Magnetic Permeability of Pigtails
The reliability and integrity of the outlet pigtail plays a vital role in the Steam Methane Reformer System. The failure of a single pigtail can cause a plant shutdown. Therefore, the outside diameter measurements of the outlet pigtails and the Magnetic Permeability are required to be checked from turnaround to turnaround to ensure the integrity of the system.
In some designs, the outlet pigtail can be used to isolate a leaking reformer tube in service without having to shut the plant down. In such situations, the inlet and outlet pigtail are required to be hydraulically nipped, or pinched, and this is where the magnetic permeability plays a significant role. Depending on the value of the permeability, the condition of the pigtail can be identified to be either brittle or ductile. Nipping a brittle pigtail can be catastrophic, whereas nipping a ductile pigtail can save a plant shutdown.
The MAGNETOSCOP 1.070 facilitates the portable and fast measurement of the relative permeability within the scope of the quality control of stainless steel. The relative permeability of a new Incolloy 800 HT pigtail is approximately 1.003.
Permeability values of a sizable number of samples together with destructive tests to determine extent of ductility, have helped determine the maximum allowable magnetic permeability for outlet pigtails for safe operation in service.
OD Measurement of Pigtails
Outlet pigtails are critical areas which need close inspection due to their location and designed function. For the detection and the evaluation of tube expansions, MP has developed a unique device to measure pigtails diametrically from the tube outlet to the manifold. These measurements are performed on two axes. This configuration has sensors that record the diameter information into proprietary software as it is being scanned in real time. This enables the evaluation of the diametrical growth of both the straight pigtail sections and the bends with their diametrical differences due to the bending process.
As compared to manual gauge testing, this new system is very fast, reliable, repeatable and provides an accurate digital diameter profile over the complete length of the pigtail.
