Short Answer:

Surge tanks are vertical storage structures used in hydraulic systems to control pressure variations and prevent water hammer. There are different types of surge tanks designed based on flow conditions and operational requirements. The main types include simple surge tanks, restricted orifice surge tanks, and differential surge tanks. Each type serves the purpose of stabilizing pressure but in slightly different ways.

A simple surge tank is an open tank that directly absorbs pressure. A restricted orifice tank limits the flow rate in and out, while a differential tank uses inner chambers to regulate water movement more precisely. Selection depends on system design, length, and flow behavior.

Detailed Explanation:

Types of surge tanks used in hydraulic systems

In long or high-pressure pipelines, especially those used in hydropower, water supply, and irrigation, surge tanks are important safety components. They are used to absorb pressure changes, reduce water hammer, and maintain flow stability. Surge tanks come in different designs, each serving a specific purpose depending on how the system operates and what kind of control is required.

Here are the major types of surge tanks used in civil and hydraulic engineering:

1. Simple Surge Tank

This is the most basic type of surge tank. It is an open vertical tank connected to the main pipeline.

How it works:

• When there is a pressure surge, the water rises in the tank and absorbs the excess energy.
• When there is a pressure drop, water from the tank flows back into the system.

Advantages:

• Easy to design and maintain.
• Immediate response to pressure changes.

Limitations:

• Sudden rise in water level during large surges.
• Not suitable for very long or high-pressure pipelines.

2. Restricted Orifice Surge Tank

This tank is similar to the simple type but has a narrow opening (orifice) at its base that controls the flow between the tank and the pipeline.

How it works:

• The restricted opening slows the inflow and outflow of water, providing a gradual pressure adjustment.

Advantages:

• Reduces sudden water level rise.
• Provides smoother operation.

Limitations:

• Slightly delayed response compared to simple tanks.
• More complex to design.

3. Differential Surge Tank

This is an advanced type of surge tank with an inner riser pipe and a surrounding outer tank. It is designed to handle high and low flow variations effectively.

How it works:

• During small flow changes, the inner riser handles the pressure.
• For larger surges, the outer tank gets involved.
• This setup provides better control over fluctuating pressures.

Advantages:

• Highly efficient in pressure regulation.
• Suitable for long and high-pressure pipelines.

Limitations:

• Expensive and complex to construct and maintain.

4. Closed Type Surge Tank (with Air Cushion)

Instead of being open to the atmosphere, this tank is sealed and contains air or gas at the top.

How it works:

• The air cushion absorbs the pressure surge like a spring.
• Water compresses the air during surges, which then pushes back when needed.

Advantages:

• Space-saving and compact.
• Works well in systems where open tanks are not feasible.

Limitations:

• Needs regular pressure checks.
• Slightly more technical operation.

Conclusion:

There are several types of surge tanks used in hydraulic systems—each designed to manage flow and pressure in different ways. Simple tanks offer direct relief, restricted orifice tanks control flow speed, differential tanks provide advanced pressure handling, and closed tanks offer compact solutions. Choosing the right type depends on the system’s pressure, flow conditions, and safety requirements.