Does anyone have any experiance with a Van Air Dryer, that has 3 recip. compressors on it?
Theese are mounted on isolators. The problem is the discharge pipe has broken twice now, evacuating the whole system at a tune of $13k each Time.
There is a p______g match going on right now between hourly who want to anchor it down solid, and the Reliability Eng. who wants to make the springs work. Long story I don't have time for right now, but I need to know where I can find a standard (API 618??) for this type compressor mounted on isolators.

Dave

If the pipe has a local natural frequency (vibration mode), then neither the base isolators nor a hard base mounting may be the solution. Structural vibration testing is needed to identify the cause of the problem. P____g into the wind only gets you wet!

Walt

Turns out both springs and tie down all show harmonics, with the 1X being affected the most by making it solid (it was less when anchored solid). The 2X and 4X however (these are three head compressors with two pistons in each head) are the biggest peaks.
The pipes themselves are not anchored in any shape or form. There is a piece of flex in both the inlet and discharge, but it will "buzz" your hand when you touch it.
IPS on the piping in vertical direction was 1.53
I believe pulsation may be resonating the piping.
I'm going to have to spend more time I suppose in that hole.

Dave

I'm not sure about vib standards but I was called out to investigate vibration on some chillers/compressors with high vibration.
vibration isolators were fitted under the chiller/compressor this reduced the vibration on there but to reduce the pipe vibration flexible joints had to be installed.
Maybe you can use a flexible joint on the discharge end
Only trying to help so If I'm taking rubbish don't be too harsh


Mike.

recip.doc (1,930 Kb, 12 downloads)

Mike,

Your 1st photo shows two compressors linked by rigid coppy tubing. The 2nd and 3rd photos shows a flexible tube section, but no indication of tube supports. It looks like the vendor has no clue as to how to control vibrations.

Walt

Dave,

I just looked at some IR air dryers and apparently it says in Step 1 in the manual that you MUST overtighten the mount and destroy the rubber bushing.

I would think that piping vibe standards would be the biggest concern but some people take some convincing. I'll bet if you and the Reliability Engineer stick to your guns and bring the installation up to recommendations it will work fine. Until somebody breaks it

Danny,

Who would be the bigger fool, the person who wrote the manual or the person who did what it says? Perhaps the rubber element was intended for shipping only!!

Walt

We have had a heck of a time finding any one who knows much about this unit, or about the Bitzer compressors.
However, I got a call this morning from the RE at the plant. He found the people who installed this unit back in 2003. They were angry that Van Air hadn't gave us their name, since they work with Van Air all the time. The folks are out of Charleston, WV and are sending a field service man up Monday. I'm going to learn something about air dryers. Of course, the first thing they told the RE was "you know you have the only one of a kind there don't you".
Seems that when air dryers get this big, they don't use refrigerant in them. He also said there are some valves in the compressors that may not be working right, as Bitzer has some problems with them, and have changed suppliers, 3 years ago! It will be interesting.

Edit: I almost forgot, Danny, When they cut the angle and put it under the feet, and then tightened down the bolts to secure the angle, they mashed the rubber washer under the nut way out. I could see one of them ripped. I don't think he has spares

Dave

No way!