The choice of the correct material based on corrosion resistance, process fluid, temperature, and cost is essential. This can be discussed with the Parker team, including a highly experienced Metallurgist, so the best solution is chosen. It is particularly critical when H2S is present within the process as this can exacerbate stress corrosion cracking.
Mixing of materials can exacerbate corrosion or reduce the longevity of the system. When this is the only available option then consideration must be given to their differing temperature and pressure ratings and how these will impact the integrity of the system.
The material and positioning of tubing clamps should be well considered during a design to ensure that the clamps themselves are corrosion resistant, cause no abrasion to the tube and are positioned such that water is free draining.
When project applications require the use of FE (Fugitive Emission) valves, the customer should ensure that the requirement for TAMAP 2 is written into the specification at an early stage.
H2S can cause embrittlement and therefore single piece valves, which avoid the use of welded connections, such as Parkers range of FE valves, will provide added security within the system.
Designs where fugitive emissions are critical need additional consideration with respect to the reduction of potential leak paths, again integral fitting technology removes both NPT connections, which are subject to stress corrosion cracking and embrittlement within the threads.
The correct handling and storage of the tube prior to installation is important. If the tube is stored externally or dragged around, it may harm the integrity of the product. The tube may pick up water and contamination/corrosion, scratches and even lose its roundness and become oval. The tube should be stored inside, off the floor, on racks to remove all these potential issues. The system should be dry air purged prior to connection to any sensitive equipment.
Tube Cutting, Deburring and Control
The tube should be cut with a sharply bladed hacksaw and the material of the blade should be of high quality. Cutting should be carried out in a sawing vice – it is recommended to use a specific tube cutter. The best advice is to remove any visible burrs inside and out using a tube deburring tool. Wipe clean when the cut is complete and make sure no swarf has entered the tube by cleaning with dry air. Parker can supply pre-cut tube lengths if required.
Tube benders should be procured from the fittings manufacturer to ensure high bending quality and accuracy. The tube bender should be of 316SS material because carbon steel tube benders are likely to leave a residue of material on harder tube compounds, which is likely be a starting point for corrosion.
A Gap Gauge should be used to check the correct installation of the tube into the fitting prior to final system testing.
It is recommended that site installers undertake at least basic training on the installation of tubes and fittings from a company approved by the fittings supplier. Parker Sales Companies and many of its local distributors worldwide can provide the Small Bore Tubing Expert (SBEx) training. This is now the norm in the North Sea, although lots of other regions have not yet implemented this. However, all end customers are underlining the importance of safety first.
This training covers both the theoretical and hands-on procedures for the correct installation of fittings and all connection aspects, as well as correct tube bending procedures. This comes with an accredited passport confirming that the person concerned has undertaken the training and it is still valid. This training is valid for 2 years and can be delivered by Parker approved trainers.
Deborah Pollard is specifications manager, North Sea, Instrumentation Products Division Europe, Parker Hannifin