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Try "pigging" the pipe in question - it worked for the City of Trail
How to clear built-up silt, corrosion - even chunks of 4x4 - from all sorts of pipes
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| A typical "mandrel" pig, as above, is often the basis for more elaborate pigs that sprout various abrasive pads and brushes |
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If you've got a blockage problem in any type of pipe - from sewer to domestic water - ICBA-member SFE (Southwestern Flowtech Environmental) Global is expert at "pigging."
And with some judicious pigging, SFE has found and removed everything from corrosion buildup, to silt and sludge, to T-shirts, bottles, chunks of 2x4 and 4x4, and even lunch boxes.
So . . . what is "pigging?"
"Simply put," says SFE's Mike Lemmen, technical services, "it's a way of cleaning, dimensioning, or inspecting any type of pipe with the use of pigs.
"And pigs are devices that move through the inside of a pipeline."
For the uninitiated, a pipeline pig can be anything from a small, bullet-shaped plug to an elaborate contraption with bristles and wings and cups and propeller-like fins: And each has its own purpose.
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This "poly" pig (polyethylene coated) has steel bristles to wire-brush the inside of a pipe. It looks and feels hard but will actually bend and deform when under hydraulic pressure inside the pipe
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"There are more than 500 types of pipeline pigs," Mr. Lemmen explains, "and they come in different sizes for just about any application."
The mechanics of pigging can seem to defy reason, and many would-be users are wary at first, Mr. Lemmen says, "particularly when they already have a flow restriction and they fear sending a pig down the line will plug everything solid, creating an even worse problem.
"But to make sure there are no blockages, we'll often start with a soft pig made from foam that will even squeeze through a one-inch hole."
Hydrostatic pressure drives the pig through the pipe, and, because that pressure will always seek the path of least resistance, the pig is forced through restrictions, around bends, even through the correct path at a T connector, and will otherwise find its way out - forcing debris along with it.
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| This domestic water line was in need of cleaning! The pipe pig can be seen being forcefully ejected ahead of accumulated rust and sediment |
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The soft pigs will tend to be cut down to the size of the prevailing restriction and will thus give a good indication of the size needed for a harder, more abrasive pig to be inserted next.
"Then we can gradually increase the size of the pigs until we reach the design dimensions of the pipe, or a size suitable for the job to be done."
Checking the nominal size of a pipe calls for a gauging pig - basically a circle of slotted sheet aluminum attached to the back of a standard mandrel (see illustration above). Sections of the aluminum will deform as they hit any obstructions.
"They give us a very accurate picture of what's happening inside the pipe," Mr. Lemmen says, explaining pipes can get pinched or buckled during installation or crushed by backfill.
Pigging turned out to be the solution for the City of Trail last year when it needed to clean out accumulated sludge and silt from a 24-inch gravity-fed sewer trunk line prior to installing a new lift station. About 2,500 feet of the sewer trunk runs along the river and is submerged for half the year during high water.
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| Mike Lemmen, technical services, with SFE Global, holds a typical soft foam pig that can squeeze through as little as a one-inch opening. This pig is often used first if there is any concern of a complete blockage |
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The line was "probably half full of silt," Mr. Lemmen says, "but the traditional flushing equipment could only stretch about 200 feet - not nearly far enough to reach between the manholes located every 500 feet.
The city was faced with the possibility of having to add several expensive access points - they're special sealed and bolted units to prevent contamination of the river water.
"However, we were able to flush each section by inserting a pig at the high end and flushing it down to the next manhole using a six-inch water pump and the river water.
"We plugged the next section so the pig forced the silt up and out into waiting pumper trucks.
Such jobs can be spectacular when watching the resulting explosive rush of silt, debris and dirty water forced out of the pipe.
And it can be surprising what finds its way into pipes in the first place.
"We've found all sorts of things in new pipe installations from T-shirts, bottles, and lunch kits. We've even removed lengths of 2x4 and even a four-foot length of 4x4 in an eight-inch sprinkler line at the grain elevator docks in Vancouver."
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| An SFE crew pushes a soft pipe pig into a gravity sewer system in preparation for cleaning |
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In that incident, SFE was able to push the 4x4 to the first elbow, dismantle the pipe at that point, and remove the problem.
Besides such cleaning chores, pigs can be used in commissioning new lines and loading the line while avoiding trapped air.
"We'll inset a pig and then run the water - or whatever fluid (which includes gasses) is being used - behind it. The fluid builds up behind the pig which then forces out the air in front of it."
But pigging is just part of SFE's work.
"Our primary focus is actually flow monitoring in both open channel (any system that depends on gravity, such as sanitary and storm sewers) and closed systems (any pipeline under pressure, such as domestic water, or oil or natural gas)."
But pigging certainly takes the limelight when it comes to catching the attention.
SFE Global was started in Aldergrove in 1990 by Glenn Cumyn - the company's president - and has since expanded to Calgary, Edmonton, Seattle and Sacramento, California.
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