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Pump Station Design

Nov 16, 2018
Video Length:  1:05:01
Presented By:  Boyd Rose with Watertronics
If you design irrigation systems, chances are you have had to integrate a pump into a design. Picking the proper pump can be an overwhelming task. Join us while we hear from Boyd Rose with Watertronics talk about basic pump design and how the type of pump you pick comes down to your water source.

Webinar Contents:

Note: The following catalog of content covered in this webinar is time stamped to allow you to follow along or skip to sections of the video that are relevant to your questions. You can also search for content on this page using the FIND command in your browser (CTRL + F in Windows, Command + F in Mac OS.)

 

  • Intro/TOC
  • Introducing Pumps
  • History and Evolution
    • Fixed-Speed
    • Variable Speed
    • Types of Pumps and Pump Stations
      • Horizontal/Centrifugal
      • Vertical Turbine
      • Canned Turbine
      • Submersible Sled
  • Current Trends and Potential Future Needs

0:00 – 5:05: Intro/TOC

5:06 – 21:59: Introducing Pumps

Centrifugal pumps (5:06)

  • A machine for moving fluid by accelerating the fluid radially outward

 

Centrifugal pump components (5:33)

  • Impeller rotating within a case (diffuser)
  • Liquid directed into the center of the rotating impeller is picked up by the impeller’s vanes, accelerated to a higher velocity by the rotation of the impeller, and discharged by centrifugal force into the diffuser.
  • A collection chamber in the casing converts much of the kinetic energy (energy resulting from velocity) into head, or pressure.

 

Illustration of centrifugal pump and components (6:57)

  • Impeller thickness: The thicker the impeller, the more water will flow.
  • Impeller diameter: The larger the diameter, the more pressure it will create.
  • Rotation speed: The faster the impeller rotates, the more flow and pressure it will create.

 

Pump station design theory (7:56)

 

Potential issues caused by hydraulics in the piping system:

  • PSI drop
  • Over-demand
  • Varying inlet PSI
  • Restrictions
  • Pipe leaks

 

Pump stations are automatic, so they’re slaves to the demand in the system they’re regulating.

 

Theory of operation (9:48)

Basic understanding of how a pump station should operate:

  • Pressure drop initiates startup (remote signal or flow)
  • Regulate pressure
  • The right number of pumps running / demand
  • Shutdown sequence

 

Characteristics of a well-designed pump station (11:50):

 

Mechanical

  • Properly sized components that match capacity
  • Piping layout that minimizes losses
    • Fabrication and layout
  • Proper use and application of sensing equipment
  • Materials of construction (cost and durability)
    • Steel pipe and salt water

 

High voltage and controls (14:40):

  • UL 508 listed or other certification
  • The panel should have some type of cooling method
  • Type of panel is rated for the environment in which it’s installed
    • Not just moisture but dust
  • Provides a level of personal safety
    • Disconnect/interlock
  • Appropriate complexity or simplicity for the application

 

Implementing pumps (17:43)

  • Pressurized (most common)
  • Open discharge

 

Fixed speed vs. variable speed (18:15)

(i.e., foot on the brake vs. cruise control)

 

Fixed speed:

  • Pressure switch on/off
  • Hydraulic valve pressure regulation
  • EBV pressure regulation
  • No pressure regulation

 

Variable speed:

  • Electronic pressure regulation
  • Varies speed of the motor

22:00 – 56:29: History and Evolution

Fixed-Speed (22:00)

Disadvantages of fixed speed:

  • Energy loss with control valve
  • Control valve requires maintenance
  • Zones need to match HP combos
  • Pressure tank can be dangerous

Bottom line: Fixed-speed pumps are less efficient and require more maintenance.

 

  • Constant speed motors/pumps
  • Pressure control valve (added complexity)
  • Full in-rush starting
  • Pressure tank
  • “Stair-step” horsepower
  • “Foot on the brake”

 

 

Variable Speed (24:50)

Variable frequency drive (VFD) advantages:

  • Varies the speed for pressure control
  • Eliminates control valve and tank
  • Low in-rush – easier on pipes
  • Pulls only the power required to meet flow demand
  • Less maintenance
  • “Cruise control”
  • 25% power savings

 

Types of Pumps and Pump Stations (25:58)

The water source defines the pump system configuration.

 

Horizontal/Centrifugal (26:31)

Note that the pump itself will remain the same across these various system types. The differences lie in the water source and the way the pump is applied and configured.

 

  • Booster (pressurized source) – most common type (27:42)

Typical city water application. The pump boosts the pressure as it sends water out to an irrigation system.

 

  • Flooded suction – next most common type (28:45)

Draws water from a tank or pond. The water source is higher than the inlet of the pump.

 

  • Suction lift (well) (29:35)

The pump is at a higher location than that of the source water.

 

Pros and cons of horizontal system types (flooded suction, boost, and lift) (31:26)

 

Pros:

  • Least expensive
  • Small size
  • Easy access
  • Parts access

 

Cons:

  • Lower efficiency
  • 3,600 RPM
  • Marginal for dirty water
  • Poor lifting capabilities

 

Vertical Turbine (33:53)

A vertical turbine has multiple pump stages. The water goes in through an intake line through natural hydraulics and is pushed – not sucked – into a manifold and out into the irrigation system.

 

Vertical turbines are commonly used in golf course irrigation.

 

Vertical turbine components (35:45)

 

Vertical turbine pros and cons (36:45)

Pros:

  • Most efficient
  • 1,800 RPM – long life
  • No “lift” issues
  • Tolerant of dirty water

 

Cons:

  • More expensive
  • Requires a wet well
  • Submersible pressure maintenance pump
  • VHS motor is expensive to repair or replace

 

Canned Turbine (38:28)

A canned turbine is a vertical turbine pump in a scenario where the water source (generally a cistern or pressurized collection) needs to be boosted.

 

Canned turbine pros and cons (39:07)

Pros:

  • Most efficient
  • 1,800 RPM – long life
  • Flooded suction but turbine efficiencies
  • No wet well

 

Cons:

  • More expensive
  • Flooded or boost intake
  • Needs a dry sump
  • VHS motor expensive to repair or replace

 

Submersible Sled (39:56)

A structure on wheels that includes a submersible pump. It’s submerged in a water source such as a pond, river, or lake, and then pumps water out.

 

Submersible sled pros and cons (41:05)

Pros:

  • Less infrastructure
  • Low noise
  • Common components
  • No wet well

 

Cons:

  • Setting and repair access more complex
  • Must remove to service
  • Must remove in winter
  • Crane access can be a challenge

 

Examples of pump station installations (42:31)

 

Question: Does Watertronics sell cycle stop valves? (44:20)

Answer: No, they do not.

 

Question: Where does the pump generally go in the line? (45:03)

Answer: It typically goes water source - back flow preventer - pump station - master valve.

 

Question: Can the pump be placed at any location on the mainline? (46:00)

Answer: It can go anywhere on the line. Just pay attention to the location of the facility that requires the pump, and then factor in the potential pressure losses.

 

Question: Does the filter go before or after the pump? (47:27)

Answer: It’s ideal to filter the water before it’s pumped, but the water is often coming from a big body, which can be hard on the filter. So the filter is typically placed after the discharge of the pump and before the irrigation.

 

Question: On VFD pumps, do stations require pump boosts pumped into the controller to activate the pump while stations are running? (48:56)

Answer: It’s fully automatic. The VFD is just used to regulate the pressure as required by the system.

 

Question: Will a booster pump work with a reclaimed system that’s pressurized? (49:54)

Answer: Yes, it will work just fine. The water quality may be a bit lower, however.

 

Question: Is it OK to have the backflow preventer down at the street with 1,000 feet before the pump? (51:27)

Answer: Yes. In fact it’s preferable to have that much distance between the backflow preventer and the pump, because the backflow can cause extra strain on the pump intake when placed closer. This setup will give the water a chance to settle down and go into the pump in a smoother way.

 

Differences between single and three-phase power (52:40)

Single-phase power has the most amperage for smaller-voltage applications. Components are more expensive, as is the power. It’s generally applied for applications of 15 horsepower or less.

 

Three-phase power allows for three phases of power to come in, and it’s set up for larger-horsepower applications.

 

Overview of cloud-based pump controlling (54:50)

56:30 – end: Current Trends and Potential Future Needs

Current trends (56:30)

  • Reduction or elimination of city water for irrigation – cuts cost
  • Automatic source water blending – less city water use
  • Water quality monitoring and management integration
  • Cloud-based monitoring and control – saves labor, no radios
  • Premium efficient motors (now mandatory) – less power, same work. These motors are optimized with less friction and less heat. (92 or 93% efficiency vs. what used to be 87% efficiency)
  • Dedicated VFDs per motor – simplifies controls, needs more cooling
  • Disinfection before delivery via UV, ozone – safety concerns
  • Skid-mounted equipment enclosures – no building permit.
  • Retrofit market requires more highly engineered systems

 

Possible future trends (1:00:14)

  • “Internet of everything” is real and can be leveraged to gain even more resource efficiencies.
  • While power is nothing without control (data is nothing without analytics), smart analytics will be able to make decisions.
  • More system integration will only create more site resource efficiencies.
  • Dynamic pressure control direct to pump to reduce unneeded pressure – could have a substantial impact on irrigation design and equally important on power systems.

 

Summary (1:01:53)

  • Water source and water quality drive the design of the pump station.
  • Make sure you accept the limitations of your choice.
  • Healthy trends are creating resource efficiencies.
  • Future trends will likely double those efficiencies in 10 years.

 

Presenter contact info:

Boyd Rose of Watertronics

Phone: (262) 337-3835

Email: boyd.rose@watertronics.com

 

Question: On a site with a 100-foot elevation change with a POC pump located in the middle, many of the valves won’t require the pump because they’ll be downhill. How does the pump handle this setup? (1:03:08)

Answer: This is where the dynamic demand control will help. The pump will simply regulate the pressure to keep up with the demand, regardless of elevation.

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