LP seat rotated, after getting off center orifice indent. Any issue?

[MichaelMc]

I got two 109s to overhaul and noticed that, in both, the indentation set that the orifice made in the LP seat is a fair bit off center. Which I assume is normal. Is this an issue if the seat gets rotated, such as after curiosity driven removal and replacement within the poppet, ? I have replacement seats for the 109s that I plan to use.

The 109 poppet’s rotation is fixed by the lever arm so, as long as you do not remove and replace the seat within the poppet, normally that seat will not rotate much.

I just got a Deep 6 second as well, and its, very nice, poppet seems to create a similar off center indent, but that poppet has no set rotational orientation within the barrel, suggesting it is not an issue? Or that you should not open the Deep 6 barrel unless you plan to replace the seat? Nothing against Deep 6 here.

I'm assuming where the indentation occurred is off center from the poppet axis and not the seat and its center being off center from the poppet axis. But that the orifice edge is on center with the barrel axis, being machined metal. And that the poppet winds up a bit canted in the barrel due to the diaphragm lever pressing on it a bit off center?? Or more simply, why are these indents off center? Maybe as they are LP seats, if the edge crosses an earlier valley in the seat, it still seals fine.

 

[northernone]

Would ignoring the direct question since I don't know the answer while suggesting perhaps you could flip the seat to it's unused side be a helpful post?

I've not had an issue with off center seating indentation yet.

Cameron

 

[MichaelMc]

Would ignoring the direct question since I don't know the answer while suggesting perhaps you could flip the seat to it's unused side be a helpful post?

I already flipped the 109 I rebuilt, though I have not yet pressurized and tuned it. Flipping partially lead to the question. The poppet and seat had looked fine, but I wondered if it had already been flipped, so I took it out and then realized the indent was off center, and started wondering how to put it back with the same rotation as before.

 

[axxel57]

It's quite common that the indention of the LP seat is off the center.
Actually it's hardly ever really clean centered.
The LP seat material is so soft and the IP so relatively low that it don't make really problems.
You might be not able to fine adjust the 2nd very well, but that problem you would have anyway trying this with a used seat.
I it bothers you (that the indention is off centered), you could dismantel the valve and check the spring base for dirt or corrosion, clean it, turn the spring, put it back together, and check if the poppet moves more straight now.
It would be a bigger problem in the 1st stage, because quite probable you would see a long creep in IP......

 

[rsingler]

Concur that off-center indenting is almost the rule for these poppets. It is indeed because of the location of the center of effort of the lever against the poppet.
Not sure I completely agree with @axxel57 though. Yes, some seats are very soft and flexible (e.g., Atomic, CoralSeaScuba aftermarket top hat seats) but others are much firmer. Axxel alluded to the problem ("You may not be able to fine adjust the 2nd very well). For firmer (read: older) seats, the groove will really prevent good sealing at your normal cracking effort. Remember, that groove has formed over many months, and reaches a depth that you'll now have to match where the new off center circle crosses the old circle. That will require a spring tension which equals poor cracking effort.

I just don't reuse the seats, but you can avoid replacing them on a service if the existing cracking effort is okay, as long as you don't remove the seat from the poppet, thus likely changing its position when it goes back in. If you leave it alone in the poppet, you're okay. But if you're servicing to clean out accumulated corrosion, spend the extra $3.50 and replace the seat. Top hat (rivet) seats are a little more, but you can make your own flat seats for pennies with a round punch of the correct diameter and a sheet of EPDM or Viton from McMaster. For Scubapro and Apeks, I use a 9/32" punch and 1/16" sheet EPDM. For Aqualung/US Divers, I use a 9/32" punch and 2 mm sheet.

CSS_Seat

• rsingler
• Dec 13, 2017

 

[Fibonacci]

Great info thanks... what about using 1.5mm and 2.0mm silicone rubber sheet to punch poppets from?
Appears to have some advantages over EPDM and Viton...

20"X20" Silicone Rubber Sheet Plate Mat High Temp Commercial Grade Black Red S11 | eBay

High quality silicone rubber with good performance of anti-aging, ozone resistance, heat-resistant, electric insulation, oil resistance, solvent resistance, corrosion resistant, nonpoisonous and tasteless, pollution-free. Working in air, water, oil and other medium at the temperature of -60°C - +260°C (moment maximum 300°C) with the high stability, reliability and surface inactive without sticky. Apply to punch all kinds of rubber seal gasket or special for PVC vacuum laminating press, wooden door vacuum laminating press, glass vacuum laminating press, solar vacuum laminating press, hot laminating press and card laminating press etc.

Material: 100% virgin silicone rubber
Tensile strength: 12Mpa
Hardness: 60 shore A
Elongation: 300%-350%
Density: 1.20+/-0.05g/cm3
Break Down Voltage: 4.5Kv
Temperature: -60°C-300°C

Not sure if creep under load is an issue with Silicon rubber vs EPDM or Viton, the material is 60 Shore hardness vs 70 for most common Viton rubber sheeting.

 

[rsingler]

Great info thanks... what about using 1.5mm and 2.0mm silicone rubber sheet to punch poppets from?
Appears to have some advantages over EPDM and Viton...

20"X20" Silicone Rubber Sheet Plate Mat High Temp Commercial Grade Black Red S11 | eBay

High quality silicone rubber with good performance of anti-aging, ozone resistance, heat-resistant, electric insulation, oil resistance, solvent resistance, corrosion resistant, nonpoisonous and tasteless, pollution-free. Working in air, water, oil and other medium at the temperature of -60°C - +260°C (moment maximum 300°C) with the high stability, reliability and surface inactive without sticky. Apply to punch all kinds of rubber seal gasket or special for PVC vacuum laminating press, wooden door vacuum laminating press, glass vacuum laminating press, solar vacuum laminating press, hot laminating press and card laminating press etc.

Material: 100% virgin silicone rubber
Tensile strength: 12Mpa
Hardness: 60 shore A
Elongation: 300%-350%
Density: 1.20+/-0.05g/cm3
Break Down Voltage: 4.5Kv
Temperature: -60°C-300°C

Not sure if creep under load is an issue with Silicon rubber vs EPDM or Viton, the material is 60 Shore hardness vs 70 for most common Viton rubber sheeting.

An interesting thought. The lower Shore is probably a good thing. Atomic seats feel like soft silicone, but I don't know what they're really made of. Creep might be an issue with a rivet style, since they usually stand proud of the poppet, but most flat seats are captured by the thin cup of the poppet and should do fine.

Only question I have is with the description under your link. The grammar makes me think it's a Chinese import. A lot will depend upon the smoothness of the faces of the sheet. For those folks that cut poppets from plain old nitrile sheet, they quickly find that Chinese sheets are horribly uneven.

I guess I'll look for same item from McMaster. It's worth a try.

I'm sure someone will weigh in with high FO2 concerns shortly, but for most mixes at intermediate pressure, it just shouldn't be an issue.

 

[rsingler]

Here's 50 shore 1/16" from McMaster
McMaster-Carr
Item #86465K23
$13.76 + shipping for 12" x 12"
That's a few hundred seats, lol!

Can't find 2mm yet

 

[Umuntu]

For Scubapro and Apeks, I use a 9/32" punch and 1/16" sheet EPDM. For Aqualung/US Divers, I use a 9/32" punch and 2 mm sheet.

I'm curious as to why you use different thickness seats for Apeks and Aqualung. They both use the same shuttle valve, and I expect that the top hat seat is the same -- although they do use different part numbers.

Also, do you punch a hole in the centre of your flat seat for balanced seconds ? The top hat seats have a hole in the centre to allow IP pressure to enter the balance chamber.

 

[rsingler]

I'm curious as to why you use different thickness seats for Apeks and Aqualung. They both use the same shuttle valve, and I expect that the top hat seat is the same -- although they do use different part numbers.

Also, do you punch a hole in the centre of your flat seat for balanced seconds ? The top hat seats have a hole in the centre to allow IP pressure to enter the balance chamber.

I just matched what came out when I first started making them. The flat seats from the two were different thicknesses.
As for rivet seats in balanced 2nds, I don't try to substitute a drilled flat seat. The seat centering depends upon the center post unless I were to cement the seat. I try not to stray from the original design too much.

So in short, OEM or aftermarket rivet seats (sure wish VDH sold them by themselves), and flat seats of whatever thickness matches what comes out. Dacor by the way, was a larger diameter than 9/32".