-SQA- SCOTTISH QUALIFICATIONS AUTHORITY. Hanover House 24 Douglas Street GLASGOW G2 7NQ NATIONAL CERTIFICATE MODULE DESCRIPTOR

Transcription

1 -SQA- SCOTTISH QUALIFICATIONS AUTHORITY Hanover House 24 Douglas Street GLASGOW G2 7NQ NATIONAL CERTIFICATE MODULE DESCRIPTOR -Module Number Session Superclass- TH -Title- GAS DISTRIBUTION: MAINS AND SERVICE OFFTAKES FROM GAS MAINS -DESCRIPTION- Purpose This module is designed to develop the knowledge and skills required to construct mains and service offtake connections from live gas mains to a maximum working pressure of 7 bar, using a range of underpressure drilling apparatus. It is aimed at those following a career in the distribution sector of the gas industry and receiving complementary industrial experience. Preferred Gas Distribution: Breathing Apparatus Entry Level (x 1/2) Gas Industry: Firefighting (x 1/2). Outcomes The student should: 1. outline the statutory requirements which govern offtake connections from live gas mains; 2. perform drill and tap operations on metallic gas mains; 3. perform branch drilling operations on metallic gas mains; 4. perform branch drilling operations on polyethylene gas mains. Assessment Procedures Acceptable performance in the module will be satisfactory achievement of all the Performance Criteria specified for each Outcome.

2 Unless otherwise indicated, the student may be assisted by one or more students in carrying out the practical exercises. However, each student in turn must be assessed as being responsible for the completion of the tasks specified. The following abbreviations are used below: PC Performance Criteria Instrument of Assessment Note: The Outcomes and PCs are mandatory and cannot be altered. The may be altered by arrangement with SQA. (Where a range of performance is indicated, this should be regarded as an extension of the PCs and is therefore mandatory.) OUTCOME 1 OUTLINE THE STATUTORY REQUIREMENTS WHICH GOVERN OFFTAKE CONNECTIONS FROM LIVE GAS MAINS PCs (a) The selection of the drilling device is correct in terms of mains pressure and drilling size. (b) The description of the procedures of authorising offtake connections from mains is correct in terms of gas industry requirements. (c) The description of maintaining a gas free environment during offtake operations is correct in terms of gas industry requirements. Restricted Response The student will be presented with an exercise consisting of restricted response questions to test comprehension of the legal requirements governing mains and service offtakes from gas mains. The exercise will consist of 7 questions allocated as follows: (i) sources of information - 1 (ii) operational procedure requirements - 2 (iii) legal requirements - 1 (iv) pressure testing requirements - 1 (v) equipment selection - 2 Satisfactory achievement of the Outcome will be based on all Performance Criteria being met. This will be demonstrated by the student producing one correct response to each of (i), (iii) and (iv) and two correct responses to each of (ii) and (v). 2

3 OUTCOME 2 PERFORM DRILL AND TAP OPERATIONS ON METALLIC GAS MAINS PCs (a) The procedures adopted for the inspection and preassembly maintenance of under pressure drilling and tapping equipment ensures operational service ability. (b) The procedures adopted for pre-drilling metallic gas main preparation are in accordance with gas industry requirements. (c) The assembly and testing of under pressure drilling and tapping equipment is in accordance with manufacturer's instructions and gas industry requirements. (d) The use of under pressure drilling and tapping equipment is correct in terms of personal safety and gas industry requirements. (e) Working practices followed are safe. Practical Exercise The student will be set an exercise consisting of a series of practical tasks to test the application of knowledge and skills required to perform drill and tap operations to metallic gas mains and insert a range of fittings. The exercise will consist of 4 tasks allocated as follows: (i) preparation of mains and drilling machine assembly; (ii) testing of assembled drilling machine; (iii) drill and tap gas main; (iv) installation and mains fitting. For tasks (i) - (iv) the student will be presented with a section of pressurised metallic main and range of tools and fittings appropriate for the completion of the given tasks. Satisfactory achievement of the Outcome will be demonstrated by the student performing each of the tasks in accordance with the Performance Criteria. OUTCOME 3 PERFORM BRANCH DRILLING OPERATIONS ON METALLIC GAS MAINS PCs (a) The procedures adopted for inspection and pre-assembly maintenance of under pressure branch drilling equipment ensure operational service ability. 3

4 (b) (c) (d) (e) (f) The procedures adopted for the preparation of parent main and pressure measurement devices fitment are in accordance with gas industry requirements. The procedures adopted to assemble branch offtake fitting and gas stopping devices are correct in terms of gas industry fitments for the given situation. The procedures adopted for drilling machine operating clearance measurements are in accordance with gas industry requirements. The use of branch drilling equipment is correct in terms of suitability and safety. Working practices followed are safe. Practical Exercise The student will be set an exercise consisting of a series of practical tasks to test the application of knowledge and skills required to perform branch drilling on metallic gas mains. The exercise will consist of 4 tasks allocated as follows: (i) (ii) (iii) (iv) preparation of main and pressure recording fitting; selection and assembly of branch connection and valve; testing of assembled branch connection; carrying out drilling operation. For tasks (i) - (iv) the student will be presented with a section of pressurised metallic main and a range of tools and fittings appropriate for the completion of the given tasks. Satisfactory achievement of the Outcome will be demonstrated by the student performing the tasks in accordance with the Performance Criteria above. OUTCOME 4 PERFORM BRANCH DRILLING OPERATIONS ON POLYETHYLENE GAS MAINS PCs (a) The procedures adopted for inspection and pre-assembly maintenance of underpressure branch drilling equipment ensure operational service ability. (b) The procedures adopted for polyethylene parent main preparation and pressure measurement devices fitment are in accordance with gas industry requirements. (c) The method of securing and fusing polyethylene branch tee is correct in terms of safety and alignment. 4

5 (d) (e) (f) The procedures adopted for soundness testing assembled polyethylene branch offtake and drilling device are in accordance with gas industry requirements. The use of polyethylene branch drilling equipment with supportive thrust clamp is correct in terms of safety and suitability. Working practices followed are safe. Practical Exercise The student will be set an exercise consisting of a series of practical tasks to test the application of knowledge and skills required to perform branch drilling operation on polyethylene gas mains. The exercise will consist of 3 tasks allocated as follows: (i) (ii) (iii) preparation of main and pressure recording fitments; fitting and support of branch connection and valve; testing of assembled branch connection and carrying out of drilling operation. For tasks (i) - (iii) the student will be presented with a section of pressurised polyethylene gas main and a range of tools and fittings appropriate for the completion of the given tasks. Satisfactory achievement of the Outcome will be demonstrated by the student performing the tasks in accordance with the Performance Criteria above. 5

6 The following sections of the descriptor are offered as guidance. They are not mandatory. CONTENT/CONTEXT Safety regulations and safe working practices and procedures should be adhered to at all times. Corresponding to Outcomes 1-4: 1. Legislation that may affect offtake connections from live gas mains to include: - The Health and Safety at Work Act The Gas Act The Gas Safety Regulations 1984 Factors relating to the authorisation of mains and service offtake connections to include: - non-routine operation procedure - authorising operation procedure - Gas Distribution Codes of Practice and Instructions The student should be aware of the range of drilling equipment available for use to include: - parent main material - diameter of parent main and offtake - pressure of parent main - type of drilling machine The student should be aware of the necessity for monitoring parent main gas flow and working pressure and of the provision for safety equipment to combat fire and minimise uncontrolled gas release. 2. Factors relating to the selection and preparation of underpressure drilling and tapping machines to include: - base plate saddle condition and selection - drill selection in relation to diameter and mains material - chain retention lug selection - slide valve operation - pressure equalising device The student should recognise the purpose and importance of adequate mains preparation prior to drilling and tapping operations to include: - removal of pipe cladding - removal of surface scale - confirmation of adequate working space - establishing of main as gas carrier - establishing of operating pressure - recording of statutory records of offtake connection 6

7 The student should follow recommended testing procedures on underpressure drilling machine to provide integrity of assembled machine. The use of underpressure drilling and tapping machines and tooling to include: - drilling and tapping - plug insertion - top and side tee insertion - removal of inserted fitting - re-centralising machine over established point - special fitting insertion. 3&4. Factors relating to the selection and preparation of underpressure drilling machines to include: - pressure range - hand operated machines - mains material and diameter - power operated machines The student should recognise the purpose and importance of adequate mains preparation prior to encompassing the parent main drilling area to include: - surface preparation - parent main ovality - proximity to joints and fittings - mains condition Correct procedures to assemble branch offtake fittings will include: - positioning offtake rise or fall - bolt tightening sequence and torque - electrofusion weld techniques - manual metal arc welding - polyethylene branch connection clamping - testing of assembled branch connection - fitting and testing of slide and gate valves to branch connections - flange table identification The use of underpressure drilling machine to include: - coupon retention device - pilot drill selection and fitting - cup drill selection and fitting - parent main pressure recording - testing of assembled drilling machine - carrying out of drilling operation - calculation of drill travel distances and 'x' factors The student should be aware of adequate safety provisions to combat fire and prevent the release of uncontrolled gas. 7

8 SUGGESTED LEARNING AND TEACHING APPROACHES Outcomes 1-4 could be introduced through formal discussion and then reinforced by workshop practice. Most instruction should be given in a workshop situation supported by practical demonstrations, followed by student participation. The safety element should be constantly stressed and assessed. Outcomes may also be achieved by use of: Slides Outcomes 3 and 4 Demonstration Outcomes 2, 3 and 4 Group Discussion Outcome 1 Questionnaires Outcomes 1, 2, 3 and 4 Practical and Outcomes 2, 3 and 4 simulated exercises Adequate time should be allocated to practical and theory sessions with every consideration being given to the subject being taught in proper subject progression. The individual's contribution to any group activities should be stressed throughout. It is recommended that a reference manual or handout is made available and issued to the student. Copyright SQA /02/98 8