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DEHN UK Ltd

Lightning as a source of ignition.Robin Earl.

1


For ATEX zones, do I need Lightning

Protection?

2


Lightning Protection for Hazardous Areas

In short if your site is covered by any of the following legislation then

then answer is: Yes

• Explosive Regulations 2014

• JSP 482 (MoD specification for lightning protection)

• DSEAR 2015

• COMAH 2015

• BSEN60079 Explosive Atmosphere Standards

• BSEN1127 Explosion Prevention & Protection Standards



The easiest applicable sources of legislation here are Explosive

Regulations 2014 and JSP482 both of which state that lightning

protection is mandatory and a minimum of a level I system in

accordance with BSEN62305 must be installed.

Both of these documents are quite clear and both are applied to very

high risk sites.

The other legislation is less obvious but there is still a considerable legal

requirement to be met, which the following slides will take you through.



ATEX 137/DSEAR Article 4 states: A site risk assessment MUST be carried out to take account of:

• The likelihood that explosive atmospheres will occur

• The installations substances and processes and their possible interactions

• Identify ALL possible ignition sources

• The scale of any anticipated effects

• BSEN 1127 Explosion Prevention and Protection lists 13 possible sources of ignition, among these are:

• 5.1 Hot Surfaces

• 5.3 Mechanically Generated Sparks

• 5.5 Stray Electric Currents

• 5.7 Lightning

• 5.7 Lightning


So what level of Lightning

Protection do I need?

6



Normally the answer to this question is quite simple, you carry out a risk

assessment in accordance with BSEN 62305:2012.

However, with these high risk sites that is not actually the immediate

action to be carried out, there are some other factors to be considered.

BSEN 62305:2012 has some recommendations and advice for us prior to

the risk assessment, that introduces minimum protection levels.



BSEN62305:2012 Part 3 paragraph 3.34 states that under the following circumstances we should consider a structure at risk of explosion:

“ Structures containing solid explosive materials or hazardous zones as determined in accordance with BSEN60079-10-1 and BSNE60079-10-2”

BSEN62305:2012 Part 2 paragraph 5.4 (the procedure to evaluate the need for protection) Note 2 states:

“Where protection against lightning is required by the authority having jurisdiction for structures with a risk of explosion, at least a class II LPS should be adopted.”

Note 3 states:

“When the damage to a structure due to lighting may also involve surrounding structure or environment, additional protection measures may be required”


Do I need Isolated Lightning

Protection?

9



So we’ve established that sites with hazardous areas and EX zones need

to have lightning protection and it should be at least level II LPS.

• To protect life

• To prevent ignition

• Adhere to BSEN 60079 & BSEN1127

• Be fully compliant with DSEAR

But what sort of lightning protection should that be?

Is it acceptable to just go with a basic or common place type of

protection?



BSEN 60079-14 Electrical Installations in Hazardous Areas states:

• Bonding connections should only be made through specifically

designed connection points and not rely on fortuitous contact. All

connections should be secured against self-loosening. This requires

the use of materials that are designed for the particular application

and are fit for purpose.

• Electrical energy carrying systems within zone 0/20 or 1/21 must

have very low power levels, produce no hot surfaces, limit current

and voltage under normal and fault conditions, reduce inductance

and capacitance and will not create electrical sparks or will have

insufficient energy to ignite the most easily ignitable concentration of

a flammable mixture



There are two types of lightning protection systems permissible under

BSEN62305:2012.

• Cross bonded, the industry standard over 90% of all LPS in the UK

will be of this type. It uses conventional conductors secured directly

to the structure (or elements of the structure itself) and all

metallic/conductive parts of the structure are connected (bonded)

into the system allowing full or partial lightning energy to travel

through the building.

• Isolated, by deliberately not bonding the conductive elements,

maintaining a separation distance and preventing the rolling sphere

from touching the structure the building is protected and no

lightning energy travels through the structure.



Clearly from the requirements of BSEN 60079-14 any conventional cross

bonded lightning protection system still presents a risk of ignition as the

potential energy levels, sparking across joints and bonds, huge inductive

voltages in conventional conductors mean that gasses, vapours and dust

are still at risk from sparks and hot surfaces.

It takes just 280 micro Joules of energy to ignite Methane gas and only

20 micro Joules to ignite Hydrogen gas. A level IV cross-bonded

lightning protection system is designed to deal with 100kV and will

certainly experience in excess of 1,000,000 Joules in a fault condition.


Effect of lightning on steel roof materials 0.7mm thick

PV array and underground pipe


Correct and incorrect installation

International Workshop 2015-07 16

Bad installation, flexible braid laid directly

onto fabric of dome, no separation or

isolation.

Good installation, isolated system with

strike point well away from ATEX zones


Good and bad practices on the same installation!

International Workshop 2015-07

Cross bonded and strike

point within ATEX zone.

Non compliant

installation to all

standards

Use of isolated masts

and meeting separation

distance is compliant to

standards



As the video clips show there is still a significant risk to be addressed, a

cross bonded system cannot prevent ignition in the high risk areas we

are looking at.

Only an isolated system can meet the requirements of BSEN60079-14

with regards to energy levels, inductance and capacitance in zones 0 or

1.

Only an isolated system with adequate SPD measures can remove the

risks of ignition from sparks, hot spots, induced energy and there by

satisfy BSEN1127.


From risk assessment to design service then installation

using accredited installers.



So to summarise, we asked the question “Do I need lightning

protection” and we have established that:

• DSEAR requires lightning protection to be installed automatically

• That lightning protection system should be level II as a minimum

(BSEN62305 5.4 note 2)

• That level II system should be isolated (BSEN62305 annexe D,

BSEN1127 & BSEN60079)

If you want to be fully compliant with DSEAR, you need to install a

minimum of a level II isolated lightning protection system with

appropriate co-ordinated SPD’s in accordance with BS 7671 18th edition.

It’s the only way to control and mitigate the risks that lightning poses as

a source of ignition.


Thank you for your attention.

Any questions?

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