Liquid Hammer & Damaged Pipe Repair
The Need & Challenge
A significant liquid hammer event on a flair line at the top level of a pipe rack resulted in pipe movement at the expansion loop. The 18” stainless steel flair line had welded shoes with horizontal guides to restrict line movement. Two support locations immediately before and after the expansion loop received damage as the line moved horizontally out of position.
The guides at the South shoe prevented the base of the shoe from moving across causing the shoe to bend and deform the bottom of the flair line. A portion of the weld against the flair line tore in the process but did not rupture the line.
The North shoe sprung out of the guides entirely and was caught against the outside of the bent guide as pipe tension attempted to return the line to its original position. A portion of the weld was also torn but did not result in a loss of containment. The line was now out of position by 3”.
The client needed to remove shoes at both locations to install enclosures and restore integrity, however both shoes were under tremendous load and removing them while the line was under tension would be an unsafe event that would cause the line to violently spring back to its original position.
Removing the shoes would also remove the vertical support against the line causing it to sag. This not only reduces the clearance required to install the enclosures but also introduces a low point in the flair line that would cause product to ‘pool’ without exiting to the flair stack. Maintaining a uniform downward sloping angle on the flair line is critical to ensure product exits the line.
The line needed to be vertically supported while the shoes were removed. It was estimated that repairs would take multiple days in an area of the facility that could only provide access for a single crane for hoisting up the enclosures. The line would also need to be lifted at multiple locations and doing so using a crane would require substantial rigging.
Solution & Outcome
The flair line was anchored horizontally using two chain falls to remove the horizontal load against both shoes. Ovolifts Multi-Jacks were installed at two support locations adjacent to the North and South shoes to lift and provide vertical support to the flair line. The lift was engineered to allow the line to freely move horizontally within the required range.
Using this setup, the line was manipulated horizontally and vertically until the load was removed from both pipe shoes making it safe for them to be removed. The expansion loop, which was currently being anchored towards the East was then restored to its original stress free position by slowly releasing tension on the two chain blocks.
At this stage the Ovolifts Multi-Jacks were still providing vertical support to the line. Crews then installed the two enclosures which were designed with the ‘ears’ at the 6 & 12 O’clock position. The bottom ‘ears’ substituted as the new pipe shoes which were shimmed to the correct height against the supporting beam, thereby maintaining the uniform downward slope of the flair line.
Safety
Engineered line lifting using Ovolifts pipe jacks eliminated risks associated with line lifting multiple locations using a crane. It also created a secure lockout for elevated loads during the multiple day project. Vertical line movement was accurately controlled by means of the pipe jacks and crew safety was improved by allowing technicians to remotely activate the jacks and manipulate the line which was under tension.
Cost Savings (reported by the contractor)
Eliminated the need for a crane, rigging and operator costs to lift the line over a 1 week period.
Value added
Ovolifts pipe jacks provided an engineered lifting solution and provided safe access for technicians to perform remedial work on the touchpoints. The footprint on site was reduced since no crane or scaffold was required and the lockout mechanism created a static structure allowing the pipe to be elevated for extended periods of time. The engineered lift also accommodated horizontal line movement which was critical for restoring the line to its original position.