Κώδικας Πρακτικής για την αντικατάσταση κύριων αγωγών με τη μέθοδο της ένθεσης σωλήνα PE σε ανενεργό μεταλλικό αγωγό (dead mains insertion)

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1 ΤΕΧΝΙΚΗ ΠΡΟΔΙΑΓΡΑΦΗ ΕΠΑ-CP-001 EN ISO 9001:2000 Κώδικας Πρακτικής για την αντικατάσταση κύριων αγωγών με τη μέθοδο της ένθεσης σωλήνα PE σε ανενεργό μεταλλικό αγωγό (dead mains insertion) ΣΥΝΤΑΞΗ: ΤΜΗΜΑ ΤΕΧΝΙΚΗΣ ΥΠΟΣΤΗΡΙΞΗΣ ΕΛΕΓΧΟΣ: ΕΠΙΤΡΟΠΗ ΤΕΧΝΙΚΩΝ ΠΡΟΔΙΑΓΡΑΦΩΝ ΕΠΑ ΑΤΤΙΚΗΣ ΕΓΚΡΙΣΗ: ΕΠΙΤΡΟΠΗ ΤΕΧΝΙΚΗΣ.ΔΙΕΥΘΥΝΣΗΣ ΕΠΑ ΑΤΤΙΚΗΣ 1 / 1 Αναθεώρηση: 0 η / Ημ/νία έγκρισης: 10/8/2002 PDF created with pdffactory Pro trial version

2 EPA ATTIKIS CODE OF PRACTICE FOR MAINS REPLACEMENT- DEAD MAINS INSERTION (PE. PIPE) 1. SCOPE This Code of Practice is intended for guidance by Engineers or their representatives responsible for the replacement of existing mains by the insertion of PE pipe and should be used in conjunction with the corresponding Procedure for operational personnel. 2. REFERENCES Unless otherwise specified this document shall be used with reference to the latest editions of related procedures, standards and specifications dealing with safety, construction planning, PE pipe welding (EN 13067), traffic management, excavations, reinstatements and materials, plant and equipment. 3. DESIGN 3.1 General Mains insertion/slip-lining using polyethylene (PE) pipe is highly suitable for existing gas mains replacements, that are predominantly straight, have few connections and can operate satisfactorily at reduced pipe diameter or considered for up-rating to a higher working pressure. However, this technique is also suitable where the existing main does have bends, branch and service connections but with additional enhancements to the insertion process including pulling as well as pushing techniques. Due attention must be made to details of existing mains records, careful planning, mains tracing, location and size of launch/reception pits, use of pipe coils and pipe trailers to maximise production and avoid delays. 3.2 Selection of insertion pipe by diameter The size of insertion pipe should be selected to give an annular clearance which is sufficient to enable the pipe to be inserted without causing damage to it. The existing pipe material, service and other fittings protruding into the main and pipe corrosion products may affect this clearance. The internal condition of the main should be examined and immediately before insertion work commences, a final check made to ensure that the selected pipe can be inserted successfully using closed circuit television (CCTV) camera inspection and survey equipment and/or a gauge proving length. Where the existing main is heavily congested with corrosion products, drag scraping using scraper pigs, rubber plungers or pull throughs. is recommended to clean the main, usually by means of inserting fibreglass flex-probe rodding from a reel and used for attaching a winch cable. The winch cable can also be used for the CCTV survey and to pull the gauge prover through the main to check if obstructions will prevent free passage or cause scoring to the insertion pipe. Polyethylene pipe scores to a depth greater than 10% of the pipe wall thickness are unacceptable and the location of any obstructions PDF created with pdffactory Pro trial version 1

3 causing such scoring or preventing free passage should be identified for removal. A guide to the selection of the preferred maximum size of pipe is given in Table 1. TABLE 1- Selection of insertion pipe size. Preferred maximum sizes. Existing main Nominal bore Insertion Pipe Outside diameter Diametrical clearance inches mm mm mm Selection of insertion pipe SDR (Standard Dimension Ratio) The pipe SDR is defined as follows: SDR = Specified outside diameter Minimum specified wall thickness The SDR should be selected giving due consideration to the maximum operating and test pressure limits for the main and should not be amended in any way as a result of insertion. Table 2 is indicative of the maximum SDR/pressure values for normal operation in the temperature range 0 C to 20 C for medium density (MD) PE pipe. Constructional and special operational requirements may dictate the use of pipe of a lower or higher SDR class or the use of higher density/performance (HD/HP) PE pipe. In this case reference should be made to the operational procedure dealing with pipe system construction for polyethylene systems and the pipe manufacturer s PE pipe ratings. 3.4 Location of excavations A thorough examination should be made of all records of the existing main, together with details of other Utilities plant along the route. Additionally, a survey of the existing main should be made using a pipe location instrument and the position of the existing main and of any changes in direction should be both recorded and marked on PDF created with pdffactory Pro trial version 2

4 the highway surface. Attempts should also be made to locate any suspected changes in depth, which may have required the use of bends, by trial hole excavation. Table 2 Maximum operating pressure limits for medium density PE pipes Pipe MDPE Pipe SDR (class) Outside Diameter Maximum operating pressure (at 0 C to 20 C ground temperature) mm bar bar bar bar / / Note: Pipe sizes indicated by a dash (-) for the various SDR ratings in the above table are not normally available with the full range of complementary fittings required for use in the gas industry, but may possibly be in development. Details should also be recorded of traffic conditions, vehicle and pedestrian crossings and access points, and any other features along the route which may affect the selection of excavations for launch, reception and intermediate pits. Wherever possible, the dual use of excavations should be made for the removal of obstructions, bends, tees, syphons, etc; or the installation of new connections as well as for use during the insertion process. However, particularly when the insertion pipe is considerably smaller than the carrier pipe, it may be possible for some minor degree bends to be retained, provided that the buckling/crimping pipe bending radius of curvature stress limits of the inserted pipe are not exceeded. Typically, a safe bending PDF created with pdffactory Pro trial version 3

5 radius for SDR 11 and SDR 17.6 pipes should not be less than 25 times, increasing to 35 times the pipe OD in very cold weather. For thinner-walled SDR 21, SDR 26 and SDR 33 pipes, these values should be increased by as much as 50 per cent. The length of main which can be inserted will be affected by the insertion pipe size and material selected, gradient, changes in direction, annular clearance, the number of services connected etc; and it is not possible to specify maximum lengths. As a general guide, in average conditions, welded pipe strings of up to 700m in length for MDPE and up to 1000m long for HDPE can be pulled into place, irrespective of diameter or SDR without excessive axial strain. However, the maximum recommended pulling loads as indicated in Table 3 must not be exceeded. Where long lengths of main are to be inserted, additional intermediate excavations may be required to obviate abortive insertion attempts. The location of all excavations should be indicated clearly on project drawings and also where possible on the highway surface. 3.5 Selection of pipe storage sites (pipe dumps) Where straight pipe lengths are to be used for insertion, a storage site or sites should be selected to provide, so far as possible, nearest available proximity to the working area, security and protection from impact damage, vandalism and with minimal obstruction to pedestrians and other road users. They should be planned in advance to ensure that the amount of PE pipe stored coincides with that required for each section of main to be inserted with sufficient space to allow pre-assembly of lengths of pipe to form pipe strings as required. During pressurisation prior to testing, pipe sticks are liable to movement and hence a site which is not accessible to the public is preferable but where this is not possible, barriers, fencing and warning signs must be erected. Where radiography of joints is required and whether or not lead screening is used, access by the public shall be prohibited to a safe distance as specified by the Engineer. To minimise on site storage and jointing requirements, transportable pipe coils and trailers should be used in preference to straight length pipe sticks. Where it is expected that pipes will be stored on site for an extended period, attention should be given particularly for larger diameter pipes, to the protection using plastic end caps/bags and support of pipe ends, to avoid ingress of debris, pipe deformation and consequent difficulties with jointing. Pipe storage, stacking and handling must be in accordance with the pipe and associated plant and equipment manufacture s safety precautions and instructions with particular attention drawn to the safe handling of pipe coils. 3.6 Relaxation, temperature effects and anchorage Polyethylene pipes exposed to high ambient temperatures or strong sunlight will expand in length and when stored in stacks or coils may even become oval in circumference. Also during insertion the length of installed PE pipe may be increased further by tensile pull-in forces but will conversely contract and reduce in length when the existing carrier PDF created with pdffactory Pro trial version 4

6 main is cold. Consequently, to address these effects, it is important to consider the following measures. Prior to installation, the PE insertion pipe, especially that supplied in coils should be checked for ovality using pipe callipers. Whilst the carrier main may have been proved using a straight gauging length, significant scoring and difficulty could arise on insertion due to reduced clearances if the inserted pipe supplied from a pipe coil is oval. To overcome this potential problem, it may be necessary to use a coiled PE pipe straightener/re-rounder or to cold-draw/pull the pipe through a re-rounding die. In this event, tensile winching forces will be increased and tend to further stretch the pipe. When the pull-in forces are released, the PE insertion pipe relaxes at an exponential decay rate. The relaxation times indicated in Part B, clause 7.1 ensure that unsafe stresses do not arise in the main if at least one end of the main is free. No relaxation period is necessary if the PE pipe is inserted by pushing. However, if the pulling operation requires high forces for long periods (i.e. over 30 min) consideration should be given by the Engineer to increasing the times for the inserted pipe to relax. Pipe volume changes occurring during relaxation should be completed before taking the first reading of the pressure test. No relaxation period is necessary prior to making the final connection after the pressure test. The coefficient of expansion for PE is about 15 times that for steel or ductile iron. Therefore, expansion or contraction of the inserted length may occur as the surface ambient temperature of the pipe equilibrates with the ground temperature. For example, the change in length of 100 m PE pipe will be 15mm per 1 C change in temperature. Depending upon local conditions, and latitude, ground temperatures at gas mains depth vary seasonally and can be from say, 20 C or more in summer down to 0 C or less in mid-winter. Where ground temperatures, are likely to be higher than 20 C, especially in summer, then it is recommended that an overnight temperature stabilisation period should be allowed, and in extreme cases as much as 24 hours. In normal circumstances, temperature stabilisation and relaxation periods are given in clauses 3.5 and 7.1 of part B of this procedure. Local anchorage of PE mains will negate temperature effects. Anchorage should be provided at tie-in and valve connections and at service and branch connections to prevent movement caused by thermal expansion. At tie in and valve connections and at intermediate excavations, fused fittings having a positive end loading capacity should be used, whilst at service and branch connections anchorage should be provided using undrilled service saddles fused to the main and encased in concrete anchor blocks. Where PE mains are exposed to the seasonal extremes of atmospheric temperature (e.g. bridge crossings) the effects of seasonal expansion and contraction should be considered on an individual basis, possibly with additional restraint using pipe hoop clamps or with consideration towards using expansion joints. PDF created with pdffactory Pro trial version 5

7 3.7 Sealing of annular openings At every location where a section of existing main is to be removed or broken for service transfers, the annular space between the inserted PE pipe and the existing main should be sealed against gas ingress using cement grout or expanding foam. Where the insertion pipe is small in relation to the existing main size or where thinwalled PE is used and additional structural support and reinforcement of the new pipe is required, consideration shall be made to pressure grouting the annular space along the whole length of the main. For long pipe strings and especially those operating at a higher working pressure above 4 bar, it is generally recommended that a pipe relaxation period of at least 24 hours has elapsed before grouting or making permanent tie-in joints and lateral connections. 3.8 Provision of alternative facilities and temporary gas supplies Where a PE pipe is to be inserted into a main to which services are connected, consideration should be given to the alternative means available to maintain gas supplies to customers. Where an alternative main is available, the temporary or permanent transfer of services may be preferred. Where there are a large number of services or where the duration of insertion work is expected to be long, a by-pass pipeline to which services are transferred may be required. A by-pass will also be required where the existing main to be replaced is a single source supply to downstream customers. The by-pass should, where exposed, be metallic and of sufficient size to adequately supply transferred services and downstream customers, as appropriate. The by-pass may be installed on the surface, but provision shall be made to preclude so far, as is reasonable, damage from vehicles. Vehicular access shall also be maintained and where necessary for this purpose, ramps over the by-pass should be provided or sections of it sleeved or notched into the surface, particularly at road junctions. Details should be recorded on the project working drawings. Where services are also considered for replacement, it is recommended that this work is undertaken in advance of mains insertion operations, to minimise on disruption that later service renewal work would potentially cause. 3.9 Customer relations To maintain good customer relations and co-operation, customer liaison, notification and advice concerning the work programme is essential prior to work commencement. PDF created with pdffactory Pro trial version 6

8 4. PREPARATION 4.1 Plant, tools and equipment In addition to the tools and equipment regularly used for pipefitting and laying, arrangements should be made for all or some of the following specialist plant and equipment to be available, as required, in accordance with the project construction plan: a) Winch (see 4.2) b) Pulling cables and flat woven webbing slings. (See 4.2) c) Reel mounted flexible fibreglass rod. Housed in a metal frame and available in lengths up to 300m long used for the installation of winch cables and draw ropes. d) Cleaning equipment. - To include scraper, wire brush and rubber pig pull throughs. e) Inspection equipment. CCTV camera, video recorder and monitor, and/or PE gauge pigs, pipe wall damage indicator to accurately measure depth of pipe wall scoring and proprietary de-beading tool. f) PE pipe coil straightener and re-rounding dies. - Suitable for all grades of PE (MD, HD and HP) in the size range 63mm to 180mm and for any wall thickness. Used for straightening/re-rounding of coiled pipe as it is dispensed and laid from a pipe coil trailer and also for reclaiming/recycling part coils. g) Pipe towing head assemblies, nose cones, pipe rollers, mechanical fuses, snap-action pipe restraining clamps and insertion trumpets. h) Heavy-duty swivel, snap-action toggle clamp. Used to attach the winch cable to the towing head assembly i) Test ends. To facilitate testing of pipe sticks and strings, test ends should preferably be used. j) Combined Wheel Excavator/Loader (>5 tonne) with hydraulic jack-up support legs and the backhoe certified and approved for lifting use applications. k) PE pipe pushing machine. 4.2 Winching, pulling and pushing operations General For small diameter (150mm dia. and below), short length (less than 100m long) mains renewals that are usually prevalent in urban areas, the weight of the insertion pipe and the axial strains involved are substantially less than the forces required for larger diameter and longer length mains insertion renewals. Consequently, pushing from the PDF created with pdffactory Pro trial version 7

9 launch pit should be considered preferable to pulling from the reception pit in these circumstances, with reduced hazard risks and precautionary safety measures required. Pushing could be considered slower than pulling, but to some extent the time element is not too significant as this would be offset by the set-up time involved if pulling with powered winches were used instead. For relatively light duty applications, pipe pushing is an effective, simple technique that offers a finer degree of control and places less strain on the insertion pipe. The most common method of pipe pushing, is to employ the use of a mechanical excavator s articulated backhoe with lifting shackle attached to a 4m to 6m long, 100mm wide flat woven polypropylene webbing sling. This can be attached at intervals to the insertion pipe string in the launch pit with a pipe-restraining clamp and backhauled gradually into the carrier main using the dipper arm. Providing the inserted pipe has free passage, as pre-proved using a gauge length pull through prior to installation, apart from frictional effects, the only constraint to this method is the weight of the pipe being installed. It is therefore essential that if this method is used, an estimate be made of the weight of the pipe length proposed for insertion to ensure that it does not exceed the safe working loads (SWL) of both the machine employed and webbing sling used. As a further safety measure, to allow for frictional effects, it is recommended that the estimated installed pipe weight should be increased by say a notional 20% to give a factor of safety margin of error in the actual weight being hauled. An approved mechanical fuse should be installed between the lifting shackle and pipe sling that is limited to the safe working load (SWL) of the sling. Under no circumstances should any persons be permitted to enter the excavation during the hauling-in of the inserted pipe and all safety measures, rules and instructions concerning the use of excavators as cranes, shackles, eyebolts, mechanical fuses, pipe clamps and lifting slings must be strictly observed. (See Appendix A, Part B) Proprietary pipe pushing machines are available, but tend to be heavy and bulky in transportation between launch and reception excavation pits and they can require regular maintenance with the potential problem of availability of spare parts. Close attention to anchorage of the machine and a system of pipe rollers needs to be set up for successful operation involving additional set-up time. Alternatively, instead of using a mechanical excavator to back-haul the insertion pipe into the parent main, hand operated winching could be used to push the inserted pipe towards the reception pit. However, whilst this method is still preferable to powered winching, close attention to anchorage of the hand winch is necessary and suitable precautions will also need to be taken to protect the winch operator from injury resulting from failure of the winch cable. Steel wire cable shall be used in preference to natural or synthetic fibre ropes. A current, valid insurance test certificate shall be available for the steel cable, ropes and winch and all must be rated for the purpose for which they are intended. The hand-operated winch can also be used at the reception pit excavation in order to pull the pipe instead of pushing. PDF created with pdffactory Pro trial version 8

10 4.2.2 Hand operated winch, cables, ropes and slings The winch shall be equipped with a dynamometer or an approved mechanical breakaway connector fuse (weak-link) which is limited to either the safe maximum allowable working load (SWL) for the cable selected or for the maximum allowable pull-in force (F) on the PE pipe selected, whichever is the smaller. - (See: Table 3) The safe working load (SWL) is usually designated at 10% of the breaking strain/load of the cable, rope or sling, but the manufacture s stamped or plated SWL value should always take precedence. To avoid over-stretching and exceeding the elasticity limits on the insertion pipe, the maximum allowable pull-in force (F) on the PE pipe, expressed in Newtons (N) is given by the following equation: F = 0.5 π D t Y Where: D is the PE pipe outside diameter, in mm. t is the pipe wall thickness, in mm. Y is the specified minimum yield stress (SMYS), in MN/m². The values for (F) indicated in Table 3 are based on this formula, (but expressed in kn) are valid for medium and high density polyethylene pipes in common use, in the size range and SDR class tabulated. For other pipe size and SDR values not shown, for either MD or HD/HP PE pipes, the value of (F) may be calculated using the above formula. As 10kN = 1 Tonne force = 1000kg.f, to convert from kn to tonnes force is to multiply those values shown in Table 3 by 10 or by 100 to convert to kg.f Power operated winch For larger diameter (>150mm and above), longer length (in excess of 100 metres) mains renewals, and where pulling forces are likely to exceed 5 tonnes (49kN), powered winching is recommended. For such heavy duty applications, a tractor or other moveable plant or vehicles fitted with Power take Off (PTO) winches shall not be used for towing-in the inserted pipe through the carrier main, only a purpose designed and static machine is permitted. The power operated winch shall be fitted with a mechanical fuse or dynamometer as detailed in A suitable size winch and cable should be selected for the anticipated pull-in forces for the size and length of insertion pipe considered, to be set up at the reception pit of the pipeline to be slip-lined. PDF created with pdffactory Pro trial version 9

11 Table 3 Maximum allowable pull-in force (F) in kn Pipe Pipe material (SDR) and maximum allowable forces (F) outside Medium Density PE High Density PE diameter SDR 11 SDR 17.6 SDR 11 SDR 17.6 mm (F) kn (F) kn (F) kn (F) kn INSTALLATION PROCEDURE. The mains insertion/slip-lining installation procedure is detailed in Part B, together with safety requirements (Appendices A and B) for operational personnel. Safety of winching operations shall be strictly observed as detailed in Appendix B. 6. INSPECTION, TESTING AND COMMISSIONING. During and following installation, the inserted main shall be inspected, tested and commissioned in accordance with those procedures specifically assigned for this purpose. However, for larger diameter insertion pipes operating in the higher-pressure range (75mb to 7bar), consideration may further apply to supplement the pneumatic pressure testing procedure with radiographic examination. Where radiography is employed, the working area shall be fenced off and all safety precautions and inspection criteria in an approved method statement provided by a certified Test Engineer/PE Pipe Welding Inspector shall apply. (Ref: EN 13067) PDF created with pdffactory Pro trial version 10

12 ΤΕΧΝΙΚΗ ΠΡΟΔΙΑΓΡΑΦΗ ΕΠΑ-CP-002 EN ISO 9001:2000 Κώδικας Πρακτικής για την αντικατάσταση κύριων αγωγών με τη μέθοδο της κατευθυνόμενης διάτρησης (guided moling and horizontal directional drilling) ΣΥΝΤΑΞΗ: TMHMA ΤΕΧΝΙΚΗΣ ΥΠΟΣΤΗΡΙΞΗΣ ΕΛΕΓΧΟΣ: ΕΠΙΤΡΟΠΗ ΤΕΧΝΙΚΩΝ ΠΡΟΔΙΑΓΡΑΦΩΝ ΕΠΑ ΑΤΤΙΚΗΣ ΕΓΚΡΙΣΗ: ΕΠΙΤΡΟΠΗ ΤΕΧΝΙΚΗΣ.ΔΙΕΥΘΥΝΣΗΣ ΕΠΑ ΑΤΤΙΚΗΣ 1 / 1 Αναθεώρηση: 0 η / Ημ/νία έγκρισης: 20/8/2002 PDF created with pdffactory Pro trial version

13 EPA ATTIKIS CODE OF PRACTISE FOR MAINS REPLACEMENT- Guided Moling and Horizontal Directional Drilling (HDD) for Polyethylene (PE) 1. SCOPE This code of Practice is intended for guidance by Engineers or their representatives responsible for the replacement of existing mains by guided moling and drilling and should be used in conjunction with the corresponding Procedure for operational personnel. 2. REFERENCES Unless otherwise specified this document shall be used with reference to the latest editions of related procedures, standards and specifications dealing with safety, construction planning, traffic management, excavations, reinstatements, materials, plant and equipment, testing and commissioning. 3. DESIGN AND METHOD SELECTION 3.1 General Whilst guided moling and drilling is a most suitable technique for new mains and services installation, it can also be a most cost-effective method for mains and service replacement. Generally in high population density areas, where there are many service connections to consider and also where environmental factors can be a major constraint, directional moling and drilling can often be preferable to other methods. In the case of mains insertion or swagelining, and even where service replacements have been undertaken in advance, the number of service transfer/connection pits can be very disruptive to the local community. This may also involve labour intensive operations on restoration of gas supplies, especially where overland bypass mains and temporary service connections have not been installed. Service transfer excavations, if left open will require a high level of protective barriers, road cones, traffic lights, signs, etc; or alternatively, traffic conditions may dictate that the excavations are plated over with heavy duty steel road plates involving placement and removal using lifting plant. Environmental factors to consider are the locations of existing gas mains, prevalence of other utilities apparatus, road traffic congestion, rail, river and water course crossings. In certain circumstances, it may be preferable to re-locate the position of a replacement main rather than carry out existing in-situ mains rehabilitation. For example, those mains situated in close proximity to, or beneath buildings, structures, ornamental features and plant installations, or other inaccessible locations, or those that may be at shallow depth and subject to potential interference damage or alternatively have been subject to landfill overburden. PDF created with pdffactory Pro trial version 1

14 Guided moling or drilling offers an effective technique to overcome some of the difficulties associated with other mains replacement methods. It has the added benefit that service replacement and transfers can be carried out after the replacement main has been installed on a less labour intensive basis and without the need to provide overland bypasses and temporary supplies to customers, whilst the existing main still remains in commission. In the case of guided drilling, the procedures detailed in Parts A & B are typical operations which may need to be varied due to the wide range of equipment available, each with its own steering mechanisms, different power ratings and lubrication needs. Guided boring equipment can be either percussive/pneumatic, hydraulic, or rotational in action or a combination of these functions and they are described below. 3.2 Percussive Impact (soil displacement) Mole Impact moling is generally the most widely used trenchless pipelaying technique and is mainly used for small diameter pipelines over short lengths. Typically, steerable impact moles (hammers), will install PE pipe in the diameter range 16mm to 63 mm within a 75mm diameter bore-hole, and at lengths of up to 60 metres, depending upon ground conditions. Non-steerable, unguided impact moles are available in larger diameters and can be fitted with an expander/mandrel, to install PE pipe up to and including 250 mm diameter but may have length limitations of only up to 25 metres. Provided prior safety precautions are taken regarding the proximity of utilities apparatus, the steerable mole can be used to produce a pilot bore-hole for single or multiple passes with the use of the larger diameter non steerable impact mole. Alternatively, where pilot boreholes are relatively straight, a winched-in expander/mole could be used in between launch and reception pits to produce a larger diameter bore. For greater distances, the practice of stitching can be employed. The performance of the mole depends upon the type and condition of the ground in which it is operating. The percussive action of the mole has the effect of compacting the earth around it, and therefore the impact mole can only be used in soils and soft friable, shales which allow for this compaction, without potentially causing damage to adjacent underground apparatus or ground heave. Impact moles can operate in most clays, silts, sands, aggregates and gravels. Isolated cobbles and small boulders are displaced or broken up, although they may tend to deflect the bore off-line. Very soft ground conditions are unsuitable, as the mole tends to drop under its own weight, which is more significant for moles greater than about 75 mm in diameter. As applies to all guided boreholing methods, before moling commences, it is essential that records of all underground services are studied to ensure that there are no pipes, ducts or cables likely to obstruct the pipe drive route between launch and reception pits. Also a safe proximity distance as specified by the utilities concerned, shall be maintained between the proposed bore and other plant in the vicinity. Trial-hole excavations, pipe and cable detection equipment together with visual inspection shall be used. Trial holes excavated during the site survey, and used to either verify the position the utilities underground records or to check ground conditions or that the proposed drive is clear of obstructions should also be considered for use as launch/intermediate and reception pits. These in turn could also be used for mains and services connections PDF created with pdffactory Pro trial version 2

15 and transfer pits, with possibly several service connections made, and radiating from the same pit. Guided moling commences just like a non-steerable impact mole with a launching cradle, which safely aligns the machine, and a sighting frame used to aim the mole at the required target area. A hydraulically operated device called a Torquer (steering wheel) and control unit are fitted at the sighting frame to start, stop, forward, reverse, fast/slow or manoeuvre the mole. Two pits are excavated, one to launch the mole and one to receive it. The launching pit will typically be about 2 metres long and up to 1 metre wide and approximately 1 metre deep. The reception pit should be at least the length of the mole plus about 200 mm to allow for its removal or possibly larger in the case of mains stitching where the reception pit becomes an intermediate pit to launch the mole again and extending the distance of installed pipe. To avoid misalignment of bores between launch, reception and intermediate pits when stitch moling is used, it is recommended that the mole is allowed to continue through, and a mole s length past the intermediate pit. It can then be reversed and removed and set-up again as a separate launch operation in the intermediate pit and targeted towards the next reception pit. It is good practice to ensure that wherever possible to minimise excavations, that as much use as possible is made of each excavation pit for multi-purpose operations. Once the mole has emerged from the target pit and the compressed air supply safely isolated, the mole is disconnected from the air hose which is reconnected to the PE pipe to be installed via a pipe-puller. By pulling the hose out of the borehole, the PE pipe is simultaneously pulled in. Whilst the pneumatically powered impact mole only operates at an average speed of 10 metres/hour, it is essential that its exact position, line and depth are continuously monitored and recorded during the guided moling operation. This is achieved by using a specialist radio-detection instrument and a transmitting sonde, located in the head of the mole, which provides pitch, depth and roll information. These details are regularly passed on from the person tracking the mole to the steering operator, so that both operators have a clear picture of the machine location, to ensure any necessary course corrections are made. Depending upon ground conditions, radius of curvatures of the borehole line can possibly be around 27 metres or less with certain machines, to course correct, avoid potential obstructions or maintain safe proximity distances from other underground apparatus. However, advice should always be sought from manufacturers and suppliers on the limitations of use for their particular machines. Installation procedures for operational personnel are detailed in Part B of this procedure, together with safety and risk assessment requirements provided in Appendix A. Although, more powerful, larger diameter, guided, pneumatic and hydraulically operated, soil displacement impact moles are in development, the same principles, as above, will also most likely apply to such future improvements in technology. PDF created with pdffactory Pro trial version 3

16 3.2.1 Summary Guided impact moling is usually considered preferable to guided drilling methods as it offers the following advantages: a) Minimal skill and training requirements. Usually on-the-job training by a qualified and experienced operator/instructor that is normally provided by the equipment supplier is sufficient. b) Capital investment, operational and maintenance costs are relatively low. c) Easily transportable by commercial vehicles with no heavy duty lifting equipment required. d) Causes least disruption to customers, road users and the general public. e) It is most useful for small diameter, short length mains and service renewals, including road crossings and house connections, under gardens and pavements up to 60 metres in length, depending upon ground conditions. f) It is suitable for average ground conditions including sand and clay. g) No expensive drilling rod stems, drilling bits or back-reamers to consider, no bentonite drilling fluid to mix, no water supply required, and no waste disposal costs including disposal of drill cuttings and surplus bentonite fluid. However impact moling does have its disadvantages as follows: a) Compaction of the surrounding soil, which is displaced during the moling operation, could cause a problem, especially in outcrops of hard compacted ground, containing rocks and large boulders, which could make progress slow and difficult. b) There is a high potential risk to interference damage to other services in the vicinity with difficulty to determine if there are any uncharted or unrecorded obstructions in the drive path of the mole and in between excavation pits. c) Largely due to ground conditions, guided impact moling is generally restricted to small diameter, short length mains and service replacements only. d) The inserted PE pipe is untraceable using traditional pipe location instruments and consequently accurate records need to be maintained. e) Impact moling is slower than guided drilling which is usually up to 10 times faster in average ground conditions. Guided drilling methods will overcome some of the limitations of impact moling and are described in section 3.3. PDF created with pdffactory Pro trial version 4

17 3.3 Guided and Horizontal Directional Drilling (HDD) Directional drilling is a very specialist operation, requiring the use of highly trained, qualified and experienced operational personnel who are accustomed to using the equipment on almost a regular daily basis. Guided, directional drilling machines, generally operate in pipe diameters ranging from 50 mm to about 1000 mm, and at drive lengths from a few metres to several kilometres, depending upon the specification of the machine selected. There is a large assortment of guided drilling rigs available, and it is recommended that the Engineer/Manager consults with equipment suppliers to establish various machine specifications and decide on the particular machine necessary to suit the required circumstances. The range of drilling machines available are usually categorised as a mini, medi or maxi classification but design and installation practices will vary between machines. However, for gas distribution purposes, the mini and medi machines are those most considered appropriate for mains replacement. Consequently, this procedure excludes machines in the maxi category, which are usually used for crossing lakes and large estuaries. The mini and medi machines are generally rated in accordance with their pullback power, i.e. up to a maximum of 4 tonnes force for mini, and between 4 and 20 tonnes force for medi. Those machines operating in excess of 20 tonnes force pulling power are classed as maxi Installation Guidelines Guided/directional drilling is carried out from a large surface mounted rig with a drill lubrication system, usually mud pumped down the drill-hole, drives the drill at the end of the bore and carries the cuttings back out of the launch hole as it re-circulates. It is usual practice, except with small pipes (< 75 mm dia.), that the first drill hole is used as a pilot bore to establish line and level before reaming to the required diameter. Once reamed, the PE insertion pipe is attached to the end of the drill string in the reception pit and pulled back through to the launch pit. Pulling forces shall not exceed half the specified minimum yield stress (SMYS) of the PE pipe in accordance with those tension limits expressed in Table 3 (Part A) and Table 4 (Part B) of the Mains Insertion Procedure. The length and diameter of the pipe to be installed is very much dependant on the type of machine employed, but in general, the pull-back force rating of whatever machine is used is the deciding factor. An estimate of the weight of the pipe to be hauled through the bore-hole with an allowance for frictional effects (say 20% uplift) is recommended and compared with the pull-back force specification of the machine employed to make sure that it is not under-rated. PDF created with pdffactory Pro trial version 5

18 All guided/directional drilling machines shall be fitted with approved safety equipment, including the use of a Faraday Mat which shall be adequately earthed, and a cable strike alarm, to protect the operatives from any accidental electricity cable strikes. The guided drilling equipment shall be capable of being guided in both vertical and horizontal directions. Launch and reception pits should be of sufficient size to enable the proper execution of the work, but usually not exceeding 5 m² for the launch pit and 3 m² for the reception pit. Wherever possible the minimum distance between launch and reception pits shall be 50 metres. The tolerance for guided drilling shall be ± 150 mm from the design line and level, produced on drawings for use by operational personnel. For PE pipe pullback purposes, it is recommended that the line of the drilled bore should not exceed a radius of 30 installation pipe diameters, and changes in direction achieved by bending the PE pipe shall not be less than a bend radius 15 times the pipe outside diameter. No joints, either butt-fused, electrofusion or approved mechanical be permitted within the cold bended pipe. Where this is not possible, an intermediate excavation may be required in which to install a standard bend. The drilling machine rig, can be either static or mobile on rubber tracks, the static machine, held within a drill frame can be used in-ground within the launch pit or as applies to the mobile rig, can also be used at surface level. When mounted at surface level, the drill is usually inclined at a launch inclination angle of between 10 and 18 depending upon differences in surface levels and can also be steered up gradients, perhaps near the reception pit at these angles. The mobile drilling rigs and larger static machines are usually self-contained with easily detachable drill rod boxes containing usually up to 50 (3 m length) drill rods. The drill rods are usually automatically loaded and unloaded for back reaming and where greater drive or shot lengths are required, the rod box can be easily and quickly exchanged for a second rod box within minutes. Accurate depth and location information should be recorded on a drilled bore log sheet at a minimum of 5 metre intervals, for all lengths of the PE pipe installed by directional drilling. Proprietary, hand- held computers, bore planner software and printer outputs are normally available for all guided drilling machines as an optional requirement. The lead drill bore head contains a transmitting sonde, the location of which is detected at surface level using a radio detection receiving instrument. Installation procedures for operational personnel are detailed in Part B of this procedure, together with safety and risk assessment requirements provided in Appendix A. PDF created with pdffactory Pro trial version 6

19 ΤΕΧΝΙΚΗ ΠΡΟΔΙΑΓΡΑΦΗ ΕΠΑ-CP-003 EN ISO 9001:2000 Κώδικας Πρακτικής για την αντικατάσταση κύριων αγωγών με τη μέθοδο της swagelining / close - fit ΣΥΝΤΑΞΗ: ΤΜΗΜΑ ΤΕΧΝΙΚΗΣ ΥΠΟΣΤΗΡΙΞΗΣ ΕΛΕΓΧΟΣ: ΕΠΙΤΡΟΠΗ ΤΕΧΝΙΚΩΝ ΠΡΟΔΙΑΓΡΑΦΩΝ ΕΠΑ ΑΤΤΙΚΗΣ ΕΓΚΡΙΣΗ: ΕΠΙΤΡΟΠΗ ΤΕΧΝΙΚΗΣ.ΔΙΕΥΘΥΝΣΗΣ ΕΠΑ ΑΤΤΙΚΗΣ 1 / 1 Αναθεώρηση: 0 η / Ημ/νία έγκρισης: 25/8/2002 PDF created with pdffactory Pro trial version

20 EPA ATTIKIS CODE OF PRACTICE FOR MAINS REPLACEMENT- Swagelining/ Close- Fit (PE. PIPE) 1. SCOPE This Code of Practice is intended for guidance by Engineers or their representatives responsible for the replacement of existing mains by Swagelining and should be used in conjunction with the corresponding Procedure for operational personnel. 2. REFERENCES Unless otherwise specified this document shall be used with reference to the latest editions of related procedures, standards and specifications dealing with safety, construction planning, traffic management, excavations, reinstatements, materials, plant and equipment, testing and commissioning. 3. DESIGN 3.1 General The most cost effective method of replacement is by PE (polyethylene) pipe mains insertion, however this has the disadvantage of considerably reducing the carrying capacity of the main being lined. Swagelining, close-fit or die drawn as this technique is commonly known, overcomes this problem, and tests have proved that about 94% of the original capacity of the existing main is retained. The process achieves diameter reduction by pulling the lining through a reduction die. The diameter of the PE pipe is reduced by 6% and increases its lengths by 4%, with no decrease in wall thickness. The winch tension which is applied to the to the liner, maintains the reduced diameter and enables it to be drawn into the existing main. When the liner is installed, the winch tension is released and the liner reverts to its original size to form a close fit. Access is required at 150 metre intervals for small bore pipelines, 300 metres for larger bores, and preferably at bends, mains connections or valve positions. The pipeline is then inspected by CCTV (Closed Circuit TV) camera and details of all service connections and junctions logged. The liner is available in both medium and high density polyethylene pipe with various wall thicknesses to meet pressure requirements. The pipe is supplied coiled or in straight lengths, butt welded on site to form a continuous length. Monitoring of the stress on the PE pipe is undertaken throughout the insertion process to ensure safe working within design criteria. Insertion lengths can be in excess of 600 metres but will vary depending upon the diameter, curvature of the main and thickness of the pipe. Swagelining can be undertaken either hot or cold, in the pipe diameter range 75mm to 600mm. PDF created with pdffactory Pro trial version 1

21 3.2 Cold swagelining Cold swagelining is the process of pulling the pipe using a specially fabricated four leaf nose cone pulling head, butt fused to the end of the PE pipe through a die at ambient temperature to reduce its diameter sufficiently to permit its entry into the main to be lined. 3.3 Hot Swagelining Hot swagelining is a process similar to cold swaging with the addition of pre-heating the PE pipe to a temperature of no greater than 70 C before entry into the die. Hot swagelining reduces towing loads. 4. SELECTION CRITERIA 4.1 Close-fit linings may be installed in various pipe materials (e.g. pit cast iron, spun iron, ductile iron, steel) provided that the original pipe is circular. 4.2 Pipe sizes up to and including 24 in. (600 mm) may be considered for replacement using the swagelining technique. 4.3 The PE liner pipe should have an original diameter slightly larger than the bore of the pipe to be lined in order to obtain a close fit. Both standard and non-standard PE pipe sizes may be used (see Table 1) 4.4 the wall thickness of the PE lining should be minimised to maximise the carrying capacity of the main. Where coiled pipe or saddle fusion joints are used, particularly in smaller pipe sizes, thicker wall pipe may be necessary. 5. SITE INVESTIGATION 5.1 Maximum use should be made of all available records. Details of material types together with the position of existing valves, plugs, bends, tees, condensate receivers, change and double collars, service connections or any other obstructions in the main should be obtained. 5.2 Details of other utilities plant must be obtained and both electricity cables and telephone ducts should be physically marked out on site. 5.3 Route inspection together with on site marking-out of the main and any recorded features should take place to assist with the validation of recorded information. 5.4 Following isolation and purging of the main, the bore should be checked at the access points and recorded. It should be noted that the internal bore of each cast iron pipe may vary along its length. PDF created with pdffactory Pro trial version 2

22 6. CLOSED CIRCUIT TELEVISION SURVEY AND MAINS CLEANING 6.1 It is essential prior to close-fit lining that the main is inspected by a CCTV camera to confirm that there are no unrecorded features and also that all debris has been removed. 6.2 Where appropriate, excavations that are required for the removal of obstructions and for the CCTV survey and mains cleaning operations should be utilised as access points 6.3 From any excavation it may be possible to survey up to 600 m of isolated main (300 m in each direction), depending upon the size of the main. 6.4 Following the CCTV survey, further mains cleaning may be required together with the removal of any obstructions which have been located during the survey. 6.5 Consideration should be given to sections of main in which gas conditioning agents may collect. 6.6 All CCTV surveys undertaken should be recorded on videotape. 6.7 Various methods of pipe cleaning may be employed. Rack-feed borers, scrapers and wire brushes used in conjunction with rubber pull throughs and a winch are usually sufficient, except where heavy encrustations are encountered. Consideration should also be given to the use of a vacuum unit for cleaning pipes having dry deposits. 6.8 Whatever method of cleaning is used, it is advisable that a further CCTV survey is undertaken to confirm that all debris has been removed from the pipe, and that the cleaning operation has been successful. 6.9 After cleaning, a towing cable should be installed in the pipe in preparation for the gauging operation All obstructions shall be removed prior to the close fit lining operation and, in the case of bends and condensate receivers, an additional metre of pipe on either side of the obstruction should be removed Any solid or liquid material found within the main shall be regarded as potentially hazardous and shall be removed and disposed of in accordance with safe working practices and any appropriate legislation. PDF created with pdffactory Pro trial version 3