I just purchased a SIHI 25hp liquid ring vacuum pump at auction ($250 for the win!) to improve on our cheap Chinese regenerative blower vacuum pumps for a 5x10 CNC. Ideally, we would like to mount this pump outside in New York state where it gets below freezing. I was unable to find any manuals or info for SIHI pumps and the phone number on their website is oddly disconnected. They seems to still be in business, but even the rep from Qunicy Pumps did not know about them or have any info. Does anyone have a contact that knows SIHI pumps or where we can get some info? It has 15,000 hours, which is a common service interval, but I have seen that most liquid rings pumps last into the 30,000 hour range.
Second question is about the cold weather operation. I do not know whether this is an oil or water fluid pump. Some like Deckker have oil filled liquid ring pumps, but most are water-based systems. Has anyone changed over a water-based pump to another fluid that is freeze-proof for operation in freezing climates? Antifreeze? Change to vacuum pump oil?
Third is the addition of VFD to liquid ring pumps. I have access to an appropriately sized VFD drive for this pump and would like to utilize both soft start and variable speed features. I have seen systems that use a vacuum gauge sensor and allow the pump to vary speed based on a setpoint vacuum level, but can not find any info about setting up such a system and what parts would be best to use for the sensor. I guess I need to actually learn how to program VFD operation beyond the basic setup and parameter settings. Any help would be greatly appreciated.