Enhancing System Integrity with Prefabricated Hookups

Introduction

In today’s industrial landscape, ensuring the reliability and efficiency of instrumentation systems is paramount. Prefabricated hookups represent a significant advancement in this arena, offering a streamlined approach to installation and maintenance of instrumentation systems. This white paper explores the advantages of using prefabricated hookups, emphasizing their role in reducing error rates, project construction times, completely nullifying fugitive emissions and maintenance overheads.

The Need for Prefabricated Hookups

Traditional field installations of instrumentation systems are often fraught with challenges, including prolonged installation times, potential leakages leading fugitive emmissions and possible errors during assembly. Prefabricated hookups, with their modular design, come pre-assembled from the manufacturer, ensuring a higher degree of reliability. They incorporate all necessary components such as piping, fittings, and valves, tailored to meet specific system requirements.

Key Benefits of Prefabricated Hookups

Reduced Construction Time in Project

• Faster Installation: The ready-to-install nature of prefabricated hookups cuts down installation time by up to 70%, significantly speeding up project timelines.
• Faster Leakage Testing: Non-destructive testing like dye penetrant test, hydrostatic pressure tests etc are done at manufacturer’s place obviating the need to performing them at site. Only the welding of the prefabricated hook-up to the process pipeline or vessel done at site needs to be tested.

Enhanced Accuracy and Reliability

• Ease of Maintenance: Designed for convenience, these units simplify routine maintenance tasks, reducing the downtime and labour involved.
• Reduced Chocking of Impulse Pipes: Internal cross-sectional area of the impulse lines with the prefabricated hook-ups (½ inch NB Sch 80 pipes) is nearly 3 times that of the tubing (12 mm OD). This minimises the chance of chocking of the impulse lines.‍

Root Isolation valves used are ball valves or gate valves. These have much lesser potential to choke compared to globe valves.

Safety and Environmental Compliance

• Leak Prevention: Most joints in prefabricated hookups are welded, which eliminates potential leak points, thereby enhancing operational safety and reducing fugitive emissions.
• Temperature Tolerance: They are engineered to withstand various operational environments, reducing the risk associated with temperature variations.

Technical Considerations

When implementing prefabricated hookups, it’s crucial to consider:

• Material Compatibility: Select materials that are compatible with the process media to prevent corrosion or degradation.
• Design Specifications: Ensure the design meets system pressure and temperature requirements.
• Installation Practices: Proper installation is key to leveraging the benefits of prefabricated hookups. It’s advisable to follow the manufacturer's guidelines strictly to avoid common pitfalls.

Problems Associated with Usage of Tubes and Tube Fittings

Tube fittings form excellent quality joints provided extreme care is taken at every stage, specially in the following:

1. Selection of Tubes: Tube should be very soft with hardness of less than RB80 although ASTM standards of tubes permit hardness upto RB90.
   Tube should have strict dimensional tolerance. Tolerance should be only in the positive side.
2. Selection of Fittings: Front ferrule of fittings, specially at the tip (i.e. the end away from back ferrule) should be hard. This may be about RC 30.
   Back ferrule should have very hard surface to a thickness of about 20 microns. This is to be obtained by case hardening.
   Inside of back ferrule should have a good quality (not less than 20 microns thick) silver plating.
3. Workmanship: Tube must be cut square and burrs should be removed completely and properly. It may be noted that tube cutters give conical end with slight bulge at the od of the tube. Cutting with hacksaw give burrs both inside and outside the tube. Using a tube cutting guide is a good practice to ensure cutting perpendicular to the tube. This also helps in hacksaw making scratches elsewhere on tube surface.
   Ensure tightening the nut for 1 ¼ turns after hand tightening.
   Ensure no scratches on the tube surface at the place where ferrules are going to hold the tube.
4. Tube Handling: Tube should not be stored in carbon steel racks to avoid mild steel contamination of the stainless steel tubes.
   Tubes should not be dragged on floor to avoid surface scratches.
   Tubes should not be coiled for the ease of transportation to avoid strain hardening by coiling and uncoiling.