Water content of a wetted pipe

[invent11]

In order to select a dryer to dry internal parts of piping & equipment after draining them from water, i need to come up w/ amount of water remained on wetted surfaces. Can anyone guide me to a table or formula to look into or calculate this amount. For piping a table that provides amount of water for unit lenght of a pipe for various nominal pipe sizes would be very helpful. Thanks for your assistance.

 

[racookpe1978]

What temperature, pressure, and humidity is ambient?
Air right? Not heated nitrogen or argon or something else?
How long will the pipe "stand" with air flow in the pipe (at the above conditions) to "dry" the interior, if any time at all, before you need it "dry" for your process?
Gravity drain: vertical pipe or horizontal or sloped? If sloped, at what angle from the horizontal?
Are you going to pass a desiccant over the pipe walls? A wiper or pig or rag?
How clean are the pipes that you want to dry? Is the water "standing up" from surface tension on a clean smooth surface, or it is covering the wall because the wall is dirty or oily or covered in scale and mill debris?
"Normal" pipe, or does it have a covering like chrome or plastic or fiberglass?

 

[invent11]

Thanks Racook here are answer to your Qs:
What temperature, pressure, and humidity is ambient? It is indoor air, temp in range of 72-104degF, atm ; RH in range 40-80% not sure the exact condition at the time we go for it , you may consider the worse case
Air right? Not heated nitrogen or argon or something else? Air
How long will the pipe "stand" with air flow in the pipe (at the above conditions) to "dry" the interior, if any time at all, before you need it "dry" for your process? 5 days,before we blow air into piping to preserve it for long plant overhaul.
Gravity drain: vertical pipe or horizontal or sloped? If sloped, at what angle from the horizontal? piping is combination of them. Consider 1% sloped pipe
Are you going to pass a desiccant over the pipe walls? A wiper or pig or rag? NO
How clean are the pipes that you want to dry? Is the water "standing up" from surface tension on a clean smooth surface, or it is covering the wall because the wall is dirty or oily or covered in scale and mill debris? Standing up from surface tension
"Normal" pipe, or does it have a covering like chrome or plastic or fiberglass? Normal

 

[LittleInch]

Whenever I've done this in the past, you need to estimate an average water film thickness. If you think paint is 50-70 microns, that gives you some idea. Do for a couple of thicknesses in an excel sheet per line size per metre and it will give you an order of magnitude water volume.

Then it is a determination of what you mean by "dry". You need to actually figure out what humiditiy level or dew point you are looking at. The lower you go the harder it is and the longer it takes....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[invent11]

Thanks LittleInch, I thought for water film thickness to go for 1 mm that is a droplet dia. I would like to know after the piping dry up, would 2 air change per hour in piping would be enough to keep the humidity in the range of 30-40%. What is governing formula that i can use to determine the # of required air change?

 

[LittleInch]

Once you've dried it to you desired "dryness" just close it up or fill it with Nitrogen - normally very dry. There's no point in trying to introduce normal air which has a higher humidity. If you just close it off where's the water going to come from?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[invent11]

Due to other considerations we cannot use N2;so in this case how many air changes are needed?

 

[racookpe1978]

Test it. Measure the humidity through an equal area pipe at different air flows.

 

[invent11]

racookpe: Do not know how i can perform test w/o a dryer. I need to come up w/ a specification to place order for a dryer in that i guess i have to include the capacity=flow rate of dryer.

 

[racookpe1978]

That's right. And you have just discovered the "why" of proprietary licenses and "company secrets" that DID cost a lot of money and "test and failures" to gain by your predecessors.

Experience is an expensive teacher. Measurements (experimental physics) are not easy; much, much more difficult that google-searched "what is the formula?" simplified theoretical formulas using assumed constants and simplified linear relationships.