What is a standard 'drip' size in water, and how do you create one?

[Scoob]

We are testing valve for seat leakage, and rather than wait 10 minutes for a reasonable volume to accumulate, we would rather count the drips.
Is there a standard drip forming device?
Or its off to the kitchen sink for testing?

 

[IRstuff]

In high school chem lab, our instructor said that a drop was 1/20th of a milliliter.

TTFN

 

[1969grad]

Why not test with low pressure air like the valve manufacturers do? If you want a really severe test use nitrogen.

Valve manufacturers rate seat tightness by classes. A bubble tight seat is at least a Class IV. Tightess seat is a Class V as I recall. You might want to compare your results to the seat tightness stds.

 

[bbuchanan]

You may find your answer by researching titration. Chemical engineers use this method to determine pH, etc. They allow a chemical to drip into the fluid and wait for a change, typically in color. The number of drips correlates to the pH or whatever. I would assume they use great care in designing the titration equipment so only one drip comes thru at a time. Perhaps Ficher Scientific or Omega may have more information. Good luck.

 

[aberta]

Scoob:
I have inspected some hydrostatic tests with valves and have found that depending on the design, some valves pass more at low pressure and others pass more at increased pressures. Can you confirm this to be so, with your tests. To make a valve tight shut-off, suppliers usually grease the seats and the disc. So we usually request the valve to be de-greased for testing.

 

[briand2]

I picked up this information in a valve manufacturer's data many years ago (don't take it as gospel!). It depicts water dripping from a tap, and it states that "The size of the drop does not indicate the size of the opening".

1 drop per second = 1/12 ounce per minute
2 drops per second = 1/3 ounce per minute
Drops breaking to stream = 2 ounces per minute
1/16" stream = 7.5 ounces per minute
1/8" stream = 23 ounces per minute
3/16" stream = 39 ounces per minute
1/4" stream = 83 ounces per minute

Sorry about the imperial units!!

Hope this helps.

Brian

 

[abbver98]

Try BS 66755 Part 1 : you can do your test in 15 seconds by you have to count the mm3 leak.

 

[ornerynorsk]

I'll concur with IRstuff. A "standard" drop is 1/20 cc. Therefore, 75,600 drops per US gallon.