In hygienic and industrial liquid processing, the efficiency of pipeline operations is crucial for improving yields, maximising productivity, and minimising waste.
Effective product recovery is essential for companies looking to optimise their processes. The best results are achieved when manufacturers use bespoke pigging systems that meet the precise requirements and needs of the process.
In this first part of our interview on pigging system design, we ask our product recovery experts how HPS designs effective pigging systems and what is taken into consideration.
General Design Considerations
Gary Joines, System Design Manager
What are the key factors to consider when designing a custom pigging system for a new facility?
There are a range of key factors to consider when designing a custom pigging system. The client’s aims and objectives are most important. Do they want to increase their yields or reduce their waste or is it something else? Pipeline specifications such as length, internal diameter, and materials are also really important.
When it comes to the product that goes through the pipeline, we consider product temperature, the likelihood of foaming or degradation, and viscosity. Batch frequency, changeover frequency, and cleaning and CIP frequency are also really important to consider, especially when it comes to calculating an estimated return on investment and the initial payback period.
In terms of general operations, we’ll consider things like control systems and panels, pumping pressure, and the availability of a suitable propellant, such as filtered compressed air, water, nitrogen, etc.
How does the pipeline material and diameter affect the design of a pigging system?
The pipeline material is usually made from stainless steel, preferably 316L stainless steel, although we can accommodate other metals as well. If the pipeline has a large diameter, say 8-inches, we may also need to consider the volume of propellant needed.
Other than that, material and diameter have very little impact on the actual design of the pigging system.
We mainly use the length and internal diameter to a) check that we have a suitable pig size, b) make sure that we quote for the right sized components, and c) provide an estimated return on investment and payback period.
What role does the viscosity of the liquid play in designing an effective pigging system?
Our pigging systems can pig just about any liquid product, regardless of viscosity. We have a saying – “if you can pump it, we can pig it” – which has proved true for the past 29 years.
The only impact that viscosity really has in designing an effective pigging system is the pump pressure, which is decided by the client anyway. We just use that information to make sure that we recommend the right equipment specifications for the client’s process and get them the highest product recovery rates possible.
Technical and Operational Aspects
Shaun Pitcher, Sales Engineer
Can you explain the process of selecting the appropriate type of propellant for a pigging system?
The process starts by asking the client about their process and product. Does it react with air, for instance? Some chemicals will, so we may need to use an inert gas, like nitrogen, and other products could be explosive or produced in a hazardous environment. Other products, like beer, need to be transferred through a line without air present to prevent product degradation and foaming.
In some cases, the client doesn’t have compressed air onsite or the changeover speed may be critical. If that’s the case then instead of using air and sending the pig to the receiving station and back to then clean the line and pig again, we can design pigging systems that are propelled by water or other cleaning chemicals and do one pigging sequence instead of two to save time.
Some products require higher pressure for pigging, which would require a liquid push, or the client may want better control over the pig speed then you can get with compressed air. A liquid push gives greater control by allowing the client to vary the pump speed and slow down the pig. A lot of the time clients who ask for this option are pigging the product to a small buffer tank or an open tank.
Air push systems have less control as, even if you turn the air off, the pig will continue to move a short distance. So, if you’re pigging into an open tank with an air push, it can get really messy. However, pigging into an enclosed tank with air is fine, so the one thing we do need to know when suggesting a propellant is the destination design.
How do you ensure that a pigging system is compatible with Clean-In-Place systems?
Again, it comes down to talking with the client about how they clean their process lines, what they clean with, how long they clean for, and what temperature they clean at. It’s also ideal to know what happens to the waste that they create.
We then design a pigging system around these requirements to fit what they currently do, or what they want to do, and where they want to send the waste.
What are the challenges of retrofitting a pigging system into existing infrastructure, and how does HPS address these challenges?
There are a few challenges. The main challenge that clients bring up is the time it takes to retrofit, as a lot of lines are considered high priority and run 24/7. Shutting the lines down for retrofitting creates downtime and lost revenue.
We handle this as best we can by ensuring that our systems are easy to integrate with minimum downtime and, if we’re installing the systems, we do as much fabrication offsite as possible. When the client or the client’s preferred installer is doing the installation, we offer our help, and we can be onsite as well to ensure that everything is fitted correctly.
Space constraints in the launch area can be an issue as well, so we bear that in mind when designing or selecting a suitable launch arrangement.
Another challenge is pipeline variation. Distilleries, for example, are notorious for having various changes in pipe diameter along a planned route, so the pipework has to be changed in order for pigging systems to be installed. Likewise, we have to be mindful of any branches in or out of the planned pigged line, and these sections have to be replaced with piggable tees or valves.
Speaking of valves, they can also pose a challenge. Butterfly valves, for example, create a blockage in the line and so they have to be changed for piggable ball valves.
Sometimes the quality of the line itself isn’t suitable for pigging. If there’s misalignment between elbows and pipes or obtrusive welding, then these need to be addressed before a pigging system can be installed. Similarly, if the pipeline layout or support isn’t great then this needs to be addressed. We’re happy to recommend improvements that need to be made and these will be highlighted as soon as we become aware of them.
Finally, the controls are something that can be a challenge in retrofitting. We need to know how the client currently controls their operations and if we can integrate into their existing controls. We can supply the control equipment, and if we’re doing that then we need to know where the client wants the control panels located and how they want them to integrate into the other control systems onsite.
Find Out More
If you’d like to find out more about HPS Product Recovery Solutions pigging systems, please get in touch!
You can reach us via email, telephone, or contact form, and a member of our team will be in touch with you as soon as possible. We look forward to hearing from you and visit the website next week for the next half of this interview!