FLUID surge

A fluid surge, also called a water hammer (for liquids) or surge pressure, occurs when a sudden change in fluid velocity causes a rapid pressure rise. This can happen when a valve is closed or opened quickly, a pump is started or stopped abruptly, or when there is a sudden change in flow conditions. The surge causes a pressure wave to travel through the pipeline, which can result in damaging effects such as pipe bursts, mechanical stress, or leaks.

This dataset and calculations are for educational purposes only.

initial hydraulic grade line

pump house arrangement

Based on the topographical survey, we established the hydraulic grade line from the tanker manifold to the atmospheric tank. For the initial analysis, we assumed no surge protection measures were in place to safeguard the pipeline from fluid surges. The system involves three parallel pumps arranged in series, pumping SAE 10W oil at 38°C from the tanker manifold. The current total static head requirement is 215 meters, which exceeds the capacity of a single set of high-lift and low-lift pumps, and can only provide a 50-meter head. Therefore, additional pumps in series are necessary to meet the total head requirements.

extreme pressure and heads

Negative pressure indicates cavitation at certain segment of the piping system without adding the hydropneumatic tank as surge suppressor (indicated by N/A above).

HEAD

HIGH LIFT PUMP SPECIFICATION based on available pump chart.

EFFICIENCY

HIGH LIFT PUMP SPECIFICATION based on available pump chart.

TRANSIENT

HIGH LIFT PUMP SPECIFICATION based on available pump chart.

vapor pressure formation

In our design, we are able to minimize the vapor pressure formation and only the maximum pressure and small amount of negative pressure will need to be mitigated for these transient events. However, note that in this case, our vapor volume is zero which was mitigated during the pump design.

At 2.1 seconds, the surge started from the check valve and travels to the atmospheric tank uphill in just 10.3 seconds at the speed of calculated wave propagation through the steel pipes.

The pressure wave propagation, with a zero-volume flow rate, fluctuates between 195m and 225m and does not dissipate over the defined time interval of 120 seconds, which could potentially cause damage to the piping system.

The force exerted at x, y, z directions including the resultant radial force which needs to be accounted for designing the pipe support if required for redundant protection (to be included in LOPA) aside from adding pressure/surge relieving (surge suppression) devices.

surge suppressor

Sizing a hydropneumatic tank (or surge tank) based on surge analysis is a critical step in controlling pressure transients (water hammer) in pipeline systems. The tank's size must be adequate to absorb or release enough fluid to maintain acceptable pressure levels during transient events such as pump shutdowns, valve closures, or sudden changes in flow.

The surge analysis provides key data such as:

Maximum and minimum pressures during transient events.
Flow rate variations over time.
Locations of potential cavitation or extreme pressure surges.

We will investigate if we need a hydropneumatic tank or other kind of surge suppressor device.

This data helps determine the required volume of fluid that the tank must absorb or release to mitigate the surge. The volume of fluid that the tank needs to accommodate is based on the flow rate changes and the duration of the transient event. Below is the transient duration even after 5600 seconds, the oscillation of surge didn't stop.

Position of the surge even after 5600 seconds in the system and still did not dissipates. However, from the table below we will be able to design appropriate hydropneumatic tank. By doing sensitivity analysis, we will be able to find the right spot of the hydraulic tank whether to use a single tank or multiple tanks.

First 25 entries of initial surge.

Last 25 entries of surge after 5600 seconds.

Peak Pressure:

The maximum pressure observed is 2002.16 kPa at 9.8 seconds.

There are other high-pressure instances close to 2000 kPa, such as 1999.68 kPa at 33.6 seconds.

Flow Rates:

The flow rate remains negative throughout this dataset, fluctuating between -5.74 m³/h and -5.25 m³/h. This suggests a persistent reverse flow during the transient event. Note that in this case, we don't have air/vapor volume occuring in the piping system.

Pressure Drop:

The pressure fluctuates after the peak values. After the pressure peaks at 2002.16 kPa, it decreases to 1938.60 kPa by 57.1 seconds.

Given with the above conditions, a designed surge suppressor device is enough to protect the pipeline without using hydropneumatic tank.

Q.E.D.

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