You are not logged in.
For SpaceNut ...
There were four topics containing the word "pressure"
I evaluated all four (and read two) before deciding this topic is different enough to deserve it's own topic
This topic is offered for gathering of information about the physics of pressure Vessels in general, as well as engineering and practical experience. The specific application I have in mind is propulsion, but the topic is not intended to be limited in application.
The impetus for this topic is an estimate by ChatGPT(4) that a pressure of 184 bars would be needed for an application.
I was curious to see what humans have achieved in construction of pressure Vessels, so the next post will provide a set of Snippets from Google to show the range of existing devices.
Over time, I am hoping our members will contribute other examples to the topic.
(th)
Online
Like button can go here
This post is a collection of Snippets from Google, in answer to an inquiry about pressure Vessels, with a focus on the high end of the range.
The target pressure of interest is 184 bar. It turns out that 184 bar is quite a modest pressure compared to existing capability.
Apache Internal Server Error objected to the intended post so I have edited the post until it passed muster.
The original question was: pressure vessel to hold 184 bar
About 22,800,000 results (0.47 seconds)
SPECIFICATIONS · Type 3 Pressure Vessel · Maximum Operating Pressure: 6,000 psi (414bar) · Minimum Burst Pressure: 18,000 psi (1,2412700 psi / 184 Bar 1 - 7. 80A60. 519013. 600 psi / 41 Bar. 120°F / 49°C. 3600 psi ... Manufacturer Accreditation – The manufacturer must
Pressure vessels that are designed to withstand 400-bar pressure (400 atmospheres) are usually designed with heavy construction. If they are designed to go into ...by A Air · 2023 · Cited by 8 — Another design achieved a pressure of 558.5 bar before helium leakage was detected and a burst pressure of 620.5 bar, which is close to the ...
... pressure rating from 184 to 300 bars (2,670 to 4,350 psi). Cylinders are ... Usable air = usable pressure × cylinder capacity = 150 bar × 18 litres per bar = 2700 ...
Apache Internal Server Error accepted the edit shown above.... the values shown are inclusive of 184 bar, but most extend well above.
From this I conclude that humans are able to build structures that can hold 184 bar or greater pressures.
(th)
Online
Like button can go here
In another search, I asked for the pressure inside an artillery barrel...
convert 310 MPa to bar
Pressure
310 Megapascal
=
3100 Bar
The reference for the figures above is: https://digital.library.unt.edu/ark:/67 … adc672863/
The work was done for the US Department of Energy. The study was on fractures in the gun barrel for a 155 mm artillery piece.
(th)
Online
Like button can go here
One of the complications with pressure vessels, is that code compliance tends to specify ductile failure modes to ensure the vessel leaks rather than fragments. This is why pressure vessels tend to be made from low alloy carbon steels. These are not particularly strong, but ductility is as important as strength. For a pressure of 184 bar, the vessel will be thick walled, as yield stress of the vessel material will be somewhere between 250 - 500MPa. This makes pressure vessels quite heavy and thick walls are difficult to weld. This is one of the reasons why British gas cooled reactors used PCRVs made from concrete with steel stressing tendons. For large stationary pressure vessels, this is an under- utilised technology. It could be very useful for applications like compressed air energy storage.
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
Offline
Like button can go here
For Calliban re #4
Thank you for contributing to this topic!
First.... can you provide a bit more detail about "difficult to weld"? Do you mean to weld two sections together, such as a pipe carrying oil from Alaska to the lower 48?
Second.... thermite is reported to be useful for welding steel rails in remote locations. By any chance, would thermite provide a strong weld if it were placed between two thick walled sections of steel to be joined?
Has this method of joining ever been done in practice, for a large object such as an oil pipeline?
(th)
Online
Like button can go here
Gateway Capabilities
https://www.nasa.gov/gateway-capabilities/
Once fully assembled, Gateway will be about one-fifth the size of the ISS and weigh approximately 63 metric tons with an interior habitable volume (sustained capability) of about 125 cubic meters
Tiangong space station open to world
https://global.chinadaily.com.cn/a/2022 … a1c3e.html
Development Status Toyota's Manned Pressurized Rover and MHI's LUPEX Rover
https://global.toyota/en/newsroom/corpo … 37662.html
Water propulsion technologies picking up steam
https://spacenews.com/water-propulsion- … -up-steam/
Spacecraft passivation – An overview of requirements, principles, and practices as applied to spacecraft pressure vessels
https://www.sciencedirect.com/science/a … 6722001021
on Mars or Titan perhaps Land travel and movemnet and energy used in a system similar to light-duty railroad locomotives?
https://www.steamlocomotive.com/locobas … ailroad=mr
Last edited by Mars_B4_Moon (2024-04-01 16:06:00)
Offline
Like button can go here
For reference in case anyone is interested, humans have achieved success in withstanding high pressure in the deep ocean on Earth.
Per Google, here are the figures for the Mariana Trench:
how many bar does a deep sea exploration vessel experience at the bottom of the deepest location in Earth's oceans?
A deep sea exploration vessel at the bottom of the deepest location on Earth, the Mariana Trench, experiences approximately 1,086 bars of pressure.
Explanation:
Pressure unit: "Bar" is the unit used to measure pressure in this context.
Location: The Mariana Trench is considered the deepest point in the ocean.
Equivalent pressure: This pressure is equivalent to roughly 15,750 pounds per square inch (psi).
How much pressure builds up at the deepest point in the ocean? | Culture Online - UCL – University College London
Apr 21, 2021
UCL
Mariana Trench - Wikipedia
At the bottom of the trench, the water column above exerts a pressure of 1,086 bar (15,750 psi), more than 1,071 times the standar...Wikipedia
How fish survive extreme pressures of ocean life - University of Leeds
Sep 28, 2022 — In one of the deepest points in the Pacific - the Mariana Trench, 11 kilometers below the sea surface - the pressure i...
University of Leeds
Show all
Show more
… the bottom of the Mariana Trench has 1,086 bars of pressure. Bars are a unit for measuring pressure, like how we use degrees Celsius to measure temperature. Sometimes pressure is also measured in 'psi' (and in the deepest point in the ocean, it is 15,750 psi).Apr 21, 2021
(th)
Online
Like button can go here
There's "hard to weld" and there's "hard to weld". The old 17-inch thick battleship armor on the Iowa-class ships was welded with very high-power arc welders and great big welding sticks. The "V" joint to do that was 17 inches wide and 17 inches deep, so it took a lot of passes at about a quarter inch per pass to fill that V. But it was non-hardened mild steel and ordinary welding stick materials, just larger ones than most people have ever seen.
You have to use the "right" stick material with each different kind of metal. Mild carbon steels all use the same kinds of rods (there's more than one), and there are different kinds intended for the Austenitic stainless steels. Neither application involves heat-treated materials, like the Martensitic stainlesses and the maraging steels. Those heat-treated alloys are almost impossible to weld after heat-treating. No arc welding or torch welding works. Spin inertia welding and electron-beam welding do work, to some extent, but it ain't easy. Those materials are far better welded first, then heat-treated afterward.
As for ductility, that goes inversely hand-in-hand with hardness, for just about any metal you want to name. If it's hard and strong, it has little ductility, and vice versa. It it has little ductility, the consequences of a failure at pressure can be extremely disastrous! You cannot have both in any real-world metal materials. For applications where "heavy" is not a killer problem, you go with high ductility and lower strength specifically to limit failure consequences. Where "heavy" is a "killer", you have to go for strength, and accept the consequences of failure (and try to design around them). That's why fatigue failures in airplanes kill more people at a blow than fatigue failures in bridges and buildings and ships.
I'm no materials expert myself, but I do know enough about it to talk with real experts quite intelligently. I had to be able to do that, in order to lead new product development design teams effectively. Narrow specialists don't do so well at that.
GW
Last edited by GW Johnson (2025-01-25 13:52:51)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
Like button can go here
For GW Johnson re #8
Thanks for this addition to the topic.
The question posted (indirectly) by PhotonBytes (in a topic about a vertical well on Mars) was about dealing with over 4000 bars of pressure in the regolith.
We humans have successfully dealt with a pressure of 1000 bar, at the bottom of the Mariana Trench. We (humans) have operated manned and unmanned vessels at that depth, on a number of occasions.
The question that arises from the scenario posed by PhotonBytes is whether any material exists that can withstand 4000 bars of compression pressure.
Begin Quote from Google Question:
what materials were used to make the pressure vessels for the deep sea vehicles that reached the bottom of the Mariana Trench?
The pressure vessels for deep sea vehicles that have reached the bottom of the Mariana Trench are primarily made from titanium alloys due to their high strength-to-weight ratio and excellent corrosion resistance, allowing them to withstand the immense pressure at such depths; most notably, the "Trieste" and "Deepsea Challenger" submersibles used titanium pressure hulls.
Key points about using titanium:
High strength:
Titanium alloys can withstand the extreme pressure at the bottom of the Mariana Trench.
Lightweight:
Compared to other strong metals, titanium is relatively lightweight, which is important for deep-sea submersibles.
Corrosion resistance:
Titanium is highly resistant to corrosion from saltwater, crucial for deep-sea operations.
The article at this link reports on analysis of Aluminum and Titanium used for deep sea pressure vessels.
The study was part of a larger work on use of hydrogen to provide power for undersea exploration vessels as compared to batteries.
https://www.sciencedirect.com/science/a … 0of%202.25.
This paper should appeal to readers with deep training in engineering.
(th)
Online
Like button can go here
External pressure on a vessel is different from internal pressure, because with external, there is a sort of mechanical instability that causes collapse, not just the compressive stress exceeding some allowable. That is unlike internal pressure, which has no mechanical instability to it.
That being said, it is possible to withstand enormous pressures with relatively ordinary materials in small sizes. As a graduate student 5+ decades ago, I used a very thick wall 300-series Austenitic stainless steel tubing for a probe into a hypersonic wind tunnel. This tubing was used routinely by the geology folks at internal pressures around 37,000 psi (2517 atm, 2550 bar).
In my application, the pressures were nowhere near that high, but the bending stresses were very, very high indeed, during wind tunnel start as the shock waves blew by. It worked OK. That's another mechanical instability case, by the way. Ordinary hypodermic tubing would string out flat along the wall of the wind tunnel. This much thicker-wall stuff survived those forces in the elastic range, actually. We had no permanent deformations test-to-test.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
Like button can go here
I spent some time looking into this for the vacuum energy storage topic.
Buckling instability is caused by insufficient second moment of area of thin skins under compression. It is why negative pressure vessels like submarine hulls are made of internal I-frames, with the pressure hull transfering load to the compressive frames. To avoid buckling instability there is a minimum required ratio between wall thickness and vessel diameter, which depends on youngs modulus of the material. I will see if I can dig out the equation. But generally, a negative pressure vessel must be substantially thicker than a positive pressure vessel for the same differential pressure.
On the plus side, depending on the application, you can use reinforced concrete, tile or cemented stone for the skin of a negative pressure vessel. Ceramic materials like this are usually substantially cheaper than steel for the same strength. But I think it may be difficult to find materials that can stand up to pressures of 4000bar (400MPa).
But I am curious to understand why it is necessary. We only need to go about 5m underground on Mars for the static rock pressure to reach 0.5bar, which is the assumed air pressure of our habitat. Why do we need to go down over 20 miles? That would seem to impose rather excessive structural requirements on a habitat. What benefit do we gain from boring quite so deep into the crust?
Last edited by Calliban (2025-01-27 09:27:11)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
Offline
Like button can go here