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The failure of a critical heat exchanger can result in unplanned maintenance, increased costs and reduced throughput. Additionally, failures can jeopardize safety and environmental goals. Therefore, a comprehensive cooling water treatment program that includes not only chemistry but also a heat exchanger reliability program is critical for the smooth and efficient operation of refineries and petrochemical plants. The purpose of a reliability program is to improve heat transfer efficiency, asset reliability, plant economics, operational safety and environmental compliance.
Ensuring the efficiency and reliability of cooling water heat exchangers using a tailored cooling water treatment program combined with a robust reliability program can help mitigate the risk of a heat exchanger failure or unplanned downtime. To implement such a program successfully, follow these three steps.
- Identify and implement a tailored cooling water chemical treatment program: Implementing an appropriate cooling water treatment program for the site depends upon water quality and other key performance indicators. The treatment program creates the baseline conditions for cooling water flowing through the system and will improve the efficiency and longevity of the entire system, from the quality of the treated water to the life of the assets and the cost of operation.
- Identify critical heat exchangers: Determining which heat exchangers could cause unplanned downtime or pose safety or environmental risks if they were to fail is crucial.
- Monitor and maintain heat exchangers: When heat exchangers are monitored and well-maintained, the need for ancillary repairs or replacements is reduced. This approach allows for planned cleanings during turnarounds without requiring the examination of each individual exchanger, and proper maintenance can also extend an exchanger’s planned useful life.
Implementation of steps one and two alone will allow the refinery or petrochemical plant to operate more efficiently and reliably but perhaps not at maximum capacity. Incorporating a heat exchanger reliability program into the overall cooling water program will allow the refinery or petrochemical plant to reach optimal efficiency and reliability while realizing cost savings.
Water treatment suppliers should provide a treatment program tailored to the specific needs of the refinery or plant and be equipped to perform flow studies on exchangers. Often, local companies can assist with conducting flow studies; this data should be gathered and used to ensure operational efficiency and to plan turnaround cleanings.
Solenis, a leading global producer of specialty chemicals, has a product portfolio for cooling water treatment that includes the ClearPointSM biofilm detection and control program and the HexEval™ performance monitoring program. The ClearPoint program comprises three parts: the OnGuard™ 3B analyzer, proprietary chemistry and technical expertise. The analyzer employs an advanced ultrasonic probe to detect biofilm growth in water systems earlier than any other commercially available technology and thus allows for modeling and monitoring of real-time biofilm levels. Proprietary chemistry provides advanced biological control, often including a proprietary chlorine stabilizer chemistry that is used to produce a patented, in situ stabilized active chlorine solution. Solenis scientists and engineers provide the technical expertise to investigate problems, recommend and implement solutions, and deliver results. The HexEval program is an advanced tool for predicting the performance of critical heat exchangers that enables refinery or plant operators to identify which heat exchangers pose the greatest risk to reliable operation due to scale, corrosion or heat exchanger fouling. Using this knowledge, plant operators can develop an action plan to optimize efficiency.
Let’s explore some real-world examples of a cooling water treatment program combined with a robust heat exchanger reliability program in action.
Improving heat transfer and reducing operating costs
A refinery in the southeastern United States was experiencing inadequate cooling in its cooling water system. Several of its exchangers experienced a reduced cooling water flow rate, which limited throughput in the hydrobon unit. Additionally, the unit was experiencing high corrosion rates on its corrosion coupons. The refinery operators brought in a water treatment team of experts to audit the cooling water system, make appropriate recommendations, and provide a treatment program to improve the cooling water system’s reliability and performance.
During the audit, the team discovered that the cooling water system was experiencing high microbiological activity, and they suspected that biofilm had formed in the system. Biofilm can cause many issues that negatively influence a cooling water system, including mechanical blocking of piping, heat exchangers, and cooling towers with living or dead biomass; loss of heat transfer efficiency due to the buildup of an insulating layer (of biofilm); loss of cooling tower performance; microbially induced corrosion (MIC); mechanical destruction of cooling towers; and hygiene risks of releasing pathogenic organisms.
The ClearPoint program was initiated at the refinery to monitor and reduce real-time biofilm before it could build up and cause more harm to the cooling system (see Figure 1). In addition to implementing a cooling water treatment program, the team implemented the HexEval program to monitor and measure heat exchanger performance.
Improving cooling water and heat exchanger reliability
Figure 1: Biofilm growth decreased significantly with the start of the new ClearPoint program. Left: Existing treatment; Center: After one week of the new program; Right: After 10 days of the new program.
Soon after the implementation of the new chemical treatment and monitoring program, tests revealed that the program had reduced biofilm thickness to less than 10 microns. As a result of this improvement, only 25% of the heat exchangers needed to be cleaned during the next turnaround, thereby saving the refinery approximately $125,000 in cleaning costs and unplanned cleanings. In addition to these cost savings, the consistent monitoring of water quality and biofilm growth led to a five-year extension of the useful life of each cooling tower to which the ClearPoint program was applied, thereby saving the refinery approximately $60,000 annually. This system cleanup also resulted in a 27% increase in total flow through the cooling loop and a 49% increase in flow to one of the critical exchangers. Over a 40-day period, heat transfer increased by 95%. With these efficiency and production improvements, the refinery increased throughput, resulting in a $240,000 annual increase in production from the hydrobon unit. Additionally, at one point the OnGuard 3B analyzer measured a spike in organic thickness that alerted the refinery operators to a process leak in the hydrobon unit.
Improving heat exchanger reliability
A refinery on the Gulf Coast of the United States, which was producing more than 500,000 bpd, was using a traditional treatment program and experiencing an average of nine unplanned heat exchanger cleanings and five heat exchanger failures per year. In each instance, the refinery operators were unable to detect the main cause of the failure prior to opening and examining the exchangers.
In 2012, the refinery implemented the ClearPoint program for biofilm detection and control and the HexEval program to monitor the reliability of the heat exchangers in the cooling system. The HexEval program includes a comprehensive online heat exchanger database and proprietary algorithms to succinctly identify scale and biofouling risks.
Using the HexEval program, the refinery archived flow studies; exchanger design information; and events, such as cleanings, retubes, or metallurgy upgrades. Each heat exchanger was assigned a criticality rating based on potential risks to production, safety, and the environment. After conducting an audit, which included a review of historical data and current flow study data that were used to generate predictive fouling rates, Solenis identified the exchangers that posed the highest risk to reliable operation. Thus, the refinery developed a heat exchanger maintenance program that identified the heat exchangers that required immediate cleaning, could wait until a scheduled turnaround, and did not yet need to be cleaned or inspected but still required monitoring.
Since implementing the biofilm detection and control program and the heat exchanger performance monitoring program, the refinery has experienced an 87% decrease in heat exchangers that are susceptible to fouling related issues. Only one unscheduled cleaning has been required and that was due to a hurricane. Figure 2 shows that an average of less than one failure per year has occurred during the last ten years. Furthermore, with proper, scheduled maintenance, the useful life of the refinery’s heat exchangers has increased. This reduction in unscheduled cleanings and heat exchanger failures has saved the refinery more than $2 million in maintenance costs and significantly improved operational efficiency.
Improving cooling water and heat exchanger reliability
Figure 2: Using the ClearPoint and HexEval programs decreases the frequency of heat exchanger failures. Note: The refinery implemented the new programs in 2012.
Improving your heat exchangers’ reliability
What would ensuring the reliability of your cooling water heat exchangers using a cooling water treatment program combined with a robust reliability program do for you? What would implementing the ClearPoint biofilm detection and control program, and the HexEval performance monitoring program do for your refinery or petrochemical plant? What might you achieve in terms of efficiency improvements, asset reliability and life extensions, production increases, and cost savings?
Consider the following:
- How many unplanned cleanings do you require each year?
- How many critical failures do you experience annually?
- How much time and money are you spending each year on unplanned maintenance?
- How much could you save by increasing the useful life of your plant assets?
Having the ability to monitor and predict the health of your cooling water system and to identify accurately specific operational risks increases the efficiency and reliability of the cooling system. Heat exchanger modeling, though often overlooked, is critical to the success of your cooling water treatment program.
Solenis has the equipment, the chemistry, and the expertise to help refiners and petrochemical manufacturers mitigate critical heat exchanger failures and keep the cooling water system operating efficiently to ensure maximum productivity.
For more information about the ClearPoint biofilm detection and control program and the HexEval performance monitoring program, or to contact an expert, visit solenis.com.
