Importance of a Plant Walk Down

By Amit Patil

January 28, 2011

It is important to make sure that all pipe supports are properly installed and functioning as per design. The improper installation or malfunctioning of even a single support may upset the whole piping system and create unbalanced forces throughout. Therefore, it becomes critical to do a walk down of the whole piping system and inspect each and every pipe support on the line, even though the overall design may incorporate several different types of pipe supports

Pipe hanger systems consist of several components to keep the piping properly suspended during the thermal operations which would be seen during the normal operating and shutdown cycles. All this deflection and movement is compensated by different types of pipe supports, which keep the piping system balanced. In the majority of the cases, the pipeline runs between two pieces of fixed equipment. The fixed equipment components act as the anchor points of the pipeline. Pipe supports are located between these anchor points and provide mobility throughout the piping system.

Because most manufacturers of the fixed equipment place limitations on the allowable loads, which can be seen at their terminal points, one should take extreme care to ensure that all pipe support components are properly installed and functioning. This methodology would ensure that the pipe loads imparted to those fixed equipment components will produce the desired reaction forces as specified by the fixed equipment manufacturers.

With the availability of modern design tools, it is possible to calculate the supporting force (and associated deflection) at each suspension point. These design methods and tools will help obtain a clear and concise understanding of what type of support is best suited for each individual application.

Understanding the critical nature of properly functioning pipe supports and how they contribute to the overall system, one should thoroughly inspect each component for proper operation during different phases of the life of the unit. This inspection survey could be done in following phases.

New Unit: – While performing the walk down survey of a new unit, one should pay particular attention to the following:Field Services - Inspecting A Constant Spring Hanger

The supports are correctly oriented for proper functioning.
All stops, locks, bands, shipping bars, etc. have been removed
The correct installed load and/or position of the supports has been established (including all required offsets)

During the initial startup phase, perform a second walk down survey to ensure that the piping system is performing as anticipated and thereby allowing the pipe supports to execute their specified applications.

Routine Maintenance: – Walk down surveys performed as part of routine maintenance, should focus on the following:

The actual operating conditions do not exceed anticipated operating conditions including loading and/or movement of the pipe supports.
Pipe supports, or any component thereof, have not been damaged during operation.
The lifespan of the pipe supports have not been exceeded.
Pipe supports have been properly maintained including lubrication, cleaning and adjustments.

At the Event of Failure or Shut down: – There could be several reasons a system failure or accident happens. When a process upset happens, some imbalanced forces and/or reactions occur throughout the system, and as a result the pipe supports may become imbalanced and fail to function properly. Thus, it becomes important to do a system walk down in order to inspect the functionality of the pipe supports and perform all necessary repairs, adjustments and/or replacements.