Blown Film Cooler

[cyrusr]

Hello All,
At our plant we use blown film coolers to provide cooling air to our blown film process. The problem that we are experiencing is that we are not able to collect all of the condensate through the condensate drains fast enough and we have "water spots" on some of our product as condensate is passed through the line.

Our current P trap design ties the two drain lines together and then has a 52" leg before tying into the drain line.

The inlet air to the system is supplied at 1250cfm and the chilling water is supplied at 55deg. Any ideas on how to remove this condensate from the system?

 

[rogzog]

cyrusr,

A few things to check would be:

Is the pipe size on the trap and drain large enough since you tied two drains together?

Is the trap deep enough for the static pressure of the unit?

Is the trap vented correctly?

rogzog

 

[MikeHalloran]

OR, consider scavenging the condensate with a centrifugal pump or a small liquid ring vacuum pump.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[HVAC68]

What's the velocity of air ? If it's higher, then there may be a moisture carry over. Try introducing a drift eliminator.

HVAC68

 

[cyrusr]

All,
Thank you for your input. I feel confident about the pipe size, and the I used the static pressure of the fan to size the P trap leg.

I will study the problem more, but I think that the condensate that goes into the two drain lines is able to flow out of the system adeqautely, it's just that not all of the condensate is making it to the bottom of the unit to be drained.

Rogzog: What vent are you referring to? I have 8 of these units draining to a larger common pipe that is sealed at one end and opened/vented at the discharge into the bulding drain. Does this line need to be ventilated? I thought that the P trap is to provide a back pressure to the drain line and prevent air from blowing through the line.

-Cyrus

 

[sterl]

Suspect that your air stream is "focused" in some fashion, if the Simple Velocity calc at the condensing face yields something less than 500 fpm....

Eliminators may certainly help...so may some well located deflectors or sheeting.

Can the air stream pass the bottom of the coil unimpeded?

 

[rogzog]

cyrusr,

What I refer to about the vent is at the P trap after the trap, on the drain side, the pipe should be vented a short distance above the condensate drain inlet to the "P".

I have encountered on several ocasions a situation where the plumbing contractor either vented the trap on the wrong side or didn't vent it at all.

If the vent is on the upstream side of the "P" and if the drain is under negative static pressure, the condensate pan can't drain because of the airflow entering through the drain. Also if it is not vented after the "P" it may become air locked and not drain properly.

If you are just getting a small amount of moisture through the sysyem, them it is probably carry over off of the coils from high air velocity over the coil. As others have sugested, mist eliminators might help.

rogzog

 

[cyrusr]

All,
Thanks again for your help. I am having the P traps reinstalled to the correct length and I think I will add the vents after the trap as suggested by Rogzog. I'll let you know how it turns out.

-Cyrus