controlling water hammer with soft starters

Using Soft Starters To Control Water Hammer Without The Headaches

Using Soft Starters To Control Water Hammer Without The Headaches

Dan Barr, PEVance Martin, PE

Dan Barr, PEVance Martin, PE

2008 Ohio AWWA State Conference, Toledo, Ohio

IntroductionIntroduction

• Noisy, Shaking, or Broken Pipes

• False SCADA Alarms

• Customer complaints

• Premature Equipment Failures

All symptoms of water hammer.

• Noisy, Shaking, or Broken Pipes

• False SCADA Alarms

• Customer complaints

• Premature Equipment Failures

All symptoms of water hammer.

What is Water Hammer?What is Water Hammer?

• Rapid pressure changes caused by rapid velocity changes.– Pump Start/Stops– Valve and Hydrant Operation – Demand Changes

• Travels as Pressure Waves

• Rapid pressure changes caused by rapid velocity changes.– Pump Start/Stops– Valve and Hydrant Operation – Demand Changes

• Travels as Pressure Waves

Stopping Water HammerStopping Water Hammer

• Soft starters can be very effective when compared with pump control valves and other controls.

• Soft starters can be very effective when compared with pump control valves and other controls.

What are Soft Starters?What are Soft Starters?

• Used with electric motors to temporarily reduce the load and torque during startup.

• Reduces mechanical stress on the motor and shaft as well as electrodynamic stress on the wires and switchgear feeding the motor.

• Housed in their own enclosure

or a MCC.

• Used with electric motors to temporarily reduce the load and torque during startup.

• Reduces mechanical stress on the motor and shaft as well as electrodynamic stress on the wires and switchgear feeding the motor.

• Housed in their own enclosure

or a MCC.

Why Soft Starters?Why Soft Starters?

• Can slowly start and stop pumps.

• Generally less expense and maintenance.

• Provide both hydraulic and electrical benefits.

• Often required by electric utilities.

• Takes up less space.

• Can slowly start and stop pumps.

• Generally less expense and maintenance.

• Provide both hydraulic and electrical benefits.

• Often required by electric utilities.

• Takes up less space.

Why not Soft Starters?Why not Soft Starters?

• Will not control water hammer caused by power failures.

– Pump control valves won’t either.

– Other means of controlling them maybe necessary.

• Potentially not sufficient when very slow stops required.

• Neither of these scenarios are common in Ohio.

• Will not control water hammer caused by power failures.

– Pump control valves won’t either.

– Other means of controlling them maybe necessary.

• Potentially not sufficient when very slow stops required.

• Neither of these scenarios are common in Ohio.

Do Soft Starters Work?Do Soft Starters Work?

• Yes, when selected, installed, programmed, and set-up properly.

The following three case studies illustrate this.

• Yes, when selected, installed, programmed, and set-up properly.

The following three case studies illustrate this.

Case 1: Improper Programming – IntroductionCase 1: Improper Programming – Introduction

• High Service Pump Start-up Problems including:

– High Pressure Transients

– Pipe Breaks

– Customer complaints

• High Service Pump Start-up Problems including:

– High Pressure Transients

– Pipe Breaks

– Customer complaints

Case 1: Improper Programming – Problem IdentifiedCase 1: Improper Programming – Problem Identified

• Soft starter programming was inappropriate.

• Soft starter used the following illustrated curve.

• Soft starter programming was inappropriate.

• Soft starter used the following illustrated curve.

Case 1: Improper Programming – Problem IdentifiedCase 1: Improper Programming – Problem Identified

• This programming let the pump stall.

• Stalling occurs when the flow stops prematurely.

– While motor is still turning.

• This programming let the pump stall.

• Stalling occurs when the flow stops prematurely.

– While motor is still turning.

Case 1: Improper Programming – SolutionCase 1: Improper Programming – Solution

• Programming revised to prevent stalling.

• Revised program shown below:

• Programming revised to prevent stalling.

• Revised program shown below:

Case 1: Improper Programming – Lesson LearnedCase 1: Improper Programming – Lesson Learned

• All programming is not equal.

• Pump control very smooth after programming changes.

• Soft starter should be supplied with a “S” curve stop program.

• Hardware did not need replacement.

• All programming is not equal.

• Pump control very smooth after programming changes.

• Soft starter should be supplied with a “S” curve stop program.

• Hardware did not need replacement.

Case 2: Inappropriate Soft Starter Style – IntroductionCase 2: Inappropriate Soft Starter Style – Introduction

• High service pump causing problems.– Unacceptable low pressure transients

– Customer complaints.

• The soft starter was not effective.

• High service pump causing problems.– Unacceptable low pressure transients

– Customer complaints.

• The soft starter was not effective.

Case 2: Inappropriate Soft Starter Style – IntroductionCase 2: Inappropriate Soft Starter Style – Introduction

• Actual Transients Recorded:• Actual Transients Recorded:

Case Study Two - Before Software Change

0

20

40

60

80

100

120

140

160

0 60 120 180 240 300 360 420

Time (Seconds)

Pre

ss

ure

(p

si)

Pump Start

Pump Stop

Case 2: Inappropriate Soft Starter Style - SolutionCase 2: Inappropriate Soft Starter Style - Solution

• Investigations by B&N and the manufacturer– The control logic could not control the transients.

– A newly developed control card was installed.

• This unit worked by controlling the current instead of the voltage or torque.

• Not as successful in controlling transients.

• Investigations by B&N and the manufacturer– The control logic could not control the transients.

– A newly developed control card was installed.

• This unit worked by controlling the current instead of the voltage or torque.

• Not as successful in controlling transients.

Case 2: Inappropriate Soft Starter Style - SolutionCase 2: Inappropriate Soft Starter Style - Solution

• This soft starter controlled motor current.

– Not as successful in controlling transients.

– More successful starters control voltage or torque.

• This soft starter controlled motor current.

– Not as successful in controlling transients.

– More successful starters control voltage or torque.

Case 2: Inappropriate Soft Starter Style – Lessons LearnedCase 2: Inappropriate Soft Starter Style – Lessons Learned

• Not all soft starters are created equal.

• Voltage or Torque control better than current control.

• Confirm soft starter manufacturer’s experience.

• Not all soft starters are created equal.

• Voltage or Torque control better than current control.

• Confirm soft starter manufacturer’s experience.

Case 3: Incorrect Settings - IntroductionCase 3: Incorrect Settings - Introduction

• Existing booster station issues

– Shutting down too quickly

– Causing low pressure transients

– Causing customer complaints.

• These soft starters same as the first case study.

• Existing booster station issues

– Shutting down too quickly

– Causing low pressure transients

– Causing customer complaints.

• These soft starters same as the first case study.

Case 3: Incorrect Settings – SolutionCase 3: Incorrect Settings – Solution

• Softstarter style and programming verified.

• Settings were examined.– Set incorrectly.

– Pump Stop duration too short.

• Settings were corrected and complaints stopped.

• Softstarter style and programming verified.

• Settings were examined.– Set incorrectly.

– Pump Stop duration too short.

• Settings were corrected and complaints stopped.

Case 3: Incorrect Settings – Lessons LearnedCase 3: Incorrect Settings – Lessons Learned

• Buying the correct soft starter is not enough.

• Field settings are just as important.

• Verify performance with recorders.

• Buying the correct soft starter is not enough.

• Field settings are just as important.

• Verify performance with recorders.

SummarySummary

• Water hammer needs to be minimized– Damages equipment

– Causes customer complaints.

• Caused by rapid changes in velocity.

• Water hammer needs to be minimized– Damages equipment

– Causes customer complaints.

• Caused by rapid changes in velocity.

SummarySummary

• Water hammer Control– Many different solutions

• Soft starters potentially great choice– Less Expensive

– Less Space

– Less Maintenance

– Can be very effective provided they are selected, supplied, installed, and set-up correctly.

• Water hammer Control– Many different solutions

• Soft starters potentially great choice– Less Expensive

– Less Space

– Less Maintenance

– Can be very effective provided they are selected, supplied, installed, and set-up correctly.

SummarySummary

• Key considerations for success– S-Curve programming

– Voltage control

– Correct field settings

– Manufacturer experience

• Verify performance

• Key considerations for success– S-Curve programming

– Voltage control

– Correct field settings

– Manufacturer experience

• Verify performance

Any Questions or Applications?

Any Questions or Applications?