Generator or Backup Options?

[allsyntax]

I have what could be a quite basic question for you electrical guru's. I have some equipment that is in a rural area. During the storm seasons, intermittent power outages can occur. This causes the equipment to shut down, and must be manually turned back on.

My first thought was to get a generator to provide as a backup. But if I had some form of a battery backup, this may suffice since the outages are brief (a few seconds?). The power requirements are 45.6 amps.

What would guys recommend from your expertise?

 

[sreid]

Use a UPS (Uninteruptable Power Supply).

http://www.apc.com/products/category.cfm?id=13&segmentID=1

 

[allsyntax]

I assume this equipment can't get wet? I'm not sure if it's applicable to field conditions, and may apply more to computer equipment.

Maybe I can set something like this up in some sort of a meter house. Any additional thoughts?

I forgot to mention its 12 HP @ 45.6 amps, which includes surge for starting.

 

[itsmoked]

12HP will be one expensive UPS.

Can you give us details on this equipment?

What's the various equipment consist of?

What exactly does the poor schmuck who has to drive out there do when restarting the system?

Is this motor 3phase?

There could be some alternatives to the brute force method of a UPS.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[allsyntax]

That's the core of my question. What are my options in your levels of electrical expertise? Use a natural gas powered electric generator? Is there a form of battery backup available out there (that would fit this application)?

The equipment is an amine processing plant. There are 4 total electric motors:

1.) 5 HP - powers pump of fluid to amine tower
2.) 5 HP - powers fan (cooling of fluid return from re-boiler)
3.) 1 HP - booster motor pushes clean amine fluid back into surge tank (supply)
4.) 1 HP - powers reflux pump, condensate from steel column to reboiler.

 

[oldfieldguy]

You're pretty well into the area where a natural gas powered backup generator would be a good choice. Auto transfer on utility loss, retransfer on utility restore, and a PLC to do an auto restart after transfer on one direction or the other are also indicated.

Battery backup is going to be pretty expensive in terms of the load, just to get a short time of ride-through, and as you look for longer periods on the backup system, the battery bank size is going to be BIG.


old field guy

 

[allsyntax]

Ok thanks for the info. Your answer leads me to a few questions:

What is a PLC, and typically what size of generator would be required to provide the power requirements? Is there a good website or rule of thumb to go by?

 

[itsmoked]

Thanks for that info.

Here is my point. If you can just pull the plug on your system and it fails/stops "safe" and an hour or a day won't hurt anything then you don't want the hassle of back up at all. You just need a way to restart things.

A generator is a theft target.
Now fuel is a target too.

It needs;
1) A thought out installation
2) regular testing
3) on site fuel storage
4) Permitting (sometimes)
5) it's own battery
6) regular servicing
7) Then you still need a way to restart things as the generator is not going to spring to life in less than a 1/4 second.

I suggest that if your system just needs a bunch of buttons pushed to restart everything than power-on timers set to start things in the normal sequence with appropriate delays would be the logical solution.

If however you need things to start in a certain order AND each thing must be working a certain way before you restart the next item (some do). Then you want to use a Smart Relay(cheap PLC) or a PLC to start things in the sequence desired and to check for conditions of interest before starting the next process.

DEF: PLC = Programmable Logic Controller.
It is a small computer system that is designed for industrial applications. It generally has a wider operating range than a PC and is somewhat hardened, and has industrial mounting, and field connections. They need programming to do what you want. Your application would probably be very easy to program.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[allsyntax]

Hey thanks for the replies.

This is a natural gas compression site. We can utilize the natural gas to power any generators.

The amine facility removes H2S, CO2 and other contaminants from the gas stream. It is important to keep this running. The agressive storm season has brought a touch of inconsistency with the electric. I feel a backup is needed for sure in case electric may go down for X days. It seems to be sensitive to any fluctuations that may occur.

Perhaps a mix between the recommendations. A PLC + natural gas driven generator inside a protected building? A battery solution has seemingly been eliminated due to the power requirements and cost effectiveness.

The equipment is already installed and is inspected everyday. The on site fuel could be the natural gas.

 

[waross]

But if I had some form of a battery backup, this may suffice since the outages are brief (a few seconds?). The power requirements are 45.6 amps.

If the system can survive until someone drives out to restart it, it should be suitable for an auto-restart.
I agree with itsmoked.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[davidbeach]

Any possibility of running a small generator off the turbine that's running the gas compressor? (Assuming that the compressor is driven by a gas fired turbine.) That way could always feed the critical load from the compressor system then you could be immune from utility problems, but could use the utility as a back up source when the compressor is down.

 

[itsmoked]

Barring davidbeach's idea being a good fit, then a gas fired generator, an automatic transfer switch, and a smart relay to run everything sounds like the ticket.

OK Size..

waross; What are the numbers?

The equipment is an amine processing plant. There are 4 total electric motors:

1.) 5 HP - powers pump of fluid to amine tower
2.) 5 HP - powers fan (cooling of fluid return from re-boiler)
3.) 1 HP - booster motor pushes clean amine fluid back into surge tank (supply)
4.) 1 HP - powers reflux pump, condensate from steel column to reboiler.

15~18kW?

You'll want to package up the smart relay and any required transfer switch controls, etc. Into a NEMA 4 enclosure. Etc.etc.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[allsyntax]

Thanks for all of the discussion. Unfortunately connecting to the natural gas compressor would not be an option.

I believe I've got a pretty good starting point now to evaluate the options available. If the thread remains open, I'll try to post back what the final setup turns out to be.

 

[waross]

15~18kW should handle a staggered start. For a simultaneous start you would want about 25 kW. (assuming 0.8 power factor)
I would be wary of possible fast transfers.
The safest and simplest way is to delay the start of the restart cycle for 15 or 20 seconds.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[allsyntax]

I figured we could stagger start each motor with about a 15 or 20 second delay like you mention by using the PLC.

Im researching generators... It looks like some come with transfer switches, but they're manual type. Hopefully a portable size generator will work. I don't know if you can post links, but I found a Guardian 5396 Centurion 17,500 watt electric start portable generator that looks like it may work. Seems to be about as big as the portables get.

 

[ykee]

I'm not sure you want a portable generator -- remember that they can walk away! If the generator is intended for this site, then fix it in place. By the time someone arrives with the portable generator, I suspect your outage will be over.

Any idea how often and how long power outages happen? Also, I was wondering about the comment you made about sensitivity -- do you run into problems with brownouts or voltage sags?

 

[allsyntax]

Yea I was thinking portable in size and would mount it down. This would be installed on site with a PLC and automatic transfer switch. We could probably use the PLC to delay the auto transfer back to primary as well so the generator doesn't just have to run for 5 minutes. Maybe let the backup run for at least an hour before transfering back.

As far as sensitivity, if any lightning strikes occur in the area or anything, the system shut's down. The potential exists for a complete outage for a few hours. It's important for the system to stay running, so I don't want to assume power will just flicker and be back to normal. I want to plan for the worst and hope for the best. If power does go out for several hours, or longer I need to have the proper equipment in place.

 

[ruggedscot]

You could always invest in some automatic motor wound 3 phase breakers - you can then configure the PLC to operate those circuit breakers depending upon the mains status. you would need to use a phase fail relay to monitor the line and have this operate the ACB's. The PLC would then need to run up your equipment in the correct sequence. Functionality would need to include if you had a power outage during the sequence and things like that. Ensure that your run up process would run up what ever happens.

Mains fails - 10 second delay starts swap over proceedure all kits requiring sequencing is dropped. The ACB incomer opens. Signal sent to generator this startsup and makes the generator phase relay happy. This times out and thens end a close signal to the generator incomer. The supply is not live to the board and your kit can go through a start up sequence. Do you need a hold off time so that if the mains came back on within say 5 minutes you would hold to generator or would you like to throw back over right away. Again think out the process for swapping back. Scheduled switch down of plant change over to utility and then sequence back up to normal operations again.

What you are talking about is quite a difficult process to think and apply some logic to - you need to eb 100% sure of your requirements and then make up a schedule of switching required and work from that. Think about how long you want to run on generators if you have switched over - put a delay in to stop say rapid back and forths if you dio have to go to generator - stops rapid drops in supply having your system fluctuate.

 

[oldfieldguy]

allsyntax-

Recently I've been reviewing some replacement packages for backup generators here.

Most of them have control packages that take care of making sure that the generator doesn't "run for 5 minutes". If the generator doesn't have it, then many transfer switches have that feature in their controllers. One or the other will likely also include a periodic start and run of the generator so you can exercise it.

There are amazing capabilities in the new equipment, to the point that I sit here scratching my head wondering if we're getting a bit TOO complex for a simple generator backup scheme.



old field guy

 

[allsyntax]

Thanks again for everyones comments.

I dont have a background with electrical details, so thats why I thought I would talk to you guys for your expertise on the subject.

Ideally, you would want to keep the setup as simple as possible. I did see where some generators have packages w/ transfer switches, but I didn't see any that were automatic.

I think the trick of complexity lies in the kW required for startup. I have 4 different motors, so I believe thats where a PLC may come into place, opposed to just having a backup generator w/ transfer switch.

ruggedscot is right, that this should be well planned out in regards to the timing. ruggedscot: You sort of lost me in your first paragraph.