Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Vacuum pump head vs atmospheric pressure

Status
Not open for further replies.
Boiler1

Boiler1

Mechanical
Joined
Jun 3, 2004
Messages
41
Location
IE
Why would the vacuum pump available head depend on atmospheric pressure - i.e. lower the pressure, lower the pump head. If the pump is discharging at the atmospheric pressure can it not create any vaccum on the suction side? Why doesnt such a thing affect the compressors?
Regards
 
Sort by date Sort by votes
You need to add more to your question here so that we ( I at least) can understand your question.

atmospheric pressure has an impact on lots of things, but I can't work out what your question is.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
Upvote 0 Downvote
You're right! the question is all over the place. Essentially, when the atmospheric pressure drops my system has to start a back up pump in order to maintain the vacuum set point. I assumeed my theoretically feasible vaccum must be somewhere between 0 and the atmospheric pressure. Cant understand is it possible to have a vacuum in the system that is higher than the atmospheric pressure. Say, if the atmospheric pressure is 1bar/750 Torr is it possible to maintain 1500 Torr in the piped vacuum system?
 
Upvote 0 Downvote
This description helps clear up why atmospheric pressure dictates vacuum performance:

Article said:
Vacuum at high altitudes
Atmospheric pressure determines the maximum vacuum force that can be achieved. And standard atmospheric pressure at sea level is 29.92 in.-Hg. But what happens at locations a mile above sea level? The maximum vacuum that can be achieved in locations above sea level will be less than 29.92-in.-Hg. The force will be limited by the ambient atmospheric pressure. Vacuum pumps have maximum vacuum ratings based on sea level conditions and must be re-rated for operation at higher elevations.

First, determine the local atmospheric pressure. A rule of thumb is that for every 1000 ft. of altitude above sea level, atmospheric pressure drops by 1 in.-Hg. Using rounded-off figures, for a city at an elevation of 5,000 ft, the atmospheric pressure is about 25 in.-Hg.

To adjust a pump rating, think of that rating as a percentage of atmospheric pressure at sea level. If a pump is rated for 25 in.-Hg, it can achieve 83.4% (25 29.92) of a sea level perfect vacuum. At a 5000-ft elevation, that same pump can achieve 83.4% of 25 in.-Hg - or a vacuum of 20.85 in.-Hg.
Click to expand...

 
Upvote 0 Downvote
Boiler 1.

I can only assume your system as you refer to it as a vacuum system is less than atmospheric pressure.

Hence it would be less than 750 torr in your example.
So 1500 torr would be 1 barg or 2 bara, i.e. MORE than atmospheric pressure

Your vacuum pressure sensor / measurement is likely to be a differential sensor so it it actually measuring the difference between atmospheric pressure and your system. Hence if the atmospheric pressure goes down then the difference goes down and it triggers the vacuum pump to operate.

I'm still not really understanding your question though... [ponder]



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Hartley Kingon
  • Question Question
Pressure Sewer Pump Station Documentation – Australia
Replies
1
Views
3K
pierreick
pierreick
dogboy74
  • Locked
  • Question Question
Dust/debris in my vacuum pump lines
Replies
14
Views
1K
Artisi
A
vasicmilos
  • Locked
  • Question Question
Vacuum pump oil
Replies
14
Views
2K
vasicmilos
vasicmilos
giuman
  • Question Question
Pump modifications
Replies
5
Views
11K
TugboatEng
TugboatEng
L
  • Question Question
Pump shaft sheared
Replies
2
Views
1K
Doug Hunter
Doug Hunter

Part and Inventory Search

Sponsor

Back
Top