Refinery operators must ask cleaning contractors the right questions, these include:
▪ What experience and technologies have been used to minimise or avoid de-bottlenecking?
▪ Which unique or innovative methods or procedures have been employed out the ordinary that will save time and money as well as improve safety?
▪ Where is the evidence of safety and experience by referrals as well as the documented site requirements?
▪ What is your understanding of the implications of how their particular activity will affect the rest of plant?
The level of fouling you or your contractor removes must be measured before and after it is removed, otherwise everything you do from then on will have dire consequences until the next shutdown.
It is imperative that you invest in the right technology, and not just the cheapest! It must be safe but quick and very efficient. The contractor must provide tangible evidence to confirm the level of fouling before it was cleaned and after it was cleaned otherwise you, the client, are in the dark as to how effective the contractor has been, other than putting the plant back online, at which point it is too late to do anything anyway.
Heat exchanger performance must be monitored, measured, recorded and archived on a regular basis regardless of how often you shut down. This will help optimize your throughput over time and likely put you in the top percentile of all refineries. Fact!
In practice, maintenance schemes for heat exchangers are based on insurance legislation, asset life desire and necessity which translates into regular inspection and cleaning. Generally however refineries, designed as they are and competing in a competitive low margin environment try to extend their shutdowns as long as possible for the benefits of capex and opex saving not least to the benefit of their shareholders to as much as 5 years cycles.
Dependent on the process, some heat exchangers will require more cleaning and integrity assessment. Thermal efficiencies and increased production are proportionate to the level of cleanliness and integrity. Remember, ensure you work smart not just hard!
So much time and money is spent on such poor levels of cleanliness. Why is this case? Because site operators can be forgiven for not knowing of the best practice. Sometimes site is driven by uniformed budget makers, short sightedness or some who just don’t want the hassle of trying something new. It all boils down to human nature or a maintenance procedure yet to be defined and followed. All the above leads to a poor level of inspection i.e. if you can’t clean it you can’t inspect it! This then leads to overheating, potential for stress cracking and naturally potential risk of catastrophic and costly failure.
Global exchanger tubes are inspected by either a “Go No Go “ gauge, eddy current or iris probes. The average number of tubes inspected is just 10%. This is like playing Russian roulette, leaving 90% of tube surface area integrity in doubt. This is what the industry believes acceptable. Corrosion that sits under scale remains to continue is corrosive process reducing the wall thickness and so too its integrity until it too is cleaned properly.
The solution is simple – clean AND inspect at the same time saving valuable downtime and enabling more tubes to be inspected. There is no conflict of interest as the client can confirm the tubes to be cleaned and inspected, the eddy current or IRIS inspection equipment does not lie and thus can be managed by any cleaning contractor.
A good debottlenecking cleaning / inspection plan starts like this:
- Historically critical and difficult to clean exchangers handed over to a true specialist with several alternative systems to cover all fouling eventualities and who can inspect at the same time on both the shell and tube side.
- Find a contractor who understands how clean clean really is, and can guarantee their results.
- Discuss with contractors who can clean and inspect in-situ without pulling thereby saving on: bolts, gaskets, scaffold, pulling, risk, third party costs and debottlenecking.
- Use traditional water jetting contractors for light to medium fouled exchangers that need to be pulled in the cleaning bay.
- Record the fouling before, during and after with digital images and video clips to confirm cleanliness and inspection levels achieved and archive them.
By avoiding the use of traditional water jetting for everything, the above practice substantially reduces debottlenecking with cleaning activities running more smoothly.