Planning Chemical Decontamination for Faster, Safer Turnarounds

Welcome to Part Two of Becht’s four-part series on chemical decontamination in refinery turnarounds. Our teams have seen firsthand how effective planning and the right chemistry make a measurable impact on turnaround performance. This series shares practical insights from real projects and highlights approaches to help refineries achieve safer, more efficient shutdowns. Read Part One here.

How can chemical decontamination save turnaround time? This is the most frequently asked question when a chemical cleaning/decontamination contractor approaches the turnaround team at any refinery. If we assume that all refineries and their turnaround teams take it for granted that there will be significant safety benefits from chemically decontaminating their process systems, then it is a fair question!

There are a number of key factors to be considered when addressing this question.

When should a chemical decontamination contractor be involved in the turnaround?

In my experience, it is never too early to involve a chemical decontamination contractor. All too frequently, the contractor is only selected once the scope for the turnaround has been set and shared with the various contract companies bidding for the chemical decontamination work.

What if the potential contractors were involved in discussions at a much earlier stage? Typically, there is a five-year gap or more between major refinery turnarounds and 80% of the scope is a repeat from the previous event. So, most refiners know what key vessels, columns, and systems will require chemical decontamination very early in the long-range planning process.

But what about the unknowns: the equipment that has never been chemically decontaminated before, either because the refinery thinks it is not possible or because there was always enough time in the past to steam it out for days? If you are a refinery turnaround team planning the next major outage, consider taking the following steps.

Review the history

• What has caused you delays in the past? Have you opened any equipment and had to re-steam because of something you found? The good old days of extended steaming out are gone – not just because of the time lost, but also because of benzene release into the work area and the obvious health and safety implications.
• Was the LEL still above the allowed threshold that sites aim for when opening vessels?
• Did a particular chemical approach produce poor results last time? Did that delay work on the vessel or column?
• Where were the unexpected pyrophoric iron sulfide (FeS) deposits? Did that create the need for secondary decontamination, which led to a delay? Certain process units may always have the potential for FeS issues, and any decontamination procedure for that unit should include a stage for oxidizing such deposits. Is there an up-to-date register of equipment that usually has pyrophoric contamination?
• Remember, pyrophoric deposits can create serious hazards when exchanger bundles are pulled, too – it is not just a vessel or column issue!
• Similarly, were there any unexpected hydrogen sulfide (H₂S) issues when certain vessels were released for maintenance?
• Even if the chemical decontamination procedure was successful, could the timescale be shortened during the next turnaround?

Integrate chemical decontamination into the shutdown procedure

Aim to incorporate the chemical decontamination procedure into your own unit shutdown (SD) procedure, tailored to the turnaround being executed. The very best teams nowadays fully integrate the chemical cleaning procedure into the SD plan. These need to be completed early and sent out for review and revision, including by Process Safety, Inspection, and related groups. The contractor can then work with Operations during the unit shutdown phase, ensuring that time savings are realized.

Set clear objectives

Set the objectives for any chemical decontamination work. What are you trying to achieve? Is the equipment on a critical path, or is it routine maintenance?

If it is on a critical path, it needs to be discussed as early as possible and then incorporated into the SD plan. Early collaboration will allow the chemical decontamination contractor to tailor the procedure for maximum effectiveness and time savings.

Plan for predictability

The SD plan will assume certain timelines for the release of decontaminated equipment. Sharing those timelines with the chemical decontamination contractor may challenge the assumptions made by the turnaround team – potentially uncovering opportunities for time savings or flagging unrealistic scheduling.

Selecting a chemical decontamination contractor

Without being subjective, a chemical decontamination contractor will usually be selected by a refinery on the basis of three key criteria:

1. Cost
2. Technology
3. Confidence

Whether the budget belongs to Operations, Capital Projects, or the turnaround team, no one wants to spend more than they need to! Thus, if the technology appears to be correct for the decontamination objective, total cost will always be the main driver in selecting a chemical decontamination contractor.

However, I firmly believe that cost also needs to be balanced against the confidence that the contractor inspires within the refinery personnel. Therefore, the lowest cost is not always the best choice.

Consider the following when reviewing the bids from chemical decontamination contractors. How do they propose delivering effective decontamination of various process systems while achieving time savings and ensuring safe working conditions? Will they:

• Undertake detailed walkdowns of the process systems to identify potential tie-in points for the chemical decontamination procedures, and learn the process loops?
• Group equipment that will require man-entry for maintenance and/or inspection together, where possible, into closed loops? Grouping equipment into larger closed loops can apply whether vapor phase or washing techniques are used; sometimes a combination of both works well.
• Bypass equipment that will not be opened, possibly by temporary “jump-overs”? This can avoid the mindset of “well, we have always cleaned that vessel in the turnaround scope – even when unnecessary!”
• Identify equipment that can be successfully decontaminated of all hazards by vapor phase chemistry? This is obviously the fastest method, but it is not the universal answer!
• Identify the equipment that will require a washing technique, whether fully flooded, cascade washed (typically columns), or by temporary installation of rotating nozzle assemblies? Washing is usually necessary where known solids are accumulated and cannot be moved by vapor phase alone.
• Highlight where H₂S and pyrophoric FeS may be expected, and incorporate safe, effective chemistry to completely remove those hazards?
• Suggest changes to the scheduled release of vessels, exchangers, and columns from Operations to the turnaround team, such that maximum use of the chemical contractor’s resources and experience could speed up equipment access for mechanical work? For example, it can sometimes prove beneficial to wash a vessel or column earlier than originally planned and transfer the spent chemical solution to a second vessel, to save filling and heating time on that second vessel and reduce effluent volumes.
• Position mobile/temporary equipment in locations least likely to interfere with major crane lifts or other post-decontamination contract work? If possible, provide a plot plan of the expected equipment laydown.
• Run temporary pipework systems through low-traffic areas to minimize trip hazards and allow installation well ahead of the turnaround start? Check that they will bring their own temporary pipework, install it, and completely rig it up to the tie-in points themselves – and not rely on the refinery to do it.
• Manage chemical effluent by positioning temporary tanks “off-block” or “off-plot” and run temporary pipework to those tanks, avoiding unnecessary vacuum truck movements during the turnaround? This also prevents the long waiting times that can be experienced by a chemical contractor if a vacuum truck cannot reach the source of the effluent on the process unit, or if no vac truck is available.
• Consider whether a suitable storage tank off-plot be utilized, even if it requires a longer pipework run? This can save on temporary tank hire charges.
• Finally – and essential, in my opinion – provide draft procedures and schematics?

There will be other ways to save time by giving the chemical decontamination contractor early access to the scope, but the above list highlights some of the most effective ways I have seen refineries and contractors work together to realize time savings before the event even begins!

These early planning decisions set the stage for selecting the right chemical approach. In my next blog, I will examine the techniques themselves, comparing vapor-phase and washing methods as well as outlining how to choose the best fit for each process unit.

If you would like to discuss how Becht can help you plan or optimize chemical decontamination during your next turnaround, contact us anytime to start the conversation.

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