PED Certification

Without prejudice to the concepts expressed in directives 85/374/CE and 92/59/CE, relating respectively to liability for damage from a defective product and to general product safety and the economic and commercial matrix of PED based on the new approach criterion (New Approach), the directives on the global approach (Global Approach) which will aim at the free movement of goods based on the philosophy of the Blue Guide will be issued shortly.

In the case of PED this will mean free movement of the pressure equipment with the same guaranteed level of safety. Since safety is the cornerstone of PED, in order to eliminate all possible sources of danger, boilers and full compliance with 626/94 are also required (“the designers choose machines, as well as protective devices that meet the essential safety requirements – Res – provided for in the laws and regulations in force”) and a serious and in-depth risk assessment (VdR) to obtain the optimum result.

It is very difficult to evaluate the risk in a generic way and without reference to specific cases given the wide typology of pressure equipment and the multiple uses of the same.

For this reason, our considerations here apply to pressure vessels and exclude steam generators, piping, valves, various instruments, etc. while considered in PED.

Although it may seem obvious, the first thing to do is to analyze the appliance to classify it according to PED and to hypothesize the problems that may arise during construction and operation.

Here it is a list of the items to consider to draw up a brief description of the tank under consideration:

• type;
• operation;
• volume;
• content;
• place of installation;
• installation context;
• diameter;
• length/height;
• base and plating thickness;
• main materials of the bottoms, the plating, the nozzles;
• number of nozzles, openings and related services;
• type of anchor.

Let’s consider a horizontal tank on saddles with a volume of 400 cubic meters to be used for the storage of LPG (propane-butane mixture). No other use has been foreseen in the design phase.

It will be installed in Italy, therefore the normative reference is the Dl 93-2000 which implements the community directive 97/23/CE (PED).

Here are the tank data: diameter 4.2 m; length 32 m; materials: P355 NL2 (UNI EN 10028.3/2000: harmonized standard) for plating and hemispherical bottoms; Astm A 333 Gr. 6 for the connection pipes; Astm A 350 LF2 for the connection flanges; Fe 510 D1 (Uni En 10025) for internal stiffening rings.

Tank equipped with two DN 600 manholes: one for servicing the nozzle connections, the other equipped with an internal ladder for inspection and maintenance during operation. It is also equipped with connections for the instrumentation and to connect it to the piping of the system.

It is intended to be buried and is supplied with two support saddles, one of which is fixed and one movable, to facilitate assembly on-site and for possible but unlikely thermal expansion, since it is buried. It must be installed on foundation plinths suitably designed, sized and built to avoid sagging.

The supply does not include safety valves and instruments. The “Description of the container” lists the characteristics of the tank taken here for example for risk assessment based on Legislative Decree 93-2000 which implements PED directive.
Annex 1 of this decree lists the essential safety requirements (Res) to be considered during the design phase and for risk assessment. They must be interpreted to take into account the design choices of the technical equipment and subsequent processing or interventions.

To identify the hazard of the events connected to the risks of using the tank, we have set three main hazard categories. It is a choice, which can also be different, made because the information can be easily organized in the form of a matrix and the results are very intuitive. In addition to the frequency, deduced using technical and historical analysis, and the relative probability of occurrence of the risky events, their dangerousness and the damage that could derive from them were assessed.

The associated risk is assessed as a function of the two variables: frequency/probability p; hazard of the event/damage resulting from d:

R = p x d

To arrive to a quantitative assessment, a range of variation from 0 to 10 was set for both variables. Their link is obtained according to the position in the assessment risk matrix.

In the boxes of the matrix, the risk factor of the event is read as a direct product of the probability and danger (damage) associated with it.

Events classified from 0 to 2 are considered with low (B) frequency/probability of occurrence; from 3 to 6 with average (M); from 7 to 10 with high (A). Events with a hazard factor (damage) between 0 and 3 are classified as a low hazard; between 4 and 6 average; between 7 and 10 high.

Five risk classes were therefore established: low (B), medium-low (M-B), medium (M), medium-high (M-A), high (A). Events with high (damage) danger are classified as high risk regardless of the associated frequency. In fact, it must be considered that events of high danger and with a high frequency/probability of occurrence generally have an associated residual risk and that, by their nature, they are particularly taken into consideration by adopting the necessary measures to eliminate them.

At this point it is necessary to establish a real list of “sources of potential risk factors” and for each of them indicate appropriately: assessments, precautionary measures and residual risks. As already said, due to the numerous construction and use typologies of the pressure equipment it is very difficult to go into details.

Based on sector studies, technical literature and long experience acquired in the construction of pressure vessels for dangerous substances, an exemplary list of potential risk factors has been drawn up for the example considered here, with each factor alongside the frequency and the danger.

The method used here to draw up a risk assessment can be adapted for many other applications: single, small, medium or even very large plants such as an entire refinery, including the “event tree” and the probability of accidents occurring in critical points.

The principles to be applied are always the same: elimination or reduction of risks to the extent possible; use of appropriate safety measures against non-eliminable risks; user information on residual risks. There is a lot of work to be done on the Res: design, manufacture, materials, specific pressure equipment.

From a strictly operational point of view, the Res are verified and complied with using a checklist which makes the work of the designer and of those who make the risk assessment easier.

Another purpose of the risk assessment is to illustrate the factors connected to the appliance and to guide the designer in taking note of all the problems that may affect its safety.

For systems at risk of major accidents, the constraints indicated in Legislative Decree 334/99 which transposes European Directive 96/82/EC (major accidents) must be observed, while for “LPG deposits in fixed tanks with a capacity greater than 5 cubic meters” the provisions of DM 10/13/1994 apply.

CE TECHNICAL FILES

Acciaierie Venete S.p.A. – Dolcè (VR)

PentaSystem S.r.l. – Badia Calavena (VR)

LaserJet S.r.l. – Cagnano di Poiana Maggiore (VI)

Paint stripping Veneta S.r.l. – Albaredo d’Adige (VR)

GBE S.p.A. – Orgiano (VI)

ADDITIONAL INVESTIGATIONS – RESIDUAL LIFES

Uteco S.p.A. – Colognola ai colli (VR)

OMV Machinery S.r.l. – Verona

Vetrerie Riunite S.p.A. – Colognola ai colli (VR)

Skretting Italia S.p.A. – Mozzecane (VR)

Quarella S.p.A. – Verona

PRESSURE EQUIPMENT

Contri Spumanti S.p.A. – Cazzono di Tramigna (VR) or 2015

CALV – Agricultural Consortium of NordEst Soc. Coop. – Verona

Social Cellar of Custozza S.a.c. – Custoza (VR)