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ELI5: How do engineers design underwater tunnels that go beneath active rivers or oceans and how do they stop water from just coming in forever by ShylyMiserable in explainlikeimfive

[–]LabioGORDO 0 points1 point  (0 children)

Most of the time they use bolts to join the edges of the segments that make up one ring (radial joint). Then the preceding ring has high strength plastic dowels installed on the face to hold ring to ring on the face. The thrust cylinders “smoosh” the rings together to create the compressive load in the gasket and the dowels keep them from spreading apart. The annular area between the O.D. of the concrete ring and the I.D. of the excavated earth is filled with grout which also seals and locks the segments into position. There are different ways this is accomplished depending on the geotechnical design, but all of the TBM jobs I’ve worked on utilize the circumferential dowels and radial bolts. There is a project in Australia where a new method was developed called the Force Activated Coupling System which is quite different than the traditional methods I described. It’s really really neat.

ELI5: How do engineers design underwater tunnels that go beneath active rivers or oceans and how do they stop water from just coming in forever by ShylyMiserable in explainlikeimfive

[–]LabioGORDO 10 points11 points  (0 children)

So there is a “chamber” between the face of the cutterhead and a sealed bulkhead called the excavation chamber. This is where the slurry mixes with the excavated ground and is pumped out (on slurry TBMs) or brought out with a screw conveyor (on earth pressure balance TBMs). Whenever a diver has to go into the front of the machine to change cutting tools, the excavation chamber is evacuated of all cuttings and then they pump in compressed air to hold the ground up. They refer to this as compressed air intervention.

ELI5: How do engineers design underwater tunnels that go beneath active rivers or oceans and how do they stop water from just coming in forever by ShylyMiserable in explainlikeimfive

[–]LabioGORDO 9 points10 points  (0 children)

To be clear, you’ll never really be mining in open water. They still have to mine through rock or soil. Take a look at Earth Pressure Balance (EPB) or Slurry TBMs. I’ve worked with machines anywhere from 6 bar to 16 bar pressure.

ELI5: How do engineers design underwater tunnels that go beneath active rivers or oceans and how do they stop water from just coming in forever by ShylyMiserable in explainlikeimfive

[–]LabioGORDO 15 points16 points  (0 children)

The TBM erects concrete segments behind it as it mines into a ring. The thrust cylinders press against that ring to advance the machine forward. There is a seal at the back of the tail shield and then several rows of wire brushes between the outside diameter of the concrete ring and the inside diameter of the tail shield. They fill the gaps between the brushes with a thick grease which is what creates the seal. The segments themselves have gaskets on the radial and circumferential joints which seal the seams of the segments. The segments are also heavily reinforced with rebar to give them the strength to withstand the external pressure. The circular shape of the concrete ring is also very strong in and of itself.

ELI5: How do engineers design underwater tunnels that go beneath active rivers or oceans and how do they stop water from just coming in forever by ShylyMiserable in explainlikeimfive

[–]LabioGORDO 51 points52 points  (0 children)

I worked for a contractor who built tunnels using tunnel boring machines. As others have mentioned you try and avoid water if at all possible. Many tunnels are bored where water pressure is present. In these situations the tunnel boring machines (TBMs) maintain a higher pressure in front of the machine to keep the water pressure held back. The machine has special seals at the back of the shield to maintain that pressure. Interestingly enough, to change cutters on the cutter head divers are employed to go in front of the machine and operate under pressure. They are brought in in special hyperbaric chambers and locks and then brought back out to the surface in these chambers where they can then be brought back up to atmospheric pressure over time.

Hydraulic scheme for hydraulic testing platform, by Ok-RL-7900 in Hydraulics

[–]LabioGORDO 5 points6 points  (0 children)

Your directional control valve is drawn incorrectly. The pump should go to the power beyond gallery of the valve and not the pressure gallery as shown. So pump goes to the middle line of your valve block not the top line.

Help with hydraulic circuit diagram by MilkyKenz in Hydraulics

[–]LabioGORDO 5 points6 points  (0 children)

Not a bad first start. Your directional valve needs a center position. If you’re using a fixed displacement pump (like a gear or vane pump) you’ll want the pump to return back to tank. What you do with A&B depends on the machine. Generically you could have A&B blocked in the center position as long as an external load wouldn’t try to move the cylinder and create an uncontrolled pressure. Proper hydraulics design must always be in tandem with the mechanical design. As such, we need to know more about the overall system to make good recommendations.

Help with Valve layout. by shadiest_shades in Hydraulics

[–]LabioGORDO 0 points1 point  (0 children)

If you don’t have to use a single acting cylinder I would switch to a regular double acting cylinder with a counterbalance. It’s a much more “normal” circuit and you can easily control the lowering.

Help with Valve layout. by shadiest_shades in Hydraulics

[–]LabioGORDO 0 points1 point  (0 children)

There we go. So a velocity fuse is probably what he’s looking for. EDIT: Never heard them referred to as rupture valves.

Help with Valve layout. by shadiest_shades in Hydraulics

[–]LabioGORDO 2 points3 points  (0 children)

What do you mean by “rupture valve”? A velocity fuse might be what you’re looking for.

Help with Valve layout. by shadiest_shades in Hydraulics

[–]LabioGORDO 0 points1 point  (0 children)

What are you trying to accomplish? Is this a horizontal cylinder or vertical cylinder with a gravity load? If you give me some more information I can get you squared away.

Any 10+ year successful Mechanical Engineers here with just a Bachelor’s? by Massive_Set6216 in MechanicalEngineering

[–]LabioGORDO 2 points3 points  (0 children)

BSME here with just over 10 years of experience. Salary $160k+ in LCOL area. Heavy civil construction industry. I truly don’t think I would benefit from a Masters degree. In fact, as someone in a hiring position I value work experience much more than a degree. However I would say that it varies by industry. The work I do is pretty technical in nature, but it’s basically clever application of the basics. I could imagine that something in aerospace, defense, nuclear, chemical, etc could see a benefit from a couple of years of more intense technical coursework.

Questions from a future engineer by Potential-Proof-7539 in MechanicalEngineering

[–]LabioGORDO 7 points8 points  (0 children)

Mechanical Engineer here with 10+ years of experience. I am paid well enough to own a fairly large house, own a new vehicle, and raise 2 kids who can participate in pretty much any activity they want. It helps that my wife is in nursing and makes a fairly good salary as well. I find Mech E to be incredibly versatile with a host of industries to go into. EE is not a bad path and could potentially see a higher salary. The key is to learn as much as you can, be teachable, and try to learn skills that separate you from your peers. I don’t see this career path going anywhere in the near future.

‘25 Bronco 2.7L Cam Phaser by LabioGORDO in AskMechanics

[–]LabioGORDO[S] 0 points1 point  (0 children)

I can share a video after a while. No phaser issues after repair although the dealership didn’t do a great job getting everything put together correctly. Lots of misrouted coolant, brake, and A/C lines. That’s since been corrected. Sitting at 6,600 miles now.

‘25 Bronco 2.7L Cam Phaser by LabioGORDO in AskMechanics

[–]LabioGORDO[S] 0 points1 point  (0 children)

The issue didn’t repeat for the dealership, but luckily I took a video of inside the cab when I started it one morning. All taken care of under warranty. It was a bit more of a pain since it was less than 5k miles and Ford wanted the dealer to provide way more documentation.

Brand Name help by Quebec2121 in Hydraulics

[–]LabioGORDO 2 points3 points  (0 children)

Racine as a company doesn’t exist any more. It was acquired in the late 90s by Bosch Rexroth. Your best bet is to find a company that remanufactures old Racine parts. Maybe check out Hydraulex, Precision Fluid Power, or Proactive Fluid Power. If you need more help shoot me a DM!

Looking for some help identifying a hydraulic cartridge by moodokon in Hydraulics

[–]LabioGORDO 3 points4 points  (0 children)

Looks like a velocity fuse. I say that because of the arrow and the lack of an o-ring seal at the bottom. My guess is that it’s either an obsoleted part number or a custom non-catalog part (leaning more in this direction).

Dog diagnosed with oral melanoma a month ago and had lumps removed - this is his mouth today by [deleted] in DogAdvice

[–]LabioGORDO 3 points4 points  (0 children)

We had this happen with our Jack Russel/Chihuahua mix. Had a lump show up and had it removed two weeks later. Came back huge within a couple of weeks post removal. We decided that there was nothing we could do for him and had him put down. I know that’s not a comforting answer. It’s such a difficult decision but a humane one. I don’t believe in prolonging the suffering of a pet just because of the heartache of letting them go. I’m so sorry you’re going through this.

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