Surge Vessels in Water Treatment: Protecting Systems from Pressure Surges

When running a water treatment plant, one of the big challenges is managing pressure surges in the pipelines. These sudden spikes, often caused by starting or stopping pumps or quickly closing valves, can lead to a phenomenon called water hammer, which creates a shock wave through the system. This can damage pipes, pumps, valves, and other equipment. That’s where surge vessels come in.

What Are Surge Vessels?

In simple terms, a surge vessel is like a shock absorber for water systems. It’s a pressurized tank that steps in when there’s a sudden change in water pressure. When a pressure surge occurs, the vessel either absorbs the excess pressure by allowing water to flow into the tank or releases water back into the system to maintain balance. This process protects the system from damage and keeps things running smoothly.

There are two common types:

• Bladder surge vessels have a flexible membrane separating air and water. When pressure builds up, the bladder compresses, and when pressure drops, it expands to release water.
• Non-bladder surge vessels allow water and air to mix, relying on compressed air to counteract pressure changes. These are simpler but may need more frequent maintenance.

Where Are They Used in Water Treatment?

Surge vessels are used in various parts of water treatment, including:

1. Pump Systems: Whenever pumps suddenly start or stop, the pressure changes can strain the system. Surge vessels help absorb these pressure spikes, protecting pumps and pipes from wear and tear.
2. Reverse Osmosis (RO) Systems: RO systems run under high pressure to push water through membranes. Any surge can damage these sensitive membranes. Surge vessels stabilize the pressure, preventing damage and keeping the system efficient.
3. Pipeline Networks: Long pipelines, especially those with changes in elevation, are prone to pressure surges. Surge vessels act as safety buffers, protecting these pipelines from potential bursts.
4. Water Hammer Prevention: This is the most common reason for installing surge vessels. Water hammer can cause significant damage over time, and the vessels act as a buffer to absorb and dampen the shockwaves.

Why Are Surge Vessels So Important?

1. Equipment Protection: They help prevent damage to pumps, valves, membranes, and pipelines by managing pressure spikes. This extends the lifespan of equipment and reduces maintenance needs.
2. System Reliability: Surge vessels keep the pressure stable, ensuring a consistent flow of water throughout the treatment process. This is especially crucial for systems like reverse osmosis, where steady pressure is a must.
3. Cost Savings: By preventing damage and reducing repairs, surge vessels save water treatment facilities significant money over time.
4. Safety: Pressure surges can create dangerous conditions. By managing these surges, surge vessels make the plant safer for workers.
5. Energy Efficiency: Surge vessels reduce the strain on pumps, making them more energy-efficient. This can lower the energy costs of running the plant.

What to Consider When Choosing a Surge Vessel

There are a few things to keep in mind when choosing the right surge vessel:

• System Pressure: The vessel needs to handle the highest pressure the system can produce. If it’s undersized, it won’t be effective.
• Volume Capacity: It should be large enough to absorb the expected pressure surges.
• Material: Surge vessels need to be made from materials that resist corrosion, especially in environments where the water may contain aggressive chemicals or be exposed to harsh conditions.
• Maintenance: Bladder surge vessels are usually lower maintenance, while non-bladder vessels might require more attention to prevent air absorption.

The Bottom Line

Surge vessels are essential in water treatment because they protect your system from pressure surges that can lead to costly damage. By absorbing these surges, they keep your equipment safe, maintain consistent pressure, save on repairs, and help ensure the smooth operation of the plant. They may require some upfront investment and regular maintenance, but the long-term benefits far outweigh the costs.

Ahmed Khaled Water and Wastewater Treatment Specialist