EHT_Ind discuss

Please be advised that I will be absent from these fora prior Tuesday/early Wednesday (Off-line 'life' again:rolleyes:) -- @Aleph(0) expects to resume participation here no later than early Monday...
Embarrassingly, it seems 'off-line life' has -once again- made 'liars' of us:rolleyes: -- That said, I can imagine no scenario preventing either of us returning to regular participation next week (i.e. that of Mon May 13, 2019).

In the meantime I'm pleased to have found made time for the following post addressing many of your recent questions/comments/suggestions! -- Hope you find it useful:)

Please note -- By way of eliminating duplication, I here advise that this post continues after ALL images!:D

So... With no further ado:


While I've never had much luck getting teflon tape to stay in place other that on a thread, and even that only after the first wrap
The 'Trick', as it were, is in winding the first several turns with a degree of tautness sufficient to achieve firm constrictive tenure to the CPVC all the while avoiding undue distortion of the 'tape'...

there are such things as teflon "O" rings. They would last much longer than the tape
The problem with solid teflon o-rings, is that it's a material with very poor elastic properties. So here's another alternative: teflon-coated buna-n (an excellent elastomer) o-rings.
While O-rings and their ilk would indeed prove more durable -- PTFE film (i.e. 'pipe thread tape') is a better choice - given that:

1) Preclusion of plasma migration demands intervention by a high-strength dielectric fluid or fluid-like 'seal' between 'plug OD' and 'well ID' surfaces... -- Properly wound, 13mm X 77μm PTFE film freely 'flows' under moderate pressure filling microscopic abrasions, 'pores', etc to less than 400pm (pico meters) as well as macroscopic irregularities. --- Please note that the function of the 'tape' is preclusion of air/ion exchange with the outside atmosphere --as opposed to-- plug-to-well isolation...

Note:
The outer turns are rather loosely wound such that said 'plastic fluidity' is greatly enhanced via 'rugae action'...

2) 'Tat' is a non-issue (for the ready, swiftly effected, remediability of same) -- As a point of information, each PTFE film application is 'good for' at least fifty plug insertion/withdrawal cycles - Said transience representing only negligible inconvenience in that common/good practice will generally leave the test leads attached to the instrument while idle...

As a point of interest - our tests have found that --for the purposes under discussion-- 'rugae-wound' PTFE film is markedly superior to 'dielectric grease' and only marginally inferior to ($300 per ounce) 'vapour proofing' compound - both of which being 'messy' gels...

Are you saying that the plasma will travel up through the gap in an unglued pipe to fitting joint? That is hard to believe. There is only about 0.001" difference between the two diameters of that joint
Re: the conditions under discussion -- Ion exchange becomes detectable (sans instrumentation) at channel major-axes > 500pm (picometers) and unacceptable at major axes > 650pm (Note that 0.001" ≈ 25.4 million picometers or ≈ 39 thousand times the maximum acceptable pore-channel major axis [650pm]). ---- To understand this - you need merely entertain the perspective that 'plasma' is as much a process as a 'substance':cool:

How truly: What's optimal from a structural/mechanical standpoint is, not uncommonly, less so from an electrical point of view! -- Especially at EMFs ≥ 40kV...

@shortbus - Re: the PTFE pipe 'unions': -- I believe this is what you have in mind?:) --- Let the reader be warned that Menards (sic) calls them 'couplers' whereas 'their' PVC 'unions' are akin to 'flare nut' assemblies:confused: -- Should your locale be bereft of Menards home centers - You may count such as a blessing sans the merest risk of taking liberties!:rolleyes::D



Note to readers: Inasmuch much as the 'stop-ridge edge' -to- tube rim distance (Ca. 25mm) is more than accommodative of PTFE (fault path extension) rib clamping and spacing purposes - you need merely cut the 'coupler' immediately each side of said 'stop ridge' -- Note, however, that a 'square' cut is essential!

Such may readily be achieved through one of (at least) two methods:

1) Best choice: via a 'clamp and wheel style' pipe cutter having a 'wheel' radius sufficient to fully penetrate the tubing wall sans wheel-hub/tubing-OD apposition...

2) Acceptable method: Via employment of a saw jig (commonly marketed as a 'mitre box').

Note that 'Shear style' tubing cutters are not recommended for their distortion of the tubing and, not uncommon, production of 'out of square' cuts!

Inasmuch as there seems to be some confusion as regards attachment of the 'banana plug socket' to the upper end caps, I offer the following by way of clarification...

The procedure:
1)
Locate center of the end-cap.
2) Drill a central bore of appropriate diameter.
3) Install the banana plug socket.
4) Secure the installation via fixing the bur with 'hot melt adhesive'

Re: 'Step 1' above -- Inasmuch as I have been unable to locate a commercial source for 'circle-center locator jigs' I was compelled to conceive/construct my own (as follows):

Required tools: A 'square' and a 'right-triangle' (note that, quite despite nomenclature, the 'square' is likewise a 'right triangle' sans a (physical) hypotenuse...




Tools assembled such that the 'hypotenuse' of the triangle-tool forms angles of π/4 (aka 45°) with the 'adjacent' and 'opposite' sides of the square. Of course said hypotenuse will define a diametric path over the plane of a circle whose circumferential surface being in apposition with both sides of the square --- Hence, said position being established, (non-coextensive) lines corresponding to the path of said hypotenuse drawn upon the circle (CIP the top of a PVC end-cap) will intersect at center of said circle...



Illustration of an end-cap -- center located as per the above described method. Note also the uninstalled 'banana plug' socket and associated hardware (included for clarity)




Banana plug sockets installed (Top/outside view)


Banana plug sockets installed (Bottom/inside view) -- Note the 'hot melt' adhesive covering the burs --Please rest assured that the function of the small compression springs will be discussed in the course of the construction presentation!:)


Very best regards
HP:)

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