Freeflowing second stage diagnosis

[wKkaY]

One of my Hog second stages has always been bubbling slightly since I bought it. I finally bought an IP gauge to diagnose it.

First stage connected to IP gauge only (other ports plugged) - 135 psi, no creep, purging the gauge valve instantly snaps back to 135 psi.

With "good" second stage connected - same as above

With "bad" second stage connected - IP creeps upwards and settles at 140 psi after a few minutes. Sometimes a hiss is heard.. Sometimes the seal is good. I have tried tuning the orifice but the only position that guarantees a seal everytime is noticably harder to breathe and purges weakly with purge fully depressed.

What's the most likely cause of this freeflow?

(Initially I thought it is first stage IP creep, fortunately I tried isolating just the first stage without anything connected and it proved otherwise)

 

[reefrat]

I am afraid this does not make sense and that is probably the reason that you have no other replies.
If the first stage is functioning correctly it should achieve an IP of whatever it is adjusted to almost instantly (usually 135 to 145 psi) and remain constant with only a slight dip when a second stage is being breathed or purged.
Changing the second stage should have no impact on the IP except maybe a second stage valve adjusted to a lower cracking pressure than the IP would begin to freeflow and not allow the set IP to be reached?
I suggest you try your experiment again and see if you get the same results, otherwise just get the "bad' second stage serviced or tuned.

 

[Jack Hammer]

One of my Hog second stages has always been bubbling slightly since I bought it. I finally bought an IP gauge to diagnose it.

First stage connected to IP gauge only (other ports plugged) - 135 psi, no creep, purging the gauge valve instantly snaps back to 135 psi.

With "good" second stage connected - same as above

With "bad" second stage connected - IP creeps upwards and settles at 140 psi after a few minutes. Sometimes a hiss is heard.. Sometimes the seal is good. I have tried tuning the orifice but the only position that guarantees a seal everytime is noticably harder to breathe and purges weakly with purge fully depressed.

What's the most likely cause of this freeflow?

(Initially I thought it is first stage IP creep, fortunately I tried isolating just the first stage without anything connected and it proved otherwise)

D3? Mine did something similar and HOG swapped out 1st stage under warranty. I was told at local shop they had a bad run and to check the serial numbers, mine was in the range. Zero issues with new 1st stage they sent me.

Sent via

 

[Blue Quaker]

Check to see if the lever is bent, or damaged.

 

[wKkaY]

I am afraid this does not make sense and that is probably the reason that you have no other replies.

Yeah the results wasn't "textbook standard" so I had no idea how to proceed either

---------- Post added November 9th, 2014 at 12:14 PM ----------

D3? Mine did something similar and HOG swapped out 1st stage under warranty. I was told at local shop they had a bad run and to check the serial numbers, mine was in the range. Zero issues with new 1st stage they sent me.

It's the D1

---------- Post added November 9th, 2014 at 12:15 PM ----------

Check to see if the lever is bent, or damaged.

Thanks, I will check this out.

---------- Post added November 9th, 2014 at 01:38 PM ----------

Check to see if the lever is bent, or damaged.

My two second stages are identical so I compared them.

The "good" one has a lever whose tips are slightly higher than the case (~1mm), and slightly lopsided (~1 degree?). The lever depresses smoothly when I press against the diaphragm (cover off).

The "bad" one has a lever whose tips are exactly where the case is and more or less flat. The lever depresses with subjectively more resistance and a "rough" feeling.

 

[LeadTurn_SD]

I am afraid this does not make sense and that is probably the reason that you have no other replies.
If the first stage is functioning correctly it should achieve an IP of whatever it is adjusted to almost instantly (usually 135 to 145 psi) and remain constant with only a slight dip when a second stage is being breathed or purged.
Changing the second stage should have no impact on the IP except maybe a second stage valve adjusted to a lower cracking pressure than the IP would begin to freeflow and not allow the set IP to be reached?
I suggest you try your experiment again and see if you get the same results, otherwise just get the "bad' second stage serviced or tuned.

1+.

The behavior I'd expect would be what I highlighted in red.

I didn't respond when I saw this post yesterday because, like reefrat, I was puzzled and hoped some of the "usual suspects" (read more experienced than I am) would jump in with an answer.

A "creeping" IP will generally cause a correctly-tuned 2nd to freeflow slightly once it reaches a high enough level; how high the IP needs to creep depends on the 2nd stage design and level of tune... I would not expect a balanced 2nd stage to freeflow if the IP only crept up as little as the OP's unless it was tuned right to the ragged edge...

A 2nd stage that is already freeflowing due to being tuned "too hot" or due to another cause (worn seat) should lower the IP slightly, depending on how badly it is freeflowing.

I'm with reefrat: Recheck the IP before moving on. If the 1st is really creeping fix that first, then once you have a stable IP, check the 2nd stages. It does sound like you probably need to tune the offending 2nd stage, possibly a "service" to replace the seat and inspect the other bits (like the orifice knife edge).

The fact that the lever on the "bad" one has a "rough" feeling when depressed (compared to the "good" one) would probably inspire me to take the 2nd apart completely and figure out why. Generally the movement should be smooth. I'd look closely at the "feet" on the lever that engage the poppet (look for rough edges, one side bent differently than the other), the inside of the air barrel (look for dirt or corrosion), inspect the spring and poppet, and finally just make sure the overall "assembly" is correct (feet of lever properly engaging the poppet, the air barrel is not slightly rotated and thus the lever is "level", not rotated slightly to one side).

Best wishes.

 

[Centrals]

I am intrigued to know why the IP of a properly tuned 1st stage will creep higher when it is attached to a 'faulty' 2nd stage.

 

[halocline]

I am intrigued to know why the IP of a properly tuned 1st stage will creep higher when it is attached to a 'faulty' 2nd stage.

It doesn't, something is wrong here.

 

[wKkaY]

Thanks, I'll find time to test this again, I'll be back after a few weeks