One of the rollers on the pump is squeaking intermittently, and I want to fix it before it drives everyone in the department insane. However, I can't figure out how to get the casing off. I thought I could just unscrew the large bolt in the center to get to the rollers, but that won't budge. Can't find any videos or documentation on cleaning or maintenance on the pump itself, either. Is there a good way to dismantle it for cleaning or is it possible to just use a bit of lubricant? If so, which?