DOI: 10.3303/CET24111051 Paper Received: 30 January 2024; Revised: 6 May 2024; Accepted: 27 July 2024 Please cite this article as: Grillone G., Muratore A., Genco E., Firenze A., Bellissimo M., Giannelli G., Nastasi V., 2024, Safe Management and Risk Evaluation of Pressure Pipes in the Process and Energy Industry, Chemical Engineering Transactions, 111, 301-306 DOI:10.3303/CET24111051 CHEMICAL ENGINEERING TRANSACTIONS VOL. 111, 2024 A publication of The Italian Association of Chemical Engineering Online at www.cetjournal.it Guest Editors: Valerio Cozzani, Bruno Fabiano, Genserik Reniers Copyright © 2024, AIDIC Servizi S.r.l. ISBN 979-12-81206-11-3; ISSN 2283-9216 Safe Management and Risk Evaluation of Pressure Pipes in the Process and Energy Industry Giovanni Grillonea,*, Antonino Muratoreb, Eleonora Gencoc, Alberto Firenzed, Maurilio Bellissimoa, Giuseppe Giannellib, Vincenzo Nastasia aInail, UOT Palermo, Viale del Fante 58/D - 90146 Palermo, Italy bInail, UOT Como, Via Petrarca 4 - 22100 Como, Italy cUniversità di Palermo, Scuola di Specializzazione in Medicina del Lavoro, Piazza delle Cliniche, 2 - 90127 Palermo, Italy dUniversità di Palermo, Dipartimento della Promozione della Salute, Materno-Infantile, di Medicina Interna e Specialistica di Eccellenza “G. D’Alessandro” (PROMISE), Piazza delle Cliniche, 2 - 90127 Palermo, Italy g.grillone@inail.it Process and energy industries include chemical plants, oil refineries and bio-refineries, power plants, etc., in which a variety of pressure equipment/assemblies are located (steam generators, reactors, heat exchangers, pressure tanks, etc.), which use a very wide range of flammable and/or toxic substances. This equipment has historically been controlled, both during construction and operation, while the pressure pipes were considered potentially "dangerous" by the legislation only with the entry into force of the first European Directive 97/23/CE (PED Directive) and the European Directive 2014/68/EU, which modifies and integrates the previous one.The PED directive introduced pressure pipes because they very often cause triggering of accidental events (fires, explosions, toxic releases), involving successively important pressure equipment (steam generators, reactors, heat exchangers, pressure tanks, etc.). Pressure pipes must be particularly monitored and maintained in Seveso establishments (Seveso Directive - 2012/18/EU).In this paper authors suggest to the employer an operational framework for the safe management of residual risks of pressure pipes, during operating phase, due to the installation, use and/or reasonably foreseeable improper use of the aforementioned pipes are described here, showing an application example.It is important to note that, nowadays, there are pipes constructed in accordance with the PED Directive and pipes built before the introduction of these European Directives (the latter lack manufacturer’s certification). Employers in Italy must manage these two different types of pipes in compliance with the Decree of the Ministry of Production Activities No. 329, issued on December 1, 2004, and the Decree of the Ministry of Labour and Social Policies issued on April 11, 2011.Furthermore, authors describe the main effects on the health of workers and citizens living near industrial plants, due to accidents causing fires, explosions and release of toxic substances.Keywords: Pressure Pipes Safety (construction and exercise), incidental events, PED directive, Seveso directive, workers’ health, citizens’ health 1. Introduction Pressure pipes are used to move liquids and gases between the various parts of an industrial plant, connecting pressure equipment such as steam generators, reactors, heat exchangers, pressure tanks, etc.. The chemical substances handled are often dangerous and can trigger fires, explosions, toxic releases with serious consequences both for human health (workers and the population living near the industrial plant) and for the surrounding environment, especially in the case of industrial plants falling within the Seveso directive (2012/18/EU), which contain high quantities of dangerous substances.The employer, in order to manage the pressure pipes present in their industrial plant, must identify those constructed according to the PED directives (97/23/EC or 2014/68/EU) and those built before the abovementioned directives. 301 Afterwards, the employer, in order to manage residual risks and to maintain regular operation of the pressure pipes, verifies that: • pipes built according with PED directives: the equipment is provided with 1) CE declaration of conformity to the PED directive, 2) identification plate on the pressure equipment, 3) use and maintenance instructions issued by the manufacturer; • pipes built before the introduction of PED directives: the equipment is built following good engineering practices. Following authors’ experience in this field, this paper offers the employer a concise framework for safely managing pressure pipes, from the construction phase to the operation phase of the pipes themselves, introducing a method for assessing risks during the operation phase with the aim of protecting health of workers, population and environment. 2. Safe management of pressure pipes during operating phase Pressure pipes, as well as pressure equipment and/or assemblies, introduce a specific risk in the workplace (even if correctly constructed and CE-PED certified) depending on: 1) use condition (pressure, temperature, physical state); 2) place of installation and possible interference with other nearby equipment; 3) type of plant; 4) contained fluid, dangerous or non-dangerous (the dangerous fluids, indicated in the PED directive as group 1, are: explosive, flammable, toxic, oxidising; while the fluids of group 2 are all the other fluids not falling within group 1); 5) Volume (vessels) and Nominal Diameter (DN). The diversity of the abovementioned conditions can lead, for the same type of pipes or pressure equipment/assembly, to different risk levels during operating phase. Main steps suggested to correctly manage pressurized pipes during the operation phase are: STEP A). Pressure pipes for the entire plant, with the relative documentation issued by the manufacturer, must be registered. The census must also include pressure pipes already existing before the entry into force of the first PED directive 97/23/EC and not CE-PED certified. STEP B). Identification of the PED risk category, both for pipes built according to the PED directive and those built before the PED directive, using: a) for pipes carrying gas: table 6 (Dangerous fluid, group 1) and table 7 (Non-Dangerous fluid, group 2) of the directive PED (Figure 1); b) for pipes carrying liquids: table 8 (Dangerous fluid, group 1) and table 9 (Non-Dangerous fluid, group 2) of the directive PED (not shown here). Table 6 of Directive PED: Dangerous fluid Note: Pipes intended to contain unstable gases belonging, according to Table 6, to categories I or II, are classified in category III (PED Directive 2014/68/EU). Table 7 of Directive PED: Non-Dangerous fluid Note: Pipes containing fluids at a temperature above 350 °C belonging, according to Table 7, to category II, are classified in category III (PED Directive 2014/68/EU). Figure 1: Table 6 (Dangerous fluid, group 1) and Table 7 (Non-Dangerous fluid, group 2) of Directive PED: identification of risk category of pressure pipes. It should be noted that for pipes included in tables 6, 7 and 8 the risk category can be: I, II or III; while for pipes falling under table 9 the risk category can be: I or II (for more details, please refer to the PED directive for all the tables relating to the pipes, i.e. tables 6, 7, 8 and 9). If pipe fall into the category lower than PED risk category I, it is allowed that the equipment do not follow the essential safety requirements included in Annex I of PED directive during the design and construction phase, and the equipment itself can be placed on the market and put into service according to the sound engineering 302 practice in use in the country of manufacture belonging to the EU, thus guaranteeing safety of use (PED 2014/68/EU, art. 4 paragraph 3, state of the art). STEP C). Carrying out maintenance interventions, internal checks and periodic checks provided by law, if required (e.g. in Italy periodic checks are regulated by the Decree of the Ministry of Product Activities No. 329, issued on December 1, 2004 and the Decree of the Ministry of Labour and Social Policies issued on April 11, 2011), in order to maintain initial compliance. STEP D). The employer carries out the risk assessment of the pressure pipes during operating phase, taking into account the specific working context and in particular taking into account: a) specific conditions and characteristics of the work to be carried out; b) risks present in working environment; c) risks arising from the use of the equipment and installations themselves; d) risks deriving from interference with other operating equipment. In the risk assessment it is also necessary to consider the cleaning and maintenance interventions of the pipes, in order to protect the maintenance workers and any other workers and/or exposed people. In this work we will focus on point D), taking for granted and carried out by the employer what provided in step A), B) and C). 3. Residual risks: measures provided by the manufacturer and adopted by employer The main preventive measures that the employer must adopt to prevent residual risks, during the operating phase of the pressure pipes, are described by the manufacturer in the use and maintenance instructions for pipes with PED certification, and in good practices for pipes built before the introduction of PED Directives. The following is a sample report derived from authors’ field experience. A. Assembly Carry out the connection of each individual pipe with plant lines and/or equipment, installation of pressure accessories, safety accessories, instruments, taking care to foresee: 1) interposition of gaskets of the type required by the class of pipe used between the flanges of all bolted flanged couplings; 2) bolts for flanged couplings of the dimensions and type required by the class of pipe used; 3) tightening of the flanged couplings in accordance with the best practices; 4) alignment of the flanges on the vertical or horizontal plane and the parallelism of the flanges themselves; 5) visual inspection, when the installation is complete, to ensure that no damage occurred during the lifting and handling of the equipment; 6) pressure test (hydraulic test and/or appropriate supplementary test). B. Commissioning Carry out the commissioning of the equipment, checking: 1) functioning and calibration of pressure and temperature measuring instruments (if any); 2) functioning and calibration of pressure and temperature measuring instruments (if any); 3) complete opening of the shut-off valves placed between the equipment and the safety devices (“PSV” safety valves, if provided) and between the discharge and the PSV (check to be repeated periodically according to current law); 4) connection of the pipe with the grounding system (if provided). The achievement of the operating pressure in each individual pipe must occur gradually. C. Operation of the equipment It is important to avoid, during the entire operational life of the equipment: 1) exceeding the pressure and temperature limits set by the manufacturer; 2) exceeding the internal/external corrosion margin foreseen by the manufacturer; 3) vibrations that can induce fatigue stress on the membranes of the equipment. In addition, the pipe, during the entire operating life, must be subjected: a) periodic checks in accordance with current laws; b) visual inspection to detect fluid leaks; c) checking the regular functioning of the pressure and temperature measuring equipment and instruments; d) checking the protective layer applied on the external surface (if any); e) control of the thickness of the pressure membranes; f) checking the functionality and calibration of all safety devices; g) check the tightness of all flanged connections; h) check of external insulation (if any). Control activities and maintenance interventions, appropriately recorded, must be carried out by specially trained personnel. Furthermore, the employer must pay attention to: 1) permissible corrosion according to the manufacturer’s recommendations; 2) permissible fatigue according to the manufacturer’s recommendations and the good state of art; 3) permissible viscous creep, according to the number of operating hours, at the specified temperatures, recommended by the manufacturer. D. Repair and modification interventions Manage repairs and/or modifications to the pipe during its entire operational life according to technical and legal regulations. E. Disposal The employer, as prescribed by the manufacturer, will carry out, at the end of the expected life, the safe decommissioning of the pipe by carrying out the appropriate reclamation operations of the surfaces wetted by the fluid, the collection of the discharged fluids, the elimination of the insulation and the disposal of materials in accordance with current regulations. 303 4. Method for risk assessment of pressure pipes during operating phase The method used assigns a value to the risk level “R” of a dangerous phenomenon by composing the severity of the damage or magnitude, “D”, and the probability, “P”, that this could occur: R = D x P (1) Equation (1), simple in its conception, is difficult to use in practice to determine the risk level of each pressure pipe. Therefore, an index method is proposed to determine the level of risk of pressure pipe by the following equation (Muratore et al., 2021): IR = ID * IP (2) where IR is the pressure pipe risk index, ID is the severity index of the damage and IP is the probability index of the damage. 4.1 Severity index of the damage ID The severity index of the damage, ID, is related to IC, which is the PED category index of the pipe: ID = IC (3) Authors propose to assign integers from 1 to 5 to the category index IC, matching the risk category PED to the possible damage size, as detailed in Table 1. Table 1: Ic PED category index Ic (*) PED Risk Category Size of damage 5 III High. Connected events can compromise the integrity of other pressure equipment in plants falling under Seveso Directive. 4 III Medium. Connected events can compromise the integrity of other pressure equipment in plants NOT falling under Seveso Directive. 3 II Medium-Low. The connected events can compromise the integrity of the main parts of pressure pipes. 2 I Low. The connected events can compromise the integrity of the main parts of pressure pipes. 1 Equipment falling in Article 4, (3) Directive 2014/68/EU (below category I) Very Low. Connected events can compromise the integrity of some parts of pressure pipes. (*) Ic is reduced by 1 unit if the equipment is built following PED Directive, because, in this case, it is guaranteed that pipe, already during construction phase, is adequate to safety essential safety requirements, differently by pipe built before the introduction of Ped Directive. 4.2 Probability index of the damage IP The probability index of the damage, IP, is related to IE, which is the exposure duration index: IP = IE (4) Authors propose to assign integers from 1 to 5 to the exposure duration index IE, matching the duration of exposure with the working frequency of the pressure pipes, as detailed in Table 2. Table 2: Ie exposure index Ie (*) Duration of exposure Frequency 5 H24/365 Loop 4 40 h / week Full time 3 20 h / week Partial time 2 8 h / week 1 day a week 1 4 h / week ½ day a week (*) Ie is reduced by 1 unit if workers are well trained on the risks associated with the use of pressure pipes. 4.3 Risk index IR Table 3 shows the risk matrix by which the risk index IR of a pressure pipe is determined, after evaluating ID and IP for the same pressure pipe by means, respectively, of Table 1 and Table 2, using relationship (2). 304 Table 3: Risk index IR= ID*IP (ID=severity index of the damage, IP=probability index of the damage) IR= IDxIP IP ID 5 10 15 20 25 4 8 12 16 20 3 6 9 12 15 2 4 6 8 10 1 2 3 4 5 For values of IR>16 the risk is high while for values 6