Five Key Ways to Protect Yourself from Pipeline Surge
- Pipeline surge is caused by sudden changes in fluid velocity in pipelines
- Surge can have consequences including risks to health and safety of employees and the general public, the environment, your pipeline’s integrity, and provide a significant financial loss
- Preventing surge includes understanding of the flow of product before (supplier) and after (delivery) it is in your line
- Pipeline operators must be able to explain surge management steps in terms of business implications, such as safe operation and maximizing throughput
- Third-party engineering firms can provide access to advanced software and expertise in modeling surges in your line
Surge is a potential issue in liquid pipeline operation. It’s relatively rare in a line that’s operating normally, but as we’ll see, there can be serious consequences when it does happen. Fortunately, there are steps that pipeline operators can take to prevent surge from happening, to reduce the magnitude of the surges and to minimize risks and damage from surges.
This post looks at five key ways to protect your pipeline from surge.
We’ll focus on pipelines that transport true liquids, such as gasoline or diesel, because they carry the greatest risk of surge. However, it is important to understand that even if you are operating a pipeline with a low risk of surge, such as one carrying ethylene, your pipeline’s design parameters must be sufficient to combat surge potential.
As product supply and demand are ever changing, pipeline operators need to understand their pipeline’s surge risk at various different operating envelopes, in order to proactively manage surge and limit reactionary measures. Being proactive can allow operations and management personnel to make well justified decisions when carrying out changes that could affect throughput.
What is surge and what causes it?
Surge is caused by sudden changes in fluid velocity in a pipeline that create pressure waves that travel back through the pipe. To occur, surge needs a pressure source and an initiating event, such as pump(s) and the inadvertent closure of a valve.
Our experience working with past and present clients as it relates to surge is mostly spent on explaining, guiding, and coaching them through transient surge scenarios. Spending this time is critical and allows us to discover unique solutions to implement depending on their unique scenario.
Consequences of pipeline surge
Surge can sometimes cause the pipeline to exceed MOP. It is important to remember that you are allowed to go up to 110% of MOP, however, it is recommended that operators do what they can to reduce surge below 100%.
The result can be flange separation, weld failures where inadequate welds exist, deformation and ruptures in pipeline and components, and leaking at joints and seals. There can be damage to pumps, valves, and other fittings.
Surges must be reported to regulatory authorities when maximum surge pressures climb above 110% MOP – and too many surges will bring scrutiny from the regulators.
In short, surges can put employee lives and safety at risk, have an impact on the community, damage the environment, be costly to repair, and take the line out of service temporarily.
Why you need all five ways to manage surge in pipelines
As pipeline specialists, here are five ways we’ve found effective for managing surge in pipelines.
1. Understand where your product’s coming from
The supplier of the product entering your pipeline may be part of your company or with a third party. In either case, they’ll be thinking of their own priorities for shipping, not about your pipeline operation. You need to protect yourself and your line.
One way to protect yourself and your line is by becoming familiar with the 3rd parties operation and their pump/tank configuration. You also need to know the characteristics of the fluid being transported, including specific gravity, viscosity, bulk modulus and other factors that influence fluid flow and surge. Having good information on the third party is using will allow you to increase the accuracy of your models.
It can be hard to get this information; suppliers may consider it confidential, or believe that you have no real need to know about their operations. They may be more willing to provide the information you need, and keep you up to date, if you explain why it’s in their best interests to provide it.
Make them aware that if you don’t have good information on the product you’re carrying, you may need to make certain assumptions, and these may be necessarily more conservative than if you had actual data. More conservative assumptions can negatively impact your operation if a credible surge scenario exists. This could come in having to cut the supplier flowrates back to reduce surge. With full information from the product supplier, you may be able to provide more flexibility on throughput and other operational factors.
2. Design your pipeline with surge at the right priority level
If it’s a new line, or if you’re making operational changes to an existing line such as adding new pumps, control valves, new 3rd party connections and other components, surge must have due consideration. Business interests may want to maximize flow, and of course the line must be as profitable as is safely possible.
It’s best to have access to software intended to perform surge analysis, either through your own company or through external professional expertise. At HT Engineering, for example, we use the Synergi Pipeline Simulator (SPS) made by Norway-based DNV.
You may need to consider multiple designs for new construction to make sure it meets all business requirements, but more importantly, all safety and integrity requirements such as surge management.
As mentioned before, we find that pipeline designers are usually well aware of surge, but they may not take it into consideration enough in their design decisions.
3. Operate your line in a way that mitigates surge and maximizes throughput
When designing a pipeline, it is important to ensure that you are not ‘double-dipping’ in conservatism on top of additional safety factors. This might cause you to be unnecessarily conservative in your operations plans, with implications for the line’s throughput and productivity.
It helps to make sure that senior management and the business development people understand the limitations on the pipeline’s capacity.
Ensure that the other integrity threats, such as cracks, internal/external corrosion, are closely watched and mitigated where pressure cycling is higher. If surge occurs, it will result in an additional stress riser in places where stress risers are already present, which could lead to catastrophic failure if the other integrity management systems in place are not properly managed.
Our experience is that there may be a need to reconfigure pumps — maybe reduce the amount stages in a pump to decrease the total deadhead if there is too much surge potential, particularly on startup and shut down.
One reason that careful planning for surge potential matters is that PHMSA and other regulators want to see that you’ve done your due diligence in understanding surge risk and what to do about it.
Click here to learn more about how to maintain integrity records, to improve pipeline operational efficiency and for PHMSA audit purposes.
4. Understand surge risk related to where your product’s going
The receiving end of the pipeline can also be a risk factor for surge, in part because it’s often a third party that puts priority on meeting its own business objectives, not on your pipeline’s surge risk.
As with the suppliers of the products carried in your line, pipeline operators must understand the receiver’s operation, including min/max receipt pressures, flowrate constraints, system design constraints, etc. And as with your pipeline’s suppliers, your receivers may consider this information confidential, or that you have no need to know it. So, explain why you need to understand the product flow after it leaves your system – sudden changes may impact the integrity of your line, and your ability to provide reliable service.
Part of protecting your line from receiver-related surge is setting up systems whereby you’re alerted when they take unexpected steps that may impact product flow.
When possible, consider putting interlock systems in place, in which if one change occurs (such as closing a valve by the receiving entity), another opens to allow flow of product. Sometimes this interlock system must be with another third party. Negotiating these agreements may be easier if you explain the consequences of surge from a business and operational viewpoint.
In some cases, there may not be an outlet to dampen surge created by an inadvertent valve closure. If you run into this, consider working with the third party to allow you view to their equipment on your SCADA or control console screens that way the console operator can take immediate action to shut down the system.
5. Have the right third-party expertise available
Third-party engineering firms such as HT Engineering can provide you with expertise that comes from focus on surge management, plus experience coming from working on many different pipelines.
As mentioned, third-party firms may provide you with the benefits of specialized software such as SPS, and the skill to use it to its full capacity.
In working with pipeline operators, we look for solutions to surge management issues that don’t cost money – avoiding capital costs where possible, finding better ways to operate existing equipment.
Your professional firm can help you find ways automation can help with surge management – and as my colleague Kirk W. Northouse explains in his blog post, without being dazzled by untried new technologies.
- In conversations with your company’s senior management, come prepared with multiple scenarios that show surge mitigation measures, as well as provide management options for business development.
- Similarly, when working with third parties outside your control (product supplier and receiver), be able to express your need for information about their operation when modeling surge for accuracy purposes, and to limit conservatism.
- Thoroughly communicate what assumptions were made, where the surge analysis was conservative, and if there are any uncertainties.
- If there is a credible surge scenario, come prepared to present your team possible solutions to allow the team to make better risk-justified decisions.