I have a machine I'm going to start on soon that requires vacuum on 4 or 6 small vacuum cups for short periods of time.
Mostly the other machines have a vacuum pump installed to get the required vacuum from. Some machines use an ejector or multiple smaller ejectors right near the cups that come one when vacuum is needed on every cycle.
I'm wondering why I couldn't have a small tank to store some vacuum and a single ejector to draw it down and just use the vacuum from that and only run the ejector when needed.
My goal is that because there is an operator near by I'd rather have the ejector come on less frequently that every time it cycles. These things are noisey and I think the users would have a better experience if it only came on once every 5 or 6 or even 10 cycles. I know how to make it work I just wonder why it's not generally done. in fact it seems the prefered way is to have an ejector on each cup that cycles every time and wondered why that would be. the noise and also the economy doesn't make sense. The only thing I can think of is some safety issue around stored vacuum that I'm not aware of or maybe the tanks have to carry a certification that is hard to get?
The vacuum pump is the best option for this but it's a little overkill for this smallish unit. their advantage in my mind is a constant drone rather than a sudden loud rushing of air. Also those things blow dust and debris around and I can better mitigate that at one point than many these are generally used in dirty areas.
One item you may be overlooking in your proposed tank design maybe a matter of simple economics. Your system will require the costs for the tank system and controls as opposed to the cost of the simple ejector(s) using an existing plant air supply, i.e. often the simplest system is the most reliable and economic both in installation and in maintenance.
Well the small ejectors from Piab are 100 bucks each and I can fit a tank, even a stainless one for 60 to 120 bucks and one bigger $200.00 piab ejector silencer and filter unit . The rest of the system would be the same as far as I can see on my thumbnail. Theres no other reason to not store vacuum in your estimation?
My above response was based on general principles and not on specific knowledge about the application of vacuum cup systems so there may be something specific to those applications that I am not aware of.
On the other hand, I do have experience in pressure and vacuum applications from a safety valve and vessel standpoint and in that respect you should not expect any problems with implosion due to vacuum with any small commercial pressure tank with standard elliptical heads.
Just as a side note of which you are probably already aware with regard to the rest of your system you will need to include a 3-way pressure and vent solenoid valve (which are readily available) between the tank and the suction cups to simultaneously seal off the tank suction and vent air into the cups for the parts release and visa versa for applying vacuum.
Thanks for your reply. are there any requirements for a tank to maintain certifications? around here for compressed air tanks have to be re-inspected every 10 years would this be so for a vacuum vessel too ? or are they just not considered?
On the vacuum cup valves yes I have a nice little festo valve I use for that.
There are no design codes in the US for pressure vessels operating at your very low pressures or vacuum services nor are there any specific testing schedule required on ASME Section VIII code vessels. Operating companies are responsible for setting their own schedules based upon their own specific operating conditions and fluids/gases etc.
As a result, I can only recommend that you consult with the organization that regulates the fabrication and operation of pressure vessels in your specific area about this issue.
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