SIZING OF REMI PLANTS

Transcription

1 SIZING OF REMI PLANTS

2 PROCEDURE "SIZING OF REMI PLANTS" 1) FOREWORD (SCOPE - OBJECTIVES - LIMITS) The sizing engineering, functional and resistance standards of a natural gas receiving, reduction and measurement plant, set by the Transporter as minimum requirements, are described in this procedure. This procedure has been drawn up in accordance with the principles set forth in current national and international technical standards and law and on the basis of the specific experience of the Transporter in the field in question: current law provisions must be observed in all cases as regards the safety, engineering, construction and maintenance of measurement instruments. The main sizing criteria for natural gas receiving, reduction and measurement plants illustrated in this procedure: provide the minimum technical-construction sizing criteria for REMI plants without ruling out the adoption, by the owner, of upgrading solutions agreed on by the parties; define pressure, temperature and flow rate parameters needed for engineering purposes; classify REMI plants according to public or non public utility and interruptibility and, on the basis of this classification, define the sizing criteria of the regulation and measurement units; said destinations are selected under the full and sole responsibility of the owner of the plant; indicate the charatersitics of materials and instruments; indicate the formulae and parameters required to calculate plant sizing; indicate the utilisation fields of the primary measurement system (volume and venturimeter measurement) and the standardised engineering configurations in accordance with national and international standards; prescribe the use of suitable equipment for automatic collection and processing of measurement data and relative remote transmission. 1.1)Plant with adjusted pressure and temperature The building blocks of REMI plants are the following, described in the order in which the gas flows: a) Upstream section, including the pipeline section between the delivery point and the upstream filter manifold, the on-off valves, the insulating joint and emergency valve (optional) b) Filtering unit (to split liquids and/or solid particles that may be in the gas) c) Preheating unit (optional) d) pressure regulation plant, including service regulators, control and emergency regulators ("monitor"), shutdown device (optional), blowdown valve e) metering plant and associated by-pass f) exit section, including downstream emergency valve, the on-off valves and the insulating joint.

3 In addition, the following elements are also components of the REMI plant : g) fuel system for the preheating unit (optional) h) odorization plant (optional) (The odorization of the gas for domestic and related use in the distribution networks is requested by the law N.1083 of The odorization plants are regulated by the rule UNI-CIG 9463 and must be installed downstream of the gas measurement. The schemes contained in this procedure do not cover the odorization plant). To assure continuity of operations the units b) c) d) are usually installed in series in two parallel lines. These lines are usually called regulation lines. Solutions different from those presented in this procedure may be adopted if equivalent or if they provide improvements from the functional point of view: the technical assessment will be carried out on a case by case basis. 1.2)Plant with pipeline pressure and temperature Measurement plant with variable pressure and temperature, in the case of particular operational conditions, can be installed, after agreement between the parties, upstream of the pressure regulation. In any event, the measurement plant will be installed immediately downstream of the filtering unit. The scope in this case only covers the measurement plant or the installation of all the plant parts described in points 1.1c 1.1d 1.1g 1.1h. 1.3)REMI plant with max upstream p 5 bar These types of plant, consistent the other sizing criteria described below, must be developed in accordance with the criteria contained in Attachment 7. The main difference with plants where max upstream p > 5 bar is that plants 5 are allowed a filtering unit with lower performance, but this must still assure the normal functioning of the downstream plant. If these plants are "Gas pressure reduction plants according to the rule UNI-CIG 8827, their development should be consistent with this rule. Attachment 7 contains its main features. In the Attachment 7 there are also some schemes valid for REMI plant with max upstream P 5 bar, not reduction plant, with Qimp. < 300 m3/h and with fiscal measurement of the volumes only. 1.4)Functional types of the plants Plants have different characteristics according to the following types of customer supplied: a) Non-Interruptible and Public Utility (Households, Hospitals, Schools, Nursing Homes, etc. for which unplanned supply interruptions will have serious impacts and may give rise to safety issues). b) Non-interruptible and not Public Utility (Industrial customers, etc. for which unplanned supply cut in the gas supply may have significant impact). c) Interruptible at any time (customers for which unplanned supply interruptions have minimal impact). These categories are assigned by the owner of the metering plant and documented as such.

4 1.5)Accessory REMI plants It may be necessary, for fiscal reasons and in order to ensure correct measurement, to have an accessory measurement plant parallel to the main one. In this case the minimum configuration (concerning an interruptible plant with supplied flow rate < 300 m3/h) is contained in the scheme FA of Attachment 7. If the plant is not interruptible or with a supplied flow rate > 300 m3/h, the same approach should be used, consistent with this procedure and attachments, and considering the possible installation of other equipment (e.g. filters or regulators). The accessory REMI plants will normally be located downstream of the main measurement plant. 1.6)Law and standard references The structure of the regulation and measurement plant described in this procedure, as far as the safety and the functional aspects are considered, complies with the rule UNI-CIG and with the rules EN (pressure regulation plant-functional requirements) EN 1776 (measurement plant-functional requirements). The solutions to be implemented for cases not covered by this procedure, or not specified in detail, should be agreed in advance with Snam Rete Gas. In designing the plant, in addition to the criteria contained in this procedure, the following rules should be taken into consideration: EC laws and Directives in force at the time of the design standards (UNI-EN-ISO) in force at the time of the design legal metrology standards possible additional requirements for particular operational cases, such as, for instance: minimum external temperature lower than 10 C, two or more REMI plants supplying the same distribution network. 1.7)Pressure equipment (Pressure Equipment Directive 97/23 CE) This Directive, applied by D.Lgs. n 93 of for REMI plants includes the following equipments: Primary measurement elements (meters, orifice-fitting) On-off valves Pressure regulators Safety and shotdown valve filters, exchangers and other containers. Therefore in the design, building and testing of these equipments one has to comply with the dispositions of the Decree mentioned above. 2) FLOW RATE, PRESSURES AND TEMPERATURES 2.1)Flow rate The flow rates, if not stated otherwise, are always expressed in m3/h at the standard conditions, i.e. in m3/h at 15 C and 1,01325 absolute bar ) Delivered flow rate (Qero) This is the max actual flow rate that the system can deliver.

5 2.1.2) Minimum flow rate (Qmin) This is the minimum flow rate actually required by the plant ) Plant flow rate (Qimp) Plant flow rate is defined as the maximum flow rate for which the size of the plant has to be determined. It is appropriate to also consider potential future enhancements. At the time of construction or reconstruction of the plant Qimp should not be lower than 125% of Qero. The maximum value of Qimp must allow normal operation of the REMI plant at Qmin.

6 Regulation line flow rate (Qlin) This is the flow rate which regulates the sizing of the regulation line according to the following scheme: PLANTS N.LINES PARAMETERS TO DEFINE Qlin VALUE CLEARLY INTERRUPTIBLE 1 LINE : Qlin = Qimp NOT INTERRUPTIBLE TO SUPPLY PUBLIC UTILITY CUSTOMERS 2 LINE : Qlin = Qimp 3 CHOICE BETWEEN: a FOR EACH LINE b - Σ 3 LINES : Qlin 0,5 Qimp : Qtot 1,5 Qimp with always 2 lines able to supply Q 2/3 Qimp. > 3 TO BE ASSESSED EVERY TIME NOT INTERRUPTIBLE TO SUPPLY NON PUBLIC UTILITY CUSTOMERS 2 LINE : Qlin Qimp/2 3 TO BE ASSESSED EVERY TIME 2.1.4) Flow rate off the end of the reading scale of the measurement plant (Qf.s.) This is the maximum flow rate which can be measured at the top end of the reading scale of the measuring plant, whose value must be increased by a certain % in relation to the flow rate delivered, to allow the correct determination of the volumes actually offtaken ) Emergency flow rate (Qemergenza) The emergency flow rate is the flow rate delivered in case of emergency by temporary equipment, and the upstream and downstream emergency valves, if present on the plant. 2.2)Pressure Where not otherwise stated, the pressure values are indicated in relative bar (o mbar). The meanings of the most useful pressure concepts are described below ) Maximum operational pressure (p max es) The maximum pressure the system may sustain during normal running conditions ) Project pressure (p pro) or (Ps) The pressure on which the design calculations are based. This pressure must be higher or equal to the maximum calibration pressure of the release device whose values are defined in the same decree referred to in the following point

7 2.2.3) Minimum operational pressure (p min) The minimum pressure the system may sustain during normal running conditions ) Testing pressure (p col) The pressure used for the mechanical resistance test of the Main Circuit. Acceptable values are those defined by: MINISTERIAL DECREE 24 NOVEMBER 1984, titled "FIRE PREVENTION RULES FOR THE TRANSPORTATION, DISTRIBUTION, STORAGE AND UTILIZATION OF NATURAL GAS WITH DENSITY NOT HIGHER THAN 0,8" LAW DECREE N 93 IMPLEMENTATION OF THE DIRECTIVE 97/23/CE CONCERNING PRESSURE EQUIPMENTS (P.E.D.) ) Pressure for field pneumatic tightness test The pressure used to test the tightness of the pipes and plants. It is equal to the maximum available operational pressure ) Upstream pressure (p mon) The pressure at the entry of any REMI. Usually the following values are identified: The maximum value (p mon max), communicated by the Transporter when defining the connection; The value for preheating sizing (p mon pre) The values of minimum contractual pressure as defined in paragraph 2 of the chapter Entry and redelivery points pressure (long period minimum contractual pressure p min L, minimum contractual pressure published yearly p min A ) ) Minimum pressure to size piping (p min P) The minimum pressure for the geometric sizing of the pipe. This value must be equal or lower than p min A and will be chosen by the designer considering the provisions of paragraph 2 of the chapter Entry and redelivery points pressure ) Adjusted pressure (p reg) The pressure at the exit of the pressure regulation unit. It may be changed according to the management needs of the plant. Its maximum value (p reg max) can be equal to the minimum pressure to size piping and affects the sizing in terms of mechanical resistance of the relevant part of the plant. The minimum value of the adjusted pressure (p reg min) experienced for the operations at the Qimp shall be used for the geometric sizing.

8 2.2.9) Minimum pressure to size the measurement (p min M) The minimum pressure to size the measurement main device and the pipes connected to it. This value will be defined according to the following table: P min M p mon pre 24 bar The minimum value between p min A * 1,4 and 35 bar 12 p mon pre < 24 bar The minimum value between p min A * 1,4 and 20 bar p mon pre < 12 bar Equal to p min A ) Measurement pressure (p mis) The pressure used to measure gas ) Downstream pressure The pressure at the exit of the REMI plant ) Differential pressure The pressure difference between the upstream and downstream intake of a measurement diaphragm ) Vent pressure The pressure for the opening of a vent valve, which is higher than the regulated pressure ) Locking pressure The pressure to close the stop valve. In the case of interruption as a result of exceeding the regulated pressure, the locking pressure is higher than the vent pressure ) Nominal pressure The nominal pressure is the conventional indication of the rel. max. pressure beyond which the mechanical stability is no longer guaranteed. Based on this, dimensions of pipe elements are set such as flanges, valves, faucets. The coupling nominal pressure project pressure should be set on the basis of the current rules related to the nominal pressure. As an example the schemes of the nominal pressures are provided.

9 SCHEME PN (UNI-EN-1333) (Valid for operational temperature up to 120 C) PN 1 Maximum project pressure in bar 2 PN Maximum project pressure in bar SCHEME ANSI (B ) CLASS Maximum project pressure in bar ANSI For operational temperature up to 50 C For operational temperature up to 100 C N.B. In cases where PN and the associated ANSI are not easily found in the market, the coupling should be done at the higher commercial PN or ANSI ) Seal pressure for the preheater and the filter The following scheme indicates, for the most frequent max operational pressures, the minimum seal pressures required by this procedure. Maximum operational pressure Bar Minimum seal pressure bar 1, On the containers it is not necessary to install safety devices (blowout disk, safety valves); unless the competent authorities expressely require it in particular cases. It is not necessary to check the sizing of such devices eventually installed. 1 I valori di PN indicati sono solo quelli per i quali le Norme UNI hanno previsto l'unificazione dei vari elementi di tubazione (flange, valvole, rubinetti, ecc.) 2 I valori sono arrotondati per difetto

10 2.3)Temperature 2.3.1) Project temperature The project temperature to be considered for the sizing of the plant in terms of mechanical resistance, are: C for the part of the plant between the upstream flange of the filter and the downstream flange of the preheater, inclusive of the possible transit pipe between the two devices C for the rest of the plant. In case of external temperature lower than 10 C the manufacturer must define the value of the minimum project temperature ) Temperature of the gas in entry A value of +5 C is normally assumed if not otherwise stated. 3) GENERAL PROVISIONS The plant has to assure regular running at different operational conditions, as follows: The plant is not subjected to significant stresses other than those associated with the gas pressure The external conditions are: temperature C humidity up to 95 % The noise level during the normal operation conditions should not be higher than the limit set at the plant s location The charts to be used within this procedure are contained in attachment 10. The REMI plant has to be built and run according to the laws and rules issued by the appropriate bodies and authorities. In addition, for the preheating plants and the pressure containers and for the electric devices, the rules issued by the competent bodies should be followed. The electric devices in places with fire and explosion danger should be reported to the appropriate local health authority (ASL) by the plant manager. 3.1)Application of the Directive 97/23/CE (P.E.D.) With reference to the content of point 1.6 all the relevant devices must comply with EC regulations and bear the EC mark as described in the same document. The article 22 (Final and temporary dispositions) of the DLgs. n 93 of defines the application of the Directive in the case of building new plants. In addition, as far as safety devices are concerned (safety valves, monitor, blocks), the essential requirements defined in the attachment 1 point 2.11 of this Decree must be satisfied. 3.2)Detail of the general dispositions The general provisions for the sizing are the following: a) It should be possible to run the measurement plant with flow rate equal to Qimp. and upstream pressure values equal to its minimum value.

11 By this principle and considering that in some cases it is convenient to have the highest downstream pressure as possible, the sizing criteria should aim to minimize the pressure losses and to assure the normal running of the plant in all the operational conditions. b) The plant by pass, in relation to point a), should not represent a bottleneck which increases the pressure losses creating utilisation problems. c) Low speed allows better regulation, lower noise and pressure losses. d) To assure an appropriate filtering (separation of the liquid and/or solid particles present in the gas) for the safe and regular running of the operations, the separating filters must be physically separated by the preheaters. e) The measuring plant is made up of a main measuring system complying with the legal metrology regulations and, if requested, by a backup system (or equipment) to be used in case of failure of the main system or as control. The main measuring system must provide in an automatic and continuous way the values of the volumes and of the calculated flow rates needed to carry out the measurement, save the data on gas quantities, the diagnostic and the operational data. These data should be readable directly at the site or transferable by telereading. The plant can be made up of one or more measuring units in parallel, so that, considering the nature of the operation (wide seasonal variation in the flow rate or specific types of offtake) and the Qimp of the plant, the flow rate offtaken always lies within the valid range to correctly determine the measured quantity. f) The pressure regulation plant should not cause oscillations and pulses which may determine measurement errors. It is preferable to insert the possible flow rate regulation downstream of the measuring plant. g) The downstream on-off valves of the regulation lines, if present, divide the plant in two parts: (based on the connection of the taps of the safety devices upstream of the on-off valve under discussion) The part upstream of the downstream on-off valves (inclusive), which must sustain the maximum upstream pressure The part downstream of the downstream on-off valves, which must sustain the expected max. regulated pressure. For the cases where these valves are not considered, the plant must sustain the upstream pressure up to the regulator (inclusive). h) Usually the removable connections must be flanged (for the valves also connections of the type welded flanged are accepted and for DN 4" also loose flanges are accepted). Threaded connections are accepted provided they assure the seal and the safety and resistance requirements required by the present rules. They should also assure, in the case of maintenance and substitution, the functionality

12 and practicability at least equal to the flanged connections and comply with the current rules. i) In general the devices should be located in a building; the standard solution anticipates: a room for the reduction and measurement devices, a room for the possible heating system and a room for the electrical equipment which cannot be installed in dangerous area. If the cabin is not built, the measurement devices should be anyway protected, therefore: The measurement devices have to be located in appropriate rooms which allow people to be present An appropriate shield for the meters has to be considered. In all cases the enclosure is necessary. 4) PARAMETERS AND FORMULAS OF COMMON USE Due to the fact that natural gas is variable in its composition and that it is not necessary to obtain absolute accuracy of the parameters commonly in use to size the plants, average indicative parameters are acceptable for this procedure and, where possible, simplified formulae. The formulae and parameters in the calculation for plant sizing are: 4.1)Parameters ρs gas volumic mass at 15 C and 1,01325 bar = 0,70 kg/m 3 Mm Vm gas molecular mass = 16,57 g/mol gas molecular volume at 15 C and 1,01325 bar = 23,64 dm3/mol σ isoentropic index = 1,31 ρsa air volumic mass at 15 C and 1,01325 abs.bar = 1,22541 kg/m3 µ gas average dynamic viscosity = 10,8 mpa.s Pb P K average barometric pressure = 1 bar absolute pressure (bar) = p + 1, where p = relative pressure in bar deviation coefficient from the law of perfect gas compared to the conditions of ρs; K = 1-0,002 p H enthalpic overflows which can be obtained, in kj/kg or in kcal/kg, from the diagram Pressure/Enthalpy for the pure gas (see attachment 1)

13 t gas temperature = 5 C, if not otherwise specified. 4.2)Formulae 4.2.1) Calculation of the pipe diameter Assuming the gas temperature equal to 5 C, the simplified formula is: 345,92* Q*(1 0,002* p) D teo = where: v*(1 + p) v = speed in m/s 345,92= numeric constant Q= flow rate in standard conditions in m3/h p = relative pressure in bar, at the entry of the pipe The theoretical diameter obtained by the above calculation must always be rounded to the normalized diameter defined at point 5.1 applying the following rule: DN 0,95 D teo 4.2.2) Calculation of the pressure loss in the pipe To calculate the pressure losses the following simplified Renouard formula valid for high and medium pressures and for values of Q/D < 150 should be used: 2 1,82 4, 82 ( ) dp = 1000 * P P 25, 24 * L * Q * D where: dp = pressure loss in mbar 1000 = numeric constant P = absolute pressure in bar, at the beginning of the pipe 25,24 = numeric constant L = length of the pipe in m Q = flow rate in standard conditions in m3/h D = internal diameter of the pipe in mm 5) NOMINAL DIAMETERS TO USE - MATERIALS 5.1)Nominal diameters (DN) The most used DN are the following: etc. with increase of 50 mm. 5.2)Materials D.M definitions apply.

14 6) TYPES OF ON-OFF VALVES TO BE USED The different types of valves, according to their location, are: a) From the delivery point to the valves upstream of the filtering unit ball valves or conic plug valves must be installed. Ball valves can also have venturi passage with ratio between the passage diameter (d) and the diameter (DN) of the valve 60%. b) Upstream and downstream valves for the preheating unit and/or of the regulation unit should be as indicated in a). c) The on-off valve of the blowdown valve must be a ball valve with full passage. d) The on-off valves of the measuring plant and of its by-pass must be ball valves (with full or venturi passage as in a) or butterfly valves, with the exception of the valve upstream of the venturimetric section which has to be a ball valve with full passage. e) Exit valves should be as indicated in d). f) For all other possible valves, the type will be defined on the basis of their function, consistent with the above criteria. 7) SIZING AND MAIN FUNCTIONAL INDICATIONS The plants will be designed following the flow schemes contained in Attachment 3. The quantity and location of the valves, of the equipment and pressure and temperature intakes must be, in their minimum configuration, that described in those schemes. They may be increased in number only to improve the plant functionality. To simplify the check and design operations, the sizing criteria described do not take into account the pressure losses through the plant, assuming that in most cases this omission is acceptable. For the plant resistance, the principles defined in the chapter General Criteria and the information supplied in the chapter Pressures apply, except for what is specified in the following points. 7.1)Diameters and maximum operational pressures of the valves, of the pipes (including the manifolds) and of connected equipments The valves must have the same DN of the pipe where they are inserted. Every section of pipe must have uniform diameter. The DN must be calculated from the theorical diameter according to the rule in point The theoretical diameter must be calculated in such a way that the speeds indicated in the following scheme should be respected with the specified flow rate and minimum pressure values. In the following scheme the maximum operational pressure values are indicated to define the project pressure relevant for the mechanical resistance of each component of the plant.

15 The details in the following points apply to the geometric sizing and in terms of mechanical resistance. For the parts of the plant not included in the scheme, the general criteria already defined apply. Regarding the number and the location of the insulating joints the present procedure assumes that REMI entry and exit sections are not underground, while the upstream and downstream pipes of such sections are underground.

16 SECTION V max m/s Flow rate Q PARAMETERS TO SIZE THE DIAMETERS SIZING PRESSURE Measure with regulated p. Measure with var. p.and t. NOTE 1 Upstream section 30 Imp p min P p min P Complying with point Pipes, valv. filter FILTER 30 Lin p min P p min P DN filter DN pipe 3 Pipes, valv. Preheat. PREHEATER 30 Lin p min P p min P DN preheat.. DN pipe 4 Pipes, valves DN upstream regulator upstream 1 regulator p min P 30 Lin p min P DN REGULATOR 5 Pipes and valv. Downstream 25 Lin < p min P < p min P See point regulators 6 Manifold downstream regulators 25 Imp < p min P < p min P See point Valv. feed. And exit measure. lines 25 Imp < p min P p min P See point Pipes downstream 25 Imp and upstream entry < p min P p min P and exit valves See point Imp measure. lines 9 By-pass pipes and valves measure lines 30 Imp < p min P p min P See point Pipes and valves series parallel 25 Imp < p min P p min P See point Pipes. Meter lines p mis METERS 25 Ero ( p min P) p min M Complying with Pipe venturimetr. line p mis 25 Ero ( p min P) p min M Complying with Manifold p min P 30 Imp p min P downstream filters 14 Manifold upstream preheating 30 Imp p min P p min P 15 Manifold upstream p min P 30 Imp p min P regulators 16 Exit section 25 Imp < p min P < p min P See point Pressures: p min P p min M p mis minimum pressure to size piping minimum pressure to size measure measure pressure

17 PRESSURE TO SIZE THE MECHANICAL ENDURANCE SECTION Measure with Measure with var. regulated p. p.and. NOTE 1 Upstream section p mon max p mon max 2 Pipes, valv. filter For the pressure containers, p mon max p mon max FILTER see point Pipes, valv. Preheat. For the pressure containers, p mon max p mon max PREHEATER. see point Pipes, valves 4 upstream 1 regulator REGULATOR p mon max p mon max Up to the 1 st valve in the gas p mon max p mon max direction p min P p min P After the 1 st valve in the gas direction Pipes and valv. 5 Downstream regulators Manifold 6 downstream regulators 7 Valv. feed. And exit measure. lines Pipes downstream 8 and upstream entry and exit valves measure. lines By-pass pipes and 9 Valves measure lines 10 Pipes and valves series parallel 11 Pipes. Meter lines METERS p mon max p min P p min P p min P p min P p min P p min P p mon max p mon max p mon max p mon max p mon max p mon max 12 Pipe venturimetr. line p min P p mon max 13 Manifold downstream filters p mon max p mon max 14 Manifold upstream preheating. p mon max p mon max 15 Manifold upstream regulators p mon max p mon max 16 Exit section p min P p min P Pressures: Up to the 1 st valve in the gas direction After the 1 st valve in the gas direction p min P p mon max minimum pressure to size piping maximum entry pressure

18 7.2)Upstream section This is the section between the delivery point and the upstream filter manifold, the latter and possible upstream emergency valve included. The general upstream on-off valve of the REMI plant (1st valve in the direction of the gas downstream of the delivery point) must be located as close as possible downstream of the delivery point. The pipes must have uniform diameter and such dimension as to satisfy the following condition: a) gas speed must be 30 m/s. To calculate the speeds the formula at point 4.2. can be used, where: Q = Q plant in m3/h P = Minimum pressure to size piping (p min P) The (optional) upstream emergency valve must be installed outside the room in the section between the general on-off valve and the next on-off valve/s. Usually it is located downstream of the upstream insulating joint and must be electrically isolated if it is by-passed from underground pipe protected by current. The valve and the connected pipes must be sized to allow the supply of the flow rate in case of emergency. 7.3)Filtering unit The filters must be efficient enough to hold both the liquid and solid particles present in the gas. In addition the filters must have such a filtering capacity as to assure the normal operations of specific equipment downstream of the same filter (es. regulator, meters, etc.) with Qimp ) Filter with condensate separator The filter can be made up by two separate stages (solid and liquid particles). The filtering element must be changeable. The minimum filtering capacity must be equal to: 98% of the solid particles 5 micron 100% of the solid particles 10 micron 95% of the weight of the carried liquid particles. The collection capacity should be no lower than 12% of the total capacity of the filter and shouldn t impact the gas flowing zone to avoid obstruction. The pressure loss through the clean filter should not be higher than 0,1 bar with flow rate equal to Qlin, with pressure equal to a p min P. The manufacturer must declare this deltapi The filter must be equipped with an indicator of the pressure loss between entry and exit (dpi), with on-off valves and possible by-pass. The DN at the entry and exit of the filter should not be lower than the DN of the pipes connected to it. A full size quick closing is recommended to substitute the filtering element in short time.

19 For the project and building criteria, the rules in force on this subject apply. In particular the provisions of point appy ) Additional filter ustream of the meters In order to avoid damage to the meters in the starting phase of the plant, additional filters can be installed upstream of the meters, and they should be removed after 2 months to avoid pressure losses or functional defects. 7.4)Heating plant and preheating unit (See note at point ) The temperature of the gas after the reduction must be regulated at an average value of 5 C and in any case cannot be lower than 0 C: this must be assured by the preheating plant for the Qimp with an upstream pressure higher or equal to that of the sizing of the preheating. The preheating plant must assure regulation of the gas temperature with variations, between minimum and maximum value, lower than 8 C (on average ± 4 C versus the regulated value). Insulation of the preheating circuit is recommended. The connection between preheaters downstream of the same preheaters is allowed by inserting an on-off valve. When the sizing pressure for the preheating is 12 bar, or the pressure overfall is 12 bar the gas preheating is optional ) Hot water preheater (Note) The main characteristics are: The DN at the entry and at the exit cannot be lower than the DN of the pipes connected to it. It is advisable to inspect the tube bundle, where the heat exchange takes place. The speed of the gas in the tube bundle, at the minimum operational pressure, should be 40 m/s The pressure loss at the gas side between entry and exit, in the worst operational conditions, must be 0,2 bar at the p min P. The manufacturer must declare this deltapi. The preheater must be provided with: On or more vent valves on the gas side An air vent valve at the side of heating fluid A vent valve for the heating fluid. For the project and building criteria, the rules in force on this subject apply. In particular the provisions in point apply. The capacity in kcal/h is obtained by the formula: where: C h * ρ Q s * = = 0, 78 * h * Q ηprer

20 ρs = gas volumic mass at 15 C and 1,01325 bar 0,7 kg/m3 η prer = preheater efficiency 0,9 Q = maximum line flow rate in m3/h in standard conditions h = enthalpic overfall in kcal/kg equal to the difference between gas enthalpy at Pv - tv conditions and gas enthalpy at Pm - Tm conditions (to be obtained on the basis of the scheme in attachment 1). Pm = absolute upstream pressure to size the preheating tm = 5 C (average value) = delivery temperature Pv = minimum absolute pressure foreseen downstream of the regulator (p reg min) tv = temperature downstream of the pressure regulator. If the capacity C is expressed in kw and the entalphic overfall h is expressed in kj/kg, the previous formula becomes: C = 0, * h * Q NOTE: This procedure deals specifically only with the cases of hot water preheating plants, since they are the most frequently used. Operational temperatures even higher than those indicated may be reached if using different preheating plants (which may be used, if complying with the rules in force). In this case, the sizing in terms of mechanical resistance should take into account the necessary correlation between temperature and pressure ) Thermal capacity The total capacity of the thermal plant in kcal/h is obtained by the formula: where: h * ρs * Q M = = 0, 86 * h * Q ηrisc * ηprer Q = max plant flow rate in m3/h = Qimp η risc = coeff. rid. efficiency boiler 0,9 Other symbols = same meaning as in If the capacity M is expressed in kw and the enthalpic overfall h in kj/kg, the previous formula becomes: M = 0, * h * Q It is advisable, for safety and operational continuity reasons, that the total thermal capacity should not be provided by just one boiler, but should be distributed at least between two boilers working in parallel ) Reduction unit feeding the heating system The unit has to be installed in the room or the area of the reduction (and measurement) equipment.

21 The feed must be shunted downstream of the measure, with steel valve, able to sustain the maximum operational pressure (usually the measurement pressure). The reduction unit has to be made up of: A pressure reducer A safety valve which avoids, in case of failure of the reducer, the maximum pressure defined downstream being exceeded. The two elements, which may be integrated in just one device, may have the casing in spheroidal iron or other suitable materials if the maximum operational pressure is 5 bar. In all other cases the casing should be made of steel. It is advisable that a backup unit is installed; in this case on the main unit, a stop valve can be inserted in the regulator, as an alternative to the safety valve. In this case on the emergency line the monitor (incorporated or not) may be installed, instead of the safety valve. 7.5)Regulation plant The regulation plant is made up by the ensemble of valves (monitor, regulator, block) and possible additional equipment such as pilots, pressure taps, service regulators, connection small pipes, safety and relief valves. The sizing criteria for the valves are provided. The calibration value has to be chosen considering the maximum acceptable pressure value in the downstream network. The pressure regulation plant should allow a regulated pressure to be obtained with a maximum variation versus the calibration value equal to 10%. If the measuring plant is not automated this variation is limited to ± 2,5%. For each regulation line the pressure reducing valve and the monitor can be two different valves, in series on the same pipe axis and with the same size characteristics (the connection between the two valves will be that provided by the manufacturer), or a single valve with the two functions. The use of fail to open regulating valves with monitor function is not allowed. The monitor has to be marked EC as safety device complying with D.Lgs. n 93 of

22 7.5.1) Design Formula With (P1 - P2) < 0,456 P1 (not in critical overfall) 3417 Q = 0,55* Cg * P1*sen * C1 P1 P2 P1 gradi With (P1 - P2) 0,456 P1 Q = 0, 55* Cg * P1 where: Q = flow rate of the valve m3/h Cg = characteristic coefficient of the valve P1 = upstream absolute pressure of the valve bar P2 = downstream absolute pressure of the valve bar C1 = ratio between Cg/Cv coefficients, where Cv is the liquid coefficient of the valve. If the value of Cg is unknown, but Cv is known, assumptions will be C1 = 30 and therefore Cg = 30 Cv ) Values of Cg and C1 The values have to be officially declared by the manufacturer and usually are published in the technical specification of the manufacturer. In particular cases if the Cg and C1 values are not available, the following values may be used for an indicative calculation: C1 = 30 2 Cg = * DN for DN up to 150 included 2 0, 654 * DN Cg = DN for DN higher than 150 If the regulator is provided with a muffler and the manufacturer doesn t define clearly the resulting Q reduction, the known Cg is multiplied by 0, ) Values of P1ande (P1 - P2) The P1 value to insert in the formulae is usually the project minimum absolute value (p min P + 1). The value of (P1 - P2) will be equal to (P1 - P reg min), with (P1 - P reg min) higher or equal to the minimum dp established by the manufacturer and lower than 0,456 P1 (in the particular cases with minimum upstream pressure equal to 0,15 relative bar, il dp will be set equal to a 40 mbar). With (P1 - P reg min) 0,456 P1, the calculation formulas don t require the value (P1-P reg min).

23 P reg min is the minimum regulated pressure value foreseen for the operations at Qimp ) Choice of the regulator The regulator to be chosen is the one as results from the calculation - able to provide a flow rate Qlin. The calculation should be performed using the formulas A or B, the Cg and C1 values described at and P1 and (P1 - P2) values described at ) Choice of the monitor (if separate) The monitor should have the same dimension characteristics of the regulator described at )Relief valve The aim of the relief valve is to avoid the increase in the regulated pressure which can happen in case of closing failure both of the regulators and monitors. As an alternative, a valve can be installed on each regulation line, or a single valve can be installed downstream of the manifold. In the case where the relief valve is installed downstream of the downstream on-off valve, it is mandatory to install, downstream the relief valve, a spherical on-off valve with full passage, sealed with lead in opening position, with DN and PN equal to those of the relief valve. The relief valves must be marked EC as safety devices complying with D.Lgs. n 93 of In the cases where this D.Lgs. allows the installation of qualified valves, in accordance with ISPESL rules, these should have the value of the coefficient of efflux K experimentally determined according to predefined criteria. In the description of the device must be included: The net area "A" of the orifice of the valve cm 2 the coefficient of efflux K resulting from the ISPESL qualification tests. The theoretical diameter "dteo" must be equal to 1/10 of the diameter of the pipe from which it is shunted the pipe on which the same is installed. The formulas to be used are: A k dteo = 4 * * π ( dteo) A = π * 4 * k 2 Based on the calculated value of A, the equal or immediately higher value, available in the market, is to be found.

24 8) MEASUREMENT PLANT The measurement plant is made up of the ensemble of devices and tools installed as measurement, backup and/or control as well as the piping needed to by-pass the gas flow. The primary element has to be designed to allow a valid measurement within the range Qero Qmin. The measurement plants have to be realized in accordance with the general criteria previously defined, as indicated at point 7.1., and complying with the technical attachments to the present procedure. 8.1)Allowed equipment and type of piping The equipment and type of piping allowed for the measurement plants are indicated for flow rate ranges Qero in the attached table (attach. 2). The standard schemes, as indicated in attach. 3b, are defined in accordance with these tables. The flow rate ranges under consideration in m3/h based on the type of the measurement primary element are the following: MEASUREMENT WITH METER MEASUREMENT WITH VENT. DIAPHRAGM Qero < Qero < < < The main criteria to define the characteristics of the metering plant are the following: a) The main measuring system must be automated with electronic data processing devices (flow computer). The m 3 /h and m 3 /d data needed for fiscal reasons must be saved (current and previous month) and transferred by telereading (switched network or GSM) according to the standards defined by the transporter. Besides, in some cases, the back-up and control equipment are required to determine, in a non automatic way, the gas quantities. b) The electronic data processing devices (flow-computers, calibrators, PTZ) must comply with: Legal metrology provisions in force on the subject issued by EEC Directive and national laws CEN rules specific for this product, currently only the EN Electronic volume conversion device associated with gas meters ISO international rules concerning the formulae to calculate the flow rates and quantities in volume and energy. c) For values of Qero < m3/h the measurement by venturimetric diaphragm is not allowed. d) The measurement by meters is allowed for every value of Qero.

25 e) If the meter with a Qmax designed on the basis of Qimp is not able to measure the minimum flow rate offtaken (e.g.: seasonal variations) it is necessary to install a meter with lower Qmax, indipendent and in parallel with the 1 meter. f) For Qero 4000 and < di m3/h a second meter equal to the first one has to be installed as back-up. The second meter, if the case e) applies, can be of a lower class provided a by-pass common to the two meters be installed. g) For Qero m3/h the piping of the plant with meters, of the same gauge, must allow connection in series. h) For Qero m3/h in the plants with two or more meters (of the same gauge) every meter has to be connected with an automated measurement chain (flow rate calculator and transmitters). i) For Qero m3/h in the venturimetric plants the automated measurement chain (transmitters, flow rate calculator) must be duplicated (see attach. 2). 8.2)Measurement with meters The volumetric meters (with expandable walls, rolling pistons, turbine) must comply with the legal requirements, the performance and the functional characteristics defined in the following documents: National metric rules EEC Directives concerning the gas meters: DPR n 857 of 23 August 1982 (71/318, 74/331, 78/365) Decree 9 September 1983 and subsequent modifications UNI-CIG 7987/7988 provisions ISO 9951 provision EN EN provisions. In accordance with what the above laws and rules define, the meter should be equipped with metric seals, plate with all the data (Qmax, Qmin, pmax, impulses/m3, ecc.) and the certificate with the calibration curve. The meters made in other EEC Countries must show on the plate the EEC mark with the approval number of the model. The meters should be equipped with two pulses emitters with characteristics complying with the above rules ) Choice of a meter a) The meters that can be installed should comply with the above requirements, and assure as minimum value a measurement range with ratio Qmax/Qmin not lower than 20:1. b) The maximum operational and measurement pressure connot be higher than the meter s Pmax.

26 c) The meters with casing made up by material different from steel (spheroidal cast iron, aluminium) may be used with the limits defined by DM as far as the maximum operational pressure and nominal diameter are concerned. d) To define the Qmax of the meter to be installed, the following steps should be followed: d1) Calculate the maximum theoretical flow rate with the following conventional formula: Qero Q maxt = 1,05* ( p + 1) where: Qmaxt = theoretical maximum flow rate m 3 /h Qero = flow rate delivered (max effective flow rate that the plant must deliver) 1,05 = increase coefficient equivalent to approx 5% compared to Qero p = relative measurement pressure in bar, according to the cases p reg for the plants at regulated p and t p min M for the measurement plants at pipeline p and t d2) Identify the meter with Qmax, based on the following table, equal or immediately higher than Qmaxt calculated as above. The Qmax values are unified, however the manufacturers may provide different DN for the same Qmax, or provide no meter with particular Qmax value. This last case may reduce the choice. Qmax DN m 3 /h mm V m/s Qmax DN m 3 /h mm V m/s Qmax m 3 /h DN mm V m/s

27 e) The pulse emitters may be low frequency if Qmax is 400 m 3 /h. For higher flow rate at least one should be high frequency. If a signal (4 20 ma) is needed of the instantaneous flow rate a high frequency emitter should be preferred independently of Qmax. NOTE The ratio Qmax/Qmin of the turbine meters is variable, because, remaining constant Qmax, Qmin changes in function of the square root of the gas density at the line conditions. The minimum flow rate in m 3 /h at the operational conditions is approximately given by the following formula: 1, 32 * Q min Q min( p) = p + 1 Qmin(p) = Qmin= Minimum flow rate m3/h at the operational pressure "p". Minimum flow rate reported in the meter plate (metrologically approved) 1 1,32= d where d = relative density (0,57392) ) Diameter of the rectilinear sections directly connected to the meters The DN of the pipe of the rectilinear sections (excluding the valves) upstream and downstream the meter, must be equal to the meter DN ) Lengths of the rectilinear sections directly connected to the meters Assuming as DN that of the meter needed to calculate a Qero = Qimp, the minimum lengths to be complied with are: a) Upstream section a1) For turbine meters: 10 DN 1 The length can be reduced to a 5 DN if a meter with integrated flow rectifier is installed, in this case the manufacturer should document the result of the tests carried out in the ways defined in EN (Annex B) rule. a2) For meters with expandable walls, with rolling pistons: 5 DN 1 b) downstream section for all types of meter: 2 DN It necessary to provide after the 2 DN enough room to insert the two thermometer pockets, to measure and control. 1 Per i contatori a parete deformabile od a turbina radiale non risulta necessario alcun tratto rettilineo. Per cui se il contatore installato è quello relativo a Qimp i tratti rettilinei non sono necessari.

28 8.2.4) By-pass of the on-off valve upstream of the meter On the measurement line with meters with DN 150 it is advisable to install a by-pass (DN 25 50) to use in the starting operations, avoiding to damage the meter. 8.3)Measurement with venturimetric diaphragm This measure can be performed if the following 3 conditions occur at the same time: Value of Qero m 3 /h DN of the measurement section 100 Measurement section 2 bar The plant must be carried out in accordance with UNI EN ISO /A1 rules, the provisions hereunder indicated and possible rules defined by following legal metrology regulations. The gauging certificate of the measurement diaphragm should comply with attach. 5. and the dimension check in accordance with these rules should be carried out by an appropriate Institute. The exact dimension of the inside diameter of the pipe should be reported with the gauging report as defined in attach. It is advisable for accuracy reasons, both for equipment reasons and for the limits set by Reynolds number, that the minimum flow rate Qmin offtaken should be lower than approximately 5 % of the F.S. Q. In fact, at that Qmin value corresponds a differential pressure value equal to 1,25 mbar (measured by the low deltapi transmitter with f.s. 100 mbar). If the plant Qmin is lower than these percentages, better solutions should be identified to measure the low flow rate, for instance by installing more measurement lines with automated insertion ) Measurement line Information relating to the whole measurement line is: a) Throttling devices Primary elements made up by diaphragm-holder of the type "Orifice Fittings" with pressure taps on the flanges are allowed. These devices allow: A better functionality and operational easiness which reduce significantly the time needed to substitute or check the diaphragm Improved ease to center the diaphragm and therefore greater guarantees of better measurements. b) Lengths of the rectilinear sections of the venturimetric section b1) Upstream section For Qimp < m 3 /h For Qimp m 3 /h L 30 DN L 50 DN

29 b2) Downstream section In all cases L 8 DN The DN to consider, to define lengths, is the one that, in accordance with the table at the following point, allows the measurement of a Q = Qimp with speed 25 m/s and with: Measurement p = p reg min (always < p min P) for plant at regulated p and t Measurement p = p min P for the measurement plant at pipe p and t. The values indicated are valid until new legal metrology criteria are introduced. c) Pipes allowed for measurement line c1) Type of pipes according to the manufacturing process Obtained by weldless cold-drawing (preferred) Obtained by weldless hot-drawing By longitudinal welding. Different types should be analyzed case by case. c2) Inside wall condition Inside walls must be clean, without corrosion and scaling, even if localized in few points. The presence of a slight rust film is allowed. d) DN of the pipe to be installed and value of the ratio between diameters The DN project calculation is carried out according to point 7.1, complying with the ß limit hereunder indicated and applying the flow rate calculation formula indicated in UNI EN ISO /A1 rule. ß value(ratio between diameters d/d): with DN 100 mm: 0,10 ß 0,7 if the lenght of the upstream section is > 40 DN, a value of ß up to a maximum of 0,75 is allowed ) Lay-out of pipes and devices in thel "entry section" A plant section defined as entry section is a plant section upstream of the rectilinear section upstream of the metering line. It should be realized in accordance with the following points: a) Once defined a reference plan (horizontal or vertical) along the axis of the measurement section, the entry section, located in the reference plan for a total length 10 DN (point c), can be made up by a single pipe, or a pipe, elbows and/or valves and/or other devices in accordance with the following points.

30 b) The gas flow in the "entry section" must always remain, even changing direction, in the same reference plan defined in a). Therefore it shouldn t be installed in the entry section: Elbows and T part on plan different from the reference one Any other device which causes a plan change, compared to the reference plan, in the gas flow. c) In the "entry section it is forbidden to install: Any regulation valve Any expansion in the diameter with ratio higher than 0,5 to 1 of the DN of the measurement section (the expansions must have length DN of the measurement section). d) The on-off valves in the "entry section" should be of the type described in point 6d. e) If the upstream rectilinear section has a length 50 DN the limits set in c) and d) do not hold and besides the rectilinear sections mentioned in a) may be on different plans and of the total length strictly necessary to connect the devices or special parts or elbows. f) The cases clearly different from those here described should be analyzed case by case ) Measurement equipment and devices The equipment and devices necessary in relation to Qero are defined in attachment 2. The ends of the reading scale of the differential pressure are: High deltapi 500 mbar Low deltapi 100 mbar It should be foreseen pressure taps, deltapi (on the diaphragm) and thermometer pocket to carry out checks in the field. All the thermometer pockets should be inserted downstream, after the gli 8 DN, on the upper generatrix of the pipe. 9) EXIT SECTION 9.1)Exit valve The last downstream valve, in the gas direction, is described in attach. 3b and 3c. Practically this may not occur. Therefore the conditions defined in 9.2 and 9.3 should be satisfied, remaining valid the design criteria above defined until the exit valve. 9.2)DN of the pipe The pipe of the exit section should have a DN to assure a speed 25 m/s.

31 9.3)Downstream emergency valve (optional) This valve should be installed outside the room, at the exit section, upstream or downstream of the exit valve. It may be located upstream or downstream of the downstream insulating joint and should be electrically isolated if shunted by underground pipe shielded by current. The emergency valve should be sized in order to be able to easily supply the emergency flow rate. 9.4)Check valve If the plant configuration or the system operations cause possible gas backflows, it is necessary to install in the exit section a check valve. 10) PERFORMANCE CRITERIA 10.1)Foreword In this chapter the main criteria to follow in assembling and installing the receiving and first gas reduction plants are described. The assembling and installing of the pre-heating plant (boiler, pipes), not considered in this chapter, should be carried out in accordance with the building and installation rules of the heating plants, applying for the boiler the safety requirements foreseen by the laws in force. 10.2)General priciples ) Safety and easy of access The design should consider in particular the safety factor. The accessibility to all the equipment of the plant should be assured and any point should be reachable by the relevant tools. An easy exit from the plant should be assured in case of emergency ) Assembling and installing The assembling and installing should not cause additional mechanical stresses besides those produced by the gas pressure. The special parts, the equipment and the pipe sections should be manufactured and installed in such a way as to comply with the criteria of verticality, horizontality and parallelism ) Cabin building The walled cabin should be built and tested in accordance with the rules issued by the competent authorities regarding the buildings as well complying with D.M. 24 November 1984 "SAFETY RULES FOR THE TRANSPORTATION, DISTRIBUTION, STORAGE AND UTILIZATION OF NATURAL GAS WITH DENSITY LOWER THAN 0,8" ) Materials The provisions of the same D.M. apply also to the materials. The pneumatic joints for the devices, impulse taps and relief of the regulating tools must be made by stainless steel. For inside diameters not greater than 10 mm, they can be also made of copper.

32 10.3)Pipes, flanged connections, special parts, releases As a rule pipes should be layed above ground or should in any case be inspectable. Underground laying is only allowed for the pipes connecting the general on-off valves and the plant. At the installation the pipes, the connections and the special parts must be perfectly internally clean. In building the piping it should be used only special parts such as: elbows, tees, weldolets, flanges, made by materials and dimensions complying with appropriate standards (ASTM, ANSI, API, MSS, etc.). The gaskets should be made in material resistant to effect of gas and to possible odorizing substances. In accordance with D.M of , for the safety valves and the release devices in the atmosphere appropriate vent pipes should be prepared to let gas in the air at appropriate height (not < to 3 m from the field), not affecting the openings of the possible boiler room. In particular the end part of the releases should be made in such a way as to let the gas vent bottom-up and to prevent rain infiltration. 10.4)Welding Welding should be carried out by qualified welders and with processes qualified by appropriate and officially recognized institutions. Contiguous weldings between pipes along the axis with distance lower than 1,5 D (with a minimum limit of 60 mm) should be avoided. 10.5)Installation of the devices For the installation of the devices and possible pneumatic joints the indications of the manufacturers should be respected as well as these criteria. Easy control and calibration should also be assured ) Separating filters and preheaters Between lines should be left enough room to let the maintenance operations to be performed. If the inspection and maintenance of the filters is not allowed by the free space, a service platform should be considered. The drainage of the devices should be separately carried outside of the possible cabin and in such a position as to assure the maximum safety and the easy collection of possible inpurities ) Regulation plants Between lines should be left enough room to let the maintenance operations to be performed. The appropriate actions should be taken in order to assure in any moment the continuity and regularity of the operations (e.g. pre-heating or tretment of the gas feeding possible additional devices such as service regulators and pilots). Devices by-passing the regulators are not allowed ) Measuring devices General principles The measurement devices and the primary elements should be installed in such a position as to assure an easy access and to easily allow the data collection, the control and calibration operations.

33 If, for specific reasons, it is necessary to install measurement devices in the open air (transmitters, recorders, calibrators, etc.) they should be shielded within appropriate protections such as: boxes, cabinets, containers. These protections should be made by appropriate materials, with such dimensions and in such a way as to avoid temperature variations outside the limits defined by the manufacturer. Measurement venturimetric section The measurement venturimetric section should be installed in accessible position, if possible at a height from the field not higher than 1 1,20 m. Meters The meter has to be installed in such a way as to avoid any mechanical stress caused by the upstream and downstream piping and according to the manufacturer s instructions. If requested, the lubricating oil must reach the set level, and be verified by suitable lamp. The meausrement pressure has to be taken by the appropriate tap Pr present on the meter. In the case of meters with expandable walls and rolling pistons even if provided with tap Pr, the operational pressure can be measured upstream of the upstream rectilinear section of the meter. 10.6)Painting and insulation The piping and all the devices should be protected against corrosion by an appropriate painting cycle. Insulation is recommended on the heat exchangers, on the water circuit and on the measurement section. 10.7)Electrical systems The gas reduction and measurement plants are locations with the potential for explosions due to the presence of inflammable gas where the electrical systems (from the 1st of July 2003, also other systems which can represent primer source) must comply with particular safety requirements. The definition of the area with explosion danger should be made in accordance with the criteria set in the CEI EN (CEI 31-30) rule and in the 1999/92/CE directive. To design the electrical system, the installation and choice of the protection according to the three types of area (0,1,2), should comply with CEI EN (CEI 31-33) rule and 94/9/CE directive. Regarding the electrical material to be used, in 1994 the CEE 94/9 directive has been issued, received by D.P.R. n 126/98, aiming to define for all products, electrical and non electrical, to be installed in the EU Countries, the essential requirements for the utilizazion zone. This directive will substitute the previous ones (76/117/CE; 79/196/CE) starting from the 1st of July The electrical devices with compliance certifications issued on the basis of old directives may be installed until and no later than the 30th of June 2003.

34 According to the law n.46/90, such electrical systems should be designed by a professional belonging to the register within his competencies, and the works of installation, transformation, expansion and extraordinary maintenance should be carried out by qualified companies, or in the case of non installing companies, by the internal technical departments which at the end of the works issue appropriate statement of compliance of the system to the standards. Such electrical systems, the grounding system, and possible devices against atmospheric discharges have to be set at work, approved and verified in accordance with D.P.R. 22 October 2001, n 462. The check of the need of a device against atmospheric discharges has to be carried out in accordance with CEI 81-4 rule or, where applicable, CEI 81-1 rule. If the protection system has to be provided, the provisions contained in CEI 81-1 apply and, where foreseen by D.P.R N.689, it has to be communicated to ISPESL. 10.8)Protection of the undergroung pipes against corrosion The metallic pipes should be coated against damage caused by the ground where the pipes are laid and the corrosion caused by possible natural or leaked electric currents. In presence of natural or leaked electric currents, besides an efficient coating, a cathodic protection is recommended. These systems should comply with the legal provisions (D.M. 24/11/1984) and with the technical rules in force. 10.9)Criteria for the pneumatic connections of the measuring devices See attachment )Criteria to install computerized measurement systems See attachment 9.

35 INDEX OF THE ATTACHMENTS Attach. 1 DIAGRAM PRESSURE ENTHALPY FOR THE NATURAL GAS (2 pages) 2 MEASUREMENT PLANT WITH FISCAL VALUE (1 page) 3 STANDARD SCHEMES FOR "REMI PLANTS" AND DESCRIPTION OF THE DEVICES 3a - regulation plant (5 pages) 3b - measurement plant with fiscal value (9 pages) 3c - REMI plants with variable pressure and temperature (4 pages) 4 MAXIMUM ALLOWED ERRORS IN THE MEASUREMENT SYSTEMS (1 page) 5 DIAPHRAGM GAUGING CERTIFICATE (1 page) 6 GAUGING OF THE MEASUREMENT SECTION (1 page) 7 REMI PLANT WITH UPSTREAM P max 5 bar (6 pages) 8 CRITERIA TO CARRY OUT THE PNEUMATIC CONNECTIONS (6 pages) 9 CRITERIA TO INSTALL COMPUTERIZED MEASUREMENT SYSTEMS (5 pages) 10 CARTHOGRAPHIC DOCUMENTATION FOR PIPELINES (15 pages)

36 ATTACH. 1 - DIAGRAM PRESSURE ENTHALPY FOR THE NATURAL GAS