Steam humidifier problem??

[remp]

I have a new air handling unit, steam humidifer just commissioned and up and running. The primary side of the humidifier is hot water at about 140degC. There is a problem with the sparge pipes (pipes with holes that deliver the steam into the AHU). They are spitting out condensate as well as steam.
The sparge pipes are sloped back towards the humidifier which is about 3m below the AHU. The slope is not the problem. There is no consensate drain in the installation. It was not reckomended. There is a pressure equelizing line between the humidifier vessel and the AHU chamber. The manufacturer says the condensate should drain back into the humidifier via the supply/sparge pipes and the pressure equelizing line between the AHU humidifier chamber and the humidifier vessel should be sufficient to allow this. The equelising line is about 1/2 coper pipe.
It looks like the steam head is driving the condensate out and not allowing it to travel back to the humidifier.
Any suggestions what I should do??

 

[quark]

Generally humidifiers are fitted with steam traps just before steam entry into the AHU. There is a least resistance path for the condensate via a sparger rather than the equalizing line. Is your equalizing line connected at the inlet of the sparger or at the other end? Are there any holes in the bottom of the sparger?

 

[lilliput1]

Did you check & make sure the holes of the sparge tubes are not pointing down?

Is there a high limit humidistat downstream that would prevent the humidifier from saturating the air in the AHU? The high limit humidistat should be set at 85%RH.

 

[friartuck]

This is a common problem. There is a manufacturer that makes a special annular sparge pipe (pipe in pipe). This arrangement allows the condensate produced in the sparge to be properly drained. I think TA steam traps do them. I will make enquiries.

You might for the time being also try turning the steam flow rate down to reduce the steam injection flow rate.

Also as Lilliput says, have you installed a limiting sensor/controller.

Friar Tuck of Sherwood

 

[remp]

The holes are pointing up and there is a high level sensor set at 75%.
Because the unit is so wide some of the sparge pipes have about 3m of copper pipe in the air stream before the sparge pipe is actually connected. Up to now this was not insulated so I think the air stream was causing the steam to condensate excessively and the normal draining technique of the humidifer was not good enough. We have insulated the pieps, but now the weather is mild and humid so there is no need for humidification. Will keep you posted.

 

[ercanbaser]

Try to shorten the steam pipe length (install the humidifier closer to AHU).

regards,

 

[lilliput1]

It is also recommended to have an airflow switch interlock (to prevent humidifier operation if no air flow) and a temperature switch for steam jacketed units (to prevent operation prior to the jacket steam condensate being at operating temperature)in addition to the high limit humidifier. Steam humidifiers should also have a manual steam shutoff valve. Optionally an automatic two position summer/winter shutoff valve can be provided to make sure humidifier is off and do not heat up the air during summer.

 

[remp]

2222

 

[ChasBean1]

Not commissioned by me, I hope. Not a steam humidifier being supplied by hot water. The unit you describe should be supplied by steam. Condensate should consist of only the steam that condenses in the tube that is impacted by (relatively) cool air temperature. These tubes should be close to atmospheric pressure and should gravity drain. By supplying pressurized hot water into the tube and relying on 100% flashing, you're prohibiting condensate drainage within the piping. There's something amiss here. I think hot water systems can be used, but I think they would be 'wet' systems that would require drainage within the AHU or duct work...