Pipe Stress 104 – Does Your Facility Need a Pipe Stress Audit?

Pipe Stress 104 – Does Your Facility Need a Pipe Stress Audit?

This is the fourth article in a series about thermal expansion or contraction, pipe stress, and the art of pipe stress analysis. In a previous article, we discussed some of the different signs to look for out in your facility that might indicate the presence of a pipe stress problem. In this article, we will discuss some of the less obvious signs that your facility may have a thermal stress issue. By the end, I hope you will have the tools to help you decide if it’s time to call in an expert to help you identify and mitigate potential problems with a Pipe Stress Audit.

Sometimes thermal stress problems are easy to spot. In our previous article we showed you some of the signs that might catch your attention when you are out walking around in your facility. Sometimes, though, the clues are not as obvious. Here are just a few of the less obvious indications that have become red flags for the team here at Matrix Technologies over the years.

Rotating Equipment

Pumps or other rotating equipment with a poor maintenance history could point to a pipe stress issue. Are you dealing with worn seals, worn bearings or alignment issues during routine maintenance? Is the base of the pump or compressor cracked? Is there a subtle, or not so subtle, vibration? Do these maintenance problems bring to mind a particular pump or centrifugal compressor at your facility? Over time we have come to realize that the nozzles on rotating equipment are some of the most sensitive and often the most overstressed components in a facility. (In a future article, we will go through an example and explain why this tends to be the case. The article will also explore how rotating equipment nozzles compare to other typical piping components and connections in terms of sensitivity to thermal growth. Keep an eye out for it!)

Management of Change

Vessels, heat exchangers or tanks that have changed service or operating conditions may also indicate a hidden thermal stress issue. It’s not uncommon for vessels in a plant to change service or for existing processes to be modified so that they are now operating at a new temperature or pressure. Even relatively small changes to the temperature could manifest as problems over long runs of attached pipe.

Similarly, when the vessel itself is operating at a new temperature it will impart new thermal movements to piping originally designed for a different operating point. Has the direction and magnitude of the equipment movement under new process conditions changed enough to create problems? Is there enough movement now to put the existing pipe into contact with support steel or with another adjacent pipe? Is there enough thermal movement to lift a pipe off its support and put additional load on the attached nozzle?

P&ID Revisions

Clouded sections of the piping and instrumentation diagram (P&ID) often indicate a change in the process conditions or new piping interconnections. Does the clouded section indicate that a vessel or tank is operating at a higher or lower temperature than before? Has a new bypass line or new interconnect line between two runs of existing pipe recently been installed? If so, then you may have an unforeseen pipe stress issue waiting to reveal itself. Admittedly, not all P&ID changes will warrant your attention in this respect. Adding new instrumentation may not significantly change the pipe stress of an existing line, so a little engineering judgment is required.

Construction or Maintenance Actions

Not every change to the structure or piping of a facility is planned for; field conditions often require that adjustments be made. When this happens, it’s important to compare piping in the field to piping on the isometrics. In particular, be aware of recent construction or maintenance activities have caused changes to previously stress analyzed piping. Analyze any alterations to these pipes for new stresses. Isometrics for stress analyzed piping are often clearly marked. Many have a note, like the one shown in the figure below, that we use here at Matrix Technologies. These piping isometrics often show a wealth of additional information, like the predicted movements and direction of hot piping.

Changes to piping aren’t the only modifications that can occur during construction or routine maintenance. Be aware of changes to steel and surrounding structures; these can affect how a pipe is supported or restrained. This is especially true if the piping was previously stress analyzed. Sometimes even small changes to the support structure can affect the overall stress of the piping run.

Figure 1 – Stress Analyzed Piping Tag for Piping Isometrics
Next Steps

You’ve spotted a shoe off of the support steel or a bent pipe, or my story about that pump with the maintenance problems reminded you of one in your own plant. Maybe it’s a dozen little maintenance items that suddenly came into focus after reading these articles. Now what? This is the point to contact a pipe stress professional and have them conduct a pipe stress audit.

Matrix has 40-plus years’ experience in dealing with pipe stress issues and strives for unmatched client service. That means we put the same care and attention into one single pump or a single run of pipe as we do into an entire facility. Add to that a track record of fixing problems that others can’t, and you will see why 90 percent of our customers are repeat clients.

But even if you don’t come to Matrix Technologies for your pipe stress problems, please remember that everyone is responsible for safety and asset protection. Please contact a professional when you notice indications like the ones we have listed here and in previous articles in your own facility.

In the next article we will look at a simple method for expansion loop sizing. This is something you can do in the field to establish safe expansion loop sizes or to quickly verify that an existing loop is adequately sized for the thermal growth in a line. Later we will talk more about the relative sensitivity of piping components to thermal stress and take a closer look at where thermally stressed lines typically fail.

Matrix Technologies is one of the largest independent process design, industrial automation engineering, and manufacturing operations management companies in North America. To learn more about thermal expansion and pipe stress analysis, contact Chris Mach, PE, Senior Consultant or Brandon Grodi, Mechanical Department Manager.

© Matrix Technologies, Inc.

Engineer, Procure and Construct (EPC)

Engineer, Procure and Construct (EPC)

Engineer, Procure, and Construct (EPC), Engineer, Procure, and Construction Manage (EPCm), and Construction Management projects require an engineering partner with in-depth experience in process design, engineering, and construction with a proven methodology for project delivery, and the ability to understand client’s requirements for the capital investment. Jerry Francis, PE, PS, Associate Director, Project Management Department discusses the benefits of partnering with Matrix Technologies for your future EPC or EPCm projects.


How to Justify a Utility Replacement Program

How to Justify a Utility Replacement Program

This is Part 2 of a multi-part series on “Managing a Decaying Industrial Utility System.” For the first article in this series, see Managing a Decaying Industrial Utility System.

The first step in a utility replacement program is securing funding to initiate the program and investigate the decaying utility system further. To do this, a business case is typically prepared, and a group of gatekeepers must approve a plan for next steps.

In some cases, a break in a utility system creates a ripple effect and triggers an emergency repair, property damage, environmental hazard and/or production outages. This single event can be enough to justify a study or program. In other cases, utility systems experience less acute failures, minor leaks are managed on a day-to-day basis, and a critical failure may be looming but has not yet occurred. In this situation, developing a return on investment for the utility system study or program can be more challenging since investing in these systems may not have an apparent return on investment and predicting future failures can be subjective. However, the risks must be communicated and understood by stakeholders with the goal to avoid a catastrophic failure from occurring.  

Utility systems that are a part of or support life safety, such as fire water, are mandated by law to be operable and maintained. Building code, fire code, OSHA and other industry standards such as the American Petroleum Institute (API) standards are incorporated into law when referenced by the local authorities having jurisdiction (AHJ). Therefore, an outage of this type of system can indirectly require a production shutdown until the system can be restored.

Assessing the risk

To best present a need for a study or program, a risk matrix can be developed that compares the likelihood of a failure versus the consequence of failure. The figure below is one example of a risk matrix provided in NFPA 1300.

From NFPA 1300, “Standard on Community Risk Assessment and Community Risk Reduction Plan Development”

The goal of a risk assessment is to identify the types of failures that are possible and the corresponding likelihood of failure and potential impact, including personnel injury, environmental risk, repair costs and lost production. To initiate a study, historical information can be used as a starting point for probability of failure and costs. However, known utility conditions may warrant an increased probability of failures.  

Looking for root causes

The risk review should also ascertain the situations that lead to a failure. Although physical conditions such as age of materials are the probable root cause of failure, often an event initiates the failure. Process changes such as starting/stopping of equipment can create an operational change and induce a failure. Other condition changes can be more subtle and are a result of a long-term fatigue, such as the heaving effects of freeze/thaw on buried utilities. By understanding the circumstances leading up to a failure, a facility may find temporary solutions to limit the risk and be prepared until a full program can be funded and executed.  

The preliminary business case for a utility replacement program will recognize if the circumstances exist to warrant further investigation and effectively present this data to stakeholders and gatekeepers. A successful outcome will be a plan on how to proceed and an approval to begin technical data gathering and a condition assessment study.

Matrix Technologies’ approach

Matrix Technologies has completed numerous infrastructure studies and master planning programs for our industrial clients over our 40-year history. We start by working with facility stakeholders to understand their goals and develop a custom approach, tailored to their needs. In general, our infrastructure evaluation, rehabilitation and replacement strategy consists of the following phases:

  • Presenting a Business Case and Justification
  • Data Gathering and Condition Assessment
  • Identifying Options for Rehabilitation or Replacement
  • Master Planning and Capital Forecasting
  • Design Considerations by Utility System
  • Documentation and Management

Future articles in this series, “Managing a Decaying Utility System,” will guide you along each phase of the process and provide considerations for designing and building specific utility systems.  The next article will address the Data Gathering and Condition assessment phase.

Matrix Technologies is one of the largest independent process design, industrial automation engineering, and manufacturing operations management companies in North America. To learn more about our utility system design and master planning services, contact Todd Green, PE, SI, CFPS, Associate Director, Mechanical and Facilities Design.

© Matrix Technologies, Inc.