Choosing Between Diaphragm and Bladder Types Surge Tanks

A surge tank is a crucial device used in various systems to buffer pressure fluctuations, ensuring smooth system operation. Surge tanks can be classified into two types based on their structure: diaphragm type and bladder type. Diaphragm surge tanks achieve buffering by pre-charging a certain pressure of nitrogen gas between the tank body and the diaphragm. On the other hand, bladder surge tanks pre-charge nitrogen gas between the tank body and the bladder.
 

Disadvantages of Diaphragm Surge Tanks

Although diaphragm surge tanks are widely used, they have some notable disadvantages:

1. Rust Prevention Issues: The tank body of diaphragm surge tanks is directly in contact with water, necessitating an internal anti-rust coating. However, during the welding process of connecting the tank interface to the body, high temperatures can oxidize the anti-rust coating. Originally silver-white, the coating turns black after welding and produces small black particles. These oxidation points, which are in constant contact with water, gradually rust, eventually leading to the entire tank rusting and potentially producing yellow water. This not only affects the aesthetic and cleanliness of the system but also its normal operation.

2. Gas Leakage from the Diaphragm: The diaphragm in a diaphragm surge tank is fixed between the two halves of the carbon steel tank through hot rolling. If not properly handled, tiny pores can form between the diaphragm and carbon steel, allowing the pre-charged gas to leak. This leakage is often undetectable but significantly impacts the tank's pressure regulation function. When gas leaks, the surge tank cannot operate properly and requires frequent gas replenishment, increasing maintenance costs and workload.

3. Weak Interface Strength: The tank wall is typically about 1 mm thick, and the interface is directly welded to the tank, resulting in limited torque resistance. During installation, the tank body must be rotated, which can easily break the interface if excessive force is applied. This issue is particularly common in air conditioning manufacturing. This design not only complicates installation but also increases the likelihood of equipment damage and higher repair costs.
 

Advantages of Bladder Surge Tanks

In contrast, bladder surge tanks overcome these disadvantages with a more rational and durable design:

1. Isolation of Water and Tank Body: Bladder surge tanks have an integrated bladder inside, where water only enters the bladder and does not contact the tank body, thus avoiding rust issues caused by welding. This design significantly extends the tank's lifespan and reduces maintenance requirements.

2. Replaceable Bladders: The bladders in bladder surge tanks are replaceable, making maintenance and replacement more convenient. If the bladder fails, it can be replaced without the need to change the entire tank, reducing maintenance costs and complexity.

3. Flange Connection: The use of a flange connection allows the interface to withstand higher torque, ensuring that the interface will not break during installation. This design enhances installation convenience and safety while improving the overall structural strength of the surge tank, ensuring long-term reliable operation.
 

Application Fields of Surge Tanks

Surge tanks are extensively used in central air conditioning, boilers, water heaters, variable frequency, and constant pressure water supply equipment. They buffer pressure fluctuations, eliminate water hammer, and stabilize pressure within the system. Here are specific application examples:

1. Central Air Conditioning Systems: Surge tanks effectively alleviate pressure fluctuations in the cooling water system, ensuring stable operation of the air conditioning system and improving energy efficiency.

2. Boiler Systems: In boiler systems, surge tanks absorb pressure fluctuations caused by water temperature changes, protecting the boiler and related equipment and extending their service life.

3. Water Heater Systems: Surge tanks in water heater systems balance pressure, prevent water hammer, and protect pipes and equipment, ensuring efficient operation of water heaters.

4. Variable Frequency and Constant Pressure Water Supply Equipment: In these systems, surge tanks smooth out pressure fluctuations, ensuring stable operation of the water supply system, reducing pump start frequency, and extending pump lifespan.

Surge tanks play an indispensable role in modern heating and water supply systems. While diaphragm surge tanks have some shortcomings, bladder surge tanks address these issues through improved structural design, offering a more reliable and durable solution. Understanding the structural characteristics and advantages of surge tanks can help in better meeting practical application needs. Proper selection and use of surge tanks not only enhance system operational efficiency but also extend equipment lifespan and reduce maintenance costs.