f H21 Phase 2B T&M: Isolation

In line with the UK government’s de-carbonisation strategy, Northern Gas Network’s (NGN) H21 project aims to demonstrate the feasibility of converting the existing <7 barg gas distribution network to 100% hydrogen. After conversion of the gas networks, hydrogen is transported from various sources through new and existing gas networks to industrial and domestic customers. Following progress on Phase 1 of the H21 programme, Phase 2 was proposed to build on the knowledge acquired to provide further quantified safety-based evidence on the suitability of the GB networks to transport 100% hydrogen. Phase 2 consisted of a number of Project Phases. Phase 2b evaluates network operational procedures conducted on a repurposed natural gas network. Identifying which of these are suitable for a 100% hydrogen network and those that may require adjustments. To achieve this, a gas demonstration facility was built at South Bank, Middlesbrough to accommodate low pressure network parameters and typical network components. A Master Test Plan (MTP) for Phase 2 was subsequently developed by NGN in collaboration with the HSE and DNV to address various aspects of existing network procedures and operations including:
♦ Emergency Response and bad practice demonstrations
♦ Finding Leaks
♦ Accessing Leaks
♦ Assessment of repair techniques
♦ Planned live gas operations
♦ Isolation techniques
♦ Commissioning and decommissioning activities
♦ Pressure regulation and maintenance procedures
♦ Pressure and flow validation
Each practical test was derived from one of the above subcategories within the master test plan. This report details the work conducted within the Isolation Operations remit completed at the NGN H21 testing facility at South Bank. The programme included four isolation operations utilising different isolation techniques and was undertaken on the buried hydrogen low pressure network within the South Bank test facility. The network contained both metallic and PE mains with different diameters throughout the grid. This allowed operations to be undertaken in conditions mirroring real life as they would be completed out on the network. The objective of these experiments is to prove routine operations that are undertaken on a day-to-day basis on the NG distribution network can be completed on 100% hydrogen networks. This report details the experimental set-up, isolation procedure and method statement used in Section 3; the results and main observations in Section 4, followed by interpretation of results and conclusions in Section 5. Appendixes at the back of the document contain photographs, diagrams and further details for each test.