Large boiler Controls of Yesteryear;

Mine use a mechanical computer with Bourdon tubes, springs, balance beams, cams, levers, etc., and a mercury/oil filled dashpot to make a mechanical signal consisting of a silver plated brass wire "finger" moving up or down to make contact with other wires in order to increase or decrease fuel to the boiler.

This electrical (28 VAC) signal triggers a pair (one runs fuel up, one down) of timing relays (similar to http://www.grainger.com/Grainger/items/1A983 )for a .2 sec off delay. There is a 220 VAC feed powering the switched circuit. They are interlocked from each other (one relay’s output disables the other as long as it is called in) because the 220v signal (from the timing relays) calls in a 3 phase reversing starter. (3 phase 450 on this line) this activates a small motor hooked to a wormgear and cam arrangement that opens or closes fuel control valves, thus regulating boiler pressure.

And yes, this was a widely used system years ago and fairly well proven reliable. If anyone can name model and manufacturer, I'll mail them a beer.

So if anyone got through that, my question stems from the problem that the original starters used vacuum tube technology to generate the low voltage required for the silver plated brass "finger" contacts (remember them?). It sensed the v-e-r-y light contact pressure well. In a pinch, after the last original starter was burned, a refit was made. This includes the 28vac power supply, the timing relays (high impedance input, a 28 vac input runs about 3/4 of a milliamp) and the reversing starter.

So here's my problem:

The fingers (about 1/16 diameter) don't always trigger the timing relays. They get dirty and sometimes a jiggle fixes it, sometimes electro clean and a coffee filter. Sometimes you have to bend them a bit to a new contact spot. A higher voltage would work, but with all that poking and prodding would result in folks getting zapped.

Would a different metal be better (gold plate the fingers)? Would DC work better? Is there a small super high impedance circuit I could use that would better sense this light contact pressure and trigger an output but still be safe to touch?

I'm told that a CMOS has the kind of high impedance input I'm looking for. What I'd like to do is to use the 12vdc that is available in the enclosure. (along with 28, 120, 220, and 450 vac).

I however, am more of a relay, motor controls, and power guy, I'm not too good when it gets to transistors and such. I'd like to also integrate the time delay with the finger sensing circuit and get the whole mess from the fingers to the reversing starter fairly bulletproof, as the rest of it is.

Thanks for reading,

 

Let me guess at the manufacturer - Baldwin Locomotive Works?
(I have some WWII-era strain gauges made by them, still in the original packaging)

CMOS IC's have very high input impedance. They don't have much in the way of drive capacity (current source/sink), on the order of a few milliamps. However, that can be used to drive transistors or Darlingtons for much higher current output.

The high input impedance would greatly reduce the wear on your contacts. De-bouncing the contacts is another matter, but that could be worked out.

What really would help us help you, is for you to post a schematic of the particular area that you are trying to replace/upgrade. This helps eliminate errors in interpreting the written word.

 

Diagram is in my photo album, I couldn't get the pics up on the post here.
Please forgive my lack of CAD.

Everything except the fingers and the 3 phase starters (I’m sure I can get 120vac coils for these if needed) can be deleted as long as I get a pulsed .2 second off delay. Like I said, I have 12VDC available and would like to probably get rid of the 28 VAC transformer since this is all it does anyway.

In the first picture, you can see the finger contact along with (not as well) the perpendicular contacts for up & down signals attached to the lugs and wires. The red & green wires on the perpendicular contacts are fairly visible, the black wire feeding the finger is harder to see.

As you can see, the finger was too short and needed lengthening.

The picture of the whole cabinet is kind of ugly. When I get this built and installed, i'm planning a rewire and have gathered most of the necessary materials. All that air stuff there hasn't worked since Nixon was president and needs to go to make room for some wireways.

You can see the output on the bigger picture, my reversing starter there, a telemechanique grainger type of thing, (M coil draw unknown, the unit is good for 6 amps 3 phase), but could be investigated. and couldn't be more than an amp. I'd like to get some LED's installed indicating up or down outputs.

So there'd be a circuit through my finger contacts that select one or the other of a pair of circuits. Each of these would trigger its own high impedance input which would output immediately, but turn off after a preset (or possibly adjustable?) delay of .1 to 2 sec, then remain inactive for about a half-second or a second, again looking for finger input. These time delay outputs would drive relays capable of calling in my reversing starter 220v coil and some indicating LEDs. I would want to use the interlock arrangement as seen on my diagram so would need DPDT.

When I get done, I'd like to bury the thing in epoxy, I'm hoping this wouldn't be a problem in my dirty, sooty, oily, HOT (120+f) boiler room. I have a machine shop available though, heatsinks would be a snap.

And no, not railway equipment. Think bigger.

 

a biiiig ship??

 

Hmm - General Electric, Steam Turbine Division?

OK, before we go any further - it sounds like could have definite human safety factors involved.

Is that correct? Or are there multiple alternate fail-safes already in place?

CMOS devices definitely have very high input impedance. However, vacuum tubes (or valves, as the UK'ers like to call them) are quite ESD safe (static-proof). CMOS devices are anything but static-proof. One high-voltage zap and they're dead - you might not even see the spark.

There are ways to help minimize the risk, but the thought of a runaway boiler does not sit well with me. It needs to be fail-safe, so that if the circuit is dead, the boiler fire cuts off.

I don't know how to do that at the moment. This could have a high risk factor to attempt to do remotely.

 

Rest assured there are plenty of overrides. The 3 phase motor controlled by my reversing starter can be mechanically overridden and the fuel controlled via a handwheel. If you turn the fuel down all the way via the handwheel, it still has a minimum flow feature to PREVENT killing the fires. This steam from the boilers is driving generators, which drive fuel pumps providing oil to the boilers. Break the chain and things get ugly.

There's also safety valves on the boilers to beat the band. Enough capacity to take the entire boiler output at full fuel flow.

There's a burner management system whose job it is to cut the fires if there's something far enough out of parameters. And you electronics guys'd love that panel, vintage 1974, all nand, nor, flip flop, etc., IC's mounted on slide out cards. Fun to work on.

Yes, it is a biiig ship. The boilers and controls are all certified and inspected by the ABS and the USCG, and I (and all my homies there) are licensed engineers. Yes, we know what we're doing in an emergency and otherwise, too.

Like I said, the controls aren't the most reliable at the moment. More likely than a runaway condition (and boiler pressure is alarmed high & low), is just a no-response condition, either of which are easily overridden and hand-fired back to equalibrium.

I would assume then that the vacuum tubes on the original starters were the high impedance inputs.

I've heard from some sources that Russia still makes & uses vacuum tubes, but what do I know? If they are still available, I'd consider them for use over a fragile IC.

To sum up, this is a 24 hour a day manned boiler room. Anything you guys can come up with can't be any worse than what I have now. Also the static concern kind of goes away once you're living in a big steel box as far I know. The enclosure for this mess is also steel, so touch the enclosure before the wingers and you're good to go right? Besides, if this works right, there should be little need to touch the fingers.

There's 2 nearly identical units tied to the fuel control that control the air. These still have the original starters and I rarely if ever have to give them attention. I'll post more pics.

GE? Well they did make our 2 turbo-generators (600KW each), our switchboard, and design our main engine turbines, which were built by Bethlehem steel in Baltimore, 1958. Close, though.

 

OK Chief, I'm looking at it, noodling over a few options.

Westinghouse?

Hmm, I wasn't aware that the USCG had any big ships?
I was on the FID, "El Zippo", CV-59 in '76. That's a big ship!
POTUS Nixon resigned two weeks before I graduated from Boot.

 

This is an American merchant vessel. Owned privately with union labor aboard. The ship is inspected by the USCG, but in their recent shift to homeland security, their marine safety division has suffered.

Most of the people they send nowadays are clowns more concerned with appearing to be some kind of a swat team "tactical" badass than actually understanding what they're looking at. Amazing what you can get by them. Amazing what stupid shit they do pick up on. Back in the day they had some really talented folks that understood what was going on. They must've been forced to retire...

We are all also personally licensed by the USCG, and I could rant about that too but nobody'd listen.

Anyway, we are also inspected by the ABS (american bureau of shipping) who are better than the USCG about knowing what's going on. But still, not many folks have any experience with steam. It's all diesel/computer controlled/magic black box/CTRL-ALT-FIX crap now.

Steam is old school. There's something satisfying about being to troubleshoot things to the smallest component and then repair them without replacing them. Remember, we are talking about American manufacturing in the '50s here. No "lean" manufacturing BS here.

Anyhow, lots of this stuff is over most folks heads. Good thing my colleagues and I really do care and try to not only maintain status quo, but make improvements. This is self-governing at its best. This is one of many many projects we have ongoing. Lots of moving parts and, like Mr. Young says; "rust never sleeps"...

 

Not westinghouse. Although Westinghouse and our mystery manufacturer were both eventually gobbled up by Siemens.

And man, I'm starting to sound old. All this "back in my day" talk. I wasn't even born for a dozen years after this heap was built.

Thanks for your help, much appreciated.