No.1 CASESTUDY
Coalescer Decon TESTIMONIAL " This result far exceeded our expectations based on previous attempts to clean and de-sludge this Coalescer " Operations Co-ordinator
NELSON PLATFORM
OVERVIEW The coalescer on the Nelson platform was suffering from instrumentation issues making the level determination within the vessel extremely inaccurate thus severely limiting performance. This was attributed to a build up of sludge and sand within the vessel. After numerous failed attempts with other companies and chemical compositions, Shell took the decision to ask Denholm MacNamee to carry out a boil out decontamination of the vessel with the objective of restoring the vessel instrumentation to its proper operating levels. The Vessel was not due to be opened after treatment and success was to be judged on improved telemetry. PROCESS
RESULT Based on previous attempts to de- sludge the vessel, operations personnel anticipated approximately 4-5 tons of debris would be removed. In reality, approximately 17 tons of debris was removed from the coalescer. Client personnel were astounded by this performance. They had provisionally planned to implement a second boil out procedure to try and ensure the required result but it was evident that this would not be required on reinstatement of the coalescer to service the telemetry performance was fully restored.
A boil out decontamination procedure was implemented using an aqueous Zyme-Flow® UN657 solution. The chemical is an aqueous formulation, a very low hazard product, and has all the necessary CEFAS certification for use offshore in the North Sea. The boil out was completed over an 18 hour processing duration including the heating of 70m3 of water. On completion, the vessel contents were drained into holding skips for settlement and disposal of residual solids.
enquiries@denholm-macnamee.com Tel: + 44 (0) 1467 629 933
Vessel Decon TESTIMONIAL " We were pleased with the decontamination results and the time savings we were able to achieve during this phase of the TAR. We will certainly look to use this process in future TAR events on the CNOCC assets in the North Sea " TAR Co-ordinator
No.2 CASESTUDY
BUZZARD PLATFORM
OVERVIEW This was the first TAR to be implemented where the decontamination process utilised steam and Zyme-Flow® UN657 to achieve vessel decontamination. The scope of work included Production Separator, 2nd Stage Separator, Degasser, Oil Metering Skid and Flare Drums. CHALLENGES The TAR was planned to be completed within a tight timeframe and expectations were that the Zyme-Flow® process would give significant reduction in time taken to free vessels for entry. As this was the first Zymeflow had been used in a TAR scenario the decontamination operation was subject to close scrutiny with the expected vessel decontamination time for 18 hours per vessel being particularly subject to close monitoring. As the platform did not have its own steam supply it was necessary to utilise Zone II rated hire steam generators.
PAST PROCEDURE In previous plant outages decontamination was achieved by a flushing and N2 purging process. Residual solids had to be brought outside the vessels for washing in order to remove remaining oil before disposal. The time taken for purging and solids washing was considerable and was difficult to quantify at the planning stage thus making overall TAR planning and implementation extremely challenging.
DECON SOLUTION It was agreed that DML would apply a Boil Out process for the large horizontal vessels (separators, drums) and a Vapour Phase of the Oil Metering Skid. Zyme-Flow® UN657 was the chemical used since it had CEFAS certification for use in North Sea. As the TAR scope of work was spread over 3 legs of the platform it was necessary to supply 3 steam boilers in order to complete the TAR within the expected time frame.
RESULTS The decontamination was carried out with all vessels being decontaminated to the required standard with no accidents, incidents or near misses. Decontamination results were acceptable within the 12-hour processing period on all vessels. The residual solids in the vessels were de-oiled and conditioned by the process thus facilitating the speed of removal from the vessels and also their disposal.
enquiries@denholm-macnamee.com Tel: + 44 (0) 1467 629 933
No.3 CASESTUDY
Separator TESTIMONIAL " Denholm did a fantastic job on that separator, beleive me. We are all delighted with the outcome " Shutdown Co- ordinator
SCOTT PLATFORM
OVERVIEW The project was the decontamination using Zyme-Flow® UN657, of the V0106 Telford Separator on the CNOCC, Scott platform in the North Sea UK Sector. CHALLENGES Previous cleans of the vessel had shown the main issues to be high solids & sludge and high LEL. A secondary consideration was the need for a small equipment footprint and low manning levels as bed space is at a premium in offshore installations. Also, chemicals used needed to meet safety and environmental requirements. PAST PROCEDURE Previous decontaminations employed N2 purging as a means of removing LEL and H2S. This has given inconsistent results and has proved difficult and time consuming to remove the contaminants. It was also almost impossible to accurately estimate the duration Denholm carried out a site survey to determine the best method of achieving decontamination and advised a boil out procedure. The Method Statement was subsequently written to allow maximum flexibility and alternatives should this be required during processing. of the purging process. DECON SOLUTION enquiries@denholm-macnamee.com Tel: + 44 (0) 1467 629 933
RESULTS The client was pleased that the boil-out process had clearly proven the chemical capability and the level of success that can be attained. The % LEL in the vessel before decontamination was fully addressed and all internal surfaces were very clean upon manned entry without the need for N2. The process was completed in 12 hours with an additional 6 hour heating up time. Residual solids were de-oiled and their removal was significantly quicker and easier than with previous cleans. The project was completed within the decon window allocated without accident, injury or near miss. The client TAR Manager was very pleased with the decontamination performance and indicated that the completion of the overall TAR within the scheduled time frame was signiificantly helped by the efficiency and success of the Zyme- Flow® decontamination which gave rapid access to the vessels for inspection and maintenance. Due to the vessel sparge line being inoperative steam was injected at various points along the base of the vessel to try and achieve steam distribution along the full length of the separator thereby providing agitation of the sludge within the separator.
Crude Exchanger TESTIMONIAL " This process has been proved to be successful and gave reduced cleaning time and minimum mechanical intervention. There is no doubt it cut down our time compared to traditional bundle pulling and jetting " Area Manager
No.4 CASESTUDY
GRANGEMOUTH REFINERY
OVERVIEW Denholm were tasked with improving the efficiency of the crude unit pre-heat exchangers between major turnarounds without pulling the tube bundles for jetting in order to maintain satisfactory operating performance. CHALLENGES Problems were regularly experienced with exchanger fouling which severely reduced performance and significantly reduced throughput. This caused unplanned outages while exchanger bundles were pulled, jetted and reinstated. Site were keen to establish a procedure for restoring exchanger performance which was quick and effective and negated the need to pull the tube bundles. PAST PROCEDURE Previous attempts at improving performance by flushing and purging showed only temporary marginal improvements. In the absence of any viable alternative operation area engineers and managers decided that bundle pulling and jetting was the best option despite the lengthy downtime that this involved, and this was the accepted method of exchanger performance improvement in between planned outages.
DECON SOLUTION In order to alleviate the exchanger performance issue Denholm proposed to steam through the exchangers shell and tube sides from top to bottom whilst injecting Zyme-Flow® UN657 at a controlled rate for 6 hours. Steam from the process was vented via the bottom drain points on both sides of the exchangers into hydrocarbon skips for disposal. On completion of steaming the exchangers were drained, purged to remove any residual aqueous condensate then returned to service. RESULTS It was established that once the heat exchangers were returned to service the performance was greatly improved and this enabled the crude unit to return to normal throughput. The increase was maintained over several months thus giving significant time and cost savings over bundle pulling and jetting. This procedure achieved the desired aim of restoring heat exchanger performance with minimal downtime.
SEE TRUE PERFORMANCE RESULT BELOW FROM CLIENT
enquiries@denholm-macnamee.com Tel: + 44 (0) 1467 629 933
No.5 CASESTUDY
Desalters TESTIMONIAL " This is a much better process and is the way forward for future TAR's " Crude Unit Area Specialist
GRANGEMOUTH REFINERY
DECON SOLUTION Denholm recommended a Boil Out procedure using Zyme-Flow® UN657 at 1.5% and Rezyd-X® Z67 at 0.5%. Duration of the process was 12 hours and after 6 hours a reduced Vapour Phase was implemented across the vapour space of the vessels to drive any light end hydrocarbons and H2S to the flare. Once the test results indicated that contaminant levels were acceptable, the desalters were isolated from the flare and vented to atmosphere. On completion of the boil out the desalters were allowed to cool to 60c. Free oil was drawn off to the slops system and the aqueous phase was pumped out into a temporary tank for subsequent disposal. RESULTS Each desalter decontamination was completed within a 24-hour timeframe, including rigging, heat up and processing. On completion of the decontamination, LEL and H2S were zero. Residual solids volume remaining was significantly lower than in previous TAR's and residual solids were essentially oil free and conditioned such that their removal was greatly facilitated. Significant time savings were achieved over previous cleans. The minimal equipment footprint for the decontamination enabled other work to continue unrestricted by the process. CLIENT COMMENTS The client was pleased that the desalter decontamination was completed in a much reduced time frame compared to previous TAR's and also that the results were much better. The residual solids were less than on previous occasions and essentially oil free making their removal and disposal a much quicker operation. Effluent volumes were massively reduced and the aqueous effluent was suitable for discharge to site effluent treatment plant.
OVERVIEW This case study is for the decontamination of 3 off Desalters during the Crude Unit 2019 TAR at a UK oil refinery. The full scope of work also included Crude units 1&2, Hydrotreater unit, Hydrocracker unit Vacuum unit and the Treatments and Sulphur units. CHALLENGES The refinery TAR team were striving to reduce the overall TAR duration and the desalter cleaning was a major factor as, in previous TAR's, this process took a week or more to complete and previous results were only average. The challenge was to improve upon the decontamination performance whilst reducing the duration of the decontamination process and minimising the equipment and manpower footprint. PAST PROCEDURE Previously, decontamination had been by circulation of a hot (80C) aqueous chemical solution for 24 hours. This required the temporary installation of some significant equipment such as circulation pumps, heat exchangers and several temporary storage tanks of 70m3 capacity, all of which was connected using 6" hard piping. Rigging/de-rigging, heat up, circulation and draining result in a duration of several days to complete the decontamination. The large equipment footprint meant that other operations in the vicinity of the desalters were impeded thus impacting adversely on the overall TAR duration. Overall quality of the clean was variable and not completely successful.
enquiries@denholm-macnamee.com Tel: + 44 (0) 1467 629 933
Refinery Columns & Vessels - FCCU, CDU, DHT Treatments & Flare Units
No.6 CASESTUDY
TESTIMONIAL " These were some of the cleanest columns seen after decontamination " Shutdown Manager
GRANGEMOUTH REFINERY
OVERVIEW The project was to decontaminate the columns and vessels on the FCCU, CDU, DHT, Treatments and Flare Units during the client 2016 TAR to make them ready for entry and inspection. CHALLENGES The refinery TAR team were under pressure to meet a challenging planned TAR duration and several of the columns & vessels included in the decontamination were considered critical path items. It was imperative that the decontamination processes were completed efficiently, safely and successfully within the allotted time frame and budgeted cost. PAST PROCEDURE Previous FCCU Tar's utilised a combination of steaming, flushing, liquid circulation and nitrogen purging to remove contaminants prior to opening columns and vessels for entry and inspection. This had proved to be time consuming and difficult to predict the duration of these operations making TAR planning a more difficult tasks. It was therefore decided that, as a result of previous success of the Zyme-Flow® products and processes, the decontamination of the units would be best achieved by implementing these processes during this TAR event.
DECON SOLUTION The most efficient means of achieving decontamination was to treat the production units as systems rather than individual vessels where ever possible and a combination of boil out and Vapour Phase processes were employed to achieve this end. Zyme-Flow® UN657 was used as the decontamination chemical. Actual processing time was a maximum of 12 hours per system/vessel, with possible reduction in processing times as indicated by test results obtained by Denholm process monitoring. RESULTS Despite some delays by the client in releasing plant for decontamination and an issue with steam supply which resulted from the client steam supply line suffering a failure the TAR decontamination was completed on time and within budget. The time lost by the delays mentioned was recovered by being able to reduce the processing time on other systems and by taking a flexible approach to the planned decontamination schedule. Actual decontamination processing times were all within the expected 12-hour period with H2S, LEL and Benzene levels being reduced to acceptable levels and no problems experienced due to pyrophoric iron sulphide. CLIENT COMMENTS Client personnel were extremely pleased by this performance as it had out-performed other previous chemical and physical treatments with had not achieved the same levels of success.
enquiries@denholm-macnamee.com Tel: + 44 (0) 1467 629 933
GasPlant Decon TESTIMONIAL " There is no doubt it cut down on our time compared to traditional water flushing and nitrogen purging from isolation to vessels being ready for entry " Shutdown Manager
No.7 CASESTUDY
SHETLAND GAS PLANT
OVERVIEW This was the first TAR carried out at the Gas Plant since its commissioning in 2016. There was no previous history of TAR performance and site had concerns regarding the levels of fouling and contamination. Expected timings and duration targets were therefore determined based on experience of other similar projects. The decontamination scope of work included MEG Filtrate Vessel & Pre-treatment Filtrate Vessel, Liquid Coalescer and Coalescer Inlet KO Drum, Produced Water Flash Drum and the Closed Drains Drum. CHALLENGES As this was the first TAR at this site, the client had no previous history information to indicate the likely levels of contamination and fouling. The planned TAR duration presented a challenge and it was important to have plant items released quickly for inspection and maintenance to maintain TAR target scheduling. PAST PROCEDURE There was no previous experience at this site for the client to draw on in planning and implementing this TAR since it was the first TAR outage at site. DECON SOLUTION A combination of Vapour Phase and Boil Out processes were applied, with vessels on the MEG unit having a Vapour Phase application of Zyme- Flow® UN657 and all other vessels decontaminated using a Boil Out process. All vessels were drained and prepared by Client Operations personnel then permits issued to Denholm for rigging of decontamination equipment. Zymeflow processing permits were then issued and decontamination commenced. enquiries@denholm-macnamee.com Tel: + 44 (0) 1467 629 933
RESULTS All vessels were decontaminated within the 12- hour time frame (apart from Closed Drain Drum which was interupted by loss of water supply to site) with H2S and LEL levels reduce to Zero and no issues with pyrophoric iron sulphide. The closed drain drum process had to be amended but once this decision was taken the drum decontamination was quickly achieved. The sludge removal from the vessels was achieved much more quickly than expected as the decontamination process also conditioned and reduced the volume of residual solids. All vessels were successfully completed within the 12-hour decontamination window apart from the Closed Drain Drum. This was due to loss of water supply to the whole site half way through the decontamination process which meant that the boilers tripped out on low water and subsequent cooling of the vessel resulted in draw back of contaminants from the flare. A nitrogen purge was applied to prevent further ingress from the flare and analysis indicated that the contaminants were present in the Vapour space of the vessel and were being removed by the Nitrogen purge. It was therefore decided, after discussion between Denholm and the client, that continued purging would be successful in quickly removing the contaminants that had been liberated from the sludge in the vessel base rather than re- commissioning the boiler. Purging continued and H2S and LEL levels quickly dropped to within acceptable limits.
No.8 CASESTUDY
OVERVIEW This case study was for the cleaning of a crude oil surge tank and also for decontamination of a Tilting Plate Separator using Zyme-Flow® UN657 in both processes. CHALLENGES This was the first time Zyme-Flow® was used on site and it was thus regarded as a trial. Client concerns were a level of sludge/solids to a depth of 1m in the tank and the separator was also expected to contain a significant volume of sludge. NORM was also expected in both the tank and the separator. The client was seeking to improve performance and to reduce time taken over previous methods. PAST PROCEDURE Previous cleans were implemented using physical/ mechanical sludge removal after completion of a flushing procedure. This method was time consuming and gave variable results. DECON SOLUTION The Tank was cleaned using a two-stage process with circulation of Zyme-Flow® in diesel oil for 12 hours at ambient temperature, followed by circulation of an aqueous Zyme-Flow® solution for a further 12 hours, again at ambient temperature. Circulation was accomplished using a rotating spray nozzle inserted in a roof hatch with circulating pump suction taken from a low point outlet at base of the tank. This process enabled treatment of the sludge within the tank whilst also washing down the tank roof side and other internal surface. The tilting plate separator was decontaminated using a standard Vapour Phase process with steam injected into each of the four sections of the separator and Zyme-Flow® dosed immediately before splitting the steam supply into each of the sections. enquiries@denholm-macnamee.com Tel: + 44 (0) 1467 629 933 Tank& Vessel Decon TESTIMONIAL " Given the success of the project RSR are leaning towards the use of the Zyme-Flow system for other projects " Maintanance Manager
FLOTTAOIL TERMINAL
RESULTS The Tank and separator were both completed within the anticipated time frame. On opening the tank hatches site personnel took photos which are shown below and the client was extremely pleased with the result of the cleans. There were no solids remaining and no traces of NORM contamination remaining within the tank. The tilting plate separator was opened and found to be clear of H2S, LEL and oil. It was apparent on opening the vessel that the plastic filters within the vessel had collapsed at some point during the service life of the separator and these were found to be piled up at the bottom of the vessel. This had resulted in some sludge being trapped. Client personnel considered that this was an unforeseen problem and in no way reflected on the performance of the decontamination. On removal of the plastic debris the remaining sludge was easily and quickly hosed out of the separator. All other internal surfaces of the separator were found to be cleaned and decontaminated. CLIENT COMMENTS Denholm reduced the time that would have been spent on vessel entry & clean out, no hydrocarbon vapours or NORM was found reducing risk of entry. They dissolved the hydrocarbons and wax so reducing the waste by a considerable amount. The Terminal Superintendent and Manager has requested them to come back on site to survey 2 vessels for the Zyme-Flow® operation after the excellent result that was achieved during the cleanout of C321& D313. Processing was maintained for a period of 8 hours after which time the test results indicated that the vessel was free of H2S & LEL. The vessel was allowed to cool overnight before opening for inspection.
OVERVIEW This case study covers the chemical decontamination of the bottoms circuit of the VDU charge system. This included the base of the Vacuum column and pre-heat feed train exchangers. This work was carried out during the 2019 TAR. CHALLENGES To help reduce the duration of the TAR it w as decided to implement a trial clean of the bottoms circuit of the vacuum unit by circulation of Rezyd- HP G71™ solution in gas oil with the intention of removing fouling thus making it unnecessary to pull the exchanger tube bundles for mechanical cleaning. This would potentially save several days over conventional methods. The vacuum unit was a critical path item in the TAR schedule. The success would be determined by the performance once the unit was recommissioned. PAST PROCEDURE Previously, the bottoms circuit had been flushed with hot gas oil as the system was brought off line and the exchanger tube bundles were pulled, taken to the wash bay to be jetted clean, then re-installed. This was a time-consuming process taking several days to complete and an alternative, shorter duration cleaning solution was desired. The decontamination of the base of the Vacuum column was included in the overall column treatment but this did not fully address the removal of heavier deposits from the base. VacUnit Bottom Circuit TESTIMONIAL " Once the Vacuum Unit was in full operation the plant ran well and it was clear that the Rezyd HP circulation was a success. We are pleased with the results " Area Specialist
No.9 CASESTUDY
GRANGEMOUTH REFINERY
DECON SOLUTION It was agreed with site to conduct a trial procedure by circulating a 2% solution of Rezyd HP G71™ in gas oil at 200-220°C for a period of 18 hours, after which a short flush out with fresh oil would be implemented. During the circulation, evaluations of the circulating liquid was carried out by client to assess any appearance and viscosity changes and strainers on the circuit were monitored to ensure that no blockages or restrictions occured. The bottoms circuit was then left intact and the main column was decontaminated using a standard Zyme-Flow® UN657 Vapour Phase process followed by a Zyme-Ox® Z50 cascade flush of the column beds to neutralise any residual pyrophoric iron sulphides. RESULTS Initially, issues heating up the process stream meant that it took 14 hours to attain a temperature of 185°C and site informed us that it may not be possible to raise the temperature much higher. Rezyd-HP™ had already been dosed and circulated throughout the system during this heat up period and so a decision was taken to continue circulation and maintain this temperature for a further 12 hours to complete the process. Samples taken by site for evaluation showed the solution to be darker and more viscous than in previous gas oil flushes although this was the only means of assessing the cleaning performance. On completion of the circulation and flush of the bottoms circuit a standard Vapour Phase was carried out on the column and at the end of the 12-hour process test results showed H2S and LEL to be zero. A 1% Zyme-Ox® Z50 cascade flush was then performed and on opening the column there were no issues with H2S, LEL or pyrophoric iron sulphides.
enquiries@denholm-macnamee.com Tel: + 44 (0) 1467 629 933
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