A Review Of Desalination Plant Manufacturer





Seawater Desalination with Reverse Osmosis Plant
All Reverse Osmosis plants are basically Desalination Vegetation but desalination is remaining referred to sea water Commonly.As sea h2o has really significant TDS requires really significant pressure to force sea water by way of membranes which are distinct then brackish drinking water membranes.

Reverse Osmosis Plant Facts:
A reverse osmosis plant is usually a producing plant, where water is purified and desalinated by forcing water via a membrane, typically referred to as a reverse osmosis method. Drinking water produced by plant RO could be utilized for numerous reasons like desalination, wastewater treatment method, plus the reclamation of dissolved minerals.

RO Plant Description
A median consuming water RO plant system requires 6 KW hrs of electrical power to desalinate a single cubic meter of water. Reverse osmosis h2o vegetation needs many different pre-therapy techniques together with softening, DE chlorination, and anti-scale cure. Adhering to pre-remedy, high amounts of stress send drinking water through a semi-permeable membrane, which retains all contaminants besides h2o.

RO Plant Layout
To enhance the performance and life of the Reverse Osmosis plant, productive pretreatment in the feed h2o is required. Array of the best pretreatment will maximize effectiveness and membrane life by minimizing:

Fouling
Scaling
Membrane Degradation
RO plant style is consisting of:

Analyzing pretreatment requirement of Reverse Osmosis Plant
In case the feed h2o has traces of large metals, it is very recommended to dose some chlorine to change the dissolved significant metals to Actual physical type, the media filter will filter the vast majority of it inside a ro drinking water purifier plant.

Reverse Osmosis Plant Number of membrane
Membrane components are a vital Element of RO crops. The proteins (mainly polyamide) that makeup membrane aspects range based on the ending clarity and consumption water seawater or brackish water and so forth

Waterman engineers Australia RO plant for seawater desalination
Waterman Engineers in Australia has intended a Reverse Osmosis (RO) plant for seawater desalination, which features several benefits more than other desalination strategies. Here are a few essential advantages of their RO plant:

Strength Effectiveness:
When compared with other desalination approaches like thermal distillation, RO involves a lot less Electricity. Waterman Engineers' RO plant utilizes Superior membrane technological innovation, letting it to function at reduce pressures and reduce overall Electrical power intake.

Environmental Effect:
RO generates much less brine discharge compared to thermal solutions, cutting down the impact on maritime ecosystems. This aligns with Australia's target environmental sustainability and conservation.

Higher H2o Purity:
The RO approach successfully gets rid of salts, minerals, and impurities, generating superior-good quality freshwater that meets stringent consuming h2o specifications. This trustworthiness is vital for providing Risk-free and clean drinking water to communities.

Modular Structure:
Waterman Engineers' RO plant employs a modular design and style, allowing for for scalability and flexibility. This is especially useful for areas with various drinking water requires, as modules may be extra or altered appropriately.

Reduced Footprint:
RO vegetation commonly Have got a smaller sized Bodily footprint when compared to thermal desalination crops, which frequently need comprehensive infrastructure for heating and cooling procedures.

Speedy Get started-Up and Shutdown:
RO plants may be started out and stopped reasonably promptly, allowing for for better responsiveness to changing water demands and emergencies.

Lower Chemical Use:
Unlike some other desalination methods, RO requires much less substances for Procedure and cleaning, reducing chemical-similar environmental fears.

Regularity in Functionality:
The RO approach is significantly less sensitive to feedwater quality fluctuations than other solutions, guaranteeing a more consistent general performance after some time.

Value-Usefulness:
While First expenditure fees can be major, RO plants are likely to get lower operational and servicing costs In the long term in comparison with thermal methods.

Reverse Osmosis (RO) is often a water purification approach that uses a partially permeable membrane to eliminate ions, unwanted molecules, and larger particles from ingesting h2o. By applying force to beat osmotic stress, it lets the passage of h2o molecules whilst rejecting contaminants, therefore developing clean drinking water on just one facet from the membrane and concentrated impurities on another.

The Performing basic principle of the Reverse Osmosis (RO) plant entails applying strain to your saline Alternative to drive h2o molecules through a semi-permeable membrane. This membrane enables only water to pass although rejecting salts, contaminants, and impurities, leading to purified drinking water within the permeate aspect plus a concentrated Option of contaminants over the brine facet.

Some great benefits of Reverse Osmosis involve developing superior-quality, clean up h2o by getting rid of contaminants, becoming productive and value-powerful eventually, demanding minimal chemical use, and getting adaptable to varied scales of operation from little house units to substantial municipal plants.

RO crops have changed Demineralisation (DM) plants because they normally supply a much more economical and value-efficient Alternative for drinking water purification. RO units Really don't involve the regeneration chemicals that resin-centered DM plants do and might get rid of a broader number of contaminants, like Desalination Plant Manufacturer dissolved solids and microorganisms.

Waterman Engineers Australia likely works by using Reverse Osmosis (RO) plants for seawater desalination by forcing seawater by way of a semi-permeable membrane to eliminate salt along with other impurities. This method creates clean, potable h2o from the ocean, addressing drinking water scarcity and furnishing a sustainable supply for a variety of needs.
 

Facts About Desalination Plant Manufacturer Revealed





Seawater Desalination with Reverse Osmosis Plant
All Reverse Osmosis vegetation are basically Desalination Vegetation but desalination is remaining referred to sea water Generally.As sea h2o has extremely substantial TDS necessitates extremely substantial tension to force sea water by means of membranes which happen to be various then brackish water membranes.

Reverse Osmosis Plant Information:
A reverse osmosis plant is often a producing plant, where by h2o is purified and desalinated by forcing h2o via a membrane, ordinarily referred to as a reverse osmosis procedure. Water produced by plant RO might be used for a number of functions like desalination, wastewater therapy, as well as the reclamation of dissolved minerals.

RO Plant Description
An average drinking h2o RO plant procedure necessitates 6 KW hours of electrical energy to desalinate 1 cubic meter of h2o. Reverse osmosis h2o vegetation demands a number of pre-treatment procedures which include softening, DE chlorination, and anti-scale cure. Adhering to pre-therapy, high amounts of stress mail drinking water through a semi-permeable membrane, which retains all contaminants except h2o.

RO Plant Design and style
To enhance the effectiveness and life of the Reverse Osmosis plant, productive pretreatment in the feed h2o is required. Array of the best pretreatment will maximize effectiveness and membrane life by cutting down:

Fouling
Scaling
Membrane Degradation
RO plant style is consisting of:

Pinpointing pretreatment necessity of Reverse Osmosis Plant
If your feed water has traces of weighty metals, it is very suggested to dose some chlorine to alter the dissolved major metals to physical kind, the media filter will filter most of it within a ro drinking water purifier plant.

Reverse Osmosis Plant Selection of membrane
Membrane factors are a significant A part of RO plants. The proteins (primarily polyamide) that make-up membrane things vary with regards to the ending clarity and consumption drinking water seawater or brackish drinking water etcetera

Waterman engineers Australia RO plant for seawater desalination
Waterman Engineers in Australia has designed a Reverse Osmosis (RO) plant for seawater desalination, which provides numerous rewards about other desalination solutions. Below are a few key great things about their RO plant:

Energy Performance:
In comparison to other desalination methods like thermal distillation, RO demands significantly less Power. Waterman Engineers' RO plant utilizes advanced membrane technologies, allowing it to work at decreased pressures and lessen Total Vitality consumption.

Environmental Effects:
RO generates a lot less brine discharge when compared to thermal strategies, decreasing the influence on marine ecosystems. This aligns with Australia's focus on environmental sustainability and conservation.

Superior Drinking water Purity:
The RO process proficiently removes salts, minerals, and impurities, developing substantial-high quality freshwater that satisfies stringent drinking drinking water standards. This dependability is crucial for giving Secure and cleanse water to communities.

Modular Layout:
Waterman Engineers' RO plant employs a modular design, making it possible for for scalability and flexibility. This is particularly beneficial for spots with varying drinking water requires, as modules may be additional or altered appropriately.

Decreased Footprint:
RO vegetation commonly have a smaller sized Bodily footprint when compared to thermal desalination crops, which often need comprehensive infrastructure for heating and cooling procedures.

Brief Start-Up and Shutdown:
RO plants may be started out and stopped somewhat immediately, allowing for much better responsiveness to altering water demands and emergencies.

Reduce Chemical Usage:
In contrast to Another desalination techniques, RO demands fewer chemicals for Procedure and cleansing, minimizing chemical-associated environmental concerns.

Regularity in General performance:
The RO system is a lot less sensitive to feedwater top quality fluctuations than other techniques, ensuring a far more steady efficiency as time passes.

Cost-Performance:
Even though initial financial investment expenditures could be significant, RO vegetation tend to obtain decrease operational and maintenance charges In the end compared to thermal approaches.

Reverse Osmosis (RO) is really a drinking water purification process that works by using a partly permeable membrane to remove ions, undesired molecules, and bigger particles from drinking drinking water. By implementing stress to overcome osmotic tension, it allows the passage of water molecules when rejecting contaminants, thus creating cleanse h2o on 1 aspect with the membrane and concentrated impurities on one other.

The Operating theory of a Reverse Osmosis (RO) plant consists of implementing pressure to some saline Resolution to pressure h2o molecules via a semi-permeable membrane. This membrane will allow only water to pass whilst rejecting salts, contaminants, and impurities, resulting in purified water around the permeate side as well as a concentrated Resolution of contaminants to the brine aspect.

The benefits of Reverse Osmosis Desalination Plant Manufacturer include things like developing superior-quality, clean up h2o by taking away contaminants, staying successful and value-successful with time, requiring minimal chemical use, and being adaptable to numerous scales of operation from little house systems to significant municipal vegetation.

RO plants have changed Demineralisation (DM) vegetation since they often give a far more effective and price-powerful Remedy for h2o purification. RO programs Do not involve the regeneration chemical compounds that resin-based DM vegetation do and can clear away a broader array of contaminants, including dissolved solids and microorganisms.

Waterman Engineers Australia very likely utilizes Reverse Osmosis (RO) vegetation for seawater desalination by forcing seawater through a semi-permeable membrane to get rid of salt and other impurities. This process makes new, potable drinking water from the ocean, addressing drinking water scarcity and furnishing a sustainable supply for a variety of needs.
 

Designing OF SHELL AND TUBE Heat Exchangers for Floating Liquefied Natural Gas (FLNG) - An Overview



Floating Liquefied Natural Gas (FLNG) production, liquefaction, and storage facilities have revolutionized the extraction and processing of natural gas from remote offshore reserves. These offshore platforms offer unprecedented flexibility and efficiency in the production of liquefied natural gas at sea. Among the crucial components of FLNG systems, heat exchangers play a pivotal role in the liquefaction process. This article explores the intricacies of heat exchanger design for FLNG, focusing on the challenges and requirements unique to these cutting-edge offshore installations, with a special emphasis on Waterman Engineers Australia's expertise in this field.

Understanding the FLNG Process: FLNG facilities essentially function as floating liquefaction plants, enabling the extraction, liquefaction, and storage of natural gas at sea. The process involves several vital steps:

 


  1. Production: Natural gas is extracted from offshore wells using production platforms or subsea systems.

  2. Gas Treatment: To ensure the purity of the gas and prevent interference with the liquefaction process (e.g., from carbon dioxide, water, and sulfur compounds), the extracted gas undergoes treatment.

  3. Liquefaction: The processed gas is cooled to extremely low temperatures, typically below -160 degrees Celsius (-256 degrees Fahrenheit), causing it to condense into liquefied natural gas (LNG). This liquefaction is necessary for efficient storage and transportation.

  4. Storage and Transportation: The produced LNG is stored in onboard tanks before being loaded onto carriers for transportation to markets.

  5.  

The Role of Heat Exchangers in FLNG: Heat exchangers are indispensable components of FLNG facilities, primarily responsible for managing the heat transfer required to chill natural gas to the liquefaction stage. This critical task involves handling extremely low temperatures and ensuring efficient heat exchange across various process streams. Key considerations in designing heat exchangers for FLNG include:

 


  1. Cryogenic Conditions: FLNG operations entail working at cryogenic temperatures, posing a significant challenge for heat exchanger design. Selecting appropriate materials, such as aluminum alloys and stainless steels, is crucial to withstand these harsh conditions. Insulation and thermal management strategies are also employed to prevent heat loss and maintain the required low temperatures.

  2. Optimizing Liquefaction Efficiency: Achieving economic viability hinges on maximizing the efficiency of the liquefaction process. Modern heat exchanger topologies like spiral-wound or plate fin heat exchangers offer improved efficiency by providing a large surface area for heat exchange in a compact design. Computational fluid dynamics (CFD) simulations are essential for optimizing heat exchanger components.

  3. Compact Design for Limited Space: Space constraints are common in offshore FLNG operations. Hence, compact heat exchanger designs like plate and frame or brazed plate heat exchangers are preferred, as they offer high surface area-to-volume ratios, enabling efficient heat exchange in a confined space.

  4. Durability in Harsh Marine Environments: FLNG heat exchangers are exposed to severe maritime conditions, including high winds, salinity, and potential wave action. Ensuring longevity requires the use of corrosion-resistant materials and coatings, along with robust monitoring and maintenance systems to detect and address corrosion issues.

  5. Operational Flexibility: FLNG operations can experience variations in gas composition, flow rates, and environmental variables. Designing heat exchangers with customizable features, control systems, and the ability to adapt to changing conditions is essential for ensuring operational flexibility.

  6. Safety Compliance: FLNG plants are subject to stringent safety regulations. Heat exchangers must incorporate safety precautions to prevent incidents such as leaks or over pressurization. This includes emergency shutdown mechanisms, temperature and pressure monitoring systems, and safety relief valves.

  7. Integration with Other Systems: Heat exchangers must seamlessly integrate with various interconnected systems within FLNG facilities, such as storage tanks, separators, and compressors. Collaborative design techniques and meticulous evaluation of the overall system structure are essential for efficient integration and optimal performance.

  8.  

Waterman Engineers Australia's Expertise in Heat Exchanger Design for FLNG: Waterman Engineers Australia is at the forefront of engineering solutions, specializing in the design of heat exchangers tailored for FLNG applications. Their expertise has significantly contributed to optimizing FLNG plants while upholding the highest standards of excellence, sustainability, and safety.

 


  • Cryogenic Expertise: Waterman Engineers Australia excels in addressing the challenges of cryogenic conditions in FLNG operations. Their team of experts possesses in-depth knowledge of designing heat exchangers capable of withstanding extremely low temperatures, a critical requirement for the liquefaction process. This expertise involves meticulous material selection, thermal management, and insulation techniques.

  • Space-Efficient Designs: Recognizing the premium placed on space in FLNG operations, Waterman Engineers Australia employs creative and space-efficient design solutions. By leveraging advanced computational fluid dynamics (CFD) models and optimization methods, they strike a balance between effectiveness and compact size, ensuring that their heat exchangers meet space limitations without compromising performance.

  • Safety Priority: Waterman Engineers Australia places safety at the forefront of their heat exchanger designs, fully understanding the stringent safety standards and regulations governing offshore activities. Their heat exchangers feature robust safety elements, including emergency shutdown mechanisms, temperature and pressure monitoring systems, and safety relief valves, to maintain integrity and compliance.

  • Operational Flexibility: Waterman Engineers Australia's heat exchangers are designed with a keen awareness of the dynamic nature of FLNG operations. They provide the necessary flexibility to adapt to fluctuations in gas composition, flow rates, and environmental factors. Their choice of corrosion-resistant materials and proactive maintenance techniques further underscores their commitment to durability.

  • Collaborative Integration: Waterman Engineers Australia employs a collaborative design approach that ensures seamless integration of their heat exchangers into the broader FLNG system. By actively participating in the overall FLNG system's design, they optimize the entire facility, ensuring that their heat exchangers complement and enhance the overall efficiency and performance of the FLNG facility.

  •  

Conclusion: Waterman Engineers Australia's heat exchangers for FLNG demonstrate a profound understanding of the complexities involved in offshore liquefaction processes. Their leadership in providing state-of-the-art heat exchanger solutions for the evolving FLNG operating landscape is driven by their expertise in cryogenic conditions, commitment to safety, space-efficient design solutions, and collaborative integration strategies.

Choose Waterman Engineers Australia's Heat Exchangers for Floating Liquefied Natural Gas (FLNG) to elevate your industrial processes to new heights. Contact them today to explore how their solutions can optimize your heat transfer applications and contribute to the success of your FLNG operations. With their expertise, you can navigate the challenges of FLNG operations with confidence and efficiency.

FAQs (Frequently Asked Questions) - Heat Exchanger Design for FLNG by Waterman Engineers Australia

Q1: What is the significance of heat exchangers in FLNG facilities?

A1: Heat exchangers are critical components in FLNG facilities as they are responsible for managing the heat transfer necessary to liquefy natural gas. They play a vital role in cooling the gas to extremely low temperatures, enabling its conversion into liquefied natural gas (LNG) for storage and transportation.

Q2: How do heat exchangers in FLNG handle cryogenic conditions?

A2: Heat exchangers in FLNG must withstand cryogenic temperatures, which is a major challenge. Waterman Engineers Australia addresses this by carefully selecting materials that can resist extreme cold, such as aluminum alloys and stainless steels. Additionally, insulation and thermal management techniques are applied to prevent heat loss and maintain the required low temperatures.

Q3: What design optimizations are employed to enhance Designing OF SHELL AND TUBE Heat Exchangers for Floating Liquefied Natural Gas (FLNG) the efficiency of heat exchangers in FLNG?

A3: To improve efficiency, modern heat exchanger topologies like spiral-wound or plate fin heat exchangers are used to provide a larger surface area for heat exchange in a compact design. Computational fluid dynamics (CFD) simulations are employed to optimize the design and arrangement of heat exchanger components.

Q4: How does Waterman Engineers Australia address space limitations in FLNG installations?

A4: Recognizing the limited space on FLNG platforms, Waterman Engineers Australia employs creative and space-efficient design solutions. They utilize advanced computational models and optimization methods to ensure that heat exchangers are both effective and compact, allowing them to fit within the space constraints without sacrificing performance.

Q5: What safety measures are incorporated into the design of heat exchangers for FLNG?

A5: Safety is a top priority in FLNG operations. Waterman Engineers Australia's heat exchangers are equipped with robust safety elements, including emergency shutdown mechanisms, temperature and pressure monitoring systems, and safety relief valves. These features are essential to prevent incidents like leaks or over pressurization.

Q6: How do Waterman Engineers Australia's heat exchangers adapt to the dynamic nature of FLNG operations?

A6: FLNG operations can experience variations in gas composition, flow rates, and environmental factors. Waterman Engineers Australia designs heat exchangers with customizable features, control systems, and the ability to adapt to changing conditions. This operational flexibility ensures optimal performance in the ever-changing offshore environment.

Q7: How does Waterman Engineers Australia ensure the longevity of their heat exchangers in harsh marine environments?

A7: Waterman Engineers Australia focuses on durability by using corrosion-resistant materials and coatings. Additionally, they implement strong maintenance and monitoring systems to detect and address potential corrosion issues, ensuring the extended life of their heat exchangers in challenging maritime conditions.

Q8: How does the collaborative integration approach benefit the performance of FLNG facilities?

A8: Waterman Engineers Australia actively participates in the design of the overall FLNG system, ensuring that their heat exchangers seamlessly integrate with other interconnected systems like storage tanks, separators, and compressors. This collaborative approach optimizes the entire facility, enhancing efficiency and performance.

Q9: Why should I choose Waterman Engineers Australia's heat exchangers for my FLNG operations?

A9: Waterman Engineers Australia's heat exchangers are designed with a deep understanding of the intricacies of FLNG operations. Their expertise in cryogenic conditions, commitment to safety, space-efficient designs, and collaborative integration strategies make them a reliable choice to optimize your heat transfer applications and contribute to the success of your FLNG operations.

Q10: How can I get in touch with Waterman Engineers Australia to discuss their heat exchanger solutions?

A10: You can contact Waterman Engineers Australia to explore their heat exchanger solutions and discuss your specific needs by visiting their website or reaching out to their dedicated team of professionals. They will be happy to assist you in enhancing the efficiency and safety of your FLNG operations.

An Unbiased View of HIU repair

Preserving and restoring your very own domestic plumbing is an important part of redesigning, but knowing it and buying the proper devices can be challenging. There are lots of points to consider for the certain pipes work. Here are several steps you can take to make sure you get started with your own personal plumbing related tasks.
If your empty in almost any device is consuming longer to drain h2o, then you might need to have your water lines expertly cleansed according to the severity of the conditions. Before you try this, there are numerous diverse items you can consider. Nonetheless, a few of them are skilled power and all sorts of goods ought to be used in combination with caution.
One important thing you can do to optimize the safety of your residence is usually to close every one of the crevices within your outside taps. Even a small break can intensify since the time of year continues and cause severe troubles later on. Reduce drips and leaks for best defense.
Thoroughly clean your dryer's lint snare. This is a good idea for many different factors, not minimal which is fireplace basic safety. Make it a point that you simply consider the lint capture and find out whether it has tears or slots inside it that could cause lint to look within your plumbing. This may lead to clogs or any other issues in the future.
If you use PEX piping for the supply lines in your home, get the right resources to do the job. PEX piping requires a totally different instrument kind than typical lines. PEX provides extensive advantages although, so don't let the various demands have you away.
Something that you can do to guard your property from any critical plumbing related problems is always to get a flood alarm. This is a device that can sound in regards in contact with h2o, alerting you if there are any problems within a certain place in the house.
Should you be looking to have new piping in your house, try to stay away from copper versions. Copper will have issues, on account of normal water and garden soil corrosion. It is also harder to put in these sorts of piping. Metallic or direct plumbing are likely to offer the highest quality and therefore are by far the most long lasting.
A good way to prevent a standard plumbing related issue is to ensure to never flush nearly anything but human being squander and toilet paper downward a potty. Other items made of document like cells, pieces of paper towels, and the like tend not to dissolve much the same way lavatory paper does and might get stuck.
If you have a horrible smell coming from your junk convenience, this is due to food items trash accumulation. You need to set ice cubes cubes, orange peels, and lime peels in to the fingertips and operate for roughly 30 seconds. After that, operate some liquefied recipe cleaning soap with the fingertips. This ought to keep up with the issue if you find not really a considerable blocking build-up.
To shield your money from unsavory local plumbers, constantly get a created estimation well before spending a cent or investing in a project. Good business people know to under-assurance and over-produce to knowledgeable buyers. When a reported amount is given, it can be highly unlikely that the local plumber will go over the projected costs from the venture.
For those who have a break inside your lavatory aquarium, you may often fix this with an epoxy resin. However, it is very challenging to keep up with this kind of upkeep, as well as the best choice might be getting in touch with the provider and purchasing a brand new tank to be installed in your bathrooms. Nevertheless, keeping some epoxy resin on hand for emergencies is a great idea.
Make sure any plumber that you just work with are designed for the kind of work you have. There are several elements to domestic plumbing and several contractors is capable of doing the majority of them, however some are more appropriate to carrying out function involved in certain locations. If want a local plumber for the septic process, obtain one which specializes in septic solutions.
Many individuals complain of very low normal water strain. While there are various issues that can induce this, a single should not be ignored when commencing your analysis. Which kind of water lines are you experiencing? In case your piping is galvanized, you will be happier just swapping your piping which will remove the issue.
Whenever you swap a water heater, make sure you reconnect the additional water pipe that sticks right out of the empty pipe, if a person could there be. The recirculation pipe assists very hot water rotate through your plumbing related method so that you won't squander normal water although warming it.
When it comes to plumbing related, there is certainly in no way an unsolvable problem. If you feel your self turning into irritated together with the project, you should try to take a break from what you really are concentrating on. The highest blunders learn to come about if you grow to be mad and inpatient, so take a rest and move outside.
It is imperative as a house owner that you know just where your primary h2o close-away from device is situated and may operate the valve in case of a crisis. The ideal starting point calculate for iced pipes is to end normal water from coming into your house in the first place. Identify the key drinking water supply control device HIU service and turn it on and off consistently to maintain it effortlessly operable in an emergency.
Aquarium-much less water heaters are an excellent space saving alternative to standard container products. They come in numerous types, some for inside and some versions are capable for exterior mounting. Aquarium-much less hot water heaters are referred to as wonderful cash savers when it comes to your normal water bill.
You should try by using a plumbing related snake or plumbing technician to unclog a clog. Water cleaners that are made to unclog the clogs in a deplete could damage the pipes. You must also use strainers to catch head of hair so it doesn't go down the sink and obtain clumped and block your strain.
While you study, pipes can be an unbelievably essential requirement to your present and upcoming home improvement and thus is understanding the various tactics and equipment. This really is so that it makes it much simpler that you can understand the thing you need to your pipes tasks. Following the tips in this post is definitely a excellent starting up position.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15