Requirements for Hygienic Pigging Systems
When implementing a product recovery, product transfer or pigging system, it’s important to take time choosing the right pigging system provider. Similarly, it’s also important to choose the right type of pig, pig detector, level of automation, type of control system, software and so on.
However, it’s easy to overlook one of the most important components: your pipeline infrastructure.
If you’re considering implementing a pigging system, this article provides advice and guidance on pipeline standards, pipework condition, compressed air or gas services, and how to avoid intrusions. It also includes a checklist for your pipeline infrastructure when setting up and running a hygienic pigging system.
Checklist for Pipeline Pigging Infrastructure
We recommend you consider all of these points before implementing a pigging system, as well as during the life of the system:
- Make sure there are no dents or damage along the length of the pipe you are intending to pig.
- Welds must be clean and have minimal intrusion into the internal bore of the pipe.
- To prevent progressive damage to the pigged pipe, use anti-vibration cushion sleeve pipe support clamps instead of metal-on-metal clamps.
- Instead of rod hangers, we recommend using rigid supports such as ‘L’ frames for the pigged pipe. This will prevent possible movement of the pipe while the hygienic pigs are propelled through it.
- If you’re using compressed air, carbon dioxide or nitrogen to propel the pig, use rigid air pipe rather than flexible air lines (flexible air lines can get distorted and prevent air flow).
For new plant or equipment, your system designers will work with you to help you choose the right specification of pipe. If you’re implementing a pigging system on existing pipework, your pigging provider will need to know the pipe diameter, material and standard. There is a wide variety of pipe codes and standards available, including ASME, ANSI, ASTM, AGA, API, AWWA, BS, ISO, DIN and so on.
For safe, effective and efficient pipeline product recovery and pigging, your pipeline must be in good condition. If not, you will need to repair it, or replace it with new pipework (if your pipework is in a condition that’s not fit for pigging, it is probably best to replace it anyway).
Compressed Air or Gas Services
If you are using air or gas to propel your pigs, you need the right level of compressed gas services available that can access your pigging system. If not, you will need to install services with the appropriate capacity (this may sound obvious but it’s surprising how often this is overlooked).
The minimum volume of air or gas required will be equal the volume of the pigged pipe.
How to Avoid Gaskets Intruding in to your Pipe.
Internal intrusion of gaskets from pipe couplings can prevent your pigging system operating properly. Tri-clamps and standard flanges in particular are connections that may have this effect.
Tri-clamps are one of the most sanitary or hygienic connections. However, this is only true if they are installed correctly. If the clamps are over-tightened during or after installation, the gaskets are likely to intrude internally into the pipe. This will cause a restriction for the pig and poses a potential contamination risk.
To help avoid this intrusion we recommend using either Teflon or Teflon envelope gaskets. These are more resistant to intrusion. Alternatively, you could consider using a different type of connection such as the I-Line fitting in the USA, RJT – CIP Modified in Australia, or SMS, IDF or DIN in Europe.
For less sanitary applications, you could consider using ‘spigot’ flanges. These flanges key together, preventing misalignment.
Find Out More
Alternatively, if you have any questions about liquid pipeline pigging for hygienic applications, or if you’re looking to improve your profitability through effective product recovery and transfer, then please get in touch.