In heavy snow are air swithes better than electric?

During heavy snows like we are currently experiencing on the NEC do air switches work any better than electric switch motors? One of the big problems in any snow is switch failures. I know air is not in vogue most places any longer but I often wondered if they were better in general and specifically better in winter?

Edit to add: I have heard from fans the DS strait rails the corridor in real bad weather. However I have not been out in a blizzard to confirm. Is this a common thing?

Good question. I've seen both fail in snow or bad weather. I guess anything works well with proper maintanance but $*** still happens.

The main cause of power switch failure is heavily packed snow/ice accumulating in the points, so switch heaters and/or human personnel are essential to keep the points clear. I guess pneumatic switches might work a little better, since the points flop over with greater force than motored switches, so a certain amount of the frozen stuff might be more easily forced out, or at least compressed into a tiny enough space for the points to move completely over, and thus for the switch to remain in correspondence.

It is true that when the weather is known to be bad in a given area, or a given switch had experienced problems earlier in the day, dispatchers will avoid using crossovers whenever possible. This is good practice on railroads all across the country, not just on Amtrak. Dispr. has to assume the worst case scenario of the switch failing, and thus mentally weigh the delay of following another train on straight-rail versus the potential extensive delay of flagging by the signal, taking switch(es) off power, cleaning them out if needed, throwing them by hand, proceeding at restricted speed, etc. etc. etc. Some power switches are not even equipped for dual (hand) operation, and in that case, a maintainer needs to be dispatched, causing even further delay.

Disclaimer: I am not a maintainer, MoW person, or dispatcher; I just "drive the bus".

So, I'm not a railroader, but I am an electrical engineer.
I really think the debate of pneumatic versus electric motor operated switch really comes down to how much force does the operating mechanism have.
Pneumatic equipment is subject to all sorts of issues with leaks and is much more prone to environmental variability.

If the main issue is packed snow and ice fouling the switch points, then there's a solution.
Use an induction heater on that short stubby rail next to the switch point. The heater can be activated by a piece of equipment known as a "Sno-Switch", which detects falling snow and activates a relay that energizes a heater element. I've spec'd several Sno-Switches for air intakes on building HVAC systems, where the intake sucks in snow during the winter. The device activates a heater element just inside the intake opening, which melts the snow and drains it out the bottom of the intake.

Using the "Sno-Switch" allows the equipment to be automatically and independently, at the switch points, but without wasting lots of energy by having it only on when there's snow.

I've always felt that pneumatic switch machines are a thing of the past. Amtrak has been replacing them everywhere on the NEC (they were a PRR standard), so there's part of the answer.

But in fact, when I saw this thread, I thought you were referring to the CN-designed switch heaters that use a supersonic air flow rather than propane or electricity to keep the points clear. These are in wide use in Canada, and seem to be well suited for places where temperatures are low and snow is fine and dry -- which covers most of Canada. And Canadians should know about living with snow.

JoshKarpoff wrote: Use an induction heater on that short stubby rail next to the switch point..

You don't want coils of wire near the tracks in electric territory. NJT found that out when testing switch heaters on the M&E - a fault in the catenary would tend to blow up the controlling electronics (afterall, the running rails are the return circuit!). it took them a while and a bit of research to find a switch heater that didn't blow up when there was a fault...

Air switches have a slight advantage because not only do they throw with more force, they also can be oscillated back at forth without fully locking to eject debris from the point gap. Of course that trick might only be able to be carried out on a US&S Model 14 interlocking machine.

Anyway, let me illustrate this point with a video!

http://www.youtube.com/watch?v=g4-_E6m_gPg

JoshKarpoff wrote:So, I'm not a railroader, but I am an electrical engineer.
I really think the debate of pneumatic versus electric motor operated switch really comes down to how much force does the operating mechanism have.
Pneumatic equipment is subject to all sorts of issues with leaks and is much more prone to environmental variability.

Before I went back for an BEE, I worked on a products pipeline. Pneumatic controls were then widely used in the industry. While they were fine in the nice warm refinery; they were sheer hell in the field. There was no way to keep every drop of water out of the air supply, and when the temp hit freezing, the fit hit the shan. Needless to say, open flames are discouraged when you have 25+ million gallons of gasoline and fuel oils on hand.

I suppose there IS one plus to air-operated switches; you can't burn out a pneumatic ram/motor. The electric ones will cook themselves with a locked shaft.

Air operated switches are a much bigger maintenance issue than electric switches. In cases of air problems occasionally a
locomotive would be dispatched to maintain air pressure in order to operate the interlocked switches. Just because the PRR
had them did not make them the best switch. I think there is too much to go wrong with them and that is probably why
Amtrak is getting rid of them. With all interlocked switches you have to have wires, cables and conduits but with air
operated switches you also need air compressors, pipes and more stuff.
Noel Weaver

I think there is too much to go wrong with them and that is probably why
Amtrak is getting rid of them. With all interlocked switches you have to have wires, cables and conduits but with air
operated switches you also need air compressors, pipes and more stuff.
Noel Weaver

Maintainers have told me that while air powered point machines do require more maintenance, they are easier to fix than electrics. So if an electric point machine dies it usually needs a whole new motor, while an electric just needs something cleaned out. It is also easier to find a fault with an air line than with an electric power cable. Air machines can also tolerate being submerged in water which is why the PATH still uses them.

Air machines (and "strong arm" points) were more popular back in the day because the only alternative way out in the field away from the power grid were low voltage DC electrics, which would take 20 to 30 seconds to throw. The high V machines throw much faster, but require a constant AC hookup. I believe Amtrak powers its electric machines from a hookup (extreme right) to the 25Hz overhead centenary so if the cat power had to be turned off the electric switches will also go dead unless there is some sort of backup power supply. Seems a little dumb putting all one's eggs in one basket like that. The air compressors work (in some fashion) off the 6000v 100Hz signal power, but if power dies one still has air in the tank to set switches to their default positions.

This topic is not specific to Amtrak, so off to General Discussion we go...

I can agree with pluses of air. They stand up very well under fault currents, the supply of which Amtrak has in quantity...

Also, underwater/wet ops are a real plus. If you go though a car wash, you'll see that the whirling brush motors are all pneumatic or hydraulic. Various folks have tried to use electric motors & they always get wet and fail.

That said, air is a major PITA in icing conditions. Does anyone make hydraulic switch motors?

Does anyone make hydraulic switch motors?

The Brits use them. They are called clamp locks and they are slow and prone to braking down. Part of the problem is that they were designed to be inexpensive (and thus not very rugged).