Revamps 2024 Issue

2024 revamps ptq

VANE-PACK RETROFITS

VACUUM HEATER UPGRADES SAFE TURNAROUNDS

TROUBLESHOOTING COLUMN FLOODING

PTQ SUPPLEMENT

HONEYWELL UOP IS CURRENTLY SURPASSING ALL TECHNOLOGY PROVIDERS IN THE VOLUME OF CO ₂ CAPTURE CAPACITY INSTALLED PER ANNUM. *

*Source: Guidehouse Insights

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3 Retrofitting vane pack separator for improved column performance Case history of a syngas production unit, which experienced high methanol content in the tail gas of the scrubber when operated at 116% of original design loads Han Yongchun, Wu Zhijiang and Ang Chew Peng Sulzer Sulzer 9 Improving preventive maintenance using equipment criticality Case study demonstrates the importance of rating equipment criticality in an effective preventive maintenance plan while reducing overall cost E. Charles Maier Becht 15 Diagnosing a premature flood in an atmospheric crude tower Diagnosing and rectifying the flooding in a crude tower emphasises the importance of conducting plant tests, as well as gamma scanning investigations and analyses Daniel Hussman, Gord Bruce, Abdullah Abufara Komi Chandi and Joshua Donohue Parkland Refining (BC) Ltd Henry Z Kister Fluor 25 Optimising cartridge tray installation Methodology for tackling site challenges and improving HSE and quality in cartridge tray installations while reducing the overall installation cost Urmilesh Tiwari Engineers India Limited 31 Vacuum heater operational cycle improvement study Coke formation creates short vacuum heater runs. Controlling film temperature and oil residence can help reduce coke formation rate inside radiant tubes Haytham Al-Barrak, Abdulaziz Mubarak and Mahendran Sella Saudi Aramco 36 From waste to clean energy: The acid path to reducing CO₂ emissions Case study explores environmental benefits of the WSA process to capture waste heat, enhance energy efficiency, and reduce the refinery carbon footprint in comparison to the Claus sulphur recovery process Igor Yu Kostromin Topsoe Cover The new polypropylene and linear low-density polyethylene process units represent an investment of more than 657 million euros. When fully operational, they will make the Repsol Sines Industrial Complex one of the most advanced in Europe due to their flexibility. Photo courtesy of Repsol.

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Retrofitting vane pack separator for improved column performance

Case history of a syngas production unit, which experienced high methanol content in the tail gas of the scrubber when operated at 116% of original design loads

Han Yongchun, Wu Zhijiang and Ang Chew Peng Sulzer

I n the production of syngas, methanol is often used for the absorption of acid gases, such as CO₂ and H₂S, as it is critical to minimise methanol content in the tail gas due to environmental regulations. The process typically involves a scrubber where wash water is used to reduce methanol content. Upgrading the existing vane pack separator in the reabsorber, upstream of the scrubber, brings about a signif- icant reduction in methanol content in the tail gas, meeting the client requirement of less than 35 ppm. Process flow and column internals In the syngas production unit of a coal chemical plant in East Asia, the tail gas exiting the reabsorber consists mainly of CO₂ with some nitrogen and a trace amount of methanol. This tail gas goes through a heat exchanger before enter- ing the bottom of the scrubber, where the gas is contacted with wash water to absorb the residual methanol, as per the simplified process flow in Figure 1 . High methanol content in the tail gas exiting the top of reabsorber C1 will affect the methanol content in the tail gas exiting the top of scrubber C2. The wash water feed rate in the scrubber is a process variable to adjust the methanol concentration in the tail gas. The only measurement of methanol concentration in the tail gas exiting reabsorber C1 is after heat exchanger E1. From operational experience, it is observed that the meth- anol concentration in the tail gas after heat exchanger E1,

before entry to scrubber C2, must be less than 350 ppm to achieve a methanol concentration of less than 35 ppm in the tail gas from the top of the scrubber. With the columns operating at 116% of original design loads, the methanol concentration in the tail gas after heat exchanger E1 outlet was high (around 900-1,400 ppm). Even with more wash water in scrubber C2, the metha- nol concentration in the tail gas from the scrubber could not be reduced to less than 35 ppm. Attempts to optimise the operating temperature and pressure of the reabsorber, in addition to the adjustment of the wash water flow rate in scrubber C2, did not bring about significant process improvements. Reabsorber C1 was equipped with 73 trays in the col- umn and a gas/liquid separator at the gas outlet. A hydraulic evaluation of the existing column internals was performed, and the results revealed that the existing trays are adequate to handle the higher loads. However, the existing gas/liquid separator, which was a vane pack, was operating beyond the overdesign margin. A conventional vane pack was specified in the original design. In general, vane packs can capture liquid droplets in the range of 10-20 um and are widely used in petrochemi- cal and gas treatment industries. Compared to knitted mesh mist eliminators, vane packs have the following unique advantages: • Higher gas handling capacity, typically 1.5 to 3 times of mesh pads • Flexible arrangement: it can be installed vertically or horizontally

Tail gas Methanol < 35ppm

Heat exchanger

Original design case and actual operation

Wash water

Vane pack before revamp

Original

Actual

design case

operation (2022)

Tray deck 73# 72# 71# 70#

Mass flows to reabsorber C1

Vapour flow Liquid flow

100% 100% 100% 100%

116% 116% 116% 134%

Hydraulic evaluation

Actual gas velocity

Pressure drop

across the vane pack

C1 Reabsorber

C2 Scrubber

Figure 1 Simplified process flow of tail gas

Table 1

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Vane pack separator

31.926 27.365 22.804 18.243 13.682

Draw o

Gas outlet

Flash feed pipe

9.122 4.561 0 Velocity (m/s)

Tray

Figure 2 Vane pack arrangement in reabsorber C1

• Big vane spacing against plugging • Robust design.

Figure 3 Vapour flow trajectory

As the existing vane pack was inadequate for the new loads, the proposed solution was to retrofit the gas/liquid separator to reduce the methanol concentration in the tail gas from reabsorber C1 to meet the methanol emission cri- teria of less than 35 ppm in the tail gas from scrubber C2. Detailed evaluation of existing vane pack The plant owner requested an evaluation of the existing vane pack’s adequacy. To analyse the actual column perfor- mance, Sulzer collected operating data, including the tail gas analysis with methanol concentration. Table 1 summarises the hydraulic evaluation of Mellachevron H51Z in the design case and actual operation case. Note that Mellachevron ‘MCV’ is the trademark for Sulzer’s vane pack. The actual operating capacity was 116% of the design case, while the existing vane pack was designed with a maximum turn-up of 110%. As the operating loads were beyond the maximum design range, there was a chance of potential liquid droplet entrainment at the vane pack considering: • Gas velocity was exceeding maximum design velocity. • The complex vapour trajectory into the vane pack located at the column side wall due to lack of space. • The presence of the inlet pipe and the flash box, which were affecting the vapour flow trajectory. All these issues caused an increase in liquid droplet entrainment in the vane pack outlet, resulting in an increase in methanol content in the tail gas exiting reabsorber C1. In the design of vane packs, both vapour flow trajectory and vapour velocity are important to performance. Poor vapour distribution into the vane packs leads to vapour velocity being higher or lower than design guidelines. If the vapour velocity is too high, re-entrainment will happen. If the vapour velocity is too low, the inertial force will be insuf- ficient, resulting in an increase in droplet cut-off size. The MCV H51Z in reabsorber C1, with layout as seen in Figure 2 , was located at the side wall of the column due to lack of space. The housing stretches 900mm into the col- umn of diameter 3,800mm, affecting the vapour flow below the housing. The layout of the housing and column internals (tray deck, draw-off, and flash box) is not symmetrical, which may cause poor vapour distribution into the vane packs. A computational fluid dynamic (CFD) simulation was per - formed to simulate the fluid flow parameters, including gas

distribution quality, gas flow trajectory, gas velocity, and pressure drop at the vane pack entry. Figure 3 shows the complex vapour flow trajectory, while Figure 4 shows the gas load factor at the vane pack entry. The gas load factor ' l ’, also called the K-factor, is used to indicate vapour veloc- ity. K-factor is influenced by many parameters, including separator internal type, operation pressure, vapour, and liq- uid physical properties. As observed in the CFD, the vapour flow distribution at the vane pack entry is non-ideal and would lead to excessive entrainment, as follows: • The inlet pipe and the flash box not only obstruct the vapour flow but also re-entrain extra liquid droplets. • The vapour rising from the tray below, at the opposite end of the vane pack, will reach the top of the column and then be routed back to the vane pack entry, generating vapour stream circulation during the process, as shown in Figure 3. • Complex vapour flow patterns with multidirectional veloc - ity vectors, influencing the MCV capture of liquid droplets and liquid drain. • Obvious red zones of high velocity at the bottom of the vane pack, potentially leading to excessive entrainment. Revamp solution The main motivation of the revamp is to reduce the meth- anol concentration in the tail gas from scrubber C2 to less than 35 ppm, achieved through lower methanol content from the overhead of reabsorber C1. To achieve this strin- gent requirement, it was observed that the methanol con- centration after heat exchanger E1 must be less than 350 ppm. The revamp targets are as follows: • Capacity at 116% of original design. • Methanol concentration after heat exchanger E1 less than 350 ppm. CFD studies have shown that the vapour flow distribu - tion into the vane pack is not ideal. However, changing the location of the vane pack may not be feasible without loss of trays below it and extensive modification work at the site, which may lengthen the installation time. Hence, Sulzer proposed a retrofit solution with the vane pack in its current location, considering two key areas of focus to ensure good gas/liquid separation performance. • No hot works on column shell. • Turnaround within four days.

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0.292 0.250 0.208 0.167 0.125 0.083 0.042 0 Gas load factor at MCV inlet (m/s)

Figure 4 Gas load factor at MCV entry

The first is the selection of a vane pack type that can meet the required capacity while maintaining at least the same separation efficiency as the existing separator. The second is the improvement of the vapour distribution at the entry of the vane pack for better separation efficiency, and discussed in more detail as follows:  Selection of the right vane pack: Sulzer selected MCV H45D, as seen in Figure 5 , which has a higher gas han - dling capacity of 25-40% compared to MCV H51Z, based on operating conditions. As per hydraulic evaluation, MCV H45D can handle the high vapour loads without requir - ing an increase in the size of the vane pack. If the existing separator was to be revamped with another conventional vane pack, 1-2 tray decks below the separator would have to be removed to create more space for a new vane pack with bigger net flow area. Removal of tray decks not only increases site modification and turnaround time but may also have an adverse effect on column performance. The use of high-performance MCV H45D does not require any trays to be removed; the housing of the existing MCV H51Z can also be reused. MCV H45D has an optimised vane blade profile, which minimises possible re-entrainment of liquid droplets. The drainpipes from the Mellachevron were also modified for better liquid drainage to enhance separation. v Improvement of vapour flow at separator entry: Vapour flow distribution at gas/liquid separator entry is one of the most important issues influencing separation efficiency. As it is often difficult to evaluate vapour flow distribution quality at vane pack entry, especially for a non-standard arrangement, a baffle plate is usually installed at the entry

Figure 5 Sulzer high-performance Mellachevron

to improve the vapour flow trajectory. For this retrofit, Sulzer installed a thin mesh pad in front of MCV H45D; this also works as a pre-conditioner, improving Mellachevron oper - ation turndown and separation efficiency with negligible pressure drop increase. The pre-conditioner work principle is presented in Figure 6 . Even though the new vane pack location is maintained with no trays below the vane pack removed, the selection of the right vane pack, which can handle the higher capacity while maintaining the separation efficiency, together with the use of the mesh pad as a pre-conditioner, can signifi - cantly improve the separation performance. Installation and revamp results In this revamp of Mellachevrons from the existing MCV H51Z to the high-performance MCV H45D, the existing housing and welding attachment for the vane pack could be reused, saving the cost and installation time for the retrofit. The existing 73 tray decks below the vane pack were also maintained. The retrofit was completed in four days, fulfill - ing the plant owner’s turnaround schedule. Reabsorber C1 with the new MCV H45D was tested at full load in 2023. The methanol concentration at the outlet of heat exchanger E1 was reduced to less than 350 ppm. As a result, the methanol concentration of the tail gas exiting scrubber C2 was able to meet the process requirement of less than 35 ppm, meeting the plant owner’s expectations. Table 2 summarises the column performance before and after the revamp.

Column performance before and after revamp

Before revamp (2022)

After revamp (2023)

Vane pack type

Sulzer MCV H51Z

Sulzer MCV H45D and mesh pre-conditioner

Flow rate to reabsorber C1, as compared to original design Maximum turn-up of Mellachevron Methanol concentration at heat exchanger E1 outlet, ppm

116% 110%

116% 130%

900-1,400

<350

Table 2

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content in the overhead, eventually resulting in less wash water used in the scrubber. Selection of a suitable vane pack for the new loadings and an understanding of the vapour flow distribution through CFD simulation are essential to the development of the retrofit solution. Great co-operation and communication between Sulzer and the plant owner were pivotal to this successful revamp, with the process require- ments met and turnaround completed within schedule. Mellachevron is the trademark for Sulzer’s vane pack and is abbreviated as MCV. References 1 Engineering Data Book , SI Version, Vol I and II, Section 1-26, 13th Edition – SI, Gas Processors Suppliers Association, 2012. Han Yong-Chun is Regional Product Manager for Separators at Sulzer Shanghai, responsible for gas/liquid and liquid/liquid separator technol- ogy and product development, supporting Chinese refining, hydrocar - bon and chemical processing industries. He holds a bachelor’s degree in chemical engineering from Dalian University of Technology. Wu Zhi-Jiang is Application Manager for Coal Chemicals and Air Separation at Sulzer Shanghai, responsible for the application and development of the mass transfer technologies in the coal chemicals and the air separation sectors in China. He holds a bachelor’s degree in chemical engineering from Changzhou University. Ang Chew Peng is Head of Global Product Management based in Sulzer Singapore. She leads a team of global product managers within the division Chemtech, responsible for the launch, marketing and knowledge management of Sulzer product portfolio, including packing, trays, separation and mixing technology. She holds a B.Eng. (Chemical) from the National University of Singapore.

Gas with ne mist

Mist free gas

Coalesced large droplets eciently removed by Mellachevron mist

KnitMesh as primary preconditioner operates beyond ooding point Coalesced large droplets fed to secondary Mellachevron mist eliminator

Separated liquid drains

Provisional gap, if required

Figure 6 Mesh pre-conditioner

Conclusion During the revamp study, it is important to evaluate the hydraulic capacity of the existing column internals to deter- mine the hydraulic bottleneck, as well as consider the opti- mal mechanical modification at the site to reduce cost and installation time. High-performance internals can offer high capacity and better separation efficiency, and when applied in revamps, they may require minimal modifications, leading to time and cost savings during the turnarounds. In this case story, the successful revamp of a reabsorber with a high-performance vane pack allows the column to operate at higher loading while reducing the methanol

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Improving preventive maintenance using equipment criticality

Case study demonstrates the importance of rating equipment criticality in an effective preventive maintenance plan while reducing overall cost

E. Charles Maier Becht

M aintenance has changed over time. It started as a reac- tive need to fix equipment when it broke. As equip - ment became more complex, repairs became more expensive. This drove the idea of ‘PM’ or maintenance that would enable equipment to last longer or fail less frequently. Preventive maintenance (PM) programmes expanded and the cost of the programmes grew as the focus was on improving their effectiveness. The focus on PM is now on maintaining its effectiveness while reducing the overall cost. Refinery maintenance is a complex process with many elements that interact with each other. For example, equip - ment reliability has a direct impact on maintenance cost. If equipment runs longer between failures, the total repair cost goes down. The run length can be a result of design, repair quality, and how the equipment is operated. Repair costs are impacted by the quality of repair plans, competence of the crafts executing the repair, and material availability. When analysing the elements that impact maintenance value, we can group them into three main categories: demand, which are the elements that result in the need for maintenance; efficiency, which are the elements that affect the efficiency of maintenance process; and support, which are the elements that support maintenance. Figure 1 shows the categories and examples of elements within each category. From benchmarking within the petrochemical industry, the contributions of the various drivers to maintenance value (measured by total cost) are: The demand driver has the largest contribution to main - tenance value. It is composed of elements that result in the need for maintenance. The quality of the PM programme is a key enabler for equipment reliability, which is a key ele - ment within the demand driver. The size of the programme has a direct correlation with maintenance value, and opti - mising it can greatly impact the demand driver. This is done through PM optimisation (PMO). PMO optimisation tools • Demand – approximately 60% • Support – approximately 20-30% • Efficiency – approximately 10-20%.

DEMAND

Items that result in the need for maintenance Examples include: Equipment reliability Operating limits Start - up procedures PM programme Maintenance strategy

EFFICIENCY

Items that aect the eciency of the maintenance process Examples include:

Planning/scheduling Productivity/tool time

Items that support maintenance Examples include:

Contractor labour Critical spares Organisational structure Warehouse

SUPPORT

Figure 1 Venn diagram explaining drivers of maintenance value

• Failure Reporting, Analysis and Corrective Action System (FRACAS). FMEA evaluates equipment at the component level, identi - fying failure modes for each component. The consequences of failure are quantified along with the probability of failure. Scenarios are considered for financial, health, safety, and envi - ronmental consequences. Mitigation strategies are developed to reduce risk to acceptable levels for each scenario. The miti - gation strategies are typically a combination of PM, predictive maintenance, and spare parts stocking strategies. A PM Library is a collection of PM by equipment type. It contains company or industry recommendations for PM. For a given piece of equipment, the recommended PM activity is adapted to local conditions (for example, climate or process) and implemented as the PM activity for that equipment. FRACAS was developed by the US Department of Defense and published in DOD MIL-STD-2155. It contains a three-step methodology. In step 1, the failure is reported, and initial data is gathered. In step 2, the failure is analysed

There are three main tools utilised for PMO: • Failure Mode and Effects Analysis (FMEA) • PM Library

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frequency. A sample risk matrix is shown in Figure 2 , where 5 is the highest frequency, and 5 is the highest consequence:  Step one of a PMO is the determination of equipment criticality, typically in a workshop format. The workshop can be made more efficient if some prework is conducted beforehand. This consists of a review of site data and pre-assignment of criticalities to selected equipment. Instrumentation equipment lends itself to pre-assignment as it can typically be categorised based on specific criticalities. For example, emergency shutdown systems can be designated as safety-critical. Safety-critical equipment refers to equipment that serves as a barrier to prevent, detect, control, mitigate, or recover from a major incident such as fire or explosion. Participants in the workshop should include: • Operations: Primary input for consequence of equipment failure. Secondary input for frequency of failure. • Engineering/reliability: Primary input for validation of pre- work assumptions, frequency of failure, and failure modes. • Crafts: Secondary input on equipment failure mode and frequency of failure. Once the equipment criticality is determined, some key checks should be done when reviewing the distribution of equipment on the risk matrix: • Safety-critical and business-critical equipment should be identified in the highest criticality on the risk matrix. • There should be a cluster of equipment considered very low criticality. • The distribution should be consistent with industry bench- marks on criticality. Based on benchmarking in the petro- chemical industry, a typical breakdown of equipment is:  Step two of a PMO is to use the equipment criticality to determine which tool to utilise for each criticality. FMEA considers the known failure modes for the equipment and results in the most comprehensive mitigation strategies for the equipment. Equipment with a high criticality should utilise this approach to determine the mitigation strategies. Examples of high-criticality equipment include equipment that is considered business-critical or safety-critical equipment. Non-essential equipment will be identified based on very low criticality. On the risk matrix, equipment failure scenarios appear as a low frequency and a low severity. A run-to-fail- ure (RTF) approach or a FRACAS approach can be used with this equipment. The PM Library can be developed quickly compared to conducting FMEA. Approaches for PM Library development include using corporate subject matter experts (SMEs) or independent third parties to develop maintenance activities and performing FMEA on generic equipment (see Figure 3 ).  Step three of a PMO is to use the recommended mitiga- tion strategies to modify the existing PM programme. The capabilities of a computerised maintenance management system (CMMS) are often not fully utilised due to a lack of ■ 10-15% of equipment is safety-critical. ■ 10-15% of equipment is business critical. ■ 30-60% of equipment is essential. ■ 20-30% of equipment is non-essential.

3 5 4 2 1

L L L L 1 L

M M

H M L L 3 M

H H

L L 2 L

M L 4 M

M M 5 H

Consequence

Figure 2 Example risk matrix

to identify the root cause of failure. In step 3, a corrective action is implemented and tracked. The FMEA approach is the most proactive of the three approaches and requires the most resources to implement. It considers all failure modes and results in the highest equip- ment availability. However, this approach does not account for the fact that considering all failure modes provides reduced benefits for lower criticality equipment. The bulk of the effort in the PM Library comes from estab- lishing the database of recommended PM. This can be done at a corporate level with only some effort at the site level to localise the activities. This approach reflects either corporate or industry-accepted practices. Without considering failure modes, the mitigation strategy can be too conservative as they occur more often than required for the risk or do not address a failure mode and are, therefore, unnecessary. It is also possible that a hidden defect is not addressed, as its failure mode was never considered. The FRACAS approach is the most reactive and the slow- est of the three as you wait for failures to occur before taking steps to mitigate future failures. PMO using equipment criticality Using only reliability-centred maintenance (RCM) or FMEA in a PMO implementation for all equipment has proven to be highly resource-intensive. Even streamlined approaches that only look at dominant failure modes have not proven to significantly reduce the resource effort. There is a need for an approach that reduces the resource effort while maintaining the overall benefit. The following approach uses equipment criticality to differentiate the specific approaches used for equipment. Equipment criticality is a consequence-based ranking pro- cess that considers the safety and business consequences of failure for individual equipment items. It is based on both the frequency and consequence of failure. If a piece of equip- ment in a low criticality process fails, it will have a lower consequence compared to an identical piece of equipment in higher criticality process. As an example, the interior lights in your car failing to operate has a lower potential consequence than your headlights or brake lights failing to operate. In a downstream refining environment, equipment down - time has varied consequences depending upon the product stream and configuration of the refinery. Therefore, it is rec - ommended that a risk matrix is utilised to determine equip- ment criticality. Risk is a combination of consequence and

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training or master data issues. Optimising the PM programme provides an opportunity to correct this gap. The design of the programme within the CMMS should be considered prior to making any changes to the existing programme. The FMEA studies will identify opportunities to move from time-based PM to condition-based PM. These opportunities should be included in the recommended mitigation strate- gies for equipment. A comparison of the existing PM tasks and frequencies with the recommendations from the FMEA studies, as well as the PM Library will identify the changes that should be made to the existing PM programme. Site resources are often unable to implement changes to the programme within the CMMS in a timely manner. For this reason, it is recommended to use corporate or third-party resources for CMMS implementation. Case study A refining company has multiple refineries, most of which are historically industry leaders in site availability. However, recent incidents raised the concern that the PM programme may not be providing adequate coverage. In addition, there was concern that the frequency and tasks within the existing programme were not aligned with industry practices. A quick analysis was performed using data from three different refin - eries to quantify the potential benefits of a PMO. The anal - ysis indicated a potential benefit of 10-20% in maintenance spend and 1-2% in availability improvement by aligning the tasks and frequencies with industry practice and ensuring that equipment was appropriately in the PM programme. Scope The refining company had an existing PM standard for its process safety management (PSM) equipment as defined by OSHA 1910.119(j). This included tasks and frequen - cies based on equipment type for rotating equipment, fixed equipment, instrumentation, and electrical equipment. It was decided to perform the PMO in a phased approach. The first phase consists of the rotating equipment, instru - mentation, and electrical equipment covered in the PSM PM programme – approximately 50% of the equipment at the refineries. Phase Two consists of the remaining equipment. This case study addresses the first phase of the programme. When looking at the approach of using FMEA for high-crit- icality equipment and the PM Library for medium- and low-criticality equipment, it was recognised that the FMEA approach had already been conducted on most of the high- criticality equipment, and little would be gained from reper- forming the FMEAs. It was, therefore, decided to use the PM Library approach for all equipment criticalities. Failure modes were not defined in the existing PM pro - gramme. Therefore, it was decided to document dominant failure modes within the programme so that the rationale for the PM activity was clear. Approach The existing criticality definitions at the refining company did not include a safety-critical definition. It was decided to add this definition and update all equipment criticalities within the scope and new definitions. A standard for equipment

3 5 4 2 1

High criticality FMEA

Medium criticality PM library

Low criticality PM library

Very low criticality FMEA

Consequence

Figure 3 Matching PMO tools to equipment criticality

criticality was developed with the new safety criticality defi - nition, while the equipment criticality workshop process and supporting tool were developed. An opportunity for improvement with the existing PM programme was to move to tasks and frequencies based on equipment criticality. A key objective was to get the widest range of input possible from others in the industry. Two PM Libraries were selected where tasks and frequencies varied based on equipment criticality. The PM Library approach was supplemented with a challenge session with industry SMEs. The SMEs provided a cross-section of the oil and gas industry’s major companies, which was broader than the two PM Libraries. The existing PM tasks and frequencies were compared to those contained within two different PM Libraries. The SMEs

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Update of existing programme

3 Site - level process (Phase 1)

Add safety - critical definition Create reliability risk index Develop tool for workshops

Gap between current PMs and updated PM tasks/ freq. from

Create criticality standard and process

Site validation of PM changes workshop

Site criticality validation workshop

Obtain site data

Assign 1st pass criticality

ID failure modes Add criticality level tasks Compare peer frequencies

Challenge session with industry SMEs

Site provides: PFD, LPOC, incident investigations, bad actors and previous criticality studies

Upload to SAP

Review with corporate SMEs

O - site resources Site resources

Follow-up and tracking of results

Agreement with site advisory groups

Updated PM tasks and frequencies for MI equipment

Figure 4 Organisation chart of the programme planned for minimising impact on site resources

were asked to comment on the results and indicate which were more consistent with their experiences. The SMEs were also asked to provide input if a task could be performed by a different method. An overall recommendation for changes based on the PM Libraries and SME comments was devel- oped for each equipment type and criticality. A major objec- tive of the programme was to minimise the impact on site resources (see Figure 4 ). To accomplish this, several key decisions were made: • Development of the criticality standard, process, and updates to the PM programme would be done at the corpo- rate level, with sign-off at the end by site advisory groups. • Site criticality workshop length would be minimised by performing a first-pass equipment criticality at the corporate level. • Existing site PM would be extracted and compared to the new standard with a recommendation provided by off-site resources. • Changes to site PM would be implemented by off-site resources. Conclusion A check performed when comparing the existing site PM programme with the PM standard was to ensure that all equipment defined as safety-critical had an appropriate PM

task. There were several cases where PM tasks were added for equipment now deemed safety-critical. Although it is too early to determine if there has been an impact on availability, a reduction in overall hours for PM was achieved at all sites. The results from the first four sites are shown in Table 1 .

Abbreviations BOM

Bill of materials

CMMS

Computerised maintenance management system

EOQ FAA

Economic order quantity

Federal aviation administration

FMEA Failure mode and effects analysis FRACAS Failure reporting, analysis, and corrective action system OEE Overall equipment effectiveness PM Preventive maintenance PMO PM optimisation PS&O Planning and scheduling optimisation RAM Reliability availability modelling RCA Root cause analysis RCM Reliability-centred maintenance SRCM Streamlined reliability-centred maintenance TPM Total productive maintenance 5S Sort, set in order, shine, standardise, and sustain (originally Seiri, Seiton, Seiso, Seiketsu and Shitsuke). References 1 Ford Motor Company, Ford Manual for Owners and Operators of Ford Cars and Trucks Detroit, Ford Motor Company, 1919. 2 History of Maintenance, Boeing Aeromagazine, QTR_04, 2006. 3 Moubray J, Reliability-centred Maintenance , ISBN 0-7506-3358-1, 1991. 4 Poor P, Zenisek D, Basl J, Historical Overview of Maintenance Management Strategies: Development from Breakdown Maintenance to Predictive Maintenance in Accordance with Four Industrial Revolutions, Proceedings of the International Conference on Industrial Engineering and Operations Management , 2019, pp.495-504. Charles Maier is the Global Maintenance Lead at Becht and resides in Charlotte, North Carolina. He has more than 30 years of experience in operations, maintenance and reliability, mainly leading improvement programmes at manufacturing sites. He holds a BS in marine engineer- ing and naval architecture from Webb Institute, Glen Cove, NY and an MS in engineering management from Southern Methodist University, Dallas, Texas. Email: cmaier@becht.com

Table 1 Reduction in overall hours for preventative mainte- nance was achieved at all four sites Note: Amount of PM hours vary based upon size of the site

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Mellapak™ – Often copied, never equaled

Mellapak™ is the most widely used structured packing worldwide introduced by Sulzer Chemtech in 1977.

The newest generation MellapakCC™, structured packing specifically developed for carbon capture, decreases operational costs through improved carbon dioxide capture, absorbing it more efficiently from flue gas streams of fossil-fueled power plants. Sulzer Chemtech’s MellapakCC™ significantly reduces the column size and the pressure drop across the carbon dioxide absorber, thus reducing capital and operational expenses and minimize the energy consumption. Carbon capture and storage or utilization (CCS/CCU) is a key strategy that businesses can adopt to reduce their CO 2 emissions. By selecting the right technologies, pressing climate change mitigation targets can be met while benefitting from new revenue streams. This packing is currently applied in several leading CCS/CCU facilities worldwide, delivering considerable process advantages. By partnering with Sulzer Chemtech – a mass transfer specialist with extensive experience in separation technology for carbon capture – tailored solutions that maximize return on investment (ROI) can be implemented. With highly effective CCS/ CCU facilities, decarbonization becomes an undertaking that can enhance sustainability and competitiveness at the same time.

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ITW Online Cleaning clean an entire Unit in as little as 24 hours on a feed - out/feed - in basis. ITW Onstream Cleaning clean an entire Unit during the run. Our proprietary chemistries dissolve and stabilize any asphaltenic/paraffinic/polymeric deposits, by transforming the same in to a fully reusable/reprocessable liquid. When applied to tank cleaning, our technologies effectively, safely and quickly recover oil from sludge, thereby eliminating wa ste generation and disposal. Pro - active application of our cleaning technologies reduces CO 2 , VOCs and greenhouse gas emissions, while reducing energy consumption thereby getting additional value by improved Operational Excellence. ITW proprietary technologies promote safe working, as they eliminate/reduce mechanical cleaning operations as well as working in confined spaces. Our Improved Degassing/Decontamination technology has unrivalled performance all in terms of contaminants elimination, quick safe entry achievement, waste disposal elimination and environmental compliance. Our patented chemistry does not create any emulsion and fluids can be easily handled by Waste Water Treatment Plant. Other proprietary technologies also include: Amine Unit Optimization, Sulphur Dissolution, Ethylene Furnace Run Length Increa se, Cleaning of Texas Towers/Packinox, Coke on catalyst Formation Reduction, Diesel/Fuel Oil Particulate and NOx Emission Reduction. ITW technologies can be applied to all the Oil & Gas Industry, including the Transportation and Energy Production industries. Sustainability improvement can be achieved by process optimization, without any major investment.

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Diagnosing a premature flood in an atmospheric crude tower

Diagnosing and rectifying the flooding in a crude tower emphasises the importance of conducting plant tests, as well as gamma scanning investigations and analyses

Daniel Hussman, Gord Bruce, Abdullah Abufara, Komi Chandi and Joshua Donohue Parkland Refining (BC) Henry Z Kister Fluor

T his investigation of a premature flood near the diesel draw of an atmospheric crude tower demonstrates the importance of conducting plant tests, judicial gamma scanning investigations and analyses, and closely checking theories against plant data and targeted tests to diagnose fractionator problems. In a 2020 turnaround, the planned mechanical work included replacing the wash section two-pass sieve trays 8-10 with in-kind, but the tray material was changed from 410 SS to carbon steel. Afterwards, the tower operated at high crude rates for 18 months without issues. In October 2021, there was a planned turnaround of an adjacent unit, during which the tower was drained, purged, and safe-parked. Upon return to service, the tower struggled to maintain high crude rates due to increased pressure drop across the bottom two-thirds of the tower. The pressure drop pro- gressively rose over the next seven months, forcing crude rate cuts of 5,000-6,000 BPD. At higher rates, the tower flooded, causing sudden loss of overflash and diesel draw (level in the side stripper). Gamma scans showed flood ini - tiating on tray 10, right above the diesel draw tray, propa- gating up the tower when the rates were raised. Several theories requiring different remedial actions were proposed. The theories were evaluated by thoroughly checking against plant tests and data, together with quan- titative analysis of the gamma scans. Based on this evalu- ation, the team concluded that entering the tower to clear foulants or repair damage or fouling was the best path forward. Upon entry, the active areas on trays 10 and 9 (diesel draw) were found heavily fouled, to the point where the sieve holes were invisible. The foulant thickness varied across the diameter of the column and could be easily removed with a metal scraper. The deposits were clay-like and sandy. The downcomers were relatively clean. Trays above and below this zone were found to be quite clean. Process description and problem definition Figure 1 is a schematic of the crude tower with typical rates and temperatures for the 18 months before the October 2021 outage. The tower differential pressure, measured between the flash zone and the vapour space above tray

24, was steady, typically 2.3-2.5 psi, or about 0.13 psi/ tray, a little on the high side, but within the range of normal operation. The crude rate was high (30,000 BPD), the die- sel pumparound rate was high (5,700 BPD), the diesel side stripper level was steady, and the overflash was steady at about 500 BPD. After the October 2021, turnaround the tower differential pressure (dP) became erratic and crude rates had to be lim- ited to 29,000 to prevent dP excursions. The diesel pump- around rate was reduced to about 4,500 BPD with a colder outlet temperature of about 225ºF. The vapour space between trays 8 and 9 has two temperature indicators that historically read the same. Following the October 2021 outage, the one on the north- east started reading 15ºF higher than the one on the south- west. Two other temperature indicators were in the vapour space between trays 6 and 7, they kept reading the same temperatures. Things took a turn for the worse following another out- age in December 2021. The dP became more erratic, often rising to about 3.5-4 psi. Liquid appeared to be accumu- lating above the diesel draw with a loss of diesel product, wash to the lower trays, and overflash. The high dP was often accompanied by some diesel ending in the jet draw from tray 16. The accumulation appeared sudden, erratic, and unpredictable. Drawing more diesel brought the dP down, but the overflash would not re-establish until the coil outlet temperature (normally about 650-655ºF) was lowered by about 5 ° F. The dependence of the flood on the coil outlet temperature suggests strong sensitivity to the vapour loading. The frequency and severity of the flooding above the die - sel draw tray increased at higher crude charge rates and high diesel pumparound flow rates. This forced the refin - ery to gradually cut charge rates, from 28,000 BPD after the December outage to 25,000 BPD just before the tower was shut down in July 2022. Diesel pumparound flow rates were further reduced to about 2,200 BPD. Troubleshooting and testing The active areas of the trays were gamma-scanned on January 25 (flooded) and January 26 (‘normal operation’). During both scans, the crude feed rate was 28,000 BPD,

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showed taller and denser froths than the NE side (blue pen). The NE sides of trays 6, 7, and possibly 9 looked dry, while the SW sides looked normal and not heavily loaded. The ‘normal operation’ scan showed flooding on tray 10 only. Trays 11 and higher were not heavily loaded, with little difference between the NE and SW chords. This veri- fies that the flooding was due to a restriction near tray 10. The taller and denser froths observed on the SW of trays 6-9 in the flooded scan persisted on tray 9 in the ‘normal operation’ scan but became much less pronounced on trays 6-8. Only tray 6 in the ‘normal operation’ scan NE side approached drying. In search for the condition at which the downcomers began to fill up, the centre downcomers of trays 6-15 were scanned (see Figure 3 ) two weeks following the active area scans. The crude feed rate was set at 28,400 BPD and the flash zone temperature at 651ºF, similar to those in the flooded active area scans. To unload the downcomers and keep them out of the flood, the diesel pumparound flow rate was lowered to 2,700 BPD compared to 3,800 BPD in the active area scans. For the ‘more loaded’ scan (blue pen), the pumparound return temperature was set the same as during the active area scans, 211ºF. For the ‘less loaded’ scan (red pen), this temperature was raised to 244ºF. The pressure drop at both tests was about 2.4 psi and stable. Figure 3 shows no flooding in the tower, as confirmed by the low dP. The active area above the tray 10 centre downcomer approached flood, but the active areas above the centre downcomers of trays 12 and 14 were not heavily loaded. This again verifies that the first active area to flood is that above tray 10. Figure 3 shows that the froth height in the downcomer from tray 10 in the more loaded scan was about double that in the less loaded scan and approached the top of the downcomer. The froth in the more loaded scan was also much denser than in the less loaded scan. In contrast, the loading difference had little effect on the froth heights and froth density in the tray 12 downcomer (which also serves the pumparound), and its froth did not approach the tray above. This strongly supports a restriction in the tray 10 downcomer, plugging on tray 10, or both. The tests established that the flood was both vapour-sen- sitive and liquid-sensitive. The vapour sensitivity was established by the observation that raising the flash zone temperature by as little as 5ºF while keeping the crude rate, pumparound rate, diesel draw rate, and pumparound return temperature constant, induced flood. The liquid sensitivity was established by a large increase in froth height and den- sity in the tray 10 downcomer, resulting from cooling the pumparound return and the experience that increasing the diesel pumparound rates can bring about flood while keep- ing other variables constant. These scans established that the tower bottleneck is a downcomer back-up flood initiating in the downcomer from tray 10 and then building up and flooding tray 10 and above. The scans also provided evidence for uneven drying up of some of the wash section trays when the liquid rate below tray 9 dropped off. The drying occurred preferen- tially on the NE.

Jet 452˚F

PA return 5700 BPD 308˚F

From diesel stripper

Diesel/PA 528˚F

8 7 6

Overash 500 BPD

Crude feed 30,000 BPD 6 6 5˚F

Steam

Resid

and the diesel pumparound flow rate was 3,800 BPD. The key parameter changed was the coil outlet temperature. In the flooded scan, the flash zone temperature was 653ºF, lowered to 646ºF to give the ‘normal operation’ scan. The pressure drop at the flooded scan ranged from 2.8 to 3.7 psi, compared to 2.3 psi and stable in the ‘normal operation’ scan. The flooded scans (see Figure 2 , blue and red pens) showed flooding propagating from tray 10 upwards to trays 17-19 (Figure 2 was cut off at tray 15, but the scans continued all the way up the tower). In the flooded region (tray 10 and up), the scans show little difference between the northeast (NE) and southwest (SW) chords. On the unflooded trays below (6 through 9), the SW side (red pen) Figure 1 Tower schematic with typical rates and tempera- tures before October 2021

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