Tape between enamelled copper wire layers in Flyback SMPS transformer?

[cupoftea]

Hi,
Our 24V input to 24V, 2A 150kHz isolated flyback works fine with the primary wound as two layers
of enamelled copper wire. (PQ20/16 bobbin)
Ns/Np = 15/10

The secondary sandwichs the primary with series windings of 8 turns and 7 turns.(triple insulated wire)

The primary 10 turns are comprised of 2 layers of 5 turns (3 strands of 0.315mm ECW) . We just wind 5 turns across the bobbin,
and then the next 5 gets wound over the top of the previous five turns..its so easy to do it like this -there is no tape between these layers.

I believe that if one layer gets a nick in the enamel then we could be taking a big risk doing this.
I believe that we should really have tape between the layers. Though we have had no problems doing it without tape
for some 2 years.
Do you think we should use tape?

 

[Easy peasy]

you haven't said what level of isolation the user / customer expects or needs

are the windings dipped or varnished after winding ?

 

[cupoftea]

Thanks, yes apologies, its full so called "mains isolation", ie, must perform to the 3500VAC isolation hipot test.
Theres no dipping or varnishing for the windings. This would be too expensive for us.

Though for this question, as you know, isolation is not important to be known, because we are speaking of the primary coil alone here.
_________________________________________________________________________________________ ____
..And..Ditto this question, but this time concerning a high side gate drive transformer for an offline 240vac two tran forward smps (as attached).
The attached shows that the secondary is two layers...we don't bother putting tape between those 2 secondary layers. Should we? What is the risk of getting a nick in the wire? We've managed fine so far, but we wonder if a "rough winder" does the job? Who knows?

 

[cupoftea]

Also, ditto the question in the case of an offline Two Transistor Forward SMPS output inductor. (as attached)
This is two layers and then two turns on top of that. (16 turns total in the one coil)
Should there be tape in between the layers?
(The 2TF has Np/ns = 15/8 and is 120kHz. 24Vout, 130W.)
As you know, this inductor suffers pulsed voltage of some 175V at the switching frequency.

It obviously works without the tape, but is it considered a risk that the wire could be nicked in production?