW generac for almost two years and it's done several multi-day outages without issue. I just have my mechanical contractor come out and do the annual maintenance on schedule, keep track of the weekly self-tests, and otherwise don't worry about it.
      - rootusrootus 2y ago
        I want one, but can't justify it. Probably be into it around 10K installed, maybe more. We've only had one multi-day outage in the 12 years we've lived here, because our wiring is all underground and it took a century level storm to wipe it out. We get occasional outages of a few minutes to a couple hours in the winter if a tree hits a power line somewhere in the nearby above-ground grid, but that's about it. I'd still love to be the only guy in the neighborhood all lit up when everyone else goes dark :). To be fair, I'd actually be #2 now, guy a few houses up the street is that beacon of light now. But still. When we were shopping for houses out in the sticks, I had that generator budgeted right into the price of the house. If I got a multi-day outage very year, it's a no brainer.
jasongill 2y ago
This is interesting, especially for me as one of the intrastate pipelines on the map crosses through my property. However, the article doesn't say what the "PIG" is (but talks at length about how the "PIG" is "launched" or "received"). Wikipedia says it's basically a passive device that gets inserted into the pipeline and pushed along by the pressure to clean or inspect the inside of the pipe.
- pfdietz 2y ago
  I believe pig is a word, not an acronym, although maybe it's a bacronym now. https://en.wikipedia.org/wiki/Pigging https://en.wikipedia.org/wiki/Pigging > Some early cleaning "pigs" were made from straw bales wrapped in barbed wire[4] while others used leather.[5] Both made a squealing noise while traveling through the pipe, sounding to some like a pig squealing,[6] which gave pigs their name.[7][8]
  - philk10 2y ago
    I worked on a PIG app several years ago, fun project - https://atomicobject.com/portfolio/microline-embedded-software-development https://atomicobject.com/portfolio/microline-embedded-softwa...
    - deleted 2y ago
      [deleted]
    - Mistletoe 2y ago
      That’s really slick and looks easy to use, good job!
  - cdibona 2y ago
    The smart pigs honestly look like a pigs snout flying down the pipe.
- engineer_22 2y ago
  I dont know about gas industry, but perhaps this will shed some light. In the drinking water industry the pig is a large foam block that is shoved in the pipe, and the weight of the fluid behind it drives it along. It is used to physically loosen the accumulated debris on the inside of the pipe. This debris concentrates behind the pig, and when the pig arrives at it's destination you remove the pig and allow the fluid (and debris) to discharge to waste for a period of time until the fluid runs clear. Some advancements include "ice pigs" which is just crushed ice. The advantage of an ice pig is you can hook up to a fire hydrant and pump the ice in, no need to access the mainline pipe itself. An ice pig will also disintegrate on its own, no need to remove it, just allow it to flow out of a downstream hydrant, any ice left behind isn't a problem.
laurensr 2y ago
In the sixties, hexavelent chromium was used as a rust inhibitor in cooling towers in a Hinkley PG&E compressor station. It caused ground water contamination affecting the health of many. https://en.wikipedia.org/wiki/Hinkley_groundwater_contamination https://en.wikipedia.org/wiki/Hinkley_groundwater_contaminat...
- whalesalad 2y ago
  https://en.wikipedia.org/wiki/Erin_Brockovich https://en.wikipedia.org/wiki/Erin_Brockovich
- aaron695 2y ago
  [dead]
cdibona 2y ago
If you wanna see cutouts of a bunch of this equipment, a pig in a transparent pipe, and just happen to be in Oman, the petroleum development museum there is super. Id imagine there's something similar in Houston, this stuff is legit fascinating.
- DowagerDave 2y ago
  One of my earliest memories when I started working in O&G many moons ago was seeing the hilarious daily report "Pig stuck in pipe". From a technology perspective it's an amazing industry, combining old-tech and human experience with some of the most advanced tech that can work in harsh environments similar to space.
coffeeshopgoth 2y ago
As a chemical/petroleum engineer, this is a great little summary of how these stations work. Good find.
Dennip 2y ago
There was a good video on B1M related to this recently https://www.youtube.com/watch?v=1eKsaGqUfvI https://www.youtube.com/watch?v=1eKsaGqUfvI

90 points by teleforce 2y ago

theoretically, compressing gas is energyless. Ie. you get back exactly the same amount of energy when decompressing as you got when compressing, so you should be able to do it with no loss. Practically, that's fairly far from true for today's technology. Gas is so cheap that we're happy to waste a bunch of energy to make the plant cheaper.

ce4 2y ago
The compressor stations are alongside the gas pipeline network. These put in the energy needed to keep the gas flowing over long distances through the network. Without those it would be just like a very very long garden watering hose that has a trickle of flow compared to a short one.
- londons_explore 2y ago
  I don't believe this to be the case. The differential pressure from one end of a gas pipeline to the other is not 1800 psi - it is more like 20 psi. You don't repeatedly recompress along the pipeline length - you compress once at the start, and decompress once at the end. The reason to use high pressures is because for a given pipe diameter (and therefore cost), you get far more gas transported at high pressures than you do at low pressures.
  - djaychela 2y ago
    It also means large storage tanks (known as gasometers in the UK) aren't needed. A couple of hundred meters of pipe at high pressure holds the same amount of gas as one of them.
    - squigg 2y ago
      As someone else who grew up seeing these across the UK, it was never clear to me why they disappeared - this explains it perfectly, thank you
  - formerly_proven 2y ago
    Most of the energy in pipelines is lost through friction inside the medium and friction between the medium and the inner wall. These are very much not reversible processes. Also the pressure differential is much bigger than you suggest. E.g. the pressure differential across NS1 was nominally around 110 bar (1600 psi) with an inlet pressure of 220 bar (3200 psi) and an outlet pressure of half that. > You don't repeatedly recompress along the pipeline length - you compress once at the start, and decompress once at the end. There are often recompression stations in pipelines precisely because pressure drops across the length, and on land it's cheaper to have those along the length of the pipeline than one really big one like NS1 had.
  - sveng 2y ago
    Interstate or longer intrastate pipelines require compressor stations every 75-100 miles. The parent article mentions this under "Compressors". As another comment states, friction is the main reason.
  - w1 2y ago
    >> You don't repeatedly recompress along the pipeline length Yes, you do. That is the primary purpose of transmission compressor stations. You may just lose a few psi per mile or something, but over the course of 100s of miles..
  - tantalor 2y ago
    Companies construct these stations along natural gas pipelines and use them to compress gas so it can continue flowing downstream to its final destination
  - tomas789 2y ago
    I don’t think that is the case. Surface roughness and directional changes are big losses. For example a single valve on a high pressure line can have a bigger pressure drop than 2 bars. So 160 km of a pipeline will drop a lot more.
happyopossum 2y ago
> theoretically, compressing gas is energyless. Ie. you get back exactly the same amount of energy when decompressing as you got when compressing That's only true in a word with incomplete physics. Friction and drag exist, there's no sense pretending a process is imperfect because of them.
HPsquared 2y ago
Expansion could only recover the "compression work done" if the pipeline between the two was perfectly insulated so no heat was lost.

DebtDeflation 2y ago

The reliability aspect of this self-contained system is quite impressive. Over the course of my life, I've personally experience many power outages, water outages, cell service outages, internet outages, etc. but never a natural gas outage.

BasilPH 2y ago
It's definitely impressive. However, natural gas outages do happen. For example Winter Storm Uri in Texas led to gas outages. Sadly, the outages and possible the loss of life connected to it could have been prevented if the gas companies hadn't fought back against stricter weatherization rules[^0]. > they made recommendations to the Railroad Commission to implement weatherization rules on the natural gas supply chain because there had been water coming up from the formations — it's called produced water, it's naturally occurring — and it was freezing at the top of the wellheads and restricting gas flow both at the wellheads and in pipelines. And yes, the Railroad Commission is not in charge of trains, but oil and gas in Texas. [^0]: https://www.volts.wtf/p/whats-the-deal-with-the-texas-railroad https://www.volts.wtf/p/whats-the-deal-with-the-texas-railro...
- toomuchtodo 2y ago
  Also, a contributing factor to gas compressor station outages in Texas during Winter Storm Uri was ERCOT (Texas' electric grid operator) load shedding without knowing they were shedding gas compressor loads. This led to reduced gas supply available for generation. > When load is being shed involuntarily, customers designated as “critical load” can be exempted. Critical load is typically demand from entities, such as hospitals, for whom a power interruption could be extremely costly. To be deemed as critical, the customer must first file paperwork. The winter storm revealed that certain parts of the natural gas supply chain – such as natural gas compressor stations – were not designated as critical load. In consequence, their power was cut, thereby reducing flows of natural gas along the state’s pipeline network and contributing to partial and complete derates at multiple natural gas power generation units. The loss of their output in turn necessitated further load shedding, potentially creating an unstable feedback loop. This represented a single point of failure in the energy supply system. https://www.bakerinstitute.org/sites/default/files/2022-02/import/ces-ercot-wp-020222_cnO6uiA.pdf https://www.bakerinstitute.org/sites/default/files/2022-02/i... (pages 13-17) https://engineering.cmu.edu/news-events/news/2023/04/25-gas-electric-interdependence.html https://engineering.cmu.edu/news-events/news/2023/04/25-gas-... ("U.S. natural gas pipelines vulnerable to electric outages") https://www.sciencedirect.com/science/article/pii/S1040619023000180 https://www.sciencedirect.com/science/article/pii/S104061902... | https://doi.org/10.1016/j.tej.2023.107251 https://doi.org/10.1016/j.tej.2023.107251 ("How vulnerable are US natural gas pipelines to electric outages?")

morninglight 2y ago

I think most people would agree with you. Electrical power outages are somewhat common, but gas delivery seems very solid. Yet when selecting a home backup generator, most people opt for a gasoline powered generator and NOT one powered by natural gas.

zrail 2y ago
Gasoline generators are significantly cheaper. There are some tri-fuel generators that can run on gasoline, propane, or natural gas, but again they're more expensive. A natural gas powered permanent standby generator is amazing for peace of mind but they're a significant investment.
- bob1029 2y ago
  I have more faith in my 2200 watt inverter generator than a typical residential standby unit. If something goes wrong with a generac, you likely need a service tech to come out. If my portable unit acts up I have a 2nd new one in a box just in case. They're so cheap you can basically afford to keep one fresh for each disaster.
  - zrail 2y ago
    Inverter units are nice, those Honda engines run forever. I've had my 26kW generac for almost two years and it's done several multi-day outages without issue. I just have my mechanical contractor come out and do the annual maintenance on schedule, keep track of the weekly self-tests, and otherwise don't worry about it.
    - rootusrootus 2y ago
      I want one, but can't justify it. Probably be into it around 10K installed, maybe more. We've only had one multi-day outage in the 12 years we've lived here, because our wiring is all underground and it took a century level storm to wipe it out. We get occasional outages of a few minutes to a couple hours in the winter if a tree hits a power line somewhere in the nearby above-ground grid, but that's about it. I'd still love to be the only guy in the neighborhood all lit up when everyone else goes dark :). To be fair, I'd actually be #2 now, guy a few houses up the street is that beacon of light now. But still. When we were shopping for houses out in the sticks, I had that generator budgeted right into the price of the house. If I got a multi-day outage very year, it's a no brainer.

jasongill 2y ago

This is interesting, especially for me as one of the intrastate pipelines on the map crosses through my property. However, the article doesn't say what the "PIG" is (but talks at length about how the "PIG" is "launched" or "received"). Wikipedia says it's basically a passive device that gets inserted into the pipeline and pushed along by the pressure to clean or inspect the inside of the pipe.

pfdietz 2y ago
I believe pig is a word, not an acronym, although maybe it's a bacronym now. https://en.wikipedia.org/wiki/Pigging https://en.wikipedia.org/wiki/Pigging > Some early cleaning "pigs" were made from straw bales wrapped in barbed wire[4] while others used leather.[5] Both made a squealing noise while traveling through the pipe, sounding to some like a pig squealing,[6] which gave pigs their name.[7][8]
- philk10 2y ago
  I worked on a PIG app several years ago, fun project - https://atomicobject.com/portfolio/microline-embedded-software-development https://atomicobject.com/portfolio/microline-embedded-softwa...
  - deleted 2y ago
    [deleted]
  - Mistletoe 2y ago
    That’s really slick and looks easy to use, good job!
- cdibona 2y ago
  The smart pigs honestly look like a pigs snout flying down the pipe.
engineer_22 2y ago
I dont know about gas industry, but perhaps this will shed some light. In the drinking water industry the pig is a large foam block that is shoved in the pipe, and the weight of the fluid behind it drives it along. It is used to physically loosen the accumulated debris on the inside of the pipe. This debris concentrates behind the pig, and when the pig arrives at it's destination you remove the pig and allow the fluid (and debris) to discharge to waste for a period of time until the fluid runs clear. Some advancements include "ice pigs" which is just crushed ice. The advantage of an ice pig is you can hook up to a fire hydrant and pump the ice in, no need to access the mainline pipe itself. An ice pig will also disintegrate on its own, no need to remove it, just allow it to flow out of a downstream hydrant, any ice left behind isn't a problem.

laurensr 2y ago

In the sixties, hexavelent chromium was used as a rust inhibitor in cooling towers in a Hinkley PG&E compressor station. It caused ground water contamination affecting the health of many. https://en.wikipedia.org/wiki/Hinkley_groundwater_contamination https://en.wikipedia.org/wiki/Hinkley_groundwater_contaminat...

whalesalad 2y ago
https://en.wikipedia.org/wiki/Erin_Brockovich https://en.wikipedia.org/wiki/Erin_Brockovich
aaron695 2y ago
[dead]

cdibona 2y ago

If you wanna see cutouts of a bunch of this equipment, a pig in a transparent pipe, and just happen to be in Oman, the petroleum development museum there is super. Id imagine there's something similar in Houston, this stuff is legit fascinating.

DowagerDave 2y ago
One of my earliest memories when I started working in O&G many moons ago was seeing the hilarious daily report "Pig stuck in pipe". From a technology perspective it's an amazing industry, combining old-tech and human experience with some of the most advanced tech that can work in harsh environments similar to space.

coffeeshopgoth 2y ago

As a chemical/petroleum engineer, this is a great little summary of how these stations work. Good find.

Dennip 2y ago

There was a good video on B1M related to this recently https://www.youtube.com/watch?v=1eKsaGqUfvI https://www.youtube.com/watch?v=1eKsaGqUfvI