P14474: Hydrostatic Test Apparatus

Detailed Design

Table of Contents

Sub-System Design

To accomplish our task we broke the System down into several subsystems:

To better understand how to design each sub-system we created Engineering Requirements for each:


Valve/Motor with Encoder

Pressure Transducer

Pipes & Fittings and Manifold


Engineering Analysis


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.

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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

Torque factors:

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.

Pipe Loss

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.

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Pipe Strength

It was also necessary to ensure the pipes would break and were strong enough to operate at 10,000 psi.

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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.

Pressure Transducer

We made calculations to ensure the transducers were appropriate for our system.

Motor Mount

We also ran a simulation on the motor mount to make sure there were no issues with stresses. From the simulations there is no concerns with stress.

Part Comparison & Selection


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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.

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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.

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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.

For the motor we selected this encoder. To ensure the motor will align with the valve we are using a flexible coupling. The mounting system can also be shimmed if further alignment is needed.

Pressure Transducer

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We are planning on using the PX309-10KG5V in combination with PX309-5KG5V and PX309-1KG5V to get quality data at different pressures.

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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.

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Schematics & Flow Charts

We created an updated more in depth System Layout

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Controller Subsystem

Compact RIO for Data Acquisition

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NI 9215: Analog Input Module for Pressure Readings

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NI 9472: Digital Output Module for Driver Pack Control

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NI 9401: Digital Input Module for Encoder Readings

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User Interface

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Flow Diagram

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State Diagram

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Controller Functional Decomposition

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Pressure Transducer

Pressure Transducer Subsystem Functional Decomposition

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Stepper Motor Driver Pack

Driver Pack Manual

Driver Pack Dimensions

Current Sourcing Wiring Diagram

Driver Pack Control Pins

Two Phase Motor Connections

Electrical Specifications

Current Selecting Switch Panel

Current Limiting Potentiometer

Bill of Material (BOM)

Preliminary Bill of Materials

Final Bill of Materials

Part Drawings

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Part 101

Part 103

Part 105

Part 107

Part 109

Part 111

Part 113


Part 101

Part 109

Part 113

Part 121

Part 123b

Part 125

Part 127

Part 129

Part 901

Ball Screw

Pipe Lengths

Final IGS File:

Final Assembly

Test Plans

Pressure Sensor(s)
Structural Integrity of Piping and Hose.
System Controller
Pressure Control System

Risk Assessment

In addition to our System Risk Assessment we created a Risk Assessment for each subsystem.


Valve & Motor

Pressure Transducer

Pipes & Fittings


Upcoming Schedule

| MSDII Preliminary Schedule

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Design Reviews

Sub-System Review

DDR Presentation

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