Did you know that water expansion tanks in a closed water system can handle pressure up to 1MPa? But why do you need an expansion tank to handle high pressure in these systems? Piping networks in domestic water systems, boilers, HVAC systems, or any other closed-loop system require an expansion tank. The tanks allow the system water to expand or contract as per requirement. These tanks are metallic and necessary in some regions per local codes and regulations.
Finding the right expansion tank for your system requires careful evaluation of the specs, installation, and maintenance-associated aspects. However, acquiring the necessary knowledge is vital to selecting your system's best water pressure tank design. This article provides information on expansion tanks, their working mechanism, usage scenarios, and selection strategies. Continue reading to learn about expansion tanks extensively!
What is an Expansion Tank?
Definition and Function
An expansion tank allows the connected fluid in a network to expand and contract while maintaining stable pressure, serving as a cushion to absorb any sudden changes in liquid volume. This function protects the piping from potential damage caused by pressure fluctuations, as network piping has pressure limits defined by fittings and material properties. Exceeding these limits can compromise safety and cause system failure. The specification of an expansion tank or expansion vessel, including volume and pressure-bearing capabilities, depends on the network.
Why Do You Need an Expansion Tank?
An expansion tank is a critical safety device for systems, especially in heating, ventilation, and domestic boiler networks. Not only does it help protect the equipment, but some local regulations mandate its use in domestic heating systems. The expansion tank also extends the system's life by mitigating the pressure fluctuations that can cause wear and tear on the materials. Let's explore why an expansion tank is necessary:
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Preventing Excessive Water Pressure:
Expansion tanks use compressed air, either with a bladder, diaphragm, or metal container, to manage the water’s expansion. This pressure control feature protects the equipment in the network. In typical HVAC or domestic piping systems, joints and valves can only handle a specific pressure before they risk bursting or breaking.- Effect on Boiler Systems:Excessive water pressure can negatively affect heat transfer, reducing the system’s efficiency by preventing proper boiling in the boiler.
- Effect on HVAC Chilled Water Systems:Low pressure from liquid contraction can cause water hammering, which may lead to pump cavitation and damage the piping system.
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Compliance with Local Codes:
Local regulations, such as the International Plumbing Code (IPC)and National Standard Plumbing Code, often require expansion tanks for safety. The codes detail aspects such as material, fitting, and design to standardize safety practices. Some key requirements include:- A boiler system with a backflow preventer must have an expansion tank.
- The expansion tank should be of adjustable, pre-charged type and rated for 86 MPaand 93°C.
- It must meet ASME BPVC Section VIIIstandards and have independent support from the piping system.
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Extending Equipment Lifespan:
By mitigating water pressure fluctuations, expansion tanks help extend the life of water heaters and associated equipment. Sudden changes in pressure can lead to cyclic fatigue in the materials, causing cracks and eventual failure. By reducing these stressors, an expansion tank prevents long-term damage and enhances system durability.
When selecting an expansion tank, it's important to ensure it meets local regulations and quality standards. Alsavo offers a range of high-quality expansion tanks, designed for both domestic and industrial use, with capacities from 8L to 24L and pressure ranges from 0.6 MPa to 1 MPa. Their tanks feature corrosion-resistant coatings and high-quality membranes, making them ideal for extending the life of your system.
Working principle and types of expansion tanks
An expansion tank works by accommodating the expansion and contraction of water in a closed system. Imagine a piping network filled with water. When the water heats up, it expands, increasing the pressure within the system. If there is no room for this expansion, the pressure can rise to dangerous levels, potentially causing the piping network to fail. Similarly, when the water cools down, the contraction can create negative pressure, causing issues like pipe collapse. Expansion tanks provide a safe space for this expansion and contraction, ensuring stable pressure and preventing damage to the system.
System Type
Whether your system needs an water expansion tank or expansion vessel depends largely on the type of system—open or closed.
- Open-Type Systems:In open systems where water is exposed to the atmosphere, such as in swimming pools, expansion tanks are not required. These systems allow water to freely expand without pressure buildup since they are open to the air.
- Closed-Type Systems:Closed systems, on the other hand, do require expansion tanks. In a closed system, such as a car radiator or a domestic heating system with a non-return valve, the water heats up and expands within a sealed loop. Because the water is not exposed to the atmosphere, an expansion tank is necessary to accommodate the expansion and maintain stable pressure.
Water Heater Capacity
The capacity of the water heater or the amount of water in the system also affects whether you need an water expansion tank. Larger volumes of water will experience greater expansion when heated, so systems with larger water capacities require expansion tanks with higher volume and pressure ratings.
Water Pressure Fluctuations
In closed systems, especially those using submersible or positive displacement (PD) pumps, pressure fluctuations are common. An expansion tank allows water to move in and out, smoothing out rapid pressure changes. Without an expansion tank, these fluctuations could cause pipes to vibrate violently or even suffer cyclic fatigue failure due to sudden changes in pressure.
By allowing water to expand and contract within the system, expansion tanks prevent dangerous pressure buildups and maintain the integrity of the piping, ensuring safe and efficient system operation.
How to Choose the Right Expansion Tank
Choosing the Right Size
Choosing the right size water expansion tank or best water pressure tank requires accurate calculations that adhere to national and local standards. The IPC 2020 Mechanical Code of New York State provides calculations that lead to an ideal volume of an expansion tank for a given pressure. The code requires an expansion tank design that adheres to the ASME BPVC as a prerequisite for calculation. Here are the formulas and snippets from the code:
1009.2 Closed-Type Expansion Tanks
Here:
Vt = Minimum volume of tanks (L).
- Vs= Volume of system, not including expansion tanks (L).
- T= Average operating temperature (°C).
- Pa= Atmospheric pressure (kPa).
- Pf= Fill pressure (kPa).
- Po= Maximum operating pressure (kPa).
Material and Quality Considerations
The ASME and IPC codes detail the material and quality considerations. However, for an average user, the material should have the following aspects:
● The material can be carbon steel painted with an anti-corrosion coat.
● It should have the capability of withstanding 0.86 MPa and 93°C.
● The material should have a 0.7 MPa tolerance.
● The use of polypropylene rubber in the diaphragm is ideal for corrosion resistance.
● A precharge of 275-414 kPa is ideal for most domestic applications.
Installation Location
Careful location selection is vital to ensure that the expansion tank works efficiently and takes in all the water surges from the system. Here are some of the factors one should consider when installing an expansion tank:
- Elevation:Installing an expansion tank at the highest location is ideal for air or steam to find a path to the tank's expansion area.
- Pump Fluctuations:To dampen the fluctuations of a system containing a pump, install the expansion tank neatly next to the pump.
- Accessibility:To ensure easy maintenance, install the tank in a location where accessibility is ensured.
- Fitting:The national code requires supporting expansion tanks independently of the piping network.
Maintenance and Replacement of Expansion Tanks
Regular Inspection
Regular inspections are essential for maintaining system health. Before starting the inspection process, ensure that the system temperature is at atmospheric conditions. The inspection process should involve the following steps:
- Start by visual inspection and observe the expansion tank. Look for damaged parts in the expansion tank or associated piping and valves.
- Press down on the Schrader valve to see if air comes out. If water comes out, the diaphragm or membrane is broken. Prepare for replacement.
- Isolate the expansion tank from the system using a valve. Disconnect the expansion tank from the system and check for debris in the expansion tank water.
- Using a pressure gauge, check the tank's pressure via the Schrader valve. If the pressure is below the initial pressure, repressurize utilizing a compressor.
- Reconnect the expansion tank back to the network of piping.
When to Replace an Expansion Tank
Expansion tanks rarely fail because of the membrane. The membrane usually takes the damage from thermal and physical fatigue. However, look for the following signs which are an indication that you need to replace the expansion tank:
- Deformation of the tank shape
- Visible corrosion
- Failure of tank pressure gauge
- Cracks and breaks on the tank body
How to Prolong the Lifespan of Your Expansion Tank
Expansion tanks are generally durable equipment that does not require frequent maintenance. However, regular inspection and maintenance can go a long way. Consider the following tips to prolong the lifespan of your expansion tank:
- Regular inspections
- Avoid extreme hot or cold temperature fluctuations in the system
- Use a tank that has high-temperature tolerance
- Go for a bladder expansion tank for domestic use
- Drain the tank regularly
- Flush the closed system with fresh water
If you want a system that is easy to maintain in case of failure, go for a bladder-type expansion tank. Alsavo platform provides a variety of replacement parts for expansion tanks to help users extend the life of their systems. They provide kits and separate components in case any part breaks down. They also offer rubber replacement membranes for the expansion tanks, which prolongs their life.
Conclusion: Should You Install an Expansion Tank?
Whether you need an expansion tank depends on your system. You need an expansion tank if you have a closed system with a check valve. The IPC, ASME, and National Standard Plumbing Codes have specifications and installation requirements for such systems. Expansion tanks provide safety, equipment protection, and system longevity. In high-pressure environments, expansion tanks take in water surges and contractions to maintain pressure and prevent bursts.
If you need an expansion tank that provides longevity and excellent inspection and maintenance features, Alsavo is your supplier. The Alsavo expansion tank section features all the necessary expansion tanks and related products to help you manage your system pressure effectively. They also have parts available for exceptional maintainability. Visit the Alsavo website to explore all your options!
FAQ
- How do I know if my system is a closed system or an open system?
If the liquid in your system is not exposed to the atmosphere at any point, it's a closed system. For example, your car's radiator is closed, whereas a swimming pool filtration system is open. Another way to tell if your system has a pressure gauge is to see if it reads above atmospheric pressure.
- What happens if I don’t install an expansion tank in a high-pressure system?
Not installing an expansion tank in a high-pressure system can lead to breakage or leakage. If your high-pressure system liquid heats up and doesn't have any place to expand, it can cause equipment failure. It can also cause noise and vibrations with inefficient system operation.
- Are there alternatives to using an expansion tank?
An alternative approach is to design a large-volume system to accommodate the changes in liquid volume due to heating and cooling. However, this is not cost-effective. Similarly, using an open system with a non-pressurized system is an alternative to expansion tanks, but it is not always feasible.
- How often should I inspect or maintain my expansion tank?
For domestic applications, annual expansion tank inspections are enough. However, regular call-up cards and preventive maintenance should occur monthly or bi-annually in industrial applications. These should include an air pressure test, diaphragm inspection, and visible inspection.
- Can I install an expansion tank, or should I hire a professional?
While installing expansion tanks is simple, hiring a professional can ensure that your equipment adheres to the local codes. Some regions may also require specialized plumbing and fitting requirements, which professionals know are necessary to ensure compliance. It's best to hire a professional for safety reasons.
