Measurement of entrapment hazards caused by drainage systems in - - PowerPoint PPT Presentation

Drowning and Safety

Measurement of entrapment hazards caused by drainage systems in swimming pools

• ir. Joost Avezaat, The Blue Cap Foundation, The Netherlands.

• The Blue Cap Foundation
• Hazard potential of drainage intakes
• Modeling suction entrapment risk
• Measurement of entrapment risk
• Experimental research
• Suction force as a guideline parameter
• Conclusion and discussion

Contents

The Blue Cap Foundation

• Founded in 2010 by the grandfather of a suction entrapment victim that

died in an Italian hotel pool.

• Non-profit knowledge and research institute.

1

Hazard potential of drainage intakes

Risk of drowning

• Entrapment by suction and entanglement of hair on the

grille covering submerged drainage intakes. Risk of severe injuries (vacuum)

• Effusion of blood (hemorrhage)
• Disembowelment
• Failure of vital organs

2

Flow in pipes is subjected to frictional effects

• Major pressure loss

∆𝑄 = 𝑔

𝑀 𝐸 𝜍𝑊2 2

• Minor pressure loss

∆𝑄 = 𝐿

𝜍𝑊2 2

Fluid dynamics

3

Pritchard, P. J., Fox, R. W., McDonald, A. T. (2011). Fox and McDonald's introduction to fluid mechanics. Çengel, Y. A., Cimbala, J. M. (2010). Fluid mechanics: fundamentals and applications.

Example:

Modeling suction entrapment risk

4

Example:

Modeling suction entrapment risk

4

Example:

Modeling suction entrapment risk

4

Example:

Modeling suction entrapment risk

𝑄𝑒𝑠𝑏𝑗𝑜 = 𝑄

𝐵 = 𝑄𝐶 − ∆𝑄𝐶𝐵

𝑄𝐶 = 𝑄𝑏𝑢𝑛 + 𝜍𝑕𝑖 + 1 2 𝜍𝑊

𝐶 2

∆𝑄𝐶𝐵 = 𝑔 𝑀 𝐸 1 2 𝜍 𝑅𝐶 + 𝑅𝐷 𝐵

2

𝐵 = 𝜌 4 𝐸2

5

Modeling suction entrapment risk

A swimmer that blocks an intake can be exposed to a large negative gauge pressure (vacuum).

• Negative gauge pressure can be predicted with analytical and

computational models.

• Magnitude largely depends on the length-diameter ratio of pipes used and

the flow velocity through these pipes.

• High risks of suction entrapment can be reduced with the design of the

piping system.

• The use of multiple drainage intakes in a drainage system does not exclude

that suction entrapment can occur.

• Though, it is often assumed that the use of multiple drainage intakes

provides sufficient protection against suction entrapment. EN 13451-3+A1 (2013). 6

Modeling suction entrapment risk

• Problems arise when modeling risk

in existing pools.

• The water circulation system is
• ften encased in concrete, making

it difficult to model and predict the negative gauge pressure. 7

Measurement of suction entrapment risk

• A solution was found in the measurement of entrapment risk.
• Measurement of the negative gauge pressure during suction

entrapment simulation. 8

Measurement of suction entrapment risk

• A solution was found in the measurement of entrapment risk.
• Measurement of the negative gauge pressure during suction

entrapment simulation. 8

Experimental research

• Testpool built for master thesis at University of Twente.
• Research the influence of system properties on entrapment risk.
• To test various safety measures and technical solutions.

9

Experimental research

• Testpool built for master thesis at University of Twente.
• Research the influence of system properties on entrapment risk.
• To test various safety measures and technical solutions.

9

Experimental research

• Blocking 1 of 1 drainage intakes (at initial Q = 35.6 m3/h)

10

Experimental research

Blocking 1 of 4 drainage intakes

Volume flow rate Q system (m3/h)

• Min. gauge pressure

PG (kPa)

• Max. gauge pressure

PG (kPa) 28.3 (1 pump) 0.51 1.01 43.0 (1 pump)

• 0.34
• 2.35

86.4 (1 pump)

• 19.95
• 23.86

108.4 (2 pumps)

• 24.89
• 29.68

11

Suction force as a guideline parameter

• Measurement of gauge pressure PG (Pa)
• Calculation of hydrostatic pressure PH (Pa)
• Increases with 9.8 kPa for each metre in depth
• Surface area of the grille covering a drain (m2)
• FSUCTION = (PH – PG)∙A
• Example:

Square grille (25 cm x 25 cm) Depth of 1 metre PG = -20 kPa. FSUCTION = 1.86 kN ≈ 190 kg of weight 12

Conclusion

• Current safety assessments rely on visual inspections.
• Protection against entrapment risks can only be

guaranteed with on-site measurements. 1. Negative gauge pressure and suction force. 2. Hair entrapment test (conform EN 13451-3). 3. Flow velocity through grille covering an intake. (≈ 0.3 m/s, at least < 0.5 m/s) 13

Conclusion

14 Obstruction test for floor outlets suction grilles (EN 13451-3).

• Dimensions are based on a 8-year-old child.
• Is protection against entrapment age related?

Conclusion

Responsibility of pool owners, operators, travel agencies:

• Plan: Assessment of entrapment risks.
• Do: Measure risks.
• Check: Evaluate the results of your assessment.
• Act: If necessary, implement safety measures.
• Unblockable grilles.
• Pressure-activated shut-off.
• Aeration and ventilation of negative gauge pressures.
• Reduce flow velocities.
• Add intakes or place them in inaccessible areas (behind barrier, buffer

tank).

• Start over to make sure that the implemented safety measures have

effect, i.e. risks are minimized to an acceptable level! 15

Discussion

16