Background
The polymerization process of ethylene gas to LDPE takes place in the High Pressure Tubular Reactor and is then further cooled down in the Inter Stage Cooler (also known as the Product Cooler). Over time, scale build up along the inner tube walls of the Inter Stage Cooler reduces heat transfer efficiency. Due to various operational conditions, this equipment may be taken out of service several times per year for cleaning to improve cooling efficiency back to optimum design capacity.
Problem
Utilizing conventional 20,000PSI hydro blasting methods, the client's standard practice is to schedule approximately an eight day turnaround/shutdown in their LDPE Unit where the hydro blasting cleaning of the Inter Stage Coolers is often considered a critical path job. Conventional 20,000 PSI methods require the removal of 56 short radius elbows in order to clean the 42 tubulars individually. The client was required to subcontract a large number of mechanical personnel to disassemble the Inter Stage Cooler, requiring extensive scaffolding in order to perform the mechanical activity and open each tubular to perform hydro blasting. Upon completion of the cleaning and inspection of the tubulars, mechanical crews re-assembled the Inter Stage Cooler to hand back over to the clients operations department for startup.
Objective
The client sought to find an alternative cleaning solution for their Inter Stage Coolers which would be a faster solution to cleaning their fouled Inter Stage Cooler. The client had utilized several contractors and cleaning methods over the years until they were introduced to the HYDROKINETIC cleaning method offered by RefSol. Previously the client had found some success with utilizing different cleaning methods. However, they were never really truly able to find a solution to reduce the cleaning time significantly enabling them to shorten their standard shutdown duration.
Solutions
RefSol utilized the patented Hydrokinetic™ cleaning method which significantly reduced the total downtime from 8 days to just 4 total days from stop to start. Utilizing Hydrokinetics eliminated much of the mechanical and scaffolding work required to perform this job previously; which saved not only time but manpower hours and cost. What enabled RefSol to complete the cleaning task more quickly and efficiently as opposed to previous methods utilized, is that Hydrokinetics™ can navigate through multiple bends and turns whereas other cleaning methods are limited. In fact, Hydrokinetics™ only required the removal of each of the inlet (QTY-4) and outlet (QTY-4) elbows. RefSol then cleaned the entire loop of tubulars from end to end in a matter of a few hours per loop.
Result
In addition to saving massive downtime the client was extremely happy with the quality of cleaning and the safe manner that the Hydrokinetic™ cleaning method is operated. By attaching the Hydrokinetic cleaning tool to each pass of the Inter Stage Cooler, it reduces the exposure to high pressure water unlike in normal hydro blasting operations utilized in the past. The induction of the sonic resonance is done remotely from a control console that is positioned in close proximity to the equipment to be cleaned. The true result of the cleaning was confirmed once the equipment was returned back to service where operations reported a significant difference in cooling after cleaning with Hydrokinetics™ in comparison to previous cleaning methods. The client reported the Inter Stage Cooler operates at optimum cooling performance. In most cases, their LDPE Unit are now able to remain in service for longer periods and are taken out of service for cleaning once or twice a year and during LDPE Unit shutdown, the cleaning of the Inter Stage Coolers are no longer considered critical path activities thanks to the availability of the Hydrokinetic™ cleaning method offered by RefSol.