Feb 25, 2019 - 4 months ago
By Supply Post
FRONT PAGE STORY: It weighed over 800 tonnes and stretched the length of a football field. Here’s how it was moved. By Graham Chandler
On the snowy night of January 6th this year, the heaviest load ever to travel Alberta roads eased out of Dacro Industries Edmonton fabrication yard. Three days later, the propylene-propane splitter—the largest vessel by volume ever constructed in Alberta—arrived at Inter Pipeline Ltd.’s Heartland Petrochemical Complex construction site near Fort Saskatchewan.
The 800-tonne, 95-metre behemoth is the first and biggest of four major moves of oversized equipment for the company’s landmark project, which will produce a recyclable plastic called polypropylene from Alberta propane feedstock.
Road moves of such unprecedented magnitude and complexity call for meticulous planning and cooperation. Planning this one started as far back as 2013, well before the decision to commence fabricating the giant vessel.
First, the proposed configuration was presented to stakeholders for consideration. The main factor in choosing the transport method was, will it distribute the load to stay within pavement and bridge loading restrictions? Pavement and bridge analyses were conducted by independent experts to ensure no damage to existing facilities would happen. And a thorough evaluation of the entire route was undertaken to make sure a load this large could negotiate all corners with minimal infrastructure improvements.
Some of the required specialized equipment came from as far away as Texas. “The trailers used were two 26 Line 4-file hydraulic platform trailers bunked with 710T turntables with load spreading mats,” explains Craig Middleton, Sr. Project Manager at Mammoet, the heavy-lift firm that handled the move. Both front and rear trailers were connected to the vessel through the turntables to allow pivoting around corners.
The load spreading mats’ purpose was to ensure the loads were distributed so as not to exceed allowable road and bridge limits. “They are essentially a series of large structural beams welded together to form a base for the turntables large enough and strong enough to put the weight of the vessel into the length of the trailer,” says Middleton. From there, the axles receive the weight through hydraulic pressure. Each axle is centred around a hydraulic cylinder that is fluidly connected to the neighbouring cylinders in the hydraulic field (four fields per trailer for stability). Dedicated operators controlled the load level to ensure stability was maintained.
“In total, we had eight counterweighted tractor units pushing and pulling in various configurations.” A lot of wheels in all: 912 tires – 832 for the trailers and 80 on the trucks.
Loading the vessel onto the trailers called for a number of steps as it was received too low and close to the fabricator’s shop. So Mammoet crews first needed to relocate it within the yard. Using 300T climbing jacks they raised it and drove self-propelled modular transporters (SPMTs) under it. In total, 48 axle lines of SPMTs were used: 24 for each end. Once relocated, the same climbing jack process was used to raise the vessel and lower it onto the highway trailers.
With the road move underway, team coordination was critical. Crews communicated closely by radio throughout the trip to make sure for example that truck power was distributed evenly on either end to ensure appropriate push/pull forces were maintained. “This way, no single tractor is overworked,” says Middleton. “Experience plays a key role in ensuring that the trucks are coordinated and configured properly.”
The trailers were steered in two ways. When cornering in tight quarters like city streets, both front and rear were steered hydraulically by remote control. Dedicated steering operators were assigned for front and rear who were guided by supervision and spotters. When on the highway, the lead truck controlled the steering via a mechanical connection of tie rods from the hitch to the trailer’s hydraulic system. “This allows all the wheels of the front trailer to steer with the movement of the trucks,” explains Middleton. “Similarly, the rear trailer hitch is connected to a frame mounted to the vessel, which steers the rear trailer to follow vessel movement.”
Manoeuvring demanded patience. Loads this size aren’t able to back up but they can be pulled in the opposite direction. Five times along the route, crews had to switch ends and do this. Each time, the trailers were manually steered while reversing to ensure each corner could be executed safely and within equipment limits.
Upon arrival climbing jacks were again employed, for unloading. “Final erection to vertical will be by Mammoet’s PCT 35DS ring crane this spring after final dressing of platforms and other external attachments are installed,” says Middleton.
He reckons the biggest challenge of the move was coordinating all parties—permitting, engineering and maintenance teams, transport supervisors and their crews. “Good involvement by the client and stakeholders ensured that everyone was working towards the same goal. In the end, teamwork is what made this job successful.”
Completion of the complex, the first of its kind in Canada, is scheduled for late 2021.