Fonar used to use Dunham Bush ACDS chillers, but when they started shipping them from Malaysia they kind of backed off of that. From what I know the last couple of years they have been buying 30 ton chillers from Trane, and having the pump system put together in the field.
The company I used to work for sold them 4 or 5 10 tons in 2000 (I think, maybe '99). We then sold them a 25 ton through KMA sales (a former DB rep). I actually went to the factory with the rep before the sale. They said it didn't keep up because it didn't work, we sent out a chiller guy, I think Chiller services it was called, and twice it was checked out OK. They never paid for the unit and sent it back aftet 6-8 months. No big deal, it happens. From then they were using Trane.
As far as I know, Fonar is the only MR outfit who buys an HVAC style chiller and has the pumps and all field built. But I haven't been in contact with them for a couple of years, so things could be much different now.
Generally you are cooling two things, a cryo compressor, and a bank of heat excahngers. The cryo compressor is kind of like a condensing unit, but for cryogenic helium. The liquid helium is what cools the actual magnet. The chilled water is kind of like condenser water (assuming you have a water cooled cryo compressor) for the cryo system. In fact on the Sumitomo compressors (used on GE and some Philips systems) it actually uses a coaxial hxr.
The heat exchangers use the chilled water to cool a loop of deionized water that cools the all of the electronics.
Don't know why I am wasting your time with this, the guys at your place can tell you all of this.
The thing about an MRI is that it means the chiller is at part load, sometimes 10-20% most of the time. It kind of depends on where it is and how it is used. In a smaller hospital, it probably is in standby more. If it is in an imaging center, that thing needs to run around the clock to make money, so it is usually cranking all the time. Since Fonar specializes in the Open MRI I would guess that most of them are in Imaging Centers. The chiller should have some way to unload, with either multiple stages or HGBP. HGBP is kind of ineffiecient if it running on standby most of the time. A large glycol reservoir kind of helps keep things stable.
Some one mentioned city water backup. At the bare minimum, you should have some way of putting city water through the cryo compressor. You can have it manual or some kind of automatic system. Filtrine, Arctichill, Liebert, and Schreiber all makes packaged boxes with everything inside so you can just hang it on the wall. If you lose water to the cryo compressor, it shuts off and then you boil off helium and then the Doctor goes nucking futs.
The hardest thing for a chiller manufacturer to deal with is that the MRI crew wants to spec one chiller that is sutiable in 100% of all sites. The chiller to sit in the direct sun in Vegas, must be the same chiller that will work in Pt. Barrow Alaska in January. This usually leads to problems. A base model should be specified to the chiller mfg, and then features specific to the site added.
Matchups-
Filtrine-IN the spec for Hitachi. Few others get in there. They are also speced for Varian (Linear Accelerator). They are not bad chillers, but super overpriced, for a machine that is just built out of Copeland condensing unit.
Arctichill- I don't think they have an OEM deal with anybody, but they get a lot of medical chillers out there. Make a nice chiller.They have a pretty nice switchover box.
Liebert- Used to have an OEM deal with Picker, who became Marconi and then bought by Philips. Unit cost too much and wasn't anything super special. Not a bad machine though.
Krause- Almost every Siemens sysem uses their 15 ton or their 25 ton. THe unit is super expensive. Like 50 or 60k. If Schreiber and arctichill get in there every once in a while.
Schreiber- They have an OEM deal with Philips, every Philips MR gets a Schreiber 10 ton. They used to supply a 4 ton for almost every CT, but the new CT doesn't need a chiller. THey also build a ton of 3 tons for GE.
Ellis and Watts- They build a pile of chillers for GE in an OEM situation. But a lot of others get chillers for GE machines because they give the siting people a lot of flexibility.
Doctors are the most demanding SOB's in the world. But if you come from market reefer then this won't be too bad of a transition.
Probably too much info, but this movie I am watching is pretty boring. Hope it helps.
Good Luck!
Clyde
[Edited by clydemule on 11-15-2004 at 11:54 PM]
