Because of new technologies, stronger or alternative materials and the growing cumulative knowledge of the industry, many lines that are or were once considered unpiggable are in fact piggable in at least some way, and Savcor Products Australia has experienced this firsthand.
Some of the most common reasons a pipeline might be considered unpiggable include the bend radius or curves being too sharp, meaning pigs cannot navigate the tight turns; improver valves being used that obstruct the line; pipeline diameter changing; temperatures outside the range of standard pigs; incompatible chemicals that destroy traditional pigs; and many more.
However, thanks to modern pigs and the use of line modifications – which can sometimes be temporary in nature – many of these issues can now be addressed and overcome.
Incompatible valves can be temporarily removed and replaced by spool pieces if a pig manufacturer determines there is no viable pig design that can pass through a particular valve. Reduced or enlarged internal diameters (ID) at valves are often not a problem for foam pigs as they can easily compress at least 25 per cent – or even more under extreme duress – and they can be modified to span gaps in valves larger than the mainline pipe ID.
It is also due to this flexibility that foam models can effectively clean pipelines with reasonable diameter changes. One line size difference, such as 10–8 inch (254–203 mm) is easily accomplished by most models and without much extra consideration. Larger jumps are possible, such as 30–24 inch (762–609 mm) with specially modified full-bodied pigs, but pressure and volume limitations of the line or equipment may be an issue.
A variety of materials
Polyurethane has long been the standard material for most pigs since at least the 1950s due to its flexibility and durability, but today cups and discs are also available in alternative materials such as ethylene propylene diene monomer, viton, silicone and others. Increased temperature resistance and a different set of chemical compatibility options are also available in cups and discs, with all these options on offer at Savcor Products Australia.
However, often lines are still not cleaned until they are well overdue. Sometimes these lines can be mostly obstructed by deposits or debris and removal of all the debris is often impossible as the pumping pressure behind the pig must be strong enough to move the material in front of the pig. At a certain point, resistance to forward motion becomes more than the pig and hydraulics of the operation can overcome, which is especially a problem in smaller and longer lines.
“However, with careful consideration, a proper pig selection and a progressive pigging plan, debris can be removed slowly, little by little, avoiding plugs and reducing the differential pressure needed to move the pig,” says Savcor Products Australia.
This article was featured in the July 2020 edition of The Australian Pipeliner. To view the magazine on your PC, Mac, tablet or mobile device, click here.
For more information visit the Savcor Products website.
If you have news you would like featured in The Australian Pipeliner contact Managing Editor David Convery at dconvery@gs-press.com.au
