Jan-2009

Online cleaning improves operational excellence

Online cleaning, followed by degassing and decontamination, can result in a significant reduction in downtime, increased run length, operation under cleaner conditions and potential avoidance of a turnaround, leading to an increase in production

Marcello Ferrara
ITW

Article Summary

Online cleaning of refinery production units has been positively proven in many severe applications such as the bottom section of visbreaker and vacuum columns with both trays and structured packing. In turnaround applications, visual inspection has confirmed positive results. An entire unit can be cleaned online in just 24–36 hours. Furthermore, online cleaning can be implemented during unit operations to recover unit performance, operate under clean conditions and improve operational excellence.

Current cleaning technologies
Today’s technology for cleaning heat exchangers includes the following procedures:
—    Flushing
—    Isolating equipment from the process and blinding
—    Removing hydrocarbons
—    Steaming out for gas removal
—    Scaffolding
—    Unbolting
—    Removing covers and distributor
—    Extracting the bundle
—    Transporting the bundle from plant to washing area
—    Hydroblasting
—    Transporting the bundle from washing area to plant
—    Inserting the bundle
—    Inserting new gaskets
—    Installing covers and distributor
—    Bolting
—    Removing blinding
—    Removing scaffolding
—    Air removal and purging
—    Performing pressure tests
—    Inserting the apparatus in the process.

All of these operations have their related costs. The bidding paid costs are to be added to the customer’s organisational costs in terms of:
—    Awarding (bid organisation, evaluation and award)
—    Planning
—    Co-ordination
—    Control during execution.

To these operational and organisational costs, huge production loss costs must also be added, followed by equipment downtime. Even more relevant are the costs associated with the decrease in performance during the run. Moreover, all these operations can suffer from different problems, such as:
—    Long time for isolating/inserting the equipment
—    Waste generation
—    Hydrocarbon emissions
—    Bundle damage
—    Difficulties in bundle extraction
—    Difficulties in unbolting
—    Hazard to workers performing mechanical operations
—    Hazard from scaffolding
—    Hazard from spills of carcinogenic (R45) products
—    Hazard to people working nearby moving equipment/vehicles
—    Hazard from bundle transportation/cleaning apparatus/cranes.
Due to continuous improvements in process safety and environmental performances, these problems are now only acceptable when there really is no other choice.

Safety and environmental factors
The hydrocarbon processing industry  continues to try and limit airborne emissions through technical efforts and investment. For example,  consider the investments and revamps required (eg, valve substitutions, insulation of flanges, double seals on pumps and double seals on tanks) to limit volatile organic compounds (VOCs), then imagine the effects of hydroblasting on these assets.

Until recently, hydroblasting was the only effective technology for cleaning heat exchangers and process equipment. However, by performing cleaning operations in a circulation loop, online cleaning eliminates all the problems associated with hydroblasting. Moreover, sludge is converted to a fully reusable/reprocessable product and the washing fluids are compatible with the hydrocarbon processing industry/combustion process. As a result, the equipment can be put on-stream immediately after cleaning.

Another problem encountered during turnaround is the duration of steam-out operations and their associated environmental problems, which directly impact equipment downtime.

Current operations
Mechanical cleaning is currently performed only where there is a stringent need for it. This suggests that equipment is being allowed to degrade to the minimum acceptable performance before cleaning. This situation arises from a number of peculiarities in the hydrocarbon processing industry.