we have been having this problem and was wondering if you find the same thing or even better a solution. After we Mod a hydro and install submersible pump units and rupture valve the noise level in the machine room and car is considerably louder than before the mod. We add isolation couplings and isolate all pipe supports. Keep as much oil in the tank as it will hold. We have tried air up mufflers and older standard mufflers and neither one seem to improve the situation. We have found the Thyssen rupture valve to be quieter than other models. We have taken to getting sound disable readings before and after to insure its not just people getting use to not hearing the elevator run. Also we have added x-tra isolation pads under the tank and under the pipe supports. Different suppliers of pump units don't seem to matter as they all seem to use the same motor pump combination. But maybe someone does a better job of isolating the unit? Anyone have a preferred unit because of this problem?

What we have found is during shipping motor gets moved around an guys were filling with oil before checking feet an pads.

If your pump units are using Imperial submersible motors they had a rash of problems due to a issue in manufacturing that had something to do with lamination on the armature. This would cause not only a good amount of noise but in some cases a great amount of pulsation which transferred over to the ride quality. It threw a lot of people off because the natural reaction was to look at the pump or muffler being that the elevator would still run a contract speed in the up direction.

We recently replaced a TKE submersible motor with a US Submersible motor on one car in a duplex and it was amazing how much quieter the US motor ran compared to the original TKE motor next to it.

Another option is these guys: www.myicdinc.com (silentknight pumping units) I havn't seen one yet but might be just the thing your looking for when it comes to a noise sensitive building.

ABE- Thanks I will check to see what motors we have but the description of pulsation is dead on to our problem. Thanks Again!!!

Added an air up muffler and it did the trick.

Was there anything in common with all the pump units that were affected? Those air mufflers work nice but from my experience they add some more maintenance to the job.

What size pipe? how long are the runs? how many 90's?

Most hydros I see these days run 2" and some long runs with more than a few 90's.

2.5" or 3" oil line for the whole run makes a huge difference in noise. The cheap round hollow Otis tank unit mufflers works pretty good then add the MEI silencer and its as quiet as can be and won't leak down the road.

3 inch line all the way standard number of 90s everything isolated well. I have noticed the pump units with GE motors and Imo pumps are much quieter than the units with Imperial motors and Allwhiler pumps.....I try not to use air up mufflers as they add maintenance where you never needed it before! But in this case it did the trick.