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by Tristian McCallion on Tue, May 11, 2021 @ 10:05 AM
Fast loop sampling systems are essential during custody transfer processes. Because of the high value and large volume of the crude oil that is typically transferred, it is imperative that the sampling and measurement systems are accurate. Fast loop sampling systems are designed to handle high flow rates in sample transport pipelines to minimize time delays for online analyzer systems. High flow rates in sample transport lines are critical to providing the high velocity needed to 1) get the sample from the pipeline to the analyzer as fast as possible, and 2) maintain homogeneity of the mixture to obtain a representative sample.
If it is found that the fast loop sampling system is not working as expected, especially during a custody transfer, the issue needs to be addressed immediately. Finding an on-the-spot solution may sound like the number one priority, but it is important to understand the source of the problem to better inform future processes involving fast loop systems to keep operations running smoothly without these types of delays. If not properly addressed, these issues may persist and become progressively worse. Repeated equipment failure or malfunction can be time-consuming and costly, especially when the sampling location is remote.
Why Is Your Fast Loop Sampling System Not Working?
While there are many reasons why a fast loop sampling system is not working as expected, the most common issues typically occur for two reasons:
- The sample is not reaching the analyzer quickly enough.
- The contents or properties of the sample are not as expected, whether this be water percentage, chemical makeup, or variations in sediment content.
The root causes of these symptoms include changes in crude oil, varying viscosity after being upgraded, equipment integrity, and mechanical damage.
System Not Operating As per Original Design
If your fast loop sampling system is not working per its original design, the following questions should be answered:
- If it was operating well, have changes been made that affect the fast loop design that are unaccounted for? Have operating parameters changed since the original design?
- Was the original design accounting for all the operating conditions or just one specific set of parameters?
- Is the original design a good design for the particular sample required?
These can be issues for remote sampling points that get little attention. When addressed, these issues can be reviewed and recommendations made to bring the Fast Loop design up to meet current operating conditions.
Below, we detail each of these root causes and what to look for:
Changes in Crude Oil
On occasion, there can be changes in water percentage while crude oil is being handled in the oil field; though, this doesn’t necessarily mean it was handled improperly. These changes are likely to cause problems during fast loop sampling. If the crude oil’s water percentage is higher than expected, this may present an inconsistent sample makeup across multiple samples of the pipeline taken in the same location.
Changes in water percentage have the potential to cause separation within the mixture, leading to the presence of a heterogeneous mixture if process conditions are not adjusted to provide a satisfactory mixture. A process engineer will have the greatest knowledge of the process conditions and requirements regarding pressure, temperature, and flow rate to best inform the next steps.
Varying Viscosity After Upgrader
After extraction and separation, bitumen goes through an upgrader facility to be chemically modified to provide better flow. This process may involve a form of thermal processing to heat and crack the heavy oil into smaller hydrocarbons to achieve a less viscous molecule that can actually be pumped. Hydrotreating to remove sulfur and reduce the nitrogen levels may also take place during this process.
Depending on the process conditions, the crude oil may come out of the upgrader facility with varying viscosities. Higher viscosity means the fluid will move at a lower flow rate and thus, lower velocity. This could mean larger time delays from the pipeline to the analyzer. Additionally, representative samples can only be assured when there is adequate mixing by the velocity of the fluid.
Equipment Integrity
Equipment integrity depends heavily on metallurgical quality and the minimization of corrosion in piping. If inadequate metallurgical processes are implemented, corrosion rates can increase, resulting in a fast loop sampling system not working.
This is particularly problematic where dead legs exist in a fast loop system. Dead legs are inherently prone to corrosion due to the lack of flow in these regions. Corrosion can lead to leaks or even catastrophic failure if left untreated. If there is a leak in the system, the pressure and flow will be affected, potentially causing delays to the analyzer.
Mechanical Damage
Mechanical damage in a fast loop system can often go unnoticed and become a problem during these processes. It is not uncommon for operators or maintenance personnel to climb over equipment and step on tubing, though mechanical damage can be the result of any number of things. This may result in a pinch or kink in tubing, or a dent or bend in piping. In any case, this can affect the flow through the system and may delay the time between the piping and the analyzer.
Determining the root cause is never an easy task. Even if the root cause of a fast loop sampling system not working properly seems clear, the best course of action is to consult with a local expert who can work alongside a process engineer to determine the exact cause
The Best Solution for Maximizing Fast Loop Sampling Reliability
If you are experiencing problems with misrepresentative samples—and time delays with your fast loop sampling system—Edmonton Valve & Fitting offers local Field Advisory Services and 24/7 technical support to ensure the root cause is identified. Our Field Advisory experts will work with you to determine the best course of action for seamless fast loop sampling operations. Edmonton Valve & Fitting brings together global knowledge and local experience with fast loop sampling systems in oil and gas to help you solve your most difficult sampling challenges.
About Tristian McCallion, Custom Solutions Manager, Edmonton Valve
Edmonton Valve has relied on McCallion for 26 years. His current title is Custom Solutions Manager. Earlier, he supervised our sales team. Before that, he managed sales throughout Edmonton and northeastern Alberta. For 12 years he also worked with Swagelok Energy Advisors across North America, training customers on steam fundamentals (TAP), testing steam traps, and conducting steam system audits.
