Learnings

Outcomes

As described this project can be split into 3 work packages: 
Work Pack 1: Detailed design of the Flow Facility  
Work Pack 2: Development of a Master Test Plan  
Work Pack 3: Materials Testing 
 
Work Pack 1: Detailed design of the Flow Facility  

The test facility will be built on the west end of Test Site West (TSW) to connect into an existing hydrogen microgrid and HyStreet build as part of the NGN H21 hydrogen project. The two projects will share the same 48” high pressure hydrogen reservoir. The facility is being built on a greenfield site and is scheduled to take 15 months to build from the signing of the contracts. 

As part of the test facility build project some offline test facilities will be fabricated for fatigue testing and leak testing in a separate blast chamber on the main Spadeadam Test Site. Due to the possibility of failure the fatigue testing has to be completed as a separate series of offline tests. Some smaller asset tests will also be completed offline prior to the online test rig being commissioned. 

The online facility is expected to take 15 months to build with 20 weeks of testing scheduled on the facility. Some offline testing can be completed alongside the build to gain information on the effect of hydrogen on some assets.  
The test facility has been designed as part of the NIA project. A range of assets of different types, sizes, and material grades are being supplied by National Grid from decommissioned assets to build a test facility that has representative sections of the NTS. Assets provided by National Grid:  

• Five lengths of 48” pipe for High Pressure reservoir (previously welded as part of H21 Phase 2a)  
• Two 18” valves
• One 18” Filter, two 10” meters, one 18” Flow Control Valve (FCV) and one 18” Non Return Valve (NRV)
• 36” ball valve and 18” bypass pipework with associated 18” valves  
• 8” FCV  
• 3” and 4” Exit site pipework and assets  
• Three lengths of 36” pipe for Low Pressure reservoir from PMC  

18” X52 pipe 

The test rig has been arranged to form a loop to allow a compressor, to generate flows of sufficient volume to test the exit site at the full range of flow rates, due to power limitations, the larger assets will only be tested at the bottom end of their capabilities. Where possible as much of the test facility is repurposed from existing assets including the valves, stands and instrumentation from each of the National Grid sites. Offline testing will be carried out on the main Spadeadam Testing Site on one of the three concrete test pads or in one of the large test chambers. The control cabin and logging facilities for each of these will be local to the test area. The natural gas for any offline testing will come from the site charge line and the hydrogen will be from packs. Offline test rigs include: 

Fatigue test rig 

Due to the possibility of a catastrophic failure the fatigue test facility will be located in one of the blast chambers at Spadeadam. The fatigue vessel will be fabricated using a series of weld types to replicate those most likely to be found on the NTS. The facility will also include a 36” ball valve, two 36” tees, four cap ends, two sweepolets and two threadolets. An open inner vessel will be fabricated to reduce the overall volume of the welded pipe to reduce the time for the fatigue cycling. Water will be pumped into the inner vessel to increase the pressure and controlled by a PLC to open an actuated outlet valve once the test pressure is achieved. This cycling will be repeated 150,000 times over a 15-month test program. 

Flange offline test rig 

The testing will include an initial leak test with water, a 100% natural gas and 100% hydrogen test. Each test will be monitored for 5 days using a pressure and a temperature transducer and joints subject to leak detection fluid. The test rig will be subjected to ambient weather conditions during the test period. 

Asset offline test rig 

Valves, filters, orifice plate and regulators will also all be represented in offline test rigs. In these examples the asset will be fitted into a small test rig and tested at 100% natural gas and then 100% hydrogen. Each test will be monitored for 5 days using a pressure and a temperature transducer. 

Rupture testing 

As part of the QRA two large scale rupture tests with 100% hydrogen have been included to investigate delayed ignition of ruptures on a buried transmission pipeline. The tests would be carried out on a modified existing facility on the fracture propagation area of Spadeadam Test Site. 
 
Work Pack 2: Development of a Master Test Plan  

This part of the final technical report details test requirements, sequences, priorities and process conditions to provide data input to quantified risk models and is complemented by the Master Test Plan (MTP) spreadsheet which details every test that is considered necessary to demonstrate NTS readiness.  

The MTP is separated by asset type and includes a comprehensive list of what tests (laboratory, off-line and flow facility) are to be carried out on each asset type. The list is extensive, but also has a bias to available decommissioned assets as it is essential to test what is on the NTS.  

Some asset types have sub-types (e.g., valve: ball or plug) and these may be supplied by different manufacturers (e.g., ball valve: Cameron or Cort). The integrity and performance characteristics of each would need to be verified by testing, but this will only be possible as assets are decommissioned and become available. National Grid is also actively seeking other assets that could potentially be tested and provide more supporting evidence of NTS readiness. Although this is not part of the current project, the facility offers this flexibility for future projects to be carried out.  

There are two types of test; off-line and Flow Facility tests. Off-line tests are for those tests that do not require flow conditions, or that have the potential to damage the Flow Facility. Off-line tests will consist of a combination of small-scale laboratory-based tests (these will be performed in the Loughborough laboratories) and full-scale tests (these will be performed at Spadeadam).  

The laboratory tests are needed to quantify materials performance characteristics, the results of which will be essential for conditioning the full-scale tests ahead of starting the main test (whether this is a pressure test or a pressure cycle fatigue test). 

The off-line full-scale tests will include leakage (seat/stem/closure tests), strength tests and pressure cycle fatigue tests. The tests to be carried out on the Flow Facility will be reserved for those assets that require flow conditions to demonstrate functionality as well as operational integrity at maximum operating pressure (the flow facility is designed for a maximum operating pressure of 70 bar). For example, accuracy of meters, slamshut firing sensitivity, vibration levels of flow control valves and regulators.  

The MTP covers the majority of possible tests. These are prioritized, and the outcome of those tests will determine the direction of the remaining tests (and future tests). Test results and observations are to be recorded within the MTP, where comments will be made to justify subsequent test parameters such as hydrogen blend, test pressures and durations. The priority tests on the MTP have been highlighted green, most of which will be tested as part of this project. These include tests on assets at maximum test pressure and at 100% hydrogen, on the basis that if the assets maintain their integrity at this upper extreme of test parameters, subsequent testing of blends and/or at lower test pressure will not be required.

The Flow Facility tests will be scheduled by the gas composition and pressure.  
The Flow Facility will initially be serviced with 100% natural gas to attain baseline measurements for comparison with hydrogen and hydrogen blends. The blend of hydrogen within the natural gas will then be increased to 2%, to 20% and ultimately to 100% hydrogen.  
 
Work Pack 3: Materials Testing 

As part of the Roadmap to FutureGrid project, the project evaluates the performance of selected vintage pipe materials in pure hydrogen and a mix of hydrogen and methane simulating hydrogen and natural gas blend.  Fracture toughness (FT) and fatigue crack growth rate (FCGR) tests were performed in 20% hydrogen  
(balanced with methane). The report summarizes the effort in the project and the results generated to date.  
 
FT tests were performed in 20% hydrogen balanced with methane on samples with various microstructures  on X60 pipe steels. A set of frequency scan tests were performed on a base metal (BM) sample in 20% hydrogen and FCGR Paris Curves were measured in 20% hydrogen and 100% hydrogen for the weld centre line (WCL) samples. Based on the performed tests, the following key points were concluded:  
 

• The J values decreased with decreasing K rate, particularly J1mm. The dependency of J0mm on the K rate was relatively weak compared to J1mm; the slope of the J-R curve was shallower for lower K rates; J0.2mm was selected as the initiation toughness in this study;  
• The K rate of 0.005 N.mm-3/2/s was selected to generate the toughness property of the materials; 
• The FT property of tested materials showed a reduction in 20% hydrogen balanced with methane compared to in air; J0.2mm for the BM sample was 127.38 N/mm in air and 48.44 N/mm in 20% hydrogen balanced with methane; 
• In 20% hydrogen, the BM sample of pipe 4286, weld center line (WCL) and heat affected zone (HAZ) samples of pipe 4304 had toughness values (J0.2mm) of 48.44, 67.11 and 84.4 N/mm, respectively. The WCL sample of pipe 4304 showed worse performance than the HAZ sample in 20% hydrogen; 
• In 100% hydrogen, the WCL sample showed further reduced toughness values compared to 20% hydrogen. The J0.2mm value is 67.11 N/mm in 20% hydrogen and reduced to 49.5 N/mm in 100% hydrogen; 
• In all results, the J0mm did not show strong dependence on the K rate, sample microstructure, and the hydrogen concentration; only small difference in J0mm between the above listed conditions were observed; this may indicate hydrogen adsorption and dissociation are more severe when fresh metal surface is available; 
• Frequency scan tests showed that FCGR of the BM sample accelerated in 20% hydrogen by 20 to 40 times compared to the in-air value; the FCGR only weakly dependent on the frequency in the range of 0.1Hz to 1mHz, with the FCGR at 1 mHz being only about 1.5x of that at 0.1 Hz;  At 0.1 Hz, the FCGR of the WCL sample in 20% hydrogen is approximately 25x of the BS7910 in air mean value; In 100% hydrogen, the FCGR further increased to 33x of the BS7910 in air mean value; the threshold ∆K appears to be lower at 100% hydrogen compared to in 20% hydrogen;

Lessons Learnt

The design of such a complex arrangement of NTS assets has led to some challenges in securing redundant and decommissioned assets to use. This process was carried in conjunction with the internal decommissioning process and so the two needed to line up in order to secure the investment to decommission thus freeing up the asset for FutureGrid. Any changes to the decommissioning plan had a knock on impact to FutureGrid and so if this could have been avoided then the design stage could have been confirmed earlier in the project. 
Discussions with the Pipeline Maintenance Centre (PMC) and NTS Stores early on the project, highlighted assets and sections of pipe that could be used for FutureGrid and the materials testing part of the project.