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Case study · Surge analysis

Surge analysis of upgraded TSE pumping stations: Al Dhaid, Sharjah

Transient analysis of two upgraded treated sewage effluent (TSE) pumping stations and their distribution networks. The study checked whether the existing surge vessels and air valves still protect the system after the capacity upgrade.

Client
Sharjah Municipality

Location
Al Dhaid, Sharjah, UAE

Scope
Pump trip, standby start, valve closure

Tools
WANDA (Deltares)

Criteria
−0.5 to 8.0 barg (AWWA)

2 stations

PS-01 and PS-02 upgraded TSE pumping stations

−1.0 barg

Minimum pressure without protection

−0.5 to 8.0 barg

Achieved with the existing vessels and air valves

1 new air valve

The only addition needed

The challenge

More capacity, same protection?

Raising the capacity of an existing pumping station changes the surge it creates. The question was whether the existing surge vessels and air valves, sized for the old duty, would still keep pressures within limits, or whether new protection was needed.

Pump station layout with bladder surge vessel
Pump station arrangement with bladder surge vessel

Our approach

Transient analysis

  1. WANDA models of both pump groups and their distribution networks fed from a common reservoir
  2. Pump trip without protection, then with the existing surge vessels
  3. Additional air valve locations tested where pressures stayed low
  4. Duty pump trip with delayed standby pump start to set a safe restart time
  5. Closure of the highest-demand tap-off valve with the duty pump running
Maximum and minimum head envelopes along the main
Maximum and minimum head along the rising main

Results

Key results

Key findings

  • Without protection, both stations see pressures down to −1.0 barg with a cavitation risk; air valves alone are not enough.
  • At PS-01, the two existing 3.5 m³ vessels plus one new air valve upstream of a check valve bring pressures within −0.5 to 8.0 barg.
  • At PS-02, the existing 5 m³ vessels and three air valves are sufficient.
  • The standby pump must start no earlier than 120 s (PS-01) or 90 s (PS-02) after a duty pump trip.
  • Tap-off valves must close in no less than 30 s.

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