Sediment Cleaning of Water Tanks

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Final Design

Team Name H2Only
Duration Fall 2016 – Spring 2017
Faculty Advisers Dr. Tao Xing
Client Scott Smith
Team Members
  • Eric Hill
  • James Rockwell
  • Marshall Bolen
  • Lucio Barajas

There are three water towers on the University of Idaho campus, three more in the city of Moscow, countless more in the United States, and they all have the same problem; sediment buildup. On campus these water tanks are either used for as potable water for drinking or chilled water for the steam plant.

Problem Statement

The Energy Plant of the University of Idaho is looking for a solution to sediment cleaning for chilled water tank. The current approach is time consuming, expensive, and the chilled water service must be stopped during the cleaning process. The current method requires the tank to be drained of almost 2.5 million gallons and having someone from facilities clean it manually. The other option is to hire scuba divers to go in the tank and remove the sediment with a vacuum. That alone costs around $55,000. Water is wasted when it is removed, and the water needs to be chilled to the correct temperature once the tank is operating again. Any chemicals used to prevent rusting and killing bio-growth is lost during the process and has to be replaced. The total cost of the operation is over $230,000 for the chilled water tank.

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Design Specifications

Small Scale Prototype Design Specifications
Description Current Status Priority
Create a semi-transparent tank (no more than 50 gallons) that can validate proof of concept Complete Medium
Acquire surrogate sediment with comparable density/viscosity Complete Medium
Scalable to full scale dimensions Complete High
Avoid re-suspension Complete High
Create evenly distributed suction through slit Complete High
Device system for collecting and disposing of sediment Complete Medium
Create automated sediment level detection Researching Low
Large Scale Prototype Design Specifications
Description Current Status Priority
Bill of materials, drawing, and system diagram that can be implemented by UI facilities staff In Progress High
Remove 95% of sediment each time system operates Complete Medium
Continue tank operation while cleaning Complete High
External sediment separation and recycle of clean water In Progress High
Easy maintenance Complete Medium
Fully automated operation In Progress Medium
Components fit within the existing tank structure and penetrations Complete High
Versatility for application in multiple tanks In Progress Medium

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Alternative Design Selection

Picture Device Pros Cons
Full Sweeping Device
Full Sweeping Suction Device Complete removal with single armature rotation
Minimal moving parts
Simple design Inexpensive
Low likelihood of complications
Minimized suction force due to large suction slit
Inability to maneuver over and around obstacles
Lack of suction control
Possibility for clogging throughout system
Lead Screw Design
Vacuum on Lead Screw Can handle larger sediment buildups
Large, localized suction force
Potential to be very versatile
Not as prone to internal buildup and clogging
Many mechanical parts
Expandable tube
Lengthy tank cleaning duration
Inability to maneuver above and around obstacles
Heavy steel lead-screw
Diaphragm in Tank
Diaphragm in Tank More localized suction
High flow rates
Turbulence would help loosen up sediment
It would clean all tank areas
It would need a large frame to support it
Costly to power the raising and lowering of the frame
Material would be costly as well
Multiple Tubes
Multiple Tubes It could reach all the areas of the tank
It would remove the sediment the fastest
Material would be costly for large tanks
Costly to create all the suction needed for all the hoses

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Picture Description
First Prototype
This model was to test the effectiveness of sediment and water removal with the head pressure we had. It was made from round PVC pipe with end caps on it. The bottom of it was machined to create a flat surface for our suction slit to be made. We also used this to find a slit size that would prevent clogging.
Second Prototype
Our second prototype was made almost entirely out of 3D printed material. Parts assembled together to test different sweeper arms and to easily make changes to our design if we needed to. The bottom slit was made the same size for all our sweeper arms.

Sweeper Arm Alternatives

Trapezoid Sweeper Arm Alternative
Semi-circular Sweeper Alternative
Rectangular Sweeper Arm (Current Choice)

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Final Prototype Design

Components Description
Model Tank
Model Tank: 1:33 scale size model tank. Will be raised four feet to simulate head pressure in actual water tank.
Slip Ring with gear
Slip Ring: This allows us to rotate our sweeper arm without having to worry about our exit pipe twisting or needing extendable pipes. It is a two part device with a bottom moving base placed around the support beam, and a stationary cap attached to an exit pipe. It has a 28 tooth gear attached to the moving base to rotate our device, and keep our motor out of the water.
Sweeper Design
Sweeper: One of our current sweeper designs. This one is easy to manufacture for the full scale size. Separation, turbulence, and re-suspension will not be an issue while it moves at the bottom of the tank. It has a slit at the bottom that creates even suction throughout the length of the sweeper.
Exit Pipe
Exit Pipe: Exit pipe drilled into the side of the tank to remove our sediment. It is attached to a pump for our prototype. The water and sediment will be removed from the tank and sent into an external separation device.
Axle: A long axle to allow us to rotate our device in our tank both manually and with a motor.

Driving Gear
Drive Gear: A nine tooth gear connected to our axle to slow down our rotation and give us more torque. More like it are attached on the other end of our axle to connect it to our motor and give us a 3 to 1 gear ratio.
Motor Mount
Motor Mount: 3D printed motor mount to keep our motor out of the water and in position to automatically run our cleaning device. Additional pieces allows us to use a different size motor. It rests on the support column of the tank.

Stepper Motor
Stepper Motor: 400 step stepper motor used to drive our cleaning device. Later upgraded to a geared stepper motor for more torque. The motor sits on the top of the motor mount.

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Team Members

Photos Bio
Eric Hill:

Major - Mechanical Engineering
Hometown - Kamiah, Idaho
Interests - Fishing, mountain biking, and skiing

James Rockwell:

Major - Mechanical Engineering
Hometown - Grangeville, Idaho
Interests- Skiing, hunting, fishing, mountain biking, and whitewater

Marshall Bolen:

Major - Mechanical Engineering
Hometown - Boise, Idaho
Interests - Hunting, fishing, sports, snowboarding

Lucio Barajas:

Major - Mechanical Engineering
Hometown – Idaho Falls, Idaho
Interests - Soccer, longboarding, video games

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Document Archive

Meeting Minutes
Fall Semester
Spring Semester

Other Documents
Team Contract
Client Interview
Design Review
Detailed Design Review
EXPO Poster
Technical Presentation
Design Report

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