Vacuum Filter Drainage System 2

[DRosero]

I need to design an automatic filter drainage system for an oil/water separator filter installed at the inlet of a vacuum pump.

My suggestion is to use an O/C (open/closed) check valve at the bottom of the filter, connected to a drain bowl with a C/O check valve connected at the bottom of the bowl.

When the first check valve is open, the second is closed; draining fluid from the filter to the bowl.
When the first check valve is closed, the second is open; draining fluid out of the bowl to ground.
At no point is the system open to the atmosphere, maintaining the vacuum.

Are there other or similar setups I could use?

Any suggestions are greatly appreciated...
drosero@rogers.com

 

[25362]

Sorry, I don't get it.

Question: Is the filter-and-bowl setup at a sufficient elevation to provide a liquid leg with a bottom seal to keep air out of the system ?

An affirmative answer would suggest the valves -if at all needed- to be left fully open all along during normal operation.

If negative, think on how would the setup be drained from vacuum to atmosphere without pressure balancing or without a suitable pumping arrangement.

Please revert with your considered comments.

 

[DRosero]

Application:
Designing a vacuum fixture that will be used in CNC aerospace manufacturing.
Problem:
Coolant can get into the vacuum lines during operation.
Solution:
Place a moisture separator before the vacuum pump.
Problem:
A moisture separator filter, located externally at the inlet of the vacuum pump, can fill up during the milling operation.
I need to drain the moisture separator filter without exposing it to the atmosphere.

Example:
If the vacuum pump is running and the moisture separator filter fills up, how can I drain it without losing vacuum pressure?
Most moisture separators have a manual drain, which is good when the vacuum pump is not operating, but opening it during vacuum operation will result in vacuum pressure loss.

Possible Solution:
Attach an Open/Close check valve (A) at the bottom of the moisture separator filter.
A second "drain tank" will be attached to this check valve.
Attached to the bottom of the "drain tank" is another, opposite, Close/Open check valve (B).
The end of second check valve is exposed to atmosphere.
These check valves are not directly located on the vacuum line, but at the bottom of the moisture separator filter.
The moisture separator filter would now have
- an inlet (air/coolant coming in) from fixture
- outlet (air exit) to the vacuum pump
- (gravity) drain, where check valve A, a drain tank, and check valve B, are connected to the bottom of the filter.

How it works:
By sychronizing the two valves, the system can be drained automatically, without exposing the vacuum line to atmosphere.

-when check valve A is open, check valve B is closed, the filter drains to the drain tank
-when check valve A closes, check valve B opens,
the drain tank is drained to atmosphere

In both situations, the system is closed to the atmosphere and the system is allowed to be drained.

Another problem:
How do I approach synchronizing two check valves?

Are there simpler solutions to this problem?

 

[quark]

We tried to do this sort of exercise with two actuated valve arrangement for condensers before vacuum pumps but it never truly worked. The main problem will be that when the pump runs and you start draining(which is an impossible case if you don't have a barometric leg of 10m height) by opening first valve and closing it then opening second valve. Air traps between the two valves and there is no way that you will push that out in second cycle.

Now your auto drain problem will create you more problems with water carryover than you have when it is manual (by the human tendency that automatic systems need not be supervised).

Regards,

 

[DRosero]

Thanks quark,

How did you solve your condenser problem?

 

[quark]

Manually draining when the vacuum pump is off and I assure you that it is the best solution as far as I am concerned.

Regards,

 

[25362]

It appears that I wasn't sufficiently clear. Please consider:
How can you drain your tank to the atmosphere if it is under vacuum ? If, on the other hand, it has been pressurized by venting it to the atmosphere, for example, by the use of a third top valve or by allowing air to enter intermittently through the drain valve, to enable its discharge, then when reconnecting the tank to the filter the system would suck in the air that entered the tank.
If this is allowed by the process in hand, then you need probably two additional valves at the top of the tank as follows:

Valve A to interconnect filter and tank at its lower portion.
Valve B to drain the tank.
Valve C to vent the tank to the atmosphere.
Valve D to renew the vacuum in the tank by connecting it to the vacuum pump at the filter's downstream.

The operations would then be:

1) Valve A and D opened enables draining the filter into the tank.
2) Close A, D and open B and C, to enable draining the tank to the atmosphere.
3) When draining is finished close B, C and reopen A and D.

The timing could be controlled by the liquid level in the tank. At "high" start operation (2), at "low" start operation (3). All valves to be tight shut-off solenoid types.

If no air is allowed to enter the vacuum pump, then you'll need an additional pump to remove the liquid accumulated in the tank on level control. In this case the tank would be in continuous contact with the filter, without the need of the "operational" valves mentioned above.

 

[quark]

25362 is right on. I was just to post the same thing but 25362 already did it. I got this idea when I was thinking about vacuum condensers yesterday night.

Regards,

 

[quark]

BTW, 25362, congratulations on being tip master of the week. The award deserves you.

Regards,

 

[25362]

To quark: thanks; I'm sure yourself, Montemayor, EM and many others are a much appropriate selection.

 

[DRosero]

Thanks quark and 25362,
I appreciate the tips. Hopefully minimal coolant enters the vacuum lines and I will not have to implement the above ideas.
If I do implement them, I will keep you posted.

Thanks again,
DEng

Dennis Rosero
Cyclone Manufacturing Inc.

 

[notnats]

For draining relatively small volumes manually we have used 2 x 25mm ball valves with a short (300mm) vertical length of 25mm pipe between them. When the top valve is open and the bottom closed, liquid drains into the pipe piece. When the top valve is closed and the bottom open, the liquid just falls out. This can be repeated several times if necessary.

To automate this, pneumatic actuators can be fitted to the valves and control the lot to drain on a time basis with a small plc or on/off cycling timer.

Not quite as neat as a passive check valve setup, but it will work.

jeff