Management of
Blue Indicating Silica Gel
in the Electricity Supply Industry
July 2001
Prepared for the
Electricity Engineers’ Association’s Safety Strategy and Policy Group
by Harvey O’Sullivan, Tri-Sheras Ltd
Contents
1.0
Introduction
2.0
Current Procedures and Practices
2.1
Handling and Use
2.2
Disposal
3.0
Identified Issues
3.1
General Information on CoCl2
3.2
Current Knowledge
4.0
Hazard Management and Relevant NZ Legislation
4.1
The Health and Safety in Employment Act 1992
4.2
Approved Code of Practice
4.3
Controlling Risks
5.0
Alternatives to Current Practices
5.1
Considerations and Contributing Factors
5.2
Options for Control
5.3
Determination of Practicability
6.0
Conclusions and Alternatives
7.0
References
Disclaimer
This report has been prepared by representatives of the electricity industry to provide
guidance on safety practices for use by the industry.
Although the report looks at good practice for electricity industry representatives, it should
not be relied on as a substitute for legislative requirements. The report should always be
used in conjunction with the applicable legislative and OSH safety and health requirements.
If there is uncertainty as to what guidelines or legislative requirements apply in any particular
situation, specialist advice should be sought. The Electricity Engineers’ Association of New
Zealand (Inc) (EEA) and the electricity industry representatives involved in formulating the
report accept no liability or responsibility for any error in or omission from the report, or any
injury, loss, damage (including indirect or consequential loss or damage) or any other claims
whatsoever caused by or resulting from any reliance on, or failure to rely on, the report.
July 2001
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Blue Indicating Silica Gel for Elect Supply Ind
1.0
Introduction
Cobalt Chloride (CoCl2) is used with Silica Gel as a moisture indicator when in breathers
used in electricity industry equipment such as transformers.
Recent correspondence has highlighted that CoCl2 has been reclassified by the European
Union (EU) as a class 2 carcinogen (“may cause cancer by inhalation”). This decision was
implemented on 1 January 2000 with a transitional period extending until 1 July 2000.
Currently in NZ, CoCl2 is not classified as a carcinogen.
The scope of this paper is as follows:
1.
The current practice for handling blue indicating silica gel in the electricity industry.
2.
The hazards that exist with handling this substance and silica gel generally.
3.
Possible alternatives to current practices.
4.
The recommended options for the electricity industry with respect to future handling
of blue indicating silica gel and other forms of silica gel.
2.0
Current Procedures and Practices
2.1
Handling and Use
Blue indicating silica gel is supplied with the breathers in transformers. Many
breathers arrive sealed and are replaced with breathers that can be accessed for
regeneration of the silica gel contents.
The silica gel is regenerated up to 2-3 times per year by removing the gel from the
breather and heating it to dry it out.
Each batch of silica gel may be regenerated up to 6 times before final disposal.
2.2
Disposal
Blue indicating silica gel is disposed of as industrial waste.
3.0
Identified Issues
3.1
General Information on CoCl2
CoCl2 is a soluble compound used in silica gel. Health effects from exposure to
Cobalt can include ‘hard-metal disease’, respiratory sensitisation, asthma, and
allergic dermatitis. The EU – hence the UK –has reclassified CoCl2 as a possible
carcinogen to humans.
In handling blue indicating silica gel, the most likely means of entry of CoCl2 into the
body is by inhalation of the dust. The process of handling, heating, and drying
repeatedly degrades silica gel, thus increasing the percentage of fine particles in the
quantity of gel over a period of time and therefore increasing the risk of inhaling
greater quantities over time.
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The relevant NZ workplace exposure standard (WES) for CoCl2 is 0.05 mgm-3
(TWA)1. This translates into a Short Term Exposure Limit2 (STEL) of 0.15mgm-3.
However, OSH may review its WES in line with the American Conference of
Governmental Industrial Hygienists (ACGIH) WES, which is 0.02mgm-3 (TWA).
3.2
Current Knowledge
3.2.1
UK Experience
Information regarding the use and handling of blue indicating silica gel in the
electricity industry was obtained from the UK.
The relevant UK WES for CoCl2 is 0.1 mgm-3 (TWA). This translates into a STEL of
0.3mgm-3.
Amorphous silica (which includes silica gel) has its own exposure limits which,
according to UK standards, is 6mgm-3 of total inhalable dust over an 8 hour period
(TWA) and 2.4mgm-3 of respirable dust3 (TWA).
Prior to the change in classification of CoCl2, the standard manufacturer’s instructions
when working with silica gel included the use of gloves and a dust respirator.
Upon reclassification, some work on environmental monitoring of CoCl2 exposure
was carried out during typical operations with silica gel; this indicated levels of CoCl2
of <0.1 mgm-3 (less than the UK WES TWA). However, this monitoring revealed that:
1. The use of amorphous silica was a more significant risk in terms of dust
inhalation than exposure to CoCl2 and necessitated the use of a dust respirator;
and
2. The presence of low levels of CoCl2 does not significantly alter the health and
safety requirements for handling and working with silica gel.
3.2.2
NZ Standards
The relevant published NZ WES are:
• 0.05 mgm-3 TWA for CoCl2 (up to 0.15 mgm-3 STEL4); and
• 10 mgm-3 TWA for silica gel
Blue indicating silica gel contains up to 1% CoCl2. Therefore, if the dust produced
meets or exceeds the WES (TWA) for silica gel, then it may contain quantities of
CoCl2 that will exceed the WES (TWA) for CoCl2. Note that 10mg of dust can contain
up to 0.1 mg of CoCl2.
Conversely, if the worker is not exposed to a quantity of silica gel dust that exceeds
half of the WES (TWA) for amorphous silica (5 mgm-3), then it is unlikely the WES
(TWA) for CoCl2 will be exceeded.
1
The amount of substance to which an employee may be exposed over an 8-hour period where it is
not proven that harm can occur. The equivalent UK standard for CoCl2 is 0.1mgm-3
2
The maximum amount of substance to which an employee may be exposed over a 15-minute
period. This limit must not be exceeded.
3
The difference is related to particle size.
4
This value is based on a calculation of three times the WES (TWA) which is the “rule of thumb” often
used by OSH. No STEL value has been published for CoCl2.
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The absolute exposure values for employees will depend upon the duration of
exposure. In some cases it may be more appropriate to use the WES (STEL) for the
threshold. However, OSH has not published these values for CoCl2 or silica gel and
advice on recommended WES (STEL) should be sought.
The control method for handling blue indicating silica gel has to recognise both the
hazards associated with the indicator and those associated with the silica gel.
4.0
Hazard Management and Relevant NZ Legislation
4.1
The Health and Safety in Employment Act 1992
This legislation requires an employer to take all practicable steps to ensure the safety
of employees (possible considerations for determining practicability are set out in
paragraph 5.3 of this paper).
In combination with a requirement to systematically identify hazards, it specifies a
hierarchy of controls, which an employer must consider to minimise the risk of harm
occurring to employees from those hazards.
The hazard management system that an employer has in place must consider these
controls in order when determining what is reasonably practicable. Additionally, it is
necessary to have cognisance of the relevant OSH guidelines and approved codes of
practice (see 4.2).
4.2
Approved Code of Practice
Although the UK has an approved code of practice (ACOP) for managing
carcinogenic substances, NZ does not appear to distinguish between carcinogens
and substances that are generally hazardous to health.
Nevertheless, the
requirements set out in the NZ ACOP, if followed, should adequately control the risk
for handling all hazardous substances.
The OSH “Approved Code of Practice for Management of Substances Hazardous to
Health” sets out the requirements for employers when handling such substances.
The ACOP emphasises the following:
•
•
•
•
The need for an assessment to be carried out to determine the nature of the risk.
This may include environmental monitoring and health surveillance of employees.
This will determine whether the exposure is significant in terms of its likelihood to
cause harm.
Ongoing monitoring and surveillance if required.
Adequate consideration to be given to substituting the substance for a less
harmful substance. The degree of practicability will be influenced by the results
of the risk assessment carried out.
The need for prudence applies particularly to those substances that are not
considered hazardous as they are likely to be used without precautionary
measures and may later be found to be hazardous.
Note that the UK ACOP covers carcinogenic substances and states that there is no
guarantee that the WES is a “safe” level of exposure to a carcinogenic substance,
particularly as many other contributory causes to cancer exist.
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Blue Indicating Silica Gel for Elect Supply Ind
4.3
Controlling Risks
Irrespective of the employer, it will be necessary to undertake a risk assessment to
determine the nature and extent of the hazard. Controls applied as a result of this
assessment may differ between employers depending on the extent of the risk
determined, and various other factors such as the exposure, the size of the
organisation, and the costs of implementing controls
Subsequent paragraphs provide some guidelines as to what may be taken into
account by each employer in implementing these controls.
5.0
Alternatives to Current Practices
5.1
Considerations and Contributing Factors
To determine the most acceptable approach to handling blue indicating silica gel,
from both a legislative and a health perspective, it is necessary to first consider the
hierarchy of controls available in its use as well as what may be considered
practicable steps in this case.
5.2
Options for Control
5.2.1
Elimination of product handling
The first control to consider is whether the hazards associated with both the CoCl2
indicator and the silica gel can be eliminated – that is, can the industry not handle the
product at all. One option is to dispose of the transformer breather assembly (or a
cartridge in it) containing the silica gel and replace it with a new one each time.
5.2.2. Substitution of CoCl2 indicator
Options for substitution of CoCl2 include:
5.2.2.1 Replace the blue indicating silica gel with one containing an alternative indicator.
The EU reclassification has resulted in silica gel manufacturers launching new
indicating silica gels with “safe” indicators. One such product is “Sorbead Orange”
which has an iron based indicator compound that changes to colourless as it
absorbs moisture.
This indicating gel, whilst available, is twice the price of the normal blue indicating
gel.
5.2.2.2 Use a non-indicating silica gel. There would then be a requirement to have a
routine time for removing the gel, drying it out, and replacing it. The drying times
would also have to be “set”, as laboratory analysis would be the only sure means of
determining the water content of the gel.
5.2.3
Isolation of both CoCl2 indicator and silica gel
An enclosed chamber may be considered as an option for isolating the operator from
the blue indicating gel when emptying or filling the breather.
5.2.4
Minimisation of the hazards
Options for minimising the hazard include:
5.2.4.1 Eliminating the regeneration of the gel. The gel could be disposed of once the
requisite amount of water is present, and the breather assembly refilled with new
gel (note that elimination in para. 5.2.1 would require disposal of the breather
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Blue Indicating Silica Gel for Elect Supply Ind
assembly). As silica gel degrades as it is repeatedly heated and dried, the use of
new gel would help ensure that dust levels are minimised during handling.
5.2.4.2 Using a ventilated booth to ensure that dust is extracted away from the operator.
5.2.4.3 Using a combination of safe handling procedures, monitoring, and effective PPE.
5.3
Determination of Practicability
5.3.1
To determine which of the controls is the most practicable, bearing in mind that this
analysis is generic and what is practicable for one organisation is not necessarily
practicable for another, the following requires consideration:
(a)
What harm could occur?
In this case, the worst case scenario is an occupational disease causing
death.
(b)
What is the current state of knowledge about the likelihood that the harm will
be suffered and the harm itself?
In the case of CoCl2, it is not known for sure that this product is a carcinogen
to humans; therefore, it is difficult for an employer to ascertain with any
degree of accuracy, the likelihood that the harm will occur.
However, for both CoCl2 and the silica gel itself, there are published WES
above which employees should not be exposed. Whilst there is no guarantee
that these will not be changed at some later date, an employer is only able to
gauge likelihood based on current knowledge.
Furthermore, it is known that inhalation of dust can cause occupational
diseases – the nature of which depends upon the composition of the dust.
(c)
What is the current state of knowledge about the means available to control
the hazard?
From the UK literature and relevant MSDS, it would appear that exposure to
blue indicating silica gel is managed by a combination of monitoring,
procedures and the following appropriate PPE:
• Respiratory protection – effective dust mask
• Protective gloves due to the drying effect of silica gel on skin and skin
sensitisation effects of CoCl2. Overalls are also recommended.
• Eye protection due to dust and the drying effects of silica gel
Some suppliers are now recommending that an alternative indicator be used
in silica gel.
(d)
July 2001
What is the availability and cost of the controls?
These should be closely examined for all options to ascertain which option is
the most effective in terms of level of risk reduction for cost outlay.
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6.
Conclusions and Alternatives.
6.1
With appropriate controls and/or procedures based on a risk assessment by each
employer, there appears to be no immediate justification for removing the blue
indicating silica gel from service.
6.2
A significant hazard may be handling the silica gel itself, irrespective of the CoCl2 or
any other indicator. Therefore, if the control adopted involves handling silica gel, then
exposure to the dust must be maintained below the relevant WES for both silica gel
and the indicator during handling. The possible controls set out below are to address
both the hazards associated with handling silica gel and those associated with the
CoCl2 indicator.
6.3
To eliminate both the hazards associated with handling silica gel and those
associated with the CoCl2 indicator, disposal of the entire silica gel containing
canister when it is saturated could be considered. The increased costs of adopting
this approach may be offset to some degree by the decreased time spent in the
regeneration of the gel and any additional costs associated with PPE, procedures,
monitoring etc.
Alternatively, regeneration of the gel whilst still in the breather may be an area for
further technical development for the industry.
6.4
Another option to minimise the risk is to eliminate the process of regenerating the
silica gel but retain and refill the breather canister. If the industry was to discontinue
regeneration of the product, then it could incur increased costs in additional product
and disposal. Given that the silica gel may be regenerated up to 6 times before
disposal, the cost increase could be 6 fold. However, these costs may be offset by
benefits such as less handling.
6.5
An alternative indicator may be considered. However, if the costs are higher than
those associated with the use of CoCl2 indicator, then the industry must bear in mind
that whilst possibly eliminating the hazard associated with the CoCl2 indicator, it still
does not mitigate the risks of handling the silica gel. Additionally, it is important that
whatever alternative indicator is used, it should still be treated as a potential hazard
and appropriate controls applied based on a risk assessment.
6.6
Silica gel containing no indicator may be an option; however, the silica gel would still
require handling. Whilst the risks associated with the CoCl2 indicator would be
eliminated, a process determining the water content of the gel would be required.
The benefits for adopting this approach would need to be compared with the
comparative risk reduction.
6.7
Whilst blue indicating gel is still available and organisations wish to use it, it may be
assessed as practicable to apply the principles set out in the NZ ACOP.
The following summarises some of the key points. However, employers are required
to familiarise themselves with the relevant code and apply in detail the necessary
principles contained in the code. Therefore, the following is not a detailed and
exhaustive list and is not intended to be used in lieu of the ACOP.
• Initial monitoring to ascertain the levels of dust produced and whether the level of
dust is likely to approach or exceed the WES for silica gel. This will enable an
approximation of the possible CoCl2 levels in the dust and whether the WES is
likely to be approached or exceeded for CoCl2.
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•
•
•
•
•
•
Possible health screening for exposed employees such as lung function testing
and blood testing if the monitoring results show a degree of exposure
approaching the WES for either or both silica gel and CoCl2.
Cognisance of any employee pre-existing conditions such as asthma.
A safe working procedure and appropriate PPE. The PPE recommended (See
5.3.1(c)) should be set out in the relevant MSDS and be appropriate for the
product and level of exposure.
Emergency procedures and disposal
Appropriate training in its use and handling as well as advice on the risks
associated with handling.
Ongoing review of the effectiveness of the controls through periodic monitoring.
6.7
Note that most of these factors must be considered when handling silica gel
irrespective of the indicator used. Therefore, appropriate procedures and PPE,
based on an employer risk assessment, are required for all alternatives unless
elimination of handling silica gel proves to be the most practicable step an
organisation should take.
6.8
Finally, if blue indicating silica gel ceases to be available and is replaced with an
alternative, the industry must still identify and control the hazards associated with the
alternative, both currently, and on an ongoing basis as information regarding the
alternative is updated.
7.0
References
•
•
•
•
•
•
July 2001
Health and Safety Commission (1999). Carcinogens ACOP. HSE Books. UK.
Department of Labour. (1992) Approved code of practice for management of
substances hazardous to health. OSH. NZ [www.osh.dol.govt.nz]
Department of Labour. (2001) Workplace Exposure Standards – Effective from
2001. OSH. NZ [www.osh.dol.govt.nz]
Department of Labour. (1992) A practical guide for completing a MOSHH
assessment. OSH. NZ
Geejay
Chemicals
MSDS
for
blue
indicating
silica
gel
[www.geejaychemicals.co.uk]
Other Sources:
• EA technology,
• HSE – UK,
• Massey University,
• Department of Labour (OSH),
• Alstom NZ.
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