Topics

Hygroscopic, deliquescent and acquiescence

Gareth G4SDW (ne G8DXY) GQRP #3339
 

The discussion on water entry into enclosures reminds me of a treasure
hunt that I organised for local children some years ago; 100 bright shiny
new £1 coins to resemble gold (It'd have to be 1000 if I repeated the
exercise today!) buried in an old ceramic pot.

To prevent damp from the soil getting in, I put the pot in a plastic bag
and then wrapped the whole caboodle in an oilskin cloth.

Perhaps an oilskin raincoat around external aerial assemblies is the answer on the
basis that water and oil don't mix?

I should like to pay tribute to the wealth of knowledge about materials science
that has been displayed by Spike; someone with whom I had previously
crossed swords in another forum.

John Fell
 

WAXOIL  is a good means of adding protection to external items , such as rotator bolts , elevation jacks and winches .It will slowly dissipate but an annual overhaul should keep things rust free .A carrier bag over winches will stop the elements removing the Waxoil - original spec versions will last approx 3 months before UV degrades them but even at £0.05 each are well worth the effort .

I was going to say Calcium Plumbate grease is also excellent on galvanised bolts etc but a trawl through the "searches" seems to indicate it has long gone .

73
John
GW0API

On Thu, 12 Sep 2019 at 09:28, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
The discussion on water entry into enclosures reminds me of a treasure
hunt that I organised for local children some years ago; 100 bright shiny
new £1 coins to resemble gold (It'd have to be 1000 if I repeated the
exercise today!) buried in an old ceramic pot.

To prevent damp from the soil getting in, I put the pot in a plastic bag
and then wrapped the whole caboodle in an oilskin cloth.

Perhaps an oilskin raincoat around external aerial assemblies is the answer on the
basis that water and oil don't mix?

I should like to pay tribute to the wealth of knowledge about materials science
that has been displayed by Spike; someone with whom I had previously
crossed swords in another forum.








Neil Smith G4DBN
 

Spike's notes were certainly an excellent summary. Perhaps there is a Scatterpoint article in the making there Spike.

I just had a peek in my 10GHz masthead kit, which is in a steel enclosure with a porthole heatsink through one wall, so a very good (bad?) cold bridge to the outside.  It was flushed with Argon the last time it was opened in Sept 2018.  It also contains about 25g of baked silica gel in a bag, and uses a semipermeable breather.  Part of the system is powered on all the time, and it has an OCXO which runs at 40C. No sign of surface rust on the tinplate boxes, and no sign of any water drips on the cold aluminium surfaces. It is very similar to the one I have on 5.7GHz:

http://www.g4dbn.uk/?p=917

A Barbour jacket for it might be overkill, but it would be a super talking point for the neighbours.

Neil G4DBN

Steve Elliston
 

DENSO tape is excellent (but claggy) to use for long-term exposed hardware/joints.
It comes in various (sticky) widths and can be found online and usually,  in plumbing shops. If it's a cable-joint wrap it first with self-amalg. I use it to protect hard-line coax joints and shackles and-things-which-must-occasionally-be-unscrewed on salt-laden  north Devon cliff tops. Good for burying too. 
73
Steve
G3XKR

Spike
 

Neil Smith G4DBN wrote:


Spike's notes were certainly an excellent summary. Perhaps there is a
Scatterpoint article in the making there Spike.

Not heard of Scatterpoint...


I just had a peek in my 10GHz masthead kit, which is in a steel
enclosure with a porthole heatsink through one wall, so a very good
(bad?) cold bridge to the outside.  It was flushed with Argon the last
time it was opened in Sept 2018.  It also contains about 25g of baked
silica gel in a bag, and uses a semipermeable breather.  Part of the
system is powered on all the time, and it has an OCXO which runs at 40C.
No sign of surface rust on the tinplate boxes, and no sign of any water
drips on the cold aluminium surfaces. It is very similar to the one I
have on 5.7GHz:

http://www.g4dbn.uk/?p=917

Nice pics.

Note that the 'cold bridge to the outside' is also a 'warm bridge into
the box', helping to keep the temperature up and the dreaded dew-point
at bay, along with the powered components in there.

The silica gel is clearly doing its stuff, but note that as the RH
falls, it becomes less able to adsorb water-vapour. One way of dealing
with this if the space is available is to use three or for times as much
(100g in your case), but given the state of the internals after a year
that might be gilding the lily. A more effective adsorbent at low RH is
an engineered product called 'molecular sieve', the stuff used to dry
gasses etc, - it isn't available on Amazon but there does seem to be
specialist suppliers out there - but I suspect this is overkill in your
case (pardon the pun).

If you were interested in the performance of the silica gel, you could
always oven-bake it to dry it out, let it cool, and weigh it on a
kitchen scale to say 1g. Reweigh it after a year in the box, and see the
amount of water-vapour it has had to deal with, hopefully not very much
at all.

--
73

Spike

Neil Smith G4DBN
 

Scatterpoint is the journal of the UK Microwave Group. http://microwavers.org.

I guess the majority of masthead amateur radio electronic installations of any size are for microwave operators.

http://www.scatterpoint.org points to the archive

Neil G4DBN

On 13/09/2019 09:29, Spike wrote:
Not heard of Scatterpoint...

 

On 13 September 2019 at 04:29 Spike <Aero.Spike@...> wrote:
that might be gilding the lily.
I assume you meant "To gild refined gold, to paint the lily".

Peter Chadwick
 

------ Original Message ------
From: "Nigel Gunn, G8IFF/W8IFF" <@W8IFF>
To: RSGB-Workshop@groups.io; "Spike" <Aero.Spike@...>
Sent: Friday, 13 Sep, 19 At 15:07
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

On 13 September 2019 at 04:29 Spike <Aero.Spike@...> wrote:
that might be gilding the lily.
I assume you meant "To gild refined gold, to paint the lily".

Andy G4JNT
 

C'mon.
Let's stop these meaningless one liners

Andy    G4JNT
Group Owner



Virus-free. www.avg.com


On Fri, 13 Sep 2019 at 16:31, Peter Chadwick via Groups.Io <g8on=btinternet.com@groups.io> wrote:


------ Original Message ------
From: "Nigel Gunn, G8IFF/W8IFF" <nigel@...>
To: RSGB-Workshop@groups.io; "Spike" <Aero.Spike@...>
Sent: Friday, 13 Sep, 19 At 15:07
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

> On 13 September 2019 at 04:29 Spike <Aero.Spike@...> wrote:

> that might be gilding the lily.

I assume you meant "To gild refined gold, to paint the lily".






Richard Harris
 

Spike mentioned that molecular sieves are much better than silica gel for absorbing moisture. In the UK molecular sieves are available from Brownell Ltd:

https://brownell.co.uk/products/desiccant-bags/molecular-sieve-bags.html

although I don't know whether the company will deal with a private individual. For a project a few years ago, I used molecular sieves for removing moisture and as I recall, a -40C dew point was possible within 30 minutes of sealing the housing.

Richard G3OTK

Neil Smith G4DBN
 

Good spot Richard.  Type 4A bead dessicant zeolite is easily available from ebay suppliers, a 250g pack is about £14 and it gets cheaper in larger amounts. ALso bagged versions are available form catering suppliers. See ebay 143180205745 as a starter for ten.

Does it need high temps for drying it after a useage cycle?

Neil G4DBN

On 14/09/2019 10:01, Richard Harris via Groups.Io wrote:
Spike mentioned that molecular sieves are much better than silica gel for absorbing moisture. In the UK molecular sieves are available from Brownell Ltd:

https://brownell.co.uk/products/desiccant-bags/molecular-sieve-bags.html

although I don't know whether the company will deal with a private individual. For a project a few years ago, I used molecular sieves for removing moisture and as I recall, a -40C dew point was possible within 30 minutes of sealing the housing.

Richard G3OTK


Neil Smith G4DBN
 

Answered my own question after <cough> reading the instructions </cough>, it needs baking at > 122C to drive off the absorbed moisture.  I just bought 2kg of 3A (should that be 3 Angstrom?) bead zeolite molecular sieve for £12 including delivery.  As Spike and Richard have said, it will be much more effective than collecting bags of silica gel and baking them. I'm looking at whether I can make a screw-on canister with a mesh lid to keep condensation at bay in my POTY radome and 5.7GHz feedhorn. I've made up a canister arrangement for the masthead boxes with a tube from the semi-permeable breather, so any air in or out has to go through the zeolite. It will be interesting to see how this arrangement works, given the (so-far) excellent results with silica gel.
https://www.ebay.co.uk/itm/Premium-Grade-3A-Molecular-Sieve-Desiccant-Camera-Silica-Gel-Moisture-damp-watch/362072324608
Neil G4DBN

Richard Harris
 

Neil,

I'm not sure whether molecular sieves can be reused by drying out at a high temperature. During my experiments I just binned used ones and got a few more from Stores.

I was very interested in what Spike had to say about water permeating through plastics, which was the reason for my experiments. At the time (about 10 years ago) I was unable to find any references to moisture permeating through plastics.

Richard G3OTK

John Fell
 

Have only encountered molecular sieves in conjunction with mass spectrometers , but I suspect you are right to ditch used items if cost is low .

Most common household injection mouldable plastics are bulked out with short strand glass fibre or talcum powder sorts of thing .
Moisture permeation occurs as a result of the failure of the bonds between the polymer and the filler .
Look at the surface of Nylon 66 that has been exposed to UV radiation and you will see the exposed glass ends . 
Good idea to overwrap your nice black shiny IP68 cable glands .....which are usually moulded in Nylon .
Talking of colour in plastics reminds me to point out that the natural colours are not too marketable , so a colour "masterbatch" pigment is often added and , you guess it , that too will degrade the moisture resistance .

PTFE based materials are good at long term , low permeability , but tend to be expensive .
Polycarbonate moulded boxes have a reasonable life capability when on the mast - I always over seal the O ring gasketed lid joint - just in case - tape is resonably cheap .
One mouldable material that I have tested and found to be very  good at blocking moisture uptake is Polyphenylene DiSulfide - even with glass filler it works well , but avoid direct UV exposure .

73
John
GW0API

On Sat, 14 Sep 2019 at 18:01, Richard Harris via Groups.Io <g3otk=yahoo.com@groups.io> wrote:
Neil,

I'm not sure whether molecular sieves can be reused by drying out at a high temperature.  During my experiments I just binned used ones and got a few more from Stores.

I was very interested in what Spike had to say about water permeating through plastics, which was the reason for my experiments.  At the time (about 10 years ago) I was unable to find any references to moisture permeating through plastics.

Richard G3OTK



John Button G8JMB
 

"... water permeating through plastics, which was the reason for my experiments.  At the time (about 10 years ago) I was unable to find any references to moisture permeating through plastics.

Richard
Maybe you did not look far enough back; about 1966, I was working at STC where they made underground telephone cable - traditionally paper insulated, several hundred cores, with a lead sheath. The lead was being replaced by an extruded polythene sheath.  However, polythene was known to be porous and the solution was an aluminium foil layer under the polythene. 

STC at N. Woolwich is long gone, like most of the British electronics industry and I don't know if such cables have gone too.

73
jOHN
g8jmb

ian hope
 

Most external Telecoms or data cables are now Petrolum jelly filled to stop water ingress.
 
ian
2E0IJH

 
Sent: Sunday, September 15, 2019 at 5:58 PM
From: "John Button G8JMB via Groups.Io" <hornpipe112@...>
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence
"... water permeating through plastics, which was the reason for my experiments.  At the time (about 10 years ago) I was unable to find any references to moisture permeating through plastics.

Richard
Maybe you did not look far enough back; about 1966, I was working at STC where they made underground telephone cable - traditionally paper insulated, several hundred cores, with a lead sheath. The lead was being replaced by an extruded polythene sheath.  However, polythene was known to be porous and the solution was an aluminium foil layer under the polythene. 

STC at N. Woolwich is long gone, like most of the British electronics industry and I don't know if such cables have gone too.

73
jOHN
g8jmb

Paul Bicknell
 

Hi john

 

We are going back paper insulation hasn’t been used for over 40 years on UG cables

And Petroleum jelly has been used on UG cables for over 50 years

 

I have even pulled out of a house single conductor mains cabling with paper and Petroleum jelly as the insulator and lead for the outer sheath

 


From: RSGB-Workshop@groups.io [mailto:RSGB-Workshop@groups.io] On Behalf Of ian hope
Sent: 15 September 2019 18:22
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

 

Most external Telecoms or data cables are now Petrolum jelly filled to stop water ingress.

 

ian

2E0IJH

 

Sent: Sunday, September 15, 2019 at 5:58 PM
From: "John Button G8JMB via Groups.Io" <hornpipe112@...>
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

"... water permeating through plastics, which was the reason for my experiments.  At the time (about 10 years ago) I was unable to find any references to moisture permeating through plastics.

Richard
Maybe you did not look far enough back; about 1966, I was working at STC where they made underground telephone cable - traditionally paper insulated, several hundred cores, with a lead sheath. The lead was being replaced by an extruded polythene sheath.  However, polythene was known to be porous and the solution was an aluminium foil layer under the polythene. 

STC at N. Woolwich is long gone, like most of the British electronics industry and I don't know if such cables have gone too.

73
jOHN
g8jmb

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8048 / Virus Database: 4793/15884 - Release Date: 08/14/18
Internal Virus Database is out of date.

ian hope
 

Paper Insulated HV cables were still used until about 10 years ago, They are now XLPE (Cross linked polyethylene).
 
Paper Insulated Lead Covered (PILC) service Cables are still Made and still specified for Certain soil conditions, Instead of XLPE CNE (combined Neutral Earth) or Split Concentric Cables.
 
 
 
Ian
2E0IJH

 
Sent: Sunday, September 15, 2019 at 6:46 PM
From: "Paul Bicknell" <paul@...>
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

Hi john

 

We are going back paper insulation hasn’t been used for over 40 years on UG cables

And Petroleum jelly has been used on UG cables for over 50 years

 

I have even pulled out of a house single conductor mains cabling with paper and Petroleum jelly as the insulator and lead for the outer sheath

 


From: RSGB-Workshop@groups.io [mailto:RSGB-Workshop@groups.io] On Behalf Of ian hope
Sent: 15 September 2019 18:22
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

 

Most external Telecoms or data cables are now Petrolum jelly filled to stop water ingress.

 

ian

2E0IJH

 

Sent: Sunday, September 15, 2019 at 5:58 PM
From: "John Button G8JMB via Groups.Io" <hornpipe112@...>
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

"... water permeating through plastics, which was the reason for my experiments.  At the time (about 10 years ago) I was unable to find any references to moisture permeating through plastics.

Richard
Maybe you did not look far enough back; about 1966, I was working at STC where they made underground telephone cable - traditionally paper insulated, several hundred cores, with a lead sheath. The lead was being replaced by an extruded polythene sheath.  However, polythene was known to be porous and the solution was an aluminium foil layer under the polythene. 

STC at N. Woolwich is long gone, like most of the British electronics industry and I don't know if such cables have gone too.

73
jOHN
g8jmb

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8048 / Virus Database: 4793/15884 - Release Date: 08/14/18
Internal Virus Database is out of date.

Richard Harris
 

John,

Many thanks for your reply. My searches for information about moisture permeating through plastics were via the internet. No search terms that I used turned up any useful references.

30+ years ago I was involved with underwater CCTV cameras and I don't recall moisture permeating through cable jackets was ever a problem - the cables would have been water blocked, perhaps for that reason.

Richard G3OTK

On Sun, Sep 15, 2019 at 05:58 PM, John Button G8JMB wrote:


"... water permeating through plastics, which was the reason for my
experiments.  At the time (about 10 years ago) I was unable to find any
references to moisture permeating through plastics.

Richard
Maybe you did not look far enough back; about 1966, I was working at STC where
they made underground telephone cable - traditionally paper insulated, several
hundred cores, with a lead sheath. The lead was being replaced by an
extruded polythene sheath.  However, polythene was known to be porous and
the solution was an aluminium foil layer under the polythene.

STC at N. Woolwich is long gone, like most of the British electronics industry
and I don't know if such cables have gone too.

73
jOHN
g8jmb

Paul Bicknell
 

Well you learn something every day 

 

RE paper and Petroleum jelly I was talking about  telephone cables  but I bought the power cables to the party so I cannot complain   interesting though

 

Good one regards Paul

 


From: RSGB-Workshop@groups.io [mailto:RSGB-Workshop@groups.io] On Behalf Of ian hope
Sent: 15 September 2019 19:16
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

 

Paper Insulated HV cables were still used until about 10 years ago, They are now XLPE (Cross linked polyethylene).

 

Paper Insulated Lead Covered (PILC) service Cables are still Made and still specified for Certain soil conditions, Instead of XLPE CNE (combined Neutral Earth) or Split Concentric Cables.

 

 

 

Ian

2E0IJH

 

Sent: Sunday, September 15, 2019 at 6:46 PM
From: "Paul Bicknell" <paul@...>
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

Hi john

 

We are going back paper insulation hasn’t been used for over 40 years on UG cables

And Petroleum jelly has been used on UG cables for over 50 years

 

I have even pulled out of a house single conductor mains cabling with paper and Petroleum jelly as the insulator and lead for the outer sheath

 


From: RSGB-Workshop@groups.io [mailto:RSGB-Workshop@groups.io] On Behalf Of ian hope
Sent: 15 September 2019 18:22
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

 

Most external Telecoms or data cables are now Petrolum jelly filled to stop water ingress.

 

ian

2E0IJH

 

Sent: Sunday, September 15, 2019 at 5:58 PM
From: "John Button G8JMB via Groups.Io" <hornpipe112@...>
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Hygroscopic, deliquescent and acquiescence

"... water permeating through plastics, which was the reason for my experiments.  At the time (about 10 years ago) I was unable to find any references to moisture permeating through plastics.

Richard
Maybe you did not look far enough back; about 1966, I was working at STC where they made underground telephone cable - traditionally paper insulated, several hundred cores, with a lead sheath. The lead was being replaced by an extruded polythene sheath.  However, polythene was known to be porous and the solution was an aluminium foil layer under the polythene. 

STC at N. Woolwich is long gone, like most of the British electronics industry and I don't know if such cables have gone too.

73
jOHN
g8jmb

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8048 / Virus Database: 4793/15884 - Release Date: 08/14/18
Internal Virus Database is out of date.

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8048 / Virus Database: 4793/15884 - Release Date: 08/14/18
Internal Virus Database is out of date.