Re: [PSES] Earthing -- Star vs Spring/Split Washers

2022-02-15 Thread Richard Nute 
 

Hello James:

 

As for resistance of the connection, I doubt that there is significant
difference.  I have tested both with a high-current-sourcing milliohmeter.
You can repeat the test and see if there is a difference in the resistance.
(Even a loose connection will still pass the high current test.)

 

A star washer is more likely to penetrate paint.  However, a stud mounted in
a panel is independent of paint.  So, a lockwasher simply locks the nut to
the stud and has little to no effect on the resistance of the connection.  

 

Best regards,

Rich

 

 

 

From: James Pawson (U3C)  
Sent: Tuesday, February 15, 2022 7:34 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Earthing -- Star vs Spring/Split Washers

 

Hello all,

 

I've given myself a regular internet headache trying to understand the
relative merits of spring vs star washers for use on an earth stud for
protective earthing purposes.

 

What is the conventional wisdom and justification? I know I can trust you
folks to be above a simple "we've always done it this way"

 

Can anyone point me towards any citable references or standards covering
this subject?

 

I promise I will write a blog post to pull the information together for
future confused generations.

 

Thanks and all the best,

James

 

 

James Pawson

The EMC Problem Solver

 

Unit 3 Compliance Ltd

EMC : Environmental & Vibration : Electrical Safety : CE & UKCA :
Consultancy

 

  www.unit3compliance.co.uk  |
 ja...@unit3compliance.co.uk 

+44(0)1274 911747  |  +44(0)7811 139957

2 Wellington Business Park, New Lane, Bradford, BD4 8AL

Registered in England and Wales # 10574298

 

 

 


-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 


All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell 

For policy questions, send mail to:
Jim Bacher:  
David Heald:

Re: [PSES] Earthing -- Star vs Spring/Split Washers

2022-02-15 Thread Doug Nix 
James,

If your concerns are above 60 Hz, i.e., you’re thinking about HF bonding as 
well as LF bonding for safety, then I have two excellent resources for you:

[1] T. Williams, K. Armstrong, EMC for Systems and Installations, 1st Ed. 
Oxford: Newnes. 2000. ISBN 0 7506 4167 3

[2] E.B. Joffe, K. Lock, Grounds for Grounding, 1st ed. Hoboken: Wiley & Sons. 
2010. ISBN 978-0471-66008-8

Both books are very good. In [1], have a look at p.121-122. In [2], have a look 
at p.335-336. Actually, Chapter 5 on bonding, starting at p. 323, is excellent.

I could recommend others, but I think those two are a great start.

Doug Nix
d...@ieee.org
+1 (519) 729-5704

> On 15-Feb-22, at 14:48, Douglas E Powell  wrote:
> 
> James,
> 
> Most safety standards have requirements for ground bond testing based on the 
> current available in the hazard. I've never seen requirements specifying the 
> type of washer other than it cannot have compressible material in the stack 
> up, as polymers or fiber washers.
> 
> Back in the day, I learned my earthing (EU) or grounding (US) for high power 
> equipment from a German expert at LGA Landesgewerbeanstalt Bayern in Nürnberg 
> and the guidance I received was to use star washers on plain metal surfaces; 
> not to cut through paint as many believe, but to dig into the metal parts to 
> provide an oxygen free connection. Yes, initial conductivity for a steel star 
> washer is not great, but the EU Liability Directive would indicate that the 
> connection needs to be reliable for up to 10 years. For a normally very low 
> current (mA) ground to launch into service at a moment's notice, and safely 
> carry away a few hundred amps, is sometimes a challenge if the long term 
> environment is in the least bit corrosive.
> 
> Notably, my mentor also allowed serrated lock washers.
> 
> Best,  Doug
> 
> Douglas E Powell
> Laporte, Colorado USA
> LinkedIn 
> 
> (UTC -07:00) Mountain Time (US-MST)
> 
> 
> 
> On Tue, Feb 15, 2022 at 8:34 AM James Pawson (U3C) 
> mailto:ja...@unit3compliance.co.uk>> wrote:
> Hello all,
> 
> 
> 
> I’ve given myself a regular internet headache trying to understand the 
> relative merits of spring vs star washers for use on an earth stud for 
> protective earthing purposes.
> 
> 
> 
> What is the conventional wisdom and justification? I know I can trust you 
> folks to be above a simple “we’ve always done it this way”
> 
> 
> 
> Can anyone point me towards any citable references or standards covering this 
> subject?
> 
> 
> 
> I promise I will write a blog post to pull the information together for 
> future confused generations.
> 
> 
> 
> Thanks and all the best,
> 
> James
> 
> 
> 
> 
> 
> James Pawson
> 
> The EMC Problem Solver
> 
> 
> 
> Unit 3 Compliance Ltd
> 
> EMC : Environmental & Vibration : Electrical Safety : CE & UKCA : Consultancy
> 
> 
> 
> www.unit3compliance.co.uk   |  
> ja...@unit3compliance.co.uk 
> +44(0)1274 911747  |  +44(0)7811 139957
> 
> 2 Wellington Business Park, New Lane, Bradford, BD4 8AL
> 
> Registered in England and Wales # 10574298
> 
> 
> 
> 
> 
> 
> 
> 
> 
>  
> This email has been checked for viruses by AVG antivirus software.
> www.avg.com 
>  -
> 
> This message is from the IEEE Product Safety Engineering Society emc-pstc 
> discussion list. To post a message to the list, send your e-mail to 
> emc-p...@ieee.org 
> 
> All emc-pstc postings are archived and searchable on the web at: 
> http://www.ieee-pses.org/emc-pstc.html 
> 
> Attachments are not permitted but the IEEE PSES Online Communities site at 
> http://product-compliance.oc.ieee.org/ 
>  can be used for graphics (in 
> well-used formats), large files, etc.
> 
> Website:  http://www.ieee-pses.org/ 
> Instructions:  http://www.ieee-pses.org/list.html (including how to 
> unsubscribe) 
> List rules:  http://www.ieee-pses.org/listrules.html 
> 
> For help, send mail to the list administrators:
> Scott Douglas sdoug...@ieee.org 
> Mike Cantwell mcantw...@ieee.org 
> 
> For policy questions, send mail to:
> Jim Bacher j.bac...@ieee.org 
> David Heald dhe...@gmail.com 
> 
> -
> 
> This message is from the IEEE Product Safety Engineering Society emc-pstc 
> discussion list. To post a message to the list, send your e-mail to 
> mailto:emc-p...@ieee.org>>
> 
> All emc-pstc postings are archived and searchable on the web at: 
>

Re: [PSES] Earthing -- Star vs Spring/Split Washers

2022-02-15 Thread Douglas E Powell 
James,

Most safety standards have requirements for ground bond testing based on
the current available in the hazard. I've never seen
requirements specifying the type of washer other than it cannot have
compressible material in the stack up, as polymers or fiber washers.

Back in the day, I learned my earthing (EU) or grounding (US) for high
power equipment from a German expert at LGA Landesgewerbeanstalt Bayern in
Nürnberg and the guidance I received was to use star washers on plain metal
surfaces; not to cut through paint as many believe, but to dig into the
metal parts to provide an oxygen free connection. Yes, initial conductivity
for a steel star washer is not great, but the EU Liability Directive would
indicate that the connection needs to be reliable for up to 10 years. For a
normally very low current (mA) ground to launch into service at a moment's
notice, and safely carry away a few hundred amps, is sometimes a challenge
if the long term environment is in the least bit corrosive.

Notably, my mentor also allowed serrated lock washers.

Best,  Doug

Douglas E Powell
Laporte, Colorado USA
LinkedIn 

(UTC -07:00) Mountain Time (US-MST)



On Tue, Feb 15, 2022 at 8:34 AM James Pawson (U3C) <
ja...@unit3compliance.co.uk> wrote:

> Hello all,
>
>
>
> I’ve given myself a regular internet headache trying to understand the
> relative merits of spring vs star washers for use on an earth stud for
> protective earthing purposes.
>
>
>
> What is the conventional wisdom and justification? I know I can trust you
> folks to be above a simple “we’ve always done it this way”
>
>
>
> Can anyone point me towards any citable references or standards covering
> this subject?
>
>
>
> I promise I will write a blog post to pull the information together for
> future confused generations.
>
>
>
> Thanks and all the best,
>
> James
>
>
>
>
>
> James Pawson
>
> The EMC Problem Solver
>
>
>
> *Unit 3 Compliance Ltd*
>
> *EMC : Environmental & Vibration : Electrical Safety : CE & UKCA :
> Consultancy*
>
>
>
> www.unit3compliance.co.uk  |  ja...@unit3compliance.co.uk
>
> +44(0)1274 911747  |  +44(0)7811 139957
>
> 2 Wellington Business Park, New Lane, Bradford, BD4 8AL
>
> Registered in England and Wales # 10574298
>
>
>
>
>
>
>
>
> --
> [image: AVG logo] 
>
> This email has been checked for viruses by AVG antivirus software.
> www.avg.com 
>
> <#m_848691752694288160_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to 
> emc-p...@ieee.org
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe) 
> List rules: http://www.ieee-pses.org/listrules.html
>
> For help, send mail to the list administrators:
> Scott Douglas sdoug...@ieee.org
> Mike Cantwell mcantw...@ieee.org
>
> For policy questions, send mail to:
> Jim Bacher j.bac...@ieee.org
> David Heald dhe...@gmail.com
>

-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 


All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell 

For policy questions, send mail to:
Jim Bacher:  
David Heald:

[PSES] Earthing -- Star vs Spring/Split Washers

2022-02-15 Thread James Pawson (U3C) 
Hello all,

 

I've given myself a regular internet headache trying to understand the
relative merits of spring vs star washers for use on an earth stud for
protective earthing purposes.

 

What is the conventional wisdom and justification? I know I can trust you
folks to be above a simple "we've always done it this way"

 

Can anyone point me towards any citable references or standards covering
this subject?

 

I promise I will write a blog post to pull the information together for
future confused generations.

 

Thanks and all the best,

James

 

 

James Pawson

The EMC Problem Solver

 

Unit 3 Compliance Ltd

EMC : Environmental & Vibration : Electrical Safety : CE & UKCA :
Consultancy

 

  www.unit3compliance.co.uk  |
 ja...@unit3compliance.co.uk 

+44(0)1274 911747  |  +44(0)7811 139957

2 Wellington Business Park, New Lane, Bradford, BD4 8AL

Registered in England and Wales # 10574298

 

 

 



-- 
This email has been checked for viruses by AVG.
https://www.avg.com

-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 


All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell 

For policy questions, send mail to:
Jim Bacher:  
David Heald:

Re: [PSES] Risk assessment versus HBSE

2022-02-15 Thread Douglas Nix 
Hi Douglas,

Glad I could help. :-)

If you are interested in some hard-core debunking of the risk matrix/decision 
tree approach, start with [17], [18], and [19]. The authors are not fans of 
these approaches as they do not hold up mathematically, even, as you say, many 
want them to seem mathematically rigorous.

WRT information for safety engineers on hazards, apart from the IEC standards 
related electric shock, and the ISO standards related to contact with hot and 
cold surfaces, I use the ACGIH TLVs and BEIs as my guidance. It doesn’t cover 
everything, but it covers all of the common hazards. 
https://portal.acgih.org/s/store#/store/browse/cat/a0s4W0g02f3QAA/tiles

I’m always happy to discuss any of this stuff, so feel free to reach out.

--
Doug Nix
d...@mac.com

“If there are no dogs in Heaven, then when I die I want to go where they went.” 
-Will Rogers



> On 14-Feb-22, at 18:21, Douglas E Powell  wrote:
> 
> Hi Doug,
> 
> This looks like a very good summary and mentions a few of the things I was, 
> in my poor attempt, trying to point out. One of my concerns about RA, and 
> FMEA in particular, is that this method does have a lot of numeric 
> computation for what is essentially a qualitative process. As such, it gives 
> the "appearance" of quantifiable due diligence, which many decision makers 
> want to see. Sad to say, when I've been involved in meetings with various 
> SMEs, I've occasionally heard discussions on how to adjust the parameters in 
> order to keep a particular risk listed on the spreadsheet but not trigger any 
> corrective actions. As with any system, there are those who would like to 
> manipulate it to their own advantage. It is for this reason that, when I am 
> leading the team effort and using a severity scale of 1 to 10, I always press 
> for mandatory action when severity is a 9 or 10 (disabling injury or worse), 
> regardless of the other parameters.
> 
> Oh, and that's a nice bibliography as well. I think I just received my summer 
> reading list.
> 
> Best,  Doug
> 
> Douglas E Powell
> Laporte, Colorado USA
> LinkedIn 
> 
> (UTC -07:00) Mountain Time (US-MST)
> 
> 
> On Mon, Feb 14, 2022 at 1:45 PM Douglas Nix 
> <0bb8ff993b10-dmarc-requ...@listserv.ieee.org 
> > wrote:
> Hi Rich,
> 
> I have to admit that I’ve been thinking about your reply all weekend.
> 
> As you know, I teach machinery risk assessment and consult in this area 
> regularly. I want to stipulate that there are some significant issues with 
> risk assessment the way it is most commonly applied in industry, see my list 
> of references on this topic at the end of my message.
> 
> The inherent subjectivity of risk assessments that are performed without 
> empirical data is unquestioned. The difficulty is that for many areas of 
> human endeavour we have no empirical data, and try as we might we cannot 
> calculate without numeric data. Nevertheless, we must be able to make 
> risk-based decisions when designing products and equipment, and so we muddle 
> along with the best tools that we have, hopefully while recognizing their 
> flaws.
> 
> The HBSE model is a good one, and it fits machinery applications as readily 
> as does risk assessment, however, the risk assessment methods that are used 
> today have a history that stretches back to the 1960s, while the HBSE model 
> is much younger. This doesn’t take away from HBSE in any way for me, but it 
> does have an impact on the broader acceptance of the method since it is not 
> yet as widely known as “conventional” risk assessment. None of the the 
> standards in the machinery safety sector recognize the method as yet, so 
> getting regulators and users to consider the method is a challenge.
> 
> HBSE also suffers from issues with lack of data when it comes to 
> characterizing some hazards, leaving the user to estimate the 
> characteristics. This brings in the biases of the person(s) doing the 
> estimating just as surely as conventional risk assessment methods.
> 
> The absence of a probability parameter in the HBSE model is an interesting 
> one, since the probability aspect is the one most subject to error in 
> conventional risk assessment. Humans are notoriously bad at estimating 
> probability. It appears to me that the absence of that parameter implies that 
> the presence of a hazard will inevitably lead to harm, which I don’t disagree 
> with. CSA Z1002, OHS risk assessment, actually states that this is the case, 
> and recommends that hazards are eliminated on this basis whenever possible.
> 
> So we’re left with this situation, I think:
> 
> 1) Risk assessment, when done quantitatively using sound statistical 
> techniques and valid data is a useful and relatively objective method to 
> provide data to decision makers,
> 2) Conventional risk assessment using subjective opinions and risk matrices 
> or decision trees

[PSES] SV: [PSES] IP Code Question

2022-02-15 Thread Amund Westin 
IP66 is for harsh outdoor conditions (industrial, offshore, ships, carwash, 
etc.)

IPX6 : powerful water jets (water hose :100 liters / minute).

 

IP67 (temporary immersion in water) 

 

Best regards Amund

 

 

 

Fra: sudhakar wasnik 
Sendt: 14. februar 2022 22:57
Til: EMC-PSTC@LISTSERV.IEEE.ORG
Emne: Re: [PSES] IP Code Question

 

“Outdoor “ …IP …  will it withstand the “ flash rain, or severe rainfall 
leading to flooding…

 

Kind Regards,

Sudhakar 

Sent from my iPhone





On Feb 14, 2022, at 12:56 PM, Charlie Blackham mailto:char...@sulisconsultants.com> > wrote:

 

I generally see outdoor telecoms enclosures specified and tested to IP66 or 
IP67, or NEMA 4X, but EN 60950-22:2006 and EN 62368-1:2020 only required IP54 
to provide PD2 environment.

 

Best regards

Charlie

 

Charlie Blackham

Sulis Consultants Ltd

Tel: +44 (0)7946 624317

Web:   https://sulisconsultants.com/ 

Registered in England and Wales, number 05466247

 

From: Douglas Nix <  
0bb8ff993b10-dmarc-requ...@listserv.ieee.org> 
Sent: 14 February 2022 19:35
To:   EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] IP Code Question

 

I agree wit Ted Eckert on this. Generally for outdoor use you’d need IP65 at 
least.

 

Doug Nix

 

"The most wasted of all days is one without laughter.” — e.e. cummings.

 

 






On 14-Feb-22, at 09:23, Brian Kunde mailto:bkundew...@gmail.com> > wrote:

 

An IP code of IPx2 implies the enclosure protects against the ingress of water 
drops at 15° tilt.  Now, most PC enclosures protect the electronics from 
occasional exposure to water drops, but it is not designed to be exposed to 
water drops continuously.  So can you rate an electronic device IP22, for 
instance, but not intend it to be used outside or in an environment where it is 
exposed to water on a regular basis?

 

Thanks for your input.  

The Other Brian

-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
mailto:emc-p...@ieee.org> >

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) 
 
List rules: http://www.ieee-pses.org/listrules.html 

For help, send mail to the list administrators:
Scott Douglas mailto:sdoug...@ieee.org> >
Mike Cantwell mailto:mcantw...@ieee.org> > 

For policy questions, send mail to:
Jim Bacher mailto:j.bac...@ieee.org> >
David Heald mailto:dhe...@gmail.com> > 

 

-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
mailto:emc-p...@ieee.org> >

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) 
 
List rules: http://www.ieee-pses.org/listrules.html 

For help, send mail to the list administrators:
Scott Douglas mailto:sdoug...@ieee.org> >
Mike Cantwell mailto:mcantw...@ieee.org> > 

For policy questions, send mail to:
Jim Bacher mailto:j.bac...@ieee.org> >
David Heald mailto:dhe...@gmail.com> > 

-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
mailto:emc-p...@ieee.org> >

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) 
 
List rules: http://www.ieee-pses.org/listrules.html 

For help, send mail to the list administrators:
Scott Douglas mailto:sdoug...@ieee.org> >
Mike Cantwell mailto:mcantw...@ieee.org> > 

For policy questions, send mail to:
Jim Bacher mailto:j.bac...@ieee.org> >
David Heald mailto:dhe...@gmail.com> > 

-