HAMMER Training Part 8: Surge Protection using Tanks and Valves Part 1

Surge Tanks, Surge Valves, and Air Valves Overview

Introduction to Storage Tanks

• The lecture covers surge tanks, surge valves, and air valves, starting with storage tanks that provide passive surge protection by holding a volume of water to mitigate surge effects.

Functionality of Storage Tanks

• Storage tanks reflect transient pulses differently than dead ends; they do not transmit pulses between systems when placed as reservoirs between pipes.

Reservoir Elements Explained

• Reservoir elements serve as infinite water sources with constant hydraulic grades, used as boundary conditions in simulations where known hydraulic grades are assumed constant during transients.

Surge Tank Characteristics

• Surge tanks can refer to both regular tank elements and specialized surge tank types in modeling software. They behave similarly during transient simulations.

Water Level Dynamics in Tanks

• Water levels in tanks vary over time due to inflow and outflow; surge tanks typically match the steady-state hydraulic grade level (HGL), remaining mostly stagnant until needed for transient events.

Simplifying Surge Tank Modeling

• In modeling software like Hammer, setting "Treat as Junction" to true allows the simulation of a surge tank's pressure as if it were floating on the system without needing initial elevation calculations.

Types of Surge Tanks: One-Way vs Two-Way

• There are two types of surge tanks:

• Two-way: Stores energy like a normal tank; allows inflow and outflow but is impractical for high head systems due to height requirements.

• One-way: Equipped with check valves that prevent inflow under normal conditions but allow water entry during pressure drops (e.g., pump shutdown).

Operational Mechanics of Two-Way Surge Tanks

• Two-way surge tanks include differential orifices for managing head loss between inflow and outflow. They may have bypass lines modeled for efficient flow management during transients.

Functionality of One-Way Surge Tanks

• One-way surge tanks utilize check valves that close under normal pressure conditions but open when system pressure drops significantly, allowing stored water into the system during emergencies.

Surge Tanks and Their Functionality

Understanding Surge Tanks

• Surge tanks are designed to manage transient events in water systems, allowing for the movement of water mass but not providing protection against operational surges due to a closed check valve.

• A simplified diagram illustrates a one-way surge tank where the water surface elevation is lower than the hydraulic grade line (HGL), indicating limitations in height during normal conditions.

Operational Mechanics

• When a down surge wave occurs, if it drops below the water surface elevation of the surge tank, the check valve opens, permitting water entry to maintain column movement and prevent further down surges.

• The report period field for surge tanks does not appear in all data views; users must access specific transient output reports to find relevant results.

Data Reporting and Analysis

• To analyze surge tank performance, users should navigate to detailed reports that include metrics such as water surface level and head loss across connections between pipes and tanks.

• Key metrics tracked include inflow rates (positive values indicate flow into the tank), spill rates (overflow when levels exceed capacity), and head loss due to resistance at pipe openings.

Surge Control Valves

• Various valves can control surges; some may induce them while others mitigate their effects. Check valves can be strategically closed during surges for better management.

• Air valves play a crucial role by admitting air into systems under negative pressure conditions, helping alleviate local high-pressure issues without offering widespread protection like surge tanks do.

Types of Surge Control Valves

• Different types of air valves exist within hydraulic models, including combination air valves that help manage pressure effectively at critical points in the system.

• Surge control valves are modeled as elements that either relieve or anticipate surges based on preset pressures. They operate using spring mechanisms that respond when pressure thresholds are exceeded.

Surge Anticipator Valves and Their Functionality

Overview of Surge Anticipator Valves

• Surge anticipator valves are designed to respond to pressure changes in a system, requiring parameters like spring constant, diameter, and threshold pressure for operation.

• These valves primarily address positive pressure spikes but may not react quickly enough during power failures due to sharp surges from pump shutdowns.

Comparison with Surge Relief Valves

• The surge anticipator valve (SAV) differs from the surge relief valve (SRV); while SRVs open at an upper pressure set point, SAVs operate based on lower pressure limits.

• SAVs can close based on either a specific threshold pressure or a time delay, providing flexibility in their operation without relying on springs.

Operational Dynamics

• A graphical representation illustrates the timing of valve opening; there is an initial delay before the valve opens when threshold pressures are reached after a pump shuts down.

• Once opened, the SAV remains fully open in anticipation of returning surges, effectively managing downsurge waves and potential vapor formation.

Closing Mechanism

• The closing mechanism of the SAV is determined by either reaching a certain threshold pressure or through a predefined time delay, allowing for adaptable responses to varying conditions.