Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


how full is the expansion tank?

how full is the expansion tank?

how full is the expansion tank?

We have a hydraulic skid with an expansion tank with a bladder inside.  It is plumbed into the piping near the pump inlet. The assembled system is carefully conditioned and bled.  The topside of the bladder get charged to a few psi with Nitrogen.  Thoughtful folks would like to be able to Confirm how full the system is from time to time.

Is there an inexpensive method of checking the approximate fluid level, or at least confirming it is above some minimum level? An electronic signal output would be nice for monitoring, but even a visual method would be better than nothing.

I've been thinking about a sight glass toward the bottom of the exp tank, but don't know if bladder diaphragms can survive rolling across a potentially sharp edged hole, plus the skid is already made. Maybe a level sensor in the plumbing near the bottom of the exp tank.


Dan Timberlake

RE: how full is the expansion tank?

How about a pressure transducer in the Gas section?

Bud Trinkel CFPE
fluidpower1 @ hotmail.com

RE: how full is the expansion tank?

Is there anywhere in the tank you could drill holes for a common tank wall sight gauge and thermometer?

Alternately, if any ports at bottom and top you could connect small hoses and run them off to a sight gauge mounted remotely. One hose to bottom of gauge, one to top for venting back to top of tank.

Or, Small nylon tubing that you could connect to top and bottom of tank, use that as a sight gauge.

Most sight gauges can easily take 5 psi.

We usually use the square bladders in tank as breathers, don't pressureize, but keeps atmospheric air from going in and out. Made in England, don't recall the name.

If anyone has more common US sources I'd appreciate names.


RE: how full is the expansion tank?

I am wondering that there is a method to calculate by a pressure gauge in the suction of the pump.(usually is fitted)
Considering that a precise gauge can give u the level.
1 ATM = 10330 mmH2O
So if u can find the specific gravity of the fluid i think you can achieve your scope....

RE: how full is the expansion tank?

If you know the volume of the tank you're charging with the nitrogen, and the pressure it was charged at, then the change in volume is inversely proportional to the change in pressure by the ideal gas law which is most likely sufficient at the temperature and pressure range you're working with.  The decrease in volume of the nitrogen is equal to the increase in bladder volume.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


White Paper - Effects of AIA Quick Guide to UL 489 or UL 1077
The function of a circuit breaker is to provide overload (thermal) and short-circuit (magnetic) protection to a circuit and its downstream components. A circuit breaker functions like an airbag in a car, protecting circuit components and people by tripping the circuit to interrupt the current flow if it detects a fault condition in the control system. Download Now
White Paper - Guide to Integrate Large-Format Additive
As with any new technology, getting into large-format 3D printing begins with investigation. The first question may be a simple one: what does “large-format” mean? For 3D printers, “large” is a relative term. Many extrusion-based (FFF) 3D printers are referred to as desktop machines, because they fit on table space. Some of these have very respectable build volumes – but when it comes to “large-format,” the machines will need their own dedicated floor space. Large-format 3D printers have significant build volumes and are most often found in professional settings, like manufacturing facilities and R&D centers. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close