Here are some essential steps to help ensure your instrumentation tube and fittings system is as safe as possible.
Step 1 – Consult the manufacturer
One of the main causes of multiple leaks in an instrumentation tube and fittings system is poor design and installation. It therefore makes sense to give careful consideration to this aspect of the system at the Front End Engineering Design (FEED) stage to reduce the risk of potential issues arising later in the project.
Seeking technical advice from the manufacturer at the early stages of a project also ensures that best practice is followed. This applies to all large industrial projects which require high pressures, chemicals and high standards of safety, including oil & gas, power generation, chemical and petrochemical, high purity and automotive.
This consultation with the manufacturer also ensures that the most efficient and cost effective design can be chosen for the project. Last minute design changes often lead to additional expense and delays. A thorough review of design and installation allows for a safer system, limiting potential leaks and situations hazardous to installers and operational personnel.
Historically, designs often have long tubing runs with multiple fittings along the route, however current best practice is to utilise direct mounting and close coupled solutions wherever possible, thus saving on both equipment and installation costs.
Step 2 – Standardisation
Standardisation also needs to be considered at an early stage in the project. This enables the engineering team to work more closely with the chosen supplier, thus multiple revisions of designs from generic to project specific are no longer required.
It avoids common mistakes, too, for instance standardisation on metric or imperial sizing avoids mixing materials, which could be potentially damaging to the product. The material choice should also be discussed with Parker’s Metallurgist so the best solution for the project is chosen, based on corrosion resistance, process fluid, temperature and cost.
Standardisation together with good design can improve the lifetime of the system and, where required, produce a safer, faster, easier maintenance procedure.
Step 3 – Leak path reduction
The industry has reached the conclusion that the use of NPT threads is an outdated method for interconnection of fittings to valves, manifolds and instruments, due to over or under tightening and stress corrosion cracking. Close Coupled solutions have been found to be much more effective, as they remove potential leak paths.
Direct mounting of transmitters and gauges to Manifolds and Monoflanges, which also use integral A-LOK® twin ferrule fitting technology, removes the requirement for NPT threads in most applications.
Using an integrated double block and bleed valve solution, such as the HiPro Double Block and Bleed, and Monoflange, compacts multiple valves into a single integrated unit and using integral A-LOK® twin ferrule technology removes further potential leaks.
Step 4 – Quality control, testing and certification
High levels of quality control are required within the industry to ensure a safe product. Consulting with the manufacturer before specifying the design, inspection and testing requirements, such as HCT traceability, PMI testing and 3.1 certification, will ensure the correct tests are incorporated into the supply chain and they are suitable and necessary for the application. Over or incorrect specification of the testing requirements can add unnecessary cost and delays to a project.
Step 5 – Temperature and pressure rating
Consultation with the product manufacturer with respect to the tube and fittings required to meet with your design pressures and temperatures can save on time and cost. Ideally components within a tubing system should be of the same material and pressure rating. The tube MUST be the lowest rated component and determines the pressure rating of the system. Only use annealed high quality seamless tube – see Parker’s recommendation on our tubing chart.
Parker Grade tube will provide all the correct specifications and the company guarantees the complete system when a complete range of its products are used. For all applications, derating will be applied to the material based on the system temperature, in addition to the process temperature, ambient temperatures particularly on facilities in areas of extreme temperatures flux can be greatly affected. Not only should the pressure and temperature ratings be considered for tube and fittings, but also for the valves and manifolds.
Deborah Pollard is specifications manager, North Sea, Instrumentation Products Division Europe, Parker Hannifin