Risking all from the start: PED technical documentation

 In News, Pressure

Introduction

Nuts and bolts, gin and tonic, Romeo and Juliet. Some things just go hand-in-hand, don’t they? And these days it seems that whenever safety is a concern, there’s invariably a requirement to undertake a risk assessment. So perhaps it’s not surprising then, as the Pressure Equipment Directive contains essential safety requirements, that whatever the choice of conformity assessment module, the manufacturer’s technical documentation must include ‘an adequate analysis and assessment of the risks’. But what lies behind that phrase? What’s required?

Background

To understand that, we first need to turn to Annex I of the Directive, which is where we will find the essential safety requirements. Right at the top of Annex I, before you get to the first essential safety requirement (which we will look at in a minute), there are four short paragraphs under the heading ‘Preliminary Observations’. It’s an innocuous heading and, like the preface of a book, the Preliminary Observations could be easily overlooked. But that would be a mistake, as they set out the context in which the essential safety requirements must be applied.

What the Preliminary Observations tell us is that whilst the essential safety requirements are compulsory, the obligations following from them only apply if a corresponding hazard exists when the equipment (by which I mean an item of pressure equipment or assembly) is used under reasonably foreseeable conditions. Consequently, the manufacturer must analyse the hazards and risks to identify those which apply to its equipment on account of pressure. It must then design and construct the equipment taking account of the analysis.

The Preliminary Observations also tell us that in interpreting and applying the essential safety requirements, the manufacturer needs to take account of the state of the art and current practice, as well as technical and economic considerations which are consistent with a high degree of health and safety protection.

As I mentioned, immediately after the Preliminary Observations comes the first essential safety requirement. It stipulates that the equipment must be safe when it’s put into service in accordance with the manufacturer’s instructions or in reasonably foreseeable conditions. The equipment must therefore be designed, manufactured, checked and, if applicable, installed with this in mind.

The principles that the manufacturer must apply when choosing the appropriate solutions are also laid down in the first essential safety requirement. And they must be applied in the following order:

  • eliminate or reduce hazards as far as is reasonably practicable;
  • apply appropriate protection measures against hazards which cannot be eliminated;
  • where appropriate, inform users of residual hazards and indicate whether it is necessary to take appropriate special measures to reduce the risks at the time of installation and/or use.

So, as a manufacturer, what do you need to do?[1]

A methodical approach

Given that the Directive can cover anything from a ball valve up to a refinery it’s perhaps not surprising that it doesn’t stipulate the methodology to be used in undertaking the risk assessment.

Nor, by the way, does it stipulate that you need to undertake the risk assessment yourself; it can be done by someone acting on your behalf. However, you remain responsible for it and for implementing any necessary protective measures.

The assessment should take account of current practice. It can be qualitative or quantitative, but should be proportionate to the complexity of equipment and the magnitude of risks. For example, hazard identification techniques such as Hazard and Operability Analysis (HAZOP) may be appropriate for large complex assemblies, but not for individual pressure accessories.

For these reasons the example method I’ve set out below is intended as a general guide, and not a ‘one-size-fits-all’. It may be used to the extent that it is appropriate for the equipment but should be deviated from where it’s necessary or desirable to do so.

Determining the limits of the equipment

The first stage is to determine and record the characteristics, extent, surroundings and circumstances of the intended use of the equipment.

Identifying the hazards

The next stage is to identify hazards and/or hazardous situations (i.e. potential sources of harm) on account of pressure that might occur during the life of the equipment in reasonably foreseeable conditions.

This enables you to identify the applicable essential safety requirements with which the equipment needs to comply.

PED Hazard Analysis

Estimating the risk

Now you need to estimate the risk for each hazard and/or hazardous situation. Risk estimation involves assessing the severity (consequence) and frequency (likelihood) of hazardous events. One method of presenting this is a risk matrix. The levels of severity and likelihood need to be defined, so that the matrix can be constructed. Below, I have created a 5 x 5 matrix, but it could be a different size, so long as it is sufficient to discriminate between the risks of the different hazardous events.

Severity

Severity Description
5 Fatality
4 Injury causing permanent impairment
3 Reversible injury requiring hospitalisation
2 Minor injury requiring first aid treatment
1 Minor injuries or discomfort – no treatment required

Likelihood

Likelihood Description
5 Frequent
4 Probable
3 Occasional
2 Remote
1 Rare

Risk Matrix

Severity /
Likelihood
1 2 3 4 5
1 Negligible Negligible Low Low Medium
2 Negligible Low Low Medium High
3 Low Low Medium High High
4 Low Medium High High Very High
5 Medium High High Very High Very High

Evaluating the risks

You then need to decide what is an acceptable level of risk, and this should be documented in your risk assessment. You can then evaluate whether the estimated risks are acceptable or whether measures are required to reduce them.

Risk reduction

In choosing the most appropriate solutions to reduce the risks, you need to apply the principles set out in the first essential safety requirement. The hazards should be eliminated, or where they cannot be eliminated they should be reduced as far as is reasonably practicable by applying appropriate protection measures.

What can be considered ‘reasonably practicable’ changes with time. Although there is no obligation to use international standards, such as EN standards, they give an indication of what is likely to be considered the state of the art at the time of their publication. This is particularly the case where they have been harmonised with the Directive.

After the protection measures have been applied, you should evaluate if an acceptable level of risk has been reached. If the risk remains unacceptably high, further protection measures should be considered. Risk evaluation is therefore an iterative process.

If there are any residual hazards, you will need to inform users of these and indicate whether any special measures are required to reduce the risks during use and/or installation.

Using harmonised standards

Using harmonised standards doesn’t relieve you of the obligation to carry out the analysis[2]. The advantage of using them, however, is that they provide a presumption of conformity with the essential safety requirements they cover.

Harmonised standards contain an Annex Z (e.g. ZA or ZB etc.), which can normally be found towards the back of a harmonised standard. An Annex Z gives a list of clauses within the standard and corresponding essential safety requirements. Compliance with the clauses gives a presumption of conformity with the corresponding essential safety requirements.

However, just because a standard contains an Annex Z doesn’t automatically mean that it’s currently harmonised. You need to check that it has been published in the Official Journal of the European Union, and this can readily be done online[3].

Using other technical specifications

Using harmonised standards is not the only way to demonstrate the conformity of the equipment. However, if you choose not to follow the harmonised standards, you won’t benefit from the presumption of conformity; you must demonstrate the conformity yourself. This means that you will need to demonstrate in detail how the technical specifications you have chosen to use provide conformity with the essential safety requirements.

Similarly, if only part of a harmonised standard is used, or it does not cover all the applicable essential safety requirements, then you will need to demonstrate how the equipment conforms to the applicable essential safety requirements not covered by it.

PED Presumption of Conformity

What should be documented

Your documentation should include the following:

  • the risk assessment method used;
  • the hazards identified;
  • the corresponding list of applicable essential safety requirements;
  • the assessment of the risks, and the acceptable level of risk;
  • the corresponding protective measures; and
  • details of how any residual hazards should be dealt with.

A final thought

No equipment is entirely safe; that is to say, completely free of risk. Consequently, there is always a possibility, however unlikely, that a harmful event might occur. Should it do so, enforcing authorities may require access to the technical documentation to ascertain if the risks were suitably assessed and appropriate protective measures implemented.

But more than that, the analysis will enable you to clearly show from the outset how the obligations of applicable essential safety requirements will be met. And that in turn will assist you in determining what else you will need to include in your technical documentation to demonstrate compliance.

[1] Guideline H-04 will cover this subject, although has yet to be finalised. (It was accepted by the WPG on 19 April 2018, but has not been accepted by WGP.)

[2] For an explanation as to why the risk assessment has to be carried out even when the manufacturer uses harmonised standards to satisfy the essential safety requirements, see footnote 152 of the ‘Blue Guide’ which can be downloaded for free from http://ec.europa.eu/DocsRoom/documents/18027

[3] A list of harmonised standards for the pressure equipment directive can be found at: https://ec.europa.eu/growth/single-market/european-standards/harmonised-standards/pressure-equipment_en (Note: Although this online list is updated regularly, it may not be complete, so be aware that, unlike the Official Journal itself, it does not have legal validity.)

Recent Posts

Leave a Comment

Contact Us

We're not around right now. But you can send us an email and we'll get back to you, asap.