Pressure testing how long and how much psi?

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Okie294life

Brush Popper and Amateur Tree Butcher
. AS Supporting Member.
Joined
Jun 25, 2018
Messages
599
Reaction score
282
Location
Arkansas
I have a mini mite pressure tester have got the saw case sealed up and holding pressure. How long should it hold positive pressure, and how many psi? How long should it hold negative pressure and how many psi?
 
+/- 8 psi on both. I start with vacuum and then pressure. Pressure first can pop a seal out and make a better seal missing a vacuum leak.

While testing, rotate the crank around. The gauge will go up and down in value but should not loose value overall.

Time, a few minutes or so per test checking for no drop. Drops then more time and searching for why.

Edit to add...
If I can't get the hand pump to build up any pressure. I hook a hose to my air compressor tank turned down to 10 psi and spay it down for finding the leak. Good continuous air source. Even put it in a bucket of water at times.
.
 
+/- 8 psi on both. I start with vacuum and then pressure. Pressure first can pop a seal out and make a better seal missing a vacuum leak.

While testing, rotate the crank around. The gauge will go up and down in value but should not loose value overall.

Time, a few minutes or so per test checking for no drop. Drops then more time and searching for why.

Edit to add...
If I can't get the hand pump to build up any pressure. I hook a hose to my air compressor tank turned down to 10 psi and spay it down for finding the leak. Good continuous air source. Even put it in a bucket of water at times.
.
 
+/- 8 psi on both. I start with vacuum and then pressure. Pressure first can pop a seal out and make a better seal missing a vacuum leak.

While testing, rotate the crank around. The gauge will go up and down in value but should not loose value overall.

Time, a few minutes or so per test checking for no drop. Drops then more time and searching for why.

Edit to add...
If I can't get the hand pump to build up any pressure. I hook a hose to my air compressor tank turned down to 10 psi and spay it down for finding the leak. Good continuous air source. Even put it in a bucket of water at times.
.
Agreed! One has to remember that when pulling vacuum, in/hg, you need to double the psi value to get the proper vacuum number. Husky states 5 to 10 psi for pressure checkout. I use 7.5 psi, middle road here. If your vacuum is given in psi, not in/hg, you need to double the psi figure to obtain you vacuum target. In this example you need to pull 15 in/hg for a proper vacuum leak test. I wait 30-seconds on both test, no loss is pass.
 
This question has been on my mind of late--how much of a seal leak will cause destruction of a 2 stroke engine by overheating from a lean mixture?

I calculate that about 10 litres per second of air goes through a 70cc saw running at 10,000 rpm, using simple cylinder volume and volumetric efficiency (which I found surprisingly high at 80%). To lean the mixture 10% would require a liter per second leak--that sounds far beyond 'micro-leak' status, that would be detectable by just blowing (or sucking) into the crankcase and hearing a loud whoosh of air going through the seal.

If holding pressure/vacuum for under 30 seconds is considered a 'fail'--why?
 

Latest posts

Back
Top