A Job Safety Execution Plan is required. mixtures of the above called, natural gas liquids (NGL's) refined products and their components

Transcription

1 TITLE Pipelines and Terminals Manual/Volume 3 - SECTION 02: SUBJECT 20: PURPOSE AND SCOPE During the normal lifetime of a pipeline it becomes necessary to add or remove piping, modify existing piping or to make repairs to the pipeline. This procedure covers the requirements for preparing a pipeline to be worked on. This includes executing nitrogen-purging activities, isolating the line to complete the work safely and finally, recommissioning the line to return to service. The procedure identifies the general steps that must be taken for High Vapour Pressure (HVP) lines, natural gas lines and Low Vapour Pressure (LVP) liquid lines such as crude oil. A Job Safety Execution Plan is required. Through proper hazard identification and reviewing the potential problem analysis, this procedure will be executed ensuring the safety of the workers on the job site. HVP products typically are those that are shipped as liquids that prefer to exist as a gas at atmospheric pressure: ethane propane butane mixtures of the above called, natural gas liquids (NGL's) LVP includes: refined products and their components crude oil condensate August 2015 Page of 9

2 REFERENCES PDM : Safety: Safety and Environmental Rules PDM : Safety: Work Permits PDM : Safety: Loss Prevention System PDM : : Energy Isolations and Lock-Outs PDM : Product Movement-Piping and Accessories: Pigging PDM : Product Movement-Valves: Valve Maintenance Hazards and PSV Servicing PDM : Product Movement-Valves: Opening, Closing, Venting, and Depressurizing High Pressure Valves ASSOCIATED DOCUMENTS 0308F10.Doc: Chemical Inhibition Trucks and Steamers Checklist 0302F16.Doc: Commissioning, Startup, and Safety Checklist 0302F09.Doc: Gas Testing Log 0308f13.Doc: Job Specific Execution Plan (JSEP) 0329F02.Doc: Picker and Winch Trucks Checklist 0104F23.Doc: Potential Problems Analysis Tools 0302F17.Doc: Purge Requirements Form 0302F18.Doc: Valve Lockout and Drawing List DEFINITIONS None NOTES AND CAUTIONS The use of equipment for the nitrogen blow down receipt that has any type of valve other than manual, introduces hazards that are not acceptable. The use of flow back tanks is required. Follow the MOC process for any deviation from this procedure. Page of 9 August 2015

3 Ensure the Regulator in each jurisdiction is notified as required. Review with CFO Regulatory Advisor to determine requirements. Bonding cables are used when breaking apart piping and draining hydrocarbons to another vessel (e.g. truck, metal pail) to prevent ignition hazards. Mobile equipment must be chocked and grounded. Liquid recovery should be secure, causing no environmental impact. Use only sufficient pressure to move the pig. Piping systems tend to stay electrically charged for a period of time after the cathodic systems have been de-energized, and may be bonded to other piping systems. Some springing from misalignment, especially in pipeline risers, should be expected. Hazards HVP gases/vapours (specific gravity is heavier than air, can auto-refrigerate causing extreme cold, pressure kicks and vapour slugs). Accumulation of H 2 S vapours (specific gravity is heavier than air) for crude oil and natural gas lines. Oxygen deficient atmosphere Atmospheric conditions (wind speed & direction). Unidentified energy source(s). Energized equipment and facilities. Overhead power lines. Mobile and rotating equipment. Overhead equipment and loads. Pressurized piping. Thermal expansion liquids in isolated piping. Incomplete decommissioning. Communication equipment (poor signal strength). Temporary piping and valves must have an adequate pressure rating. Purge equipment (pressure trucks, nitrogen pumps, tube trailers etc.) must have connection piping/hoses rated for service. All hoses must be protected against over-pressure with the use of Pressure Relief Valves and/or Thermal Relief Valves. Hoses must be pressure tested within the last 12 months. PSV's are required between the pipeline and bottle trucks to protect associated hoses from over-pressure. PSV's must be used to protect the pipeline from over-pressure August 2015 Page of 9

4 situations when utilizing a nitrogen pump or pressure unit. PSV's must be certified within last 12 months. PROCEDURE A JSEP that provides a description of site specific procedures is required. The JSEP must be approved. Ensure product quality considerations are included in the JSEP as applicable. Distillate is the preferred buffer to be used on purges. The use of alternate buffers requires approval. Special Equipment Wind direction indicator (anti-static and fire retardant) Certified pressure gauges (ensure proper range). Self-contained or supplied air breathing apparatus. Required number and type of pigs Diesel fuel or other approved buffer. High-pressure thermal relief valve, pre-tested to required pressure. Low pressure thermal relief valve, pre-tested to required pressure. Nitrogen Pump/Tube trailer c/w hoses and PSV set at the required pressure. Bottle truck c/w hoses Flow back tank/vacuum truck(s) c/w hoses Blow down manifold at receiving pig trap Picker truck, certified annually (or in accordance with Provincial guidelines). Planning Plans for decommissioning and isolation should be made well in advance to ensure these activities go smoothly and that all required materials and services are in place. Page of 9 August 2015

5 Preparation Execution Existing process and instrumentation diagrams should be reviewed and the contractor and operations personnel should review the work site to identify hazards and determine personnel and equipment requirements. Personnel should be familiar with and understand the properties of the product in the pipeline (e.g. the vapour pressure of the gas). The hazards of the work location in relation to the product in the pipeline should be considered. These might include the hazards inside a building, an excavated bell hole, a natural low spot, or next to a highway. Review the job scope and tour site(s) to understand specific task requirements. Flow control valves, back pressure valves, sample points, check valves, meters, etc. are examples of items to be identified and included in the JSEP. Complete a JSEP. Complete a Valve Lockout and Drawing List 0302f18. Consider using P&ID to identify work locations including valve lockouts. Complete Purge Requirements Form. 0302f17 Interface with appropriate group (eg. Operations Control Center, NGL group, Supply, etc.) to schedule timing for pipeline shutdown. In the planning stages, consider the total length of the pigs vs. the length of the trap to allow receiving all pigs at one time. 1. Notify the Operations Control Center that the nitrogen purge is ready to start and have them shut down the pipeline while leaving valves in their normal operating position. 2. Lock-out the pumps, if applicable. 3. Lock-out pipeline inlet valve(s). 4. At the pig sending trap: Isolate, drain and install the line PSV at less than the current line MOP. Connect the nitrogen and/or liquid pumping units 5. Launch the first pig with the required volume of nitrogen, calculated from the Purge Requirement 0302f17 form. Note: Leave the receiving end in normal operation August 2015 Page of 9

6 until the pig, at the leading edge of the calculated volume of nitrogen, is within the pre-determined distance, and timing, from the receiving trap. 6. Launch the second pig with nitrogen to remove product sheen and residue at the pre-determined rate. 7. Launch the third pig, if required, with nitrogen at the pre-determined rate. 8. Continue pumping nitrogen at the maximum pre-determined rate. 9. Track pigs, using technology, and metered volumes. Have OCC take meter readings to assist in tracking the purge pigs. 10. At the pig receiving trap Isolate, drain and install the blow down manifold, PSV. The PSV must be set less than the pressure rating of the lowest rated receiving equipment Connect the receiving flow back tank, bottle truck, as applicable, to the blow down manifold 11. Discontinue nitrogen pumping when the first pig reaches the pre-determined volume or distance from the receiving trap. 12. When the calculated volume is within the pre-determined distance from the receiving trap, divert the product flow from the mainline and into the Bottle truck or Flow Back tank. 13. Notify OCC that the nitrogen purge is complete. 14. Control the fill rate of the receiving equipment with the blow down manifold valve downstream of the receiving pig trap. 15. Monitor receiving equipment level and pressures. 16. Continue flowing into the receiving equipment until each pig has entered the receiving trap. Initially, product will flow into the Bottle truck/flow Back Tank with the buffer and/or nitrogen following. It may be necessary to shut down and remove each pig from the trap as it comes in. 17. Open the receiving trap valve and open the vent valve to the FlowBack tank Vent the nitrogen pressure with liquid carry-over from the pipeline Page of 9 August 2015

7 Monitor venting until there is no carry-over of liquids/product mist plus approximately 30 minutes Regulate the flow to control foaming and potential over-pressure. 18. Stop venting and connect to blowdown muffler or atmospheric vent Vent the remaining nitrogen through the pig trap. Do not vent through the pig trap door. Depending on the volume of nitrogen to be be vented, methods and and valves to vent will vary. 19. Vent until line pressure at both ends reaches atmosphere Check the pipeline for LEL while venting. LEL must be below 10 %. Check LEL at both pig traps and other vents or drain valves that are available while venting to ensure a successful purge. If the LEL level is above 10 %, repeat purging as required Isolation 1. Close, lock-out and tag all remaining valves to complete the isolation of the pipeline. Refer to the Valve Lockout and Drawing List. If using P&ID s, identify locations of lock-outs on the drawings. 2. Install correctly sized blinds or blind flanges at isolation points. Ensure proper pressure rating and Opening Process Equipment requirements are met if required.. 3. Complete a leak check at all isolation points. 4. Execute repair etc, that drove the purge to take place. Complete any applicable interface documentation, including lock box transfer, to allow other parties to execute the planned work on the pipeline. Recommissioning 1. Complete Commissioning, Start up Safety Checklist 0302f16 or use JSEP to document all commissioning activities 2. Inspect the pipeline with the contractor. August 2015 Page of 9

8 Ensure all work activities have been completed. 3. Complete any applicable interface documentation, including lock box transfer, to allow recommissioning activities to commence 4. Remove all blinds. Check Valve Lockout and Drawing List for all blind locations. 5. Reconnect piping as required. 6. Verify the total length of the pigs vs. the length of the trap to allow for receiving all pigs at one time 7. Remove locks from all valves required to fill the pipeline. Refer to Valve Lockout and Drawing List or P&ID's for lock-out locations. 8. Notify OCC that the pipeline is ready to be recommissioned. 9. Spot and connect the nitrogen pump at the pig sending trap. For LVP products, a nitrogen blanket is not required Ensure that a PSV is on the pig sending trap if using nitrogen. 10. For HVP products, pressure line up with nitrogen to pre-determined pressure depending on product and season 11. Disconnect nitrogen and connect the liquid pressure truck at the pig-sending trap to introduce buffer fluid (usually diesel or refined oil) into the line for HVP or Mogas. 12. Launch the first pig with buffer fluid at the pre-determined rate. 13. Spot and connect the receiving equipment into the vent line at pig receiving trap to receive vented nitrogen. (Ensure that a PSV is on the pig-receiving trap.) 14. Unlock product pumps and open inlet valves 15. Have the OCC take meter readings to assist in tracking the purge pigs. 16. When using buffer fluid, launch the second pig with the pipeline product using the pump at the pre-determined rate. 17. Have OCC pump product and assist in tracking the Recommissioning pigs. 18. Continue pumping at a rate no greater than 3 m/s to prevent static build-up 19. While maintaining back pressure, open valve on blow down manifold to receiving equipment and vent the nitrogen from the pig-receiving trap Page of 9 August 2015

9 20. Track pigs with technology and metered volumes 21. Notify OCC to discontinue pumping when first pig approaches trap. For LVP products, only one pig is used. Therefore, product can then flow into the mainline. 22. If no buffer fluid is used, disconnect the receiving equipment 23. Spot and connect the bottle truck at the pig-receiving trap. 24. Consider equipment spacing guidelines, wind direction and evacuation locations. 25. Continue the product flow from the mainline into the truck until all pigs have entered the receiving trap. 26. Control the bottle truck fill rate with the blowdown manifold valve 27. It may be necessary to remove each pig from the trap as it comes in. 28. Isolate the pig trap and retrieve pigs. 29. Remove all remaining locks. 30. Position valves back into normal operating position. 31. Monitor all locations including drains, vents and flanges for any signs of leakage. 32. Notify the OCC that the pipeline has been re-filled and normal operations can resume. 33. Remove any equipment such as pig traps, if installed, and replace the blinds. 34. Re-check all locations for leaks. August 2015 Page of 9