Maintenance Guide: Inspection of Industrial Pipe Supports and Ties

1. Scope and Purpose

This practical maintenance guide was developed for technicians and engineers responsible for the integrity of industrial piping systems in a variety of industries, including chemical, petrochemical, food and beverage, pharmaceutical and steel. It details procedures for inspecting spring brackets, rigid rod tie rods, and tie down clips. The main objective is to guarantee the structural stability of the pipes, prevent premature failures due to corrosion, fatigue, overload or misalignment, and maintain the flexibility and operational safety of the system. Rigorous inspection is critical to extend component life, optimize process performance and ensure compliance with safety standards, such as NBR 15575 regarding durability and structural performance, and NR-12 guidelines for safe operation of industrial equipment.

Preventive and predictive maintenance of piping supports is essential as failures in these components can lead to serious consequences, including dangerous fluid leaks, damage to adjacent equipment, interruption of production and risks to personnel. Inspections should be carried out during scheduled maintenance shutdowns or at regular intervals in accordance with the plant's predictive maintenance program, and immediately after events such as hydraulic shocks, extreme temperature fluctuations or abnormal vibrations.

2. Safety Precautions

Attention: Security is non-negotiable. Before starting any inspection or maintenance activity on piping supports, it is mandatory to strictly follow the plant's safety procedures.

• Lockout and Tagout (LOTO): Ensure that all process lines associated with the section of piping to be inspected are depressurized, drained and isolated from energy sources (electrical, hydraulic, pneumatic) through Lockout and Tagout (LOTO) procedures, in accordance with NR-10 and NR-12.
• Personal Protective Equipment (PPE): Always use the appropriate PPE for the task, including, but not limited to: safety helmet (NBR 8221), protective glasses (NBR ISO 16321-1), safety gloves (NBR ISO 374-1/2018), safety shoes with steel toe caps (NBR ISO 20345), ear protectors (if necessary, NBR 16072) and flame-retardant clothing (if applicable).
• Hot Surfaces: Pipes and supports can be extremely hot or cold. Wear thermal gloves and take precautions to avoid burns or frostbite.
• Working at Height: When working at height, use safe lifting platforms or scaffolding that is properly assembled and inspected, with mandatory use of a paratrooper-style safety belt and double lanyard, in accordance with NR-35.
• Confined Spaces: If the inspection involves entry into confined spaces, strictly follow NR-33, including work permit, atmospheric monitoring and rescue team on standby.
• Chemicals: Be aware of fluids transported in piping. In case of spills, follow emergency procedures for hazardous chemicals.

3. Tools and Materials Required

Proper preparation of tools and materials is essential for the efficient and safe execution of the inspection.

4. Pre-Maintenance Inspection Checklist

Perform this checklist to ensure all conditions are in place for an efficient and safe inspection.

5. Detailed Inspection Procedure (Step by Step)

This procedure must be followed sequentially to ensure a complete and accurate assessment of the piping supports.

5.1. General Visual Inspection of the System

1. Document Current Conditions: Before any intervention, use the camera to record the general condition of the supports and pipes, focusing on visible anomalies.
2. Identify Supports: Compare supports in the field to technical drawings (P&ID and isometrics) to confirm their locations and types.
3. Check General Alignment: Observe the piping alignment. Noticeable misalignments may indicate support failures or excessive load.

5.2. Measuring Spring Deflection on Variable Supports

Variable spring supports are designed to allow vertical movement of piping due to thermal expansion/contraction while maintaining a constant load. Spring deflection indicates the load being supported.

1. Locate Deflection Indicator: Identify the spring deflection scale or pointer, usually located on the outside of the bracket housing. Some mounts may have magnetic indicators or displays.
2. Record Current Reading: With the steel tape measure, measure the position of the pointer or observe the reading directly on the scale. Record the value in millimeters (mm).
3. Compare to Design Deflection: Consult the technical documentation (spring bracket datasheet) to find the design deflection or expected operating range (e.g. 80 mm ± 5 mm).
4. Analyze Deflections:
   • If the reading is significantly below the design deflection (spring fully compressed), this indicates overload on the support or loss of support elsewhere on the line. The piping may be "hanging".
   • If the reading is significantly above the design deflection (spring fully extended), this indicates that the bracket is underloaded or that the piping is "pushing" upward. There may be inadequate support or restricted movement elsewhere.
5. Cleaning and Checking: Clean the indicator area and check that the pointer moves freely. Inspect the spring housing for signs of corrosion, cracks or damage.
6. Common errors: Not cleaning the indicator before reading, ignoring small fluctuations in the reading due to pipe vibration, recording readings without reference to the design point. Always validate the reading under stable process conditions.

5.3. Checking Rigid Rod Ties and Shock Absorbers

Rigid tie rods provide a fixed fulcrum for the piping, controlling movement in specific directions. Snubbers allow slow movement but restrict fast movement (such as in seismic events or hydraulic shocks).

1. Inspect Rods and Pins:
   • Corrosion: Examine the entire length of rods and pins for signs of surface or deep corrosion. Pay special attention to areas near threads and connections.
   • Warping/Distortion: Use the spirit level to check the verticality and alignment of the rods. Any visible warping is a sign of overloading.
   • Cracks: Look for cracks, especially in welds, eyelets and areas of high stress concentration. Clean the surface with a wire brush and degreaser to make it easier to see.
2. Check Nuts and Locknuts: Confirm proper tightening of all nuts and locknuts. Damaged threads or excessive play indicate problems. Use the feeler gauge to check the clearance between nuts and eyelets. There should be no noticeable play (maximum 0.1 mm).
3. Assess Connections and Eyelets: Inspect the upper and lower connection points (eyebolts, clevises) for wear, hole stretching, corrosion, and damage to the connection pins. Pins must be secure and free from excessive wear.
4. Snubbers – Additional Inspection:
   • Leaks: Check for hydraulic fluid leaks or signs of contamination in the hydraulic shock absorbers.
   • Clearances and Connections: Inspect the clearances in the rods and mechanical connections of the shock absorbers. Any excessive play (above 1 mm) may compromise its operation.
   • General Condition: Assess the general condition of the shock absorber housing, looking for deformations, cracks or damage.
5. Common mistakes: Neglecting to inspect threads and pins, underestimating the importance of corrosion on tie rods, not differentiating between a hydraulic shock absorber and a mechanical one during inspection.

5.4. Assessing the Condition of Pipe Clamps

Clamps are essential components for fixing and directing the piping. Failure to do so can lead to excessive movement or localized collapse.

1. Inspect Clamps (U-bolts, C-Clamps, Shoe Brackets):
   • Cracks and Warps: Examine the clamp structure for cracks, warps, dents, or any deformation that indicates overload or structural failure.
   • Corrosion: Check for the presence of severe corrosion, especially at the interfaces between the clamp and the piping, and on the screw threads.
   • Contact with Piping: Ensure that the clamp is making even contact with the piping and that there are no excessive gaps that allow unwanted movement. Use the feeler gauge; Gaps greater than 0.5 mm may indicate poor fit.
2. Check Fastening Bolts and Nuts:
   • Integrity: Inspect bolts and nuts for corrosion, damaged threads, warping or signs of over-tightening (bolt stretching).
   • Tightness: Check the tightness of all screws. Loose screws are a common cause of vibration and wear.
   • Applied Torque: Use the torque wrench to check the screw torque. Torque values ​​are critical and must be consulted in the clamp manufacturer's manual or in the piping design. In the absence of specification, use the following indicative values for Class 8.8 (NBR ISO 898-1) steel screws, assuming clean and lubricated threads:
     • M10 screw: 45 Nm to 55 Nm
     • M12 screw: 75 Nm to 85 Nm
     • M14 screw: 120 Nm to 140 Nm
     • M16 screw: 180 Nm to 200 Nm
     • M20 screw: 350 Nm to 400 Nm

     Always apply torque in a criss-cross pattern and in multiple stages (e.g., 50%, 75%, 100% of final torque) to ensure even tightening.

3. Inspect Coatings and Insulation: If there are anti-corrosion coatings, thermal insulation, or vibration dampers between the clamp and the piping, check their integrity. Damage can lead to corrosion under insulation (CUI) or damping failure.
4. Common mistakes: Not using a torque wrench, overestimating the torque and stripping the thread, ignoring small corrosion spots under the insulation, failing to check the locknut that prevents loosening.

5.5. Inspection of Fixed and Sliding Supports

Fixed supports prevent movement of the pipeline in all directions except axially, while sliding supports allow longitudinal movement but support vertical load.

1. Fixed Supports:
   • Structural Integrity: Examine the support base, welds and fastening screws for cracks, deformation, corrosion or signs of structural failure.
   • Contact with Piping: Check that the piping is firmly seated on the support without excessive play.
2. Slip Supports (Shoes):
   • Skid Plates: Inspect skid plates (usually PTFE or graphite) for wear, damage, or misalignment. There must be a smooth and clean surface for movement.
   • Movement Release: Ensure that there are no obstructions that impede the longitudinal movement of the piping. Side clearances must be sufficient (generally 3-5 mm on each side) to allow for thermal expansion.
   • Corrosion: Check for corrosion at the interface of the support with the piping and the support structure.
3. Common mistakes: Not checking the condition of the slide plates, allowing debris to accumulate on the slide supports, ignoring signs of crushing or excessive friction.

6. Post-Maintenance Verification Checklist

After any adjustments or repairs, run this checklist to confirm restoration of functionality and safety.

7. Troubleshooting Guide

This section provides guidance for diagnosing and correcting common problems found in piping support systems.

8. Recommended Maintenance Schedule

The frequency of inspections may vary depending on the operating environment, piping criticality and local regulations. This schedule is a general reference.

9. Spare Parts Reference

Maintaining an adequate stock of spare parts is crucial to minimizing downtime. Always consult the manufacturer's documentation for exact specifications.

For full technical details and procurement, please visit the UNITEC-D e-catalog: www.unitecd.com/e-catalog/

10. References

• ABNT NBR 15575: Buildings – Performance.
• Regulatory Standard NR-10: Safety in Electrical Installations and Services.
• Regulatory Standard NR-12: Workplace Safety in Machines and Equipment.
• Regulatory Standard NR-33: Health and Safety when Working in Confined Spaces.
• Regulatory Standard NR-35: Work at Height.
• NBR ISO 898-1: Mechanical properties of fasteners made of carbon steel and alloy steel - Part 1: Screws, pins and studs.
• NBR ISO 6789-1: Screw tightening tools – Manual torque tools – Part 1: Requirements and test methods for verifying design conformity and manufacturing quality: Technical requirements.
• NBR NM 204-1: Measuring Instruments – Tape Measures – Part 1: General requirements for length tapes.
• NBR ISO 20345: Personal protective equipment – ​​Safety footwear.
• NBR 8221: Safety helmet.
• NBR ISO 16321-1: Personal eye protection – Eye and facial protectors for industrial use – Part 1: General requirements.
• NBR ISO 374-1/2018: Protective gloves against dangerous chemicals and microorganisms.
• NBR 16072: Hearing protectors – Selection and use guide.
• Pipe Support Engineering Manuals (e.g. ASME B31.1, B31.3).
• Original Equipment Manufacturer (OEM) Manuals.