Table of Contents
Sub-System DesignTo accomplish our task we broke the System down into several subsystems:
- Valve & Motor
- Pressure Transducer
- Pipe & Fittings
To better understand how to design each sub-system we created Engineering Requirements for each:
To better understand the valve design we needed to know the pressure drop across it as this would limit the minimum pressure that could be generated in the enclosure. To do this we use the Cv values from the valves to find pressure drop.
From engineering analysis and requirements it was decided that the max acceptable pressure loss is 100psi. We decided that 50 psi for each the valve and drain pipes were tolerable. The valves highlighted green represent valves that pass this criteria. Using the above formula and solving for Cv we found the min Cv value to be 2.4. This is the critical number required for the valve.
A motor is needed to control the valve. The motor depends on valve torque
- Stem Torque
There are too many unknown variables and no mathematical model for estimation. Luckily the manufacturer of the valve we selected provided an opening torque graph. From this we got an opening torque of approximately 11 oz-in. We needed this value to select our motor and gearbox.
One of the issues that arose was that the pressure at the outlet of the valve cannot be assumed to be zero. The drain pipe restricts the flow of the water so we calculated the pressure that is created. Assuming the values for the pump. We also had to estimate the lengths of the pipe and roughness values of the interior of the pipe.
It was also necessary to ensure the pipes would break and were strong enough to operate at 10,000 psi.
These calculations are used later in the comparisons and selections.
We decided to design our own manifold to connect the pressure transducers instead of connecting them all with pipes and fittings due to size and budget constraints. To ensure the manifold could withstand the 10,000 psi pressure we ran a simulation. From this simulation it was found that the pressure on the corners were rather high and above our perceived safety range. The simulation has difficulties with edges like that but in our opinion we don't feel confident in its safety over time. With our budget concerns, machining ability, and consultation with Dr. Varela it was decided to continue with producing it out of Aluminum with the recommendation to Cooper to replace it with Stainless Steel.
We made calculations to ensure the transducers were appropriate for our system.
Part Comparison & Selection
From this we were initially planning on using the NI USB-6211. After consultation with Professor Wellin, it was decided we need a rugged DAQ and the NI CRIO-9075 was selected
Initially we compared the following valves.
From this we had selected a Parker Ball Valve. After consultation with Parker's engineers we discovered there will be an issue with erosion in the valve with our application. We then had to start our search over. We ended up finding a valve from Swagelok that fit our reqirements. It has a Cv value of 5.1 and can handle the 10,000 psi which were our main requirements. This valve being a Needle Valve means that it has multiple rotations which provides more precision for our system. An issue that this valve causes though, is that the stem translates as it rotates which is something we must design around.
Motor & Mounting
We selected a stepper motor and gearbox to drive our system. Our mounting design allows for a minimum of ¾ inch freedom in all 3 directions and allows for the translation of the valve stem by utilizing a ball bearing slide. We had an alternate design to handle the translation. We dismissed it due to complexities and cost.
We are planning on using the PX309-10KG5V in combination with PX309-5KG5V and PX309-1KG5V to get quality data at different pressures.
From this we are planning on using 1" XXS Black Iron Pipe
The enclosure is made of bent sheet metal with a hinged door to allow quick access to transducer shut-off valves. It bolts right to the wall and protects critical components.
Schematics & Flow ChartsWe created an updated more in depth System Layout
Stepper Motor Driver Pack
Bill of Material (BOM)
Final IGS File:
- Pressure Sensor(s)
- Apply varying pressures to sensor(s) to verify output matches expected values.
- Calibrate sensor(s) as necessary.
- Structural Integrity of Piping and Hose.
- Perform calculations to determine approximate pressure for conduit failure.
- System Controller
- Simulate logic before programming the controller to debug as necessary.
- Apply stimulus to controller to recreate input from pressure sensor and observe output waveforms to verify functionality.
- Pressure Control System
- Apply stimuli to pressure controller to simulate input from test controller to verify functionality and response time.
- Attach to test controller and apply stimuli to
- This simulates input from pressure sensor and can be used to verify reaction time and functionality of pressure controller.