Triennium Work Report WORKING COMMITTEE 4: DISTRIBUTION

Transcription

1 Triennium Work Report October 2009 WORKING COMMITTEE 4: DISTRIBUTION Chair: Jeremy Bending United Kingdom Study Group 4.2: An evaluation and determination of leading practices used in the industry for the management of leakage from gas distribution systems Chair: Steve Vick United Kingdom 1

2 Table of Contents 1 Introduction, Objectives and Recommendations WOC 4 Survey Introduction & Objectives Average Company Profile Pipe Material Other Observations Methodology Data Analysis Leakage Quantification and Classification How leakage is currently quantified The annual number of public reported escapes ( PRE s )handled by companies The resultant action following PREs Current tolerated levels of unaccounted for gas ( UAG ) Storage of leakage data on a single database Publishing of leakage data to regulatory authorities on a regular review period basis The main drivers to leakage management policy Policies Targets Ranking of Parameters Parameters used in leak classification Repair policies Repair policies for the maximum life of Class 2 and Class 3 leaks prior to making a repair Approaches to manage leakage Pressure management Leakage forecasting methods Other methods used to manage leakage Best Practices Appendix A Members of Study Group Appendix B List of graphs

3 1 Introduction, Objectives and Recommendations Methane is a significant greenhouse gas and leakage is perceived to contribute to depletion of the ozone layer. Leakage also presents safety, economic and operational challenges to distribution operators. The objectives of the study were to analyse the ability of distribution network operators to quantify leakage from distribution systems, the effectiveness of their approaches and how they measured it. The Study Group has drawn the following conclusions from the results of its survey of world gas companies on the subject of the management of gas leakage and have added their recommendations as appropriate: Reference section 4.1.4: After anomalies were removed an average figure of 2.7% was determined as the industry average for unaccounted for gas. Recommendation: A figure of a maximum of 2.7% could be used as a useful benchmark for companies unaccounted for gas Reference section 4.1.6: The intervention of national regulators and other government bodies in enforcing leakage reduction policies is perceived as a new trend. Reference sections 4.2.2, 4.4 and 4.6:The replacement of cast iron pipes in particular, but also pipes of any material with high leakage that have been identified by historical data, is the key factor in reducing leakage. The reduction in leakage achieved will be directly related to the rate of replacement of such pipes. Recommendation: Companies may wish to bench mark themselves against the best practice methods highlighted in Section 5 Reference section 4.2.3: Despite all the many changes in the gas industry due to widespread deregulation, the responses to our survey highlight the continuing high priority given to the safety aspect of leakage reduction. Recommendation: It is felt that gas companies will need to increasingly be aware of the importance of the environmental effects of leakage. Reference section 4.5: The use of pressure management as a tool to minimise leakage was found to be restricted to a very small proportion of companies. 2 WOC 4 Survey 2.1 Introduction & Objectives In order to establish a common dataset to support each of its study group s work, WOC4 prepared a questionnaire that requested data and opinions from every member organisation registered with WOC4. The international professional services company GHD ( generously hosted the questionnaire and provided a valuable resource in chasing, interpreting and collating responses. The American Gas Association (AGA), who circulated the questionnaire to all its member organisations, also assisted the survey. The survey was conducted under the auspices of the IGU during The main reasons to conduct this survey were to acquire data from each respondent on: The size of the networks they operate. The numbers of gas consumers served. The pressure regimes within the networks operated. The mix of pipe age, sizes and materials in use. The extent to which the management of these assets is supported by computer systems. How management and maintenance strategies are supported by computer systems. 3

4 Forty-eight responses were received to the questionnaire providing a substantial source of information for the Study Group. Working Committee 4 is satisfied with the high response that it received on its questionnaire. Through the contribution of so many companies it is possible to make reliable statements about best practice in gas distribution. The companies are located in 24 different countries, distributed over 6 of the 8 regions defined by the IGU. This is a significant increase in response from the previous triennium where a total 17 countries responded. The countries that responded to the questionnaire are listed below and are grouped in their region. Asia Asia Pacific CIS countries Europe Latin America and Caribbean North America Pakistan Australia, Japan Russian Federation Austria, Belgium, Bosnia and Herzegovina, Czech Republic, Denmark, France, Germany, Hungary, Ireland, Italy, Netherlands, Serbia, Slovak Republic, Slovenia, Spain, Turkey, United Kingdom Argentina, Brazil USA The map below shows the regions and the number of countries/companies that responded. North America 1/13 Europe 17/24 CIS 1/2 Asia 1/1 Latin America & Caribbean 2/2 24/48 Countries/Organisations Asia Pacific 2/6 Fig. 2.1 : World map showing questionnaire respondent distribution per region The two regions from which data was not able to be obtained are the Middle East and Africa. Information was gathered from companies that operate gas networks that serve a total of more than 85 million customers, comprising 1.2 million km of gas mains. As the diagram above shows, the European region accounts for 53% of the data gathered and, as such, dominates the data for gas mains length and number of customers serviced. This has greatly influenced the results of the survey. Conversely, data from only two distribution companies operating in the CIS region was requested, as incorporating data from all the distribution companies that operate in that region (with millions of customers) would have overwhelmed the results. As a result the data from the CIS region appears to be low. The chart below shows the relative distribution of number of customers serviced by the responding companies per region. 4

5 Number of customers by respondents/region Number of customers (1,000) 50,000 40,000 30,000 20,000 10,000 0 Region Fig. 2.2 : Number of customers per respondent and region 2.2 Average Company Profile Based on the data an average distribution company has been defined. The tables below show key characteristics, such as materials and pressure. From the 1,708 km of other material, approximately 1,042 km can be attributed proportionally to two European countries that construct mains using PVC-Cpe material and one Australian company that utilises nylon. Average Distribution Company 15,000 12,000 Km 9,000 6,000 3,000 0 PE Coated steel Other Cast iron Ductile iron Uncoated steel Europe Asia Pacific North America Latin America Asia CIS Mains material Fig. 2.3 : Average distribution respondent profile 5

6 For each respondent company an average of 1.8 million customers is served. The following chart shows material and pressure breakdowns for each region. Note that the category other includes the use of PVC and nylon. Europe Pipe Pressure Comparitive Percent Break Down 100% other More than 16 bar More than 5 less than 16 bar More than 2 less than 5 bar More than 100mbar less than 2 bar Less than 100mbar 80% Length of Pipe 60% 40% 20% 0% Country Fig. 2.4 : Pipe material and pressure breakdown per region The following chart shows the pressure breakdown for the 17 European countries that provided data. % Pipe Type Comparitive Break Down Per Region 100% 90% 80% 70% Length of Pipe 60% 50% 40% Other Polyethylene Cast Iron - Ductile Cast Iron - Case Steel - Uncoated Steel - Coated 30% 20% 10% 0% Asia Asia Pacific C.I.S. Countries Europe Latin American & Carribean Country North America Fig. 2.5 : Gas mains pressure breakdown per European respondent (17) 6

7 There are many reasons why the composition of pressure breakdown differs between these European countries, including: individual operators choosing a particular pressure regime based on engineering judgment and local circumstances; networks founded in town gas distribution (such as some countries in the north west of Europe); and age of network, with more recent installations transporting gas via newer materials such as polyethylene (PE) and at noticeably higher pressures. 2.3 Pipe Material Regions which have the greatest percent usage of PE pipe (such as Europe at 56%) also have the greatest percent of 2 5 bar pressure (corresponding at 37%). It would appear that countries are installing newer PE pipe with corresponding higher distribution pressures, particularly in the 2-5 bar range. CIS countries also show a strong correlation between PE pipe and the 2 5 bar pressure range (at 26%). However, certain countries do not exhibit this relationship. One European country (country 2 in the chart above) that has over 50% PE pipe also has negligible lengths of pipe running in the 2-5 bar pressure range. It also has the largest percentage of cast iron pipe, which would indicate that a large portion of their gas delivery network is not recently constructed. The large majority of this distribution network, at over 80%, runs at the lowest pressure band or less than 100 mbar. One possible (common) explanation for this is that a complete cast iron network has not undergone replacement with PE; the entire system cannot be run at a higher pressure until all cast iron has been removed. Where cast iron networks have been slowly replaced Another determining factoring this is the extensive introduction of low pressure systems transporting manufactured town gas during the industrial revolution; this started in North West Europe and subsequently spread throughout the rest of Europe and North America. Alternatively one European country has taken a technical decision to replace low-pressure cast iron pipe with medium-pressure only small-diameter PE pipe. Another European country (country 11 in the chart above) operates over 70% PE pipe but has only a small fraction of its network running in the 2-5 bar range, with over 80% in the 100 mbar - 2 bar range. However it does not have a significant percentage of cast iron piping in its network. It appears to be similar, with respect to type and pressure, to the breakdown that is seen in North American pipelines. 2.4 Other Observations In Europe and Asia-Pacific) there is high utilisation of other materials (at approximately 9% for each) as alternatives to steel, cast iron and PE. Some countries in particular use alternative materials, such as European country 3 in the chart above, which uses PVC-CPE in more than 50% of its network. This is common in low pressure (up to 100 mbar) situations. CIS countries are uniquely characterised by the absence of cast iron and the relatively high percentage of uncoated steel (22%). 3 Methodology Methane is a significant greenhouse gas and leakage is perceived to contribute to depletion of the ozone layer. Leakage also presents safety, economic and operational challenges to distribution operators. The terms of reference of Study Group 4.2 (SG4.2) was to determine the process necessary for the evaluation and determination of leading practices used in the industry for the management of leakage from gas distribution systems. Leading practices were to be based on a review of commonly defined metrics of operational performance. The committee also sought to identify Best Practices in Leakage Management Systems and to review existing and newly emerging technologies for leakage control. 7

8 With the above terms of reference and objectives in mind, SG4.2 formulated a questionnaire and focused on six separate areas, namely: 1. How is leakage currently quantified by distribution operators 2. Identification of the main drivers influencing the approach to leakage management 3. Repair Policies existing in different companies 4. An analysis of the differing approaches used to manage leakage 5. The use of Pressure Management as a tool to control leakage 6. The use of Leakage Forecasting Methodologies to control leakage. Within each of the above 6 general areas, SG4.2 asked specific questions of companies, to determine the best practices in use by the operators. Reading this report and a study of its conclusions will let operators judge for themselves where they are placed when benchmarked against other operators. Section 4 of this report shows an analysis of the findings graphically illustrated where appropriate and some general comments on the findings as noted by the study group committee members. 4 Data Analysis In this section an analysis of the data received in answer to the questionnaire is presented and general comment made on observations by the committee. The questionnaire is reproduced in the appendix. 4.1 Leakage Quantification and Classification How leakage is currently quantified The chart below shows the methods for companies to quantify their leakage and the numerical comparison between the popularity of each method. The question asked companies to identify all the methods they used to quantify leakage, that is to say companies could choose from 1 to 4 of the different methods. It reveals that the ranking of the methods used by companies is as follows:- 1. Planned leakage surveys-85% of respondents 2. Public reported escapes-75% of respondents 3. Third party damage to the network-73% of respondents 4. Unaccounted for gas calculation-44% 0f respondents Public Reported Escapes Planned Leakage Surveys Third Party Damage to the Network Unaccounted For Gas Calculation Fig. 4.1 : Methods of quantifying leakage 8

9 4.1.2 The annual number of public reported escapes ( PRE s )handled by companies The relevant responses of 28 companies were analysed in this section, other responses being of the nature not recorded, not relevant, (Transmission Companies for example), or no response was received. There was extensive divergence in the number of recorded PRE s (from 1 to 314,000), from which the following observations are offered: 47% of respondents record less than 1,000 PRE s per year 75% of respondents record less than 10,000 PRE s per year The resultant action following PREs The following table has been generated to indicate the type of action required following the receipt of a PRE: Percentage of Totals Resulted in Mains Repair Resulted in Service Pipe Repair No Leak Detected Other 25% 40% 17% 18% This table indicates that 40% of recorded PREs occur on service pipes. This perhaps indicates that more emphasis needs to be put on the replacement of service pipes of inferior materials such as un-protected mild steel and lead, though no data was available to allow any comparison of service leakage by pipe material. It may also point to a higher incidence of third party damage to service pipes, which are often laid at shallower depths than mains and subject to damage from minor works. A surprisingly high percentage, 17%, of PREs (1 in six) results in no leak being detected Current tolerated levels of unaccounted for gas ( UAG ) It should be noted that UAG is not just leakage from a network but includes other factors such as theft by gas consumers and meter corrections. 54% of the 46 companies surveyed have indicated a current documented tolerated level for Unaccounted for Gas, while 46% do not have an official level. A further analysis of the data received shows that on average, the UAG% level was 4% across 43 of the companies. Two companies had an exceptionally high level of UAG and, when these were removed from the equation, the average recorded industry UAG is 2.7%. Companies can benchmark themselves against 2.7% UAG and see where their recorded level rests relative to other Operators. Other findings in relation to Quantification of Leakage came from the following questions: Storage of leakage data on a single database 72% of companies now record leakage levels on a single database Publishing of leakage data to regulatory authorities on a regular review period basis 89% of companies are required to publish leakage data to the regulatory authorities on a regular review period basis. 9

10 4.2 The main drivers to leakage management policy Policies In this section the study group sought to establish if companies have a leakage management policy. 58% of Companies responded that they had a specific policy on leakage reduction and 48% of respondents said that the policy was self imposed and not influenced by outside parties, such as the Regulatory Authority. 10% of Companies said that their Policies were mandatory for regulatory compliance Targets A summary of the leakage targets that companies set for themselves are set out below: Setting a numerical maximum number of leaks, or maximum number of leaks per unit length of their networks that they aim to be below on an annual basis. These targets are sometimes linked also to the ageing of leaks e.g. no more than a set target number of leaks must be more than 100 days old. Aiming to reduce leaks by a target % of the their annual total Aiming to eliminate Class 1 and 2 leaks immediately Ranking of Parameters The study group sought to determine from Operators the ranking of parameters that had an influence on their leakage management strategy and the allowable leakage levels in their companies. The chart below illustrates the findings: scale of relative importance Safety Regulatory Operational Economic Enviromental Fig. 4.2 : Ranking of leakage management priorities The table shows that safety clearly ranks as the highest priority followed by regulatory influence with operational, economic and environmental considerations all on a similar level. The results do point to the need for companies to raise their awareness to the environmental impact of gas leakage. 10

11 4.2.4 Parameters used in leak classification 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Gas in Air Reading (%) Proximity to a Building Building Type Type of Ground (Vented/Unvented) Pipe Material Pipe Pressure Importance 1 [less important] Importance 2 Importance 3 Importance 4 Importance 5 Importance 6 [more important] Importance [unanswered] Fig. 4.3 : Parameters used in leak classification Analysis of the above data reveals a ranking of the parameters as follows: 1. Proximity to a building 2. The % of gas in air reading 3. The pipe operating pressure 4. The type of building 5. The type of ground(vented/unvented) 6. The pipe material The following questions were also asked under this heading: How often does your company conduct a full survey of the low pressure mains network? 34 respondents complete a full survey in less than 6 years. Only 3 respondents complete such a survey in less than 1 year. How often does your company conduct a full survey of the medium pressure mains network (<5 bar)? 38 respondents complete such a survey in less than 6 years, 7 in not more than 1 year. 11

12 4.3 Repair policies Repair policies for the maximum life of Class 2 and Class 3 leaks prior to making a repair In order to help interpretation of the data the study group put forward the following definitions for Classes of leaks. Definitions do differ slightly from company to company but the following are generally accepted by all. Class 1 This is a leak that represents an existing or probable hazard to persons or property. Response must be immediate and the leak repaired or continuous action must be taken until the conditions are no longer hazardous. Class 2 A leak that is recognized as being non-hazardous at the time of detection, but justifies scheduled repair based on probable future hazard. Response to the leak must be made within 7 days. Class 3 A leak that is non-hazardous at the time of detection and can be reasonably expected to remain nonhazardous. Response to the leak made in time periods greater than 7 days Companies were asked if they had a policy on the life of Class 2 and Class 3 leaks and the responses are tabulated as below. 40 Number of respondents Class 2 Class 3 Yes No Unanswered Fig. 4.4 : Policies on Class 2 and 3 leaks It can be seen that a large majority of companies have a policy on the life of Class 2 leaks but only just over half have a policy for the life of Class 3 leaks. Data was also acquired for the actual maximum life of such leaks. Class 2 Leak: 33% of respondents complete repairs on Class 2 leaks in less than 3 months 54% complete repairs on Class 2 in less than 6 months 70% complete repairs on Class 2 in under a year 100% complete repairs on Class 2 inside 15 months Class 3 Leak: 51% indicated that Class 3 leaks have a life of less than 1 year prior to repair 16% indicated between 1 year and 5 years for Class 3 repairs 33% indicated between 5 and 8 years 12

13 Organisations were also asked to comment on interim surveys carried out on Class 2 and 3 leaks whilst they awaited repair. 53% of respondents indicated that they survey Class 2 leaks and 48% survey Class 3s. 50% of companies also indicated that they re-survey such leaks after repair. 4.4 Approaches to manage leakage 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Pressure Management Condition of the LP Network Odourisation Replacement Predictive Leakage Methodologies Asset Management Importance 1 [less important] Importance 2 Importance 3 Importance 4 Importance 5 Importance 6 [more importance] Importance [unanswered] Fig. 4.5 : Approaches to manage leakage Analysis of the responses to the question reveal the following ranking of the approaches to managing leakage: 1. Pipe replacement 2. Odourisation 3. Asset management 4. Predictive leakage methodologies 5. Pressure management 6. Condition of the LP network Organisations provided information on the frequency of mains replacement in their networks. The working group have used their judgement on interpreting the responses received and would suggest that the rate of replacement as a percentage of the total of an organisation s network, varied from 0.1% to 5% across the responses received. 13

14 4.5 Pressure management Organisations were asked a number of questions relating to how Pressure Management was operated on their network. NB: It should be noted that the members of the Study Group identified the fact that pressure management is generally not used as a means to reduce leakage but to ensure the correct pressure is available in networks for other reasons such as providing the correct pressure for appliance operation. In discussions only a very small number of network operators were identified as using pressure management as a means to manage leakage. The following is a summary of the responses received in the survey: Approximately 50% of respondents indicated that their organisations operated Electronic Closed Loop Network Systems. 66% of respondents indicated that loggers were utilised in the operation of their networks. Only 38% of respondents used Clock Control as a means of Pressure Management. 56% of respondents made seasonal adjustments to the operating pressures. 40% returned Pressure Field Data by telephone, 23% by wireless technology and 37% by other means, including radio, charts, paper and scada. This graph demonstrates the frequency of data capture. Hourly Daily Weekly Other Fig. 4.5 : Frequency of collecting pressure data Other frequencies were predominantly continuous monitoring or by exception. 4.6 Leakage forecasting methods Only 35% of respondents indicated that they implement methods for forecasting leakage. The following is a summary of the methods used: Use of historical leakage data from a company s network to predict future patterns of leakage. Predictions based on the type and age of pipe materials in a company s network. The following summarises the various measures of the effectiveness as understood by the respondents: Comparison of the % of leakage/unit length of network year on year Comparison of UAG year on year and often against benchmarks established by the companies concerned Comparison of the actual number of recorded leaks or pipe fractures year on year and again, often against benchmarks set. The annual cost of leak repairs is compared by some companies Only 4 respondents had no comparison method in place. 14

15 4.7 Other methods used to manage leakage The responses to this question revealed only one different technique from those already discussed in this report. One respondent used the technique of internally spraying their cast iron mains with an anaerobic sealant in an effort to reduce joint leakage. 5 Best Practices The study group have identified as best practice the following:- Establishing and continually up-dating data bases of historical gas leakage from distribution networks based both on public reported escapes and on leakage survey results Carrying out leakage surveys of the network at bench marked frequencies and up-dating the above data bases Using specially developed software to analyse the above data bases and prioritise either the replacement or repair of identified sections of the network. An example of the effect of using such an approach can be seen in the graph of the reduction in leakage achieved by one company over a ten year period. Having reached an acceptable base line level the company s aim is to maintain that level by use of its data base and software to prioritise future pipe replacement or repair. The effect of either reduced or increased replacement can be predicted as shown and the actual rate may depend on economic considerations as increased rates of replacement yield diminishing returns. It is noted that some network operators using such an approach, but with still a relatively large proportion of cast iron in their networks, may need to continue to replace it at an accelerated rate for overriding safety considerations. % in comparison to Predicted future leakage base replacement 0 Fig. 5.1 : History of gas leakage since 1997 in example company 15

16 6 Appendix A Members of Study Group 4.2 Mr. Steve Vick (Chair)-UK Mr. William Kearney (Vice Chair)-Ireland Mr. Wim Ploem-Netherlands Mr. Vladislov Karasevich-Russia Mr. Kim Vrancken-Belgium Mr Libor Cagala-Czech Republic Mr Mehmedalija Sijaric-Bosnia Mr Bodo Kipker-Germany Mr Kenichi Matsushita-Japan Mr Stefano Cagnoli-Italy Mrs Natalia Kruglova-Russia Ms Anna Martynova-Russia 7 Appendix B List of graphs and Figures Fig. 2.1 : World map showing questionnaire respondent distribution per region Fig. 2.2 : Number of customers per respondent and region Fig. 2.3 : Average distribution respondent profile Fig. 2.4 : Pipe material and pressure breakdown per region Fig. 2.5 : Gas mains pressure breakdown per European respondent (17) Fig. 4.1 : Methods of quantifying leakage Fig. 4.2 : Ranking of leakage management priorities Fig. 4.3 : Parameters used in leak classification Fig. 4.4 : Policies on Class 2 and 3 leaks Fig. 4.5 : Approaches to manage leakage Fig. 4.5 : Frequency of collecting pressure data Fig. 5.1 : History of gas leakage since 1997 in example company 16