Ben Webb
BSME Northwestern Univ.
ME CAPSTONE DESIGN
Project Dates: January 2016 - June 2016
In January of 2016, as part of Northwestern's ME Capstone Design Project course, I was paired with a team of four other engineering undergraduate students, and we were given asked by our client, DOW Chemical, to help them improve their hydroblasting cleaning process. hydroblasting is a cleaning process similar to pressure washing, however hydroblasting utilizes water pressures ranging from 5,000psi to 40,000psi (and sometimes even higher). DOW uses this method to clean process equipment, and my team was asked to specifically look into potential damage caused to heat exchangers as a result of hydroblasting. The image to the left shows a pair of new heat exchangers, similar to the ones DOW uses hydrobalsting to clean.
One of the major challenges of this project was refining the request given by DOW Chemical into an engineering challenge that we could tackle of the course of a two quarter (6 month) project. As a result of this effort, we reached the following project definition, taken directly from our final report:
"Our client, The DOW Chemical Company, uses a process called hydroblasting to clean process equipment used in their chemical plants. The goal of this project is to evaluate damage incurred on process equipment as a result of hydroblasting, and to ascertain:
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If such damage does occur as a result of the high pressure jet
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The extent of the damage to the metal
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The minimum operating conditions which cause damage (“hard limits”)
The team is evaluating three operating parameters during testing: water pressure, flow rate, and lance velocity.[1] All other potential variables, such as water quality, nozzle type/size, nozzle rotational velocity, and tube diameter will be accounted for by DOW in their analyses of our results."
With the task at hand clearly defined, we were able to proceed with the engineering design element of the project, where my team used an iterative design process to create a functioning test rig to explore the effects of ultra high pressure water jet impact on metals.
[1] Water pressure will be tested in the range of 5k – 40k psi. Flow rate will be tested in the range of 1 – 6 gpm. Lance velocity will be tested in the range of 2 – 12 in/s.
Going into this project, no one on my team knew anything about hydroblasting, so that was the first question that needed to be answered. We conducted weeks worth of research into the hydroblasting process, reading literature from industry publications, studying the fluid mechanics behind hydroblasting, and consulting with industry experts at Veolia North America, DOW's local hydroblasting provider. Using what we learned, we were able to effectively plan out our project, utilizing Gantt charts to create a project timeline and track milestones for the upcoming design phase. Through research, we were able to determine that a jet impinging on a plate would provide a sufficient model of a hydroblasting jet in operation, giving us a direction to move in for the next step, the design process.
A typical hydroblasting lance, here the water pressure is very low to make capturing this image possible.
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Research and Planning
02
Design
Once we narrowed down our project definition to test only by varying pressure, flow rate, and lance (nozzle) velocity, we were able to identify the basic needs of our test rig; It would need to move metal samples under a high pressure water jet at precise speeds, while maintaining the proper flow rate and pressure characteristics for the test. We brainstormed methods of achieving this, considering designs that used gravity move samples without electricity, and a rotary motion design, among others. We settled on a gantry style motion system that would allow us to control the speed of the sample(s) in one direction, and precisely position them in the other. This allowed for multiple samples to be tested at once, and for multiple passes under the jet to be performed on the same sample. The gallery to the left shows a brief pictorial summary of our design evolution.
Conceptual design evolution
Approach
The Challenge
Results
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Results Blurb
about this big
Results photo gallery
Final results blurb with possibly more pictures
This big?
Video Project Overview:
Video filmed and owned by Veolia NA. Used with permission
Heat exchangers or "process equipment" in the context of this project.
03
Iteration, Prototyping
The initial gantry prototype
Once we decided on a conceptual design, we needed to prototype and test it, in order to determine if it would meet our needs, and how to best improve on the design for the final test rig. Once the basic design of the system was determined, we created a prototype system, which was used for validation testing. The image to the right shows this initial system once it was completed. Validation testing proved extremely valuable, as we were able to determine that the first prototype was woefully under-designed. It was incapable of moving the test plate at a sufficient speed, and the support for the test plate was too flimsy to maintain a constant standoff distance from the nozzle. It was clear that more engineering analysis and design needed to be done.