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helno posted:
I'd hate to imagine the impingement damage to the turbine blading. I'd have thought it would have been the other way around with high quality high pressure steam that gets reused as low pressure wet steam. I've only heard wet steam go down our headers once when one of the moisture traps failed and it sounded like the rumble of death.
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| # ? May 2, 2013 04:00 |
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| # ? May 18, 2013 08:33 |
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I didn't even know "dry steam" was a thing 
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| # ? May 2, 2013 15:24 |
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Captain Foo posted:I didn't even know "dry steam" was a thing It's more jargon than a "scientific" term. "Wet" and "dry" steam are referring to the relative amount of condensate in the line.
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| # ? May 2, 2013 16:01 |
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Captain Foo posted:I didn't even know "dry steam" was a thing Dry steam is superheated steam, i.e. water above the boiling point. Water at its saturation point is actually a mixture of liquid water and steam, which is called wet steam, and referred to using a parameter Χ, "quality", which is the mass fraction of the water that is in the gaseous state.
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| # ? May 2, 2013 16:17 |
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Captain Foo posted:I didn't even know "dry steam" was a thing Also hot steam and cold steam. Also the temperatures of the water at various points, and whether it's expected to be boiling there or not. You can have 600C water in one point, and everything's OK, and 25C water somewhere else that really should be boiling there.
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| # ? May 2, 2013 16:25 |
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helno posted:GE EHC mark II for large steam turbines. Hope you really like op-amp's. I'm sure they've done the maths and all, but holy poo poo. Captain Foo posted:I didn't even know "dry steam" was a thing Not only is it a thing, but it's an invisible thing that will kill you dead very loving quickly. Get a pinhole leak in a pipe, and it'll basically do this to anything that passes through it: http://www.youtube.com/watch?v=iXgsCPFhSgc Steam scares the living poo poo out of me for good reason.
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| # ? May 2, 2013 18:28 |
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Two Finger posted:
And this is what happens when you get cold water accidentally dripping on super heated steam pipes causing steam hammer: http://www.youtube.com/watch?v=SImhkapRuIs There was a tow truck right over when it erupted, you don't want to know what happened. Steam is fantastic in its uses, but when it goes wrong..
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| # ? May 2, 2013 20:26 |
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M_Gargantua posted:I'd hate to imagine the impingement damage to the turbine blading. I'd have thought it would have been the other way around with high quality high pressure steam that gets reused as low pressure wet steam. I've only heard wet steam go down our headers once when one of the moisture traps failed and it sounded like the rumble of death. The steam is 4.4 MPa but only around 250 degree celsius because it is being boiled by 305 degree water at 9.8 Mpa. I don't know the math or have the exact numbers but I have heard that it is about 0.1% moisture when it gets to the valve chest. At full power we boil about 1200 kg per second per unit (we have 8 units). The older LP turbines look like a sandblaster have been taken to the last few stages due to impingement damage. We only turn at 1800 rpm so it is not as bad as the plants that run 3600.
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| # ? May 3, 2013 02:20 |
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Expanding saturated steam from a quality of 1 down to about 0.9 (or in some cases down to 0.85 or so) is actually a pretty common cycle, or at least it was. Superheat is a newer addition to the cycle, because it's a bitch and a half to add heat to dry steam (heat transfer coefficient similar to that of air).
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| # ? May 3, 2013 05:45 |
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TyroneGoldstein posted:And this is what happens when you get cold water accidentally dripping on super heated steam pipes causing steam hammer: As I've stated before, steam scares the living hell out of me for good reason. I can't remember the exact figure, but I think water will expand up to like 1400 times its original volume when it becomes steam.
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| # ? May 3, 2013 22:52 |
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FrozenVent posted:Wait, H2 as in hydrogen? I worked at a plant that had a significant hydrogen leak, and the main concern was running out.
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| # ? May 4, 2013 01:38 |
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This is an example of a boiler explosion. http://www.youtube.com/watch?v=fCej2OQSKnY There's write up with better pictures here. Another boiler explosion here. http://www.youtube.com/watch?v=PsSVfAg1kRg
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| # ? May 4, 2013 22:47 |
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I live in the UK and in our fuse box the first set of fuses says 415V 80A/100A, should I be frightened of arc flashes from them when they fail? What's the difference between the neutral and ground pins in a plug? I was told by a school physics teacher (some years ago) that a shaver socket is safer than a regular power outlet because if I came into contact with a wire I wouldn't be completing the circuit and so wouldn't receive a shock, is that true?
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| # ? May 7, 2013 14:22 |
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Crankit posted:I live in the UK and in our fuse box the first set of fuses says 415V 80A/100A, should I be frightened of arc flashes from them when they fail? What's the difference between the neutral and ground pins in a plug? I was told by a school physics teacher (some years ago) that a shaver socket is safer than a regular power outlet because if I came into contact with a wire I wouldn't be completing the circuit and so wouldn't receive a shock, is that true? Fuses are designed to keep arcs in, so no problem there. The neutral pin goes back to the source of your power, typically the transformer on the pole. The ground pin goes to the earth at your panel. Usually there's a bond between the two there. The fundamental difference is that the neutral pin is designed to carry current under normal circumstances (it's the second wire of a complete circuit) where the ground pin should only have current/voltage on it in a fault condition. Going from memory here, but shaver sockets in the UK are usually powered by isolation transformers and are therefore ungrounded. So accidentally touching one wire doesn't give a complete circuit to anything, as the transformer isn't connected to ground. Touching both wires will still shock you, but maybe not kill you because the transformer is power limited (I think). Other parts of the world use a GFCI (ground fault circuit interruptor). If you touch one wire and complete a circuit to ground, the outlet senses the ground fault current and shuts the power off.
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| # ? May 7, 2013 16:59 |
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babyeatingpsychopath posted:Fuses are designed to keep arcs in, so no problem there. Pretty much this. But you would absolutely not want to do something like pull them with the power (I think you call that "mains") turned on. Is there a switch, and underneath that three fuses? Both circuit breakers and fuses have a maximum current rating in kiloamps. So the fuse may have a label like this: 600V 50A 100kAIC The 100kAIC indicates it can interrupt up to 100,000 amps. For fuses it isn't difficult to get fuses rated at 100,000 or even 200,000 amps of fault. Circuit breakers are much more expensive. We have some breakers at work (HFDs and HKDs from Eaton, fairly common industrial three-pole breakers) that are rated at 65kAIC at 480V, and they aren't cheap. I think the idea for sticking with higher capacities is so that if we change or salvage equipment later in its life, there's a better chance we can reuse the equipment rather than saying "Crap, this is rated too small for other places in the plant. Chuck it." The fault level is limited mainly by the impedance of the source (the transformer feeding the system) and the impedance of the cable from the transformer to where the fault is) as well as if there are current-limiting devices in between. If you have a fault that exceeds the rated capacity of the interrupting device, it may violently fail to interrupt the fault. I've seen pictures of circuit breakers exploding like a bomb when their capacity is interrupted. Medium and large circuit breakers (thousands of volts and thousands of amps and up) have their fault rating in MVA. A breaker may have a 500MVA fault rating (500 million volt-amps). Three-Phase fucked around with this message at May 7, 2013 around 23:04 |
| # ? May 7, 2013 23:01 |
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, but it reflects poorly on the forums. 
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| # ? May 18, 2013 08:33 |
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babyeatingpsychopath posted:Fuses are designed to keep arcs in, so no problem there. And hopefully they are not exposed. I mean, they have some kind of cover them, right?
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| # ? May 9, 2013 22:22 |
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