Uncategorized

October 2018

Recently a specialty chemical plant in Canada had an issue with a waste storage tank that contained some environmentally “unfriendly” contents.  The outflow valves from this holding tank were slowly decaying and even with redundant valving there appeared to be no way to replace the faulty valves without draining down the entire tank.   The contents of the tank were going to require very expensive  specialty hazardous  material  teams,  tankers, storage and disposal to drain and remove. The company contacted COB industries with their situation to see if it was possible to freeze the contents of the outflow line to allow for repair.  The conversation revealed that many of the general guidelines suggested by COB for freeze site selection were in question.

1) proximity to a potential heat source.  The outflow line was welded directly to the wall of the storage tank which would act like a heat sink when trying to attempt a freeze.  2) Distance to a closed valve.  A series of redundant valves were placed very close together going downstream from the storage tank wall. This included an encapsulated valve that had been leaking for quite some time.  3) Distance to a valve or fitting. In this case a flange connection was only 5” away from the only available freeze site.  The standard 2” Accu Jacket was just over 8” long.  All of these factors created what would typically be a “no go” situation for a freeze selection but with limited options it was agreed to attempt to freeze the line.  A COB freeze technician was dispatched to the site and after a walk through and series of discussions with plant staff the okay was given to attempt the freeze.  To make matters worse the area was experiencing a heat wave and the freeze location was in direct sunlight with no way to shade the area.

A custom 2” Accu Jacket had been built to fit precisely between the tank wall and the flange and the fit turned out to be nearly perfect.  Only a little trimming of one of the bolts was required to make a good connection.  Extra LN was bought in  and staged nearby as it was expected that more time and nitrogen would be required to freeze the 2” line due to the tank wicking temperature away from the freeze site, the ambient conditions.  Not to mention the unexpected placement of heat tracing on the outflow lines running year round(normally a 2” line would take approximately 30 minutes to freeze).  The leaky valving actually helped in this situation because it allowed for visual confirmation of the freeze when the constant dripped stopped after 50 minutes.  It was suggested that the freeze be held for another 10 minutes with all of the downstream valves held open and this confirmed the freeze integrity.  The flange was unbolted and the concerns of a freeze plug stretching across the 2 flange faces making separation difficult (or impossible) were unproven as the ambient conditions prevented more growth of the ice plug and only a little trimming with a quickly fashioned “ice plug trimming tool” (a hacksaw blade with  protective handle made by duct tape at one end) cleared away the ice and allowed for quick fitup of the new manifold by plant personnel.

July 2018
Recently a large northwest utility had a potential environmental issue with an abandoned pipeline that traversed a protected area in Oregon.  The US Army Corps of Engineers had chosen the area to replenish a natural salmon hatchery that had been cut off from the Willamette River many years ago when a train crossing was built.

It was determined that the line would have to be removed in order to allow for the construction of the new river access.  The line had been filled with water when it was abandoned and the highly contaminated water now posed a considerable problem.  Removing and disposing of the water would be a logistical nightmare as the line was miles long and the site was a mile from the nearest accessible road.  It was determined that creating 2 ice plugs on either side of the access stream and removing only the water between the ice plugs so the lines could be capped and the cut off pipe removed would be the best option.  COB Industries was contacted about the feasibility of the idea and availability of the equipment required to conduct the project in an urgent fashion as the project was on going and time was imperative.

Within a week the equipment was available (including borrowing a 10” freeze jacket from another customer) and a COB representative was dispatched to the site to provide training and consulting while the project progressed.  Logistics at the site were quite formidable as no vehicles other than UTV’s were allowed to access the site via a pedestrian foot path(heavy equipment was bought in via rail).  This meant bringing the liquid nitrogen supply in 1 tank at a time from over a mile away.  (It was determined that over 16 liquid nitrogen dewars would be required to perform this double 10” freeze.)    Adding to the problems the area was experiencing record heat which would make any freeze even harder.

Two pits were excavated on either side of the creek access exposing the pipe and the anti corrosion coating was removed.  Once the pits were open and secured the freeze equipment was installed. Freezing commenced early the following morning. Due to the record high temperatures combined with little to no shade on the pipe (or freeze equipment) higher pressure nitrogen supply was required.  The freeze was begun and the added flow rate of nitrogen was able to overcome the heat load in the environment and the ice plugs were successfully completed.

The pipe was cut on both sides and the remaining contaminated water drained to disposal containers that would have to be taken away.  Waiting welders quickly capped the open ends.   The freeze equipment was shut down and the ice plugs allowed to thaw naturally.  The proposed river access refurbishment was allowed to continue the following week bringing life back to a vital natural habitat.