iahr2015 - discussion on the acceptance criteria for physical model testing of pumping stations,...

7 augustus 2015

Discussion on the acceptance criteria for physical

model testing of intake pumping stations

Physical model testing

7 augustus 2015

Physical model testing of pumping stations is

performed to ensure suppling hydraulically proper

feed flow towards the pumps to:

• Increase of lifetime and reduction of maintainance cost

• Maintain the efficiency of the pump

• Ensure pump capacity

Physical model testing

7 augustus 2015

Physical model testing of pumping stations is

performed to ensure suppling hydraulically proper

feed flow towards the pumps to:

• Increase of lifetime and reduction of maintainance cost

• Maintain the efficiency of the pump

• Ensure pump capacity

Acceptance criteria

7 augustus 2015

Vortices Pre-rotation Velocity variations

Acceptance criteria - Vortices

7 augustus 2015

Acceptance criteria – Pre-rotation

7 augustus 2015

“Preswirl alters the inlet velocity vector at the impeller vanes, resulting in undesired changes

in pump performance characteristics, including potential vibration” - ANSI/HI

“Except for some special cases, …, pump performance near the highest efficiency point is

influenced only slightly by rotating flow” - TSJ-S002

ANSI/HI

• long term average (600 s)

- 100% < 5

• short term (10-30 s)

˗ 90% < 5

˗ 100% < 7

IIHR

• long term average (300 s)

- 100% < 5

Recent research – Pre-rotation

7 augustus 2015

10 s 10-40% higher

than 30 s

accuracy 0.3°

accuracy 0.35°

ANSI/HI

• short term (10-30 s)

˗ 90% < 5

˗ 100% < 7

IIHR

• long term average (300 s)

- 100% < 5

ANSI/HI

• long term average (600 s)

- 100% < 5

Acceptance criteria - Velocity variations

7 augustus 2015

not required - TSJ-S002

required - ANSI/HI & IIHR

ANSI/HI

• Temporal variation < 10%

• Spatial variation < 10%

Local velocity compared to cross

sectional average:

vlocal – vaverage < + 10% vaverage

IIHR

• Spatial variation <5%

Local velocity compared to

average on concentric circle:

vlocal – vcircle < + 5% vcircle

vlocal

vaverage

vlocal

vcircle

Velocity

measurements

Measurement

location Impeller level

Bell mouth throat - ANSI/HI & IIHR

Acceptance criteria- Velocity variations

7 augustus 2015

impeller

throat

Recent research - Velocity variations

7 augustus 2015

throat impeller

throat impeller

Measurement

location Impeller level

Bell mouth throat - ANSI/HI & IIHR

Optimisation of the feed flow

7 augustus 2015

7 augustus 2015

Reference Backwall splitter

Recent research - Optimisation of the feed flow

Modifications have (sometimes) a local effect

Example: Backwall splitter decreases the velocity at the back

No other effects observed

Summary

7 augustus 2015

Vortices

Examination of a pumping station with respect to vortices is consistent

Pre-rotation

The acceptability of the feed flow with respect to pre-rotation depends on

• the used standard

• the interpretation of the acceptance criterion

Velocity variations

The acceptability of the feed flow with respect to velocity variations depends on

• the used standard

• the interpretation of the acceptance criterion

Modifications to the pump compartment have a limited effect on the velocity variations