In many scientific applications, even the simplest of parts must be incredibly accurate. Steel pipes are no exception to this, being the building block of many kinds of equipment that need precisely controlled temperature. The rigour needed to plan, manufacture and test these parts so that those using them can have utmost confidence in them is something Fieldhouse Engineering has displayed consistently over many years.
Our customer in this case study is the UK Research and Innovation department of the UK government, who are supplying these parts to be used at CERN’s cutting edge research laboratories in Switzerland. They required 4 sets of cryogenic lines – steel pipes that carry liquid helium in order to remove heat from a system. This project used many of our skills and disciplines including:
- Metrology Expertise – Custom Jig Design and Laser Scanning
- Precise Stainless Steel Pipe Bending
- Coded Welding and Acid Cleaning
- Helium Leak Testing
- Pressure Testing
- Full Certification Clearances and Complete Process Documentation
The client provided a full specification listing dimensions and requirements. Fieldhouse Engineering fulfilled these requirements and provided all the necessary testing and documentation to ensure full confidence in their application.
Bespoke Pipe Fabrications:
We started by designing custom jigs for each pipe, so that we had a clear reference point for how each piece was to be formed. The jigs were made from a combination of aluminium extrusions and custom 3D printed parts. Every pipe was then bent into the specified angle in our workshop, with meticulous attention to detail. Overall, we produced 50 individual pipes for the system.
To assemble the parts, specialist welding methodologies must be employed, with full traceability along the production line. Each and every weld had be planned, inspected and verified. For the more complex machining operations, we rely on trusted local businesses, where we have oversight to ensure quality.
Ensuring Quality in the Build
Although most of the material was supplied by the client, anything supplied in house was done with full material certification and therefore full traceability.
Dimensional accuracy of the final parts is of utmost priority. To ensure that the pipes are correct to the blueprints, we had each jig laser scanned before the pipe is fitted. This way, imperfections could be identified to within a tenth of a millimetre. Additionally, all critical measurement tools used in the manufacture process were professionally calibrated and certified.
Cleaning the finished parts was also a technical hurdle. Abrasive forms of cleaning could wear down the metal, which could compromise the performance of the entire system. Instead, we immersed the pipes in a series of cleaning solutions, including phosphoric acid, demineralised water, pickling solution and 25% Nitic acid. The final parts were dried with warm air, inspected and signed off. Attention to detail is extremely important for this project, but we have the experience and care to fulfil this.
Pictures of lasers and cleaning
Rigorous Testing
With the parts clean, the question of quality control arises. How do you ensure you don’t have any leaks when working with such precise equipment? We use outside-in helium testing with our in house equipment. The pipes were placed in an environment filled with helium. A vacuum was created within the pipes and mass spectrometry used to detect any leaked helium in the centre of the line. Radiography and visual inspection was also carried out on all welds to ensure there were no concerns with leaks. This is done across all of the pipes and then on individual features if needed. Similar leak tests are conducted in house after each sub assembly is made in order to reduce rework time if there are issues with the welds.
To verify that the system can hold up to the desired stresses of its operation, we also conduct a pressure test. Here, the pipework is sealed up and filled with nitrogen to a pressure of 2.7 bar for more than half an our. This is over the expected operational pressure and proves that no weaknesses have been created in the fabrication process. This is conducted with certified equipment to national standards. A second test is then conducted at cryogenic temperatures in a custom designed bath of liquid nitrogen to ensure consistent results after thermal cycling.
Project Delivery
In addition to the final parts, we provided full documentation and reviews at regular intervals. This included a cost breakdown for this multi-year project, clear quality assurance guidelines to ISO 9001 levels, full risk assessments and multiple technical reports. Key KPIs are tracked to make sure we are on time and in budget with multiple pre-approved contingencies to make sure we can pivot our workflow and still deliver a product to CERN’s specifications.
When completed, the parts were transported to the laboratory in custom made boxes lined with protective foam to to reduce risk of damage in transport.
Fieldhouse Engineering have an extensive record of delivering projects just like this one, where accuracy is paramount and the price is fair. If you think your company has a project we can help with, please get in contact today.