Boilers are essential in residential or industrial heating applications. However, due to two-phase flow or steam/water, they can produce loud noise and vibrations in the system. Sometimes, the furthest radiator from the boiler may need a more heated water flow rate to fulfill user requirements. That's where hydraulic separators come in. They allow boilers to operate at a specific power and flow rate, adjusting to maintain a fixed temperature difference between cold and hot ports. It leads to even heating and smoother water flow.
This comprehensive guide to hydraulic separators will detail how they work, their advantages, accessories, types, and sizes. It will also address the maintenance aspects of the hydraulic separator so that users can maintain its efficiency during operation. Let's begin with a brief overview of hydraulic separators.
1. Overview and Working Principles of Hydraulic Separators
Most home systems will work fine without hydraulic separators, but owing to rising energy prices, it's better to have more control over the boiler's energy requirements. Hydraulic separators improve the efficiency and reliability of a heating system. Knowing what they are and how they work is a building block to understanding how they improve efficiency.
What is a Hydraulic Separator?
By definition, hydraulic separators separate the primary and secondary circuits so that they can have their respective flow rates. Here, the primary circuit refers to the boiler circuit containing a pump that flows water through the boiler and back to the separators using a piping network. The secondary circuit can include a pump or regulating valve that allows fluid to flow through the floor heating, radiators, industrial heaters, or all.
Hydraulic Separator, Buffer, and Low-Loss Header
Manufacturers or industrialists may often interchangeably use the terms hydraulic separator, buffer, and low-loss header. It is crucial to address these terms to clarify to our readers that we may use them in specific contexts within the blog. Each of these devices has distinct features. Here are the details:
- Hydraulic Separator: It separates two hydraulic circuits to operate independently while allowing mass exchange as needed. We will explain its working mechanism in detail in the next section.
- Buffer: Buffers can increase boiler efficiency by allowing the boiler to remain off for some time. They store some heat and continue to supply the secondary circuit when the requirement is low.
- Low-Loss Header: In the case of multiple boilers or heat users from the boiler, low-loss headers minimize pressure drop and heat loss in the hot water distribution system.
We can conclude that a single device can act as all three if we study these three devices. Our guideline will use hydraulic separators and focus on their primary purpose. However, we will mention the secondary functions within their functionalities, such as acting as a buffer or low-loss header.
Working Mechanisms and Functions of Hydraulic Separators
Understanding how boilers and heating components work is crucial to understanding the function and mechanism of a hydraulic separator. It will establish the knowledge base to fully grasp the separator's mechanism and importance.
Boilers Working Mechanism
Boilers are heat exchangers that add heat to the fluid passing through their circuit. They can have a pump that maintains flow through the boiler coils. For a boiler to remain efficient, it should have a specific temperature difference between its hot and cold ports. That temperature difference (ΔT) for boilers is usually between 5 and 10°C.
When the heating demand increases, the flow to heat-rejecting components such as radiators or floor heaters increases. It causes the return cold water temperature of the boiler to drop. The boiler will vary its pumping speed to adjust the demand and supply. It can add more heat to the system.
Hydraulic Separator Mechanism
Assume there is no hydraulic separator within the boiler system. The change in pump speed when demand increases or decreases can cause varying flow rates for the users, which can cause uneven heating and, in some cases, no heating for the furthest components. Hydraulic separators allow multiple boilers and pumps in primary or secondary load circuits. They connect the two circuits and form a junction that helps separate flow rates for the primary and secondary circuits.
As you can see in the diagram below, the hydraulic separator working mechanism has three cases that we can discuss.
- Gpr<Gsec: If the primary circuit (Gpr) has a lower flow rate than the secondary circuit (Gsec), the hydraulic separator will allow the path for the secondary circuit to maintain its flow rate and heating.
- Gpr=Gsec: This happens when the demand from the load components balances the boiler's production. Since the flow rates match, the hydraulic separator passes both fluids through and acts as a pipe.
- Gpr>Gsec: If the primary flow is higher than the secondary flow, the boiler will recirculate some of its flow back to the pump to operate at its desired flow rate.
Functions of Hydraulic Separators
As we mentioned earlier, hydraulic separators can perform a variety of functions. It can perform the buffer, flow separator, and low-loss header functions. Here are its primary and secondary functions:
Primary Functions
- Provide flow paths for primary and secondary pumps to maintain their respective flow rates.
- Stabilize and homogenize the heat transfer capability among heat loads such as radiators, floor heaters, or domestic water heater components.
- Ensure that the flow rates and circuit pressure remain stable without fluctuation to prolong equipment life.
- Improve the efficiency of the whole system.
Secondary Functions
- It prevents water hammers by separating air and steam particles and slowing the flow.
- It allows the sediments to settle down, allowing the circuit to flush out unwanted particles.
- Prevents corrosion by extracting corrosion
- Hydraulic separators physically separate the primary and secondary circuits, eliminating interference and ensuring stable flow and pressure.
- It helps maintain thermal balance in different temperature zones, avoids heat waste, and improves system efficiency.
- It can cope with the pressure and flow requirements of different circuits, reduce pump wear, and extend the life of the equipment.
2. Advantages and Limitations of Hydraulic Separators
Hydraulic separators allow multiple advantages in different circuits. It can be a boiler or cooling circuit. However, the boiler circuits are more complex as they can contain steam, causing two-phase flow. Let's weigh out the pros and cons of using hydraulic separators:
Advantages
● Higher Stability
The system maintains a stable state as the hydraulic separator provides a path for the boiler pump and the load pumps to keep their flow rates. There are no vibrations or excessive pressure points throughout the circuit, leading to better stability.
● Increase in Equipment Life
Their life increases as the pumps operate without significant pressure and flow rate fluctuations. Cyclic fatigue on the system components also reduces, extending the equipment's life.
● Energy Efficiency
Hydraulic separators allow more than one pump to be used in a boiler circuit, resulting in energy efficiency, known as the square rule in engineering. Two pumps consume less power than a single pump.
Limitations
● High Initial Cost
Utilizing hydraulic separators in your circuit can lead to higher initial costs. Hydraulic separators can become expensive on an industrial scale and generally have high transportation costs.
● Take Up Space
The hydraulic separators that come with the buffer tank feature can be significant. They can be as large as may take up a lot of space in some small systems.
3. Components of Hydraulic Separators
Now that we know what a hydraulic separator is and how it works, we can move on to understanding the components of hydraulic separators. The knowledge of components will help us find the right hydraulic separator for our application.
● High-Discharge Automatic Air Vent with Service Check
The component removes air and steam from the circuit if they are present. The water passing through the connecting ports opens into the section with baffles. These baffles disrupt the flow, causing air and steam to flow to the top. The accumulation triggers the relief mechanism and steam/air vents to the outside. There is also a check button to release the mechanism.
● Temperature Pocket Well
Hydraulic separators can also feature temperature wells that measure the temperature of water flowing into and out of the separator. These wells provide insights into system temperature regulation and efficiency.
● Drain Valve with End Cap
As mentioned earlier in the blog, sediments in the circuit water can settle at the bottom of the hydraulic separator. A drain valve can remove these sediments and corrosion particles by a simple open-and-close mechanism. It can also come with an end cap to add a layer of protection from misoperation.
● Insulation Jacket Kit
As the whole assembly of hydraulic separators is usually metal, it is susceptible to heat transfer, which can lower the system's efficiency. Some manufacturers, like Alsavo, provide insulation jacket kits with a hydraulic separator for a more homogenized look and perfect fitting for a high-efficiency system.
● Connection Ports
depending on the system scale in which you will connect your hydraulic separator, it can feature a single boiler and multiple load connection. The connector can be of standard DN (Diameter Nominal) or NPS (Nominal Pipe Size).
4. How to Choose the Right Hydraulic Separator
Selecting a suitable hydraulic separator for your system ensures proper operation. Here are some factors to consider when purchasing a hydraulic separator:
System Size and Capacity
System size and capacity come first when selecting the hydraulic separator. Consider your piping diameter, flow rates, and connection requirements. To determine the right size of the hydraulic separator, you need to do the following:
- Max Flow: Determine the maximum flow rate in your circuit. The maximum flow rate will likely be the flow rate of your boiler pump. However, every system can be unique, so note the highest flow rate of your system. Use that to search for a hydraulic separator.
- Residence Time: It is the time the fluid will stay within the hydraulic separator
Residence Time = Separator Volume / Flow Rate
- Separator Volume: We can rearrange the residence time formula to determine the separator volume.
System Type
There are many types of hydraulic separators. Some may provide a path for varying flow rates between primary and secondary circuits, while others can offer steam/air separation using baffle plates. Observe your circuit and see if your system requires degassing or decontamination.
Functional Requirements and Applications
Hydraulic separators provide various additional functions that are not their primary purpose. They can provide pressure stabilization, relief, monitoring, temperature gauges, draining, and venting features. Hydraulic separators are widely used in HVAC, heating, and industrial hydraulic systems to ensure stability. Features such as acting like buffer tanks and low-loss headers are value additions.
5. Maintenance of Hydraulic Separators
Hydraulic separators are usually maintenance-free components. However, users can improve their efficiency by performing weekly or daily inspections based on the flow rate and expected sedimentation or venting requirements. Here are things to check during your regular inspection.
Regular Inspection and Cleaning
- Insulation Removal: Because hydraulic separators are inside insulation, leakages can occur and damage the material. Therefore, regular visual inspection after the insulation removal is essential.
- Dirt Accumulation: Depending on the size of the system, dirt can accumulate at the drain port. Regularly draining the port keeps the system efficient and reduces the chances of corrosion or clogging.
- Filter Replacement: In some cases, the hydraulic separator will have a filtering function. The filter element must be replaced or cleaned regularly to maintain efficiency.
System Calibration and Adjustment
- Calibration of Guages: If the hydraulic separator features temperature gauges, then annual calibration of these gauges can result in accurate readings.
- Calibration of Flow: Regularly calibrate the system flow and balance to ensure the long-term performance of the hydraulic separator and system stability.
Conclusion
As an essential part of the hydraulic system, the hydraulic separator can effectively manage the primary and secondary circuits to keep the system running stably. Optimizing fluid flow and heat transfer improves system efficiency and extends equipment life. Although the installation cost is high for large systems, especially HVAC and industrial applications, its benefits far outweigh the investment. Choosing the suitable hydraulic separator, combined with regular maintenance and care, can ensure the long-term efficient operation of the system. The Alsavo platform offers a wide range of hydraulic separators to meet the needs of different systems and help achieve optimal performance in all types of projects.
FAQ
- What size hydraulic separator is best for my system?
The size of the hydraulic separator depends on the maximum flow rate in your system. Manufacturers size them based on the maximum flow rate. However, if your hydraulic separator also has a sediment separation feature, use the formula “Residence Time = Separator Volume / Flow Rate” to find the separator volume.
- How can a hydraulic separator improve HVAC efficiency?
In heating applications, hydraulic separators can install multiple pumps for loads and multiple pumps for boilers. Collectively, they require lower power than a single pump. They also allow better control over loads like radiators or floor heating without unwanted pressure or temperature fluctuations.
- Are hydraulic separators necessary for small-scale heating systems?
Hydraulic separators are equally beneficial in large or small-scale heating systems. In small-scale heating systems, they can provide efficient, noise-free operation with higher efficiency. This leads to even heating or cooling across all devices and improves the setup's efficiency.
- How often should I clean or replace filters in a hydraulic separator?
Depending on the type of filters you have in your hydraulic separator, the frequencies of replacement and cleaning can vary. Typically, inspecting and cleaning filters on a monthly basis is ideal for efficient operation. However, the replacement strategy can be every 6 months to 1 year for sediment filters and carbon filters. For mechanical filters, it can be once every 1-2 years.
- What are the main differences between air and dirt-removal hydraulic separators?
When installed vertically on top of the hydraulic separator, the air hydraulic separator features a vent valve that activates when there is enough air or steam collecting at the top. Dirt-removal hydraulic separators have drain valves that remove dirt and sediment that collect at the bottom.
