This takes place in a junior-level Chemical Engineering Laboratory I course. Usually there are around a dozen students in the course, and I have run this activity with and without TA support. This activity usually takes place over the course of 3 weeks, from the third to fifth week of a 14-semester course.

• Various fittings and pieces of tubing for identification
• Calipers (analog recommended)
• Wrenches of various sizes
• Teflon tape
• Tubing benders
• Tubing cutters
• Copper tubing (1/4" recommended)
• Brass fittings (1/4" tees, MF pipe adapters, ball valves, and ferrule-nut assemblies recommended)
• Small gas tank (McMaster-Carr Item#9888K9 recommended)
  
• Pressure gauge (Omega Item#PGS-25L-100 recommended)
• Rotameter (Omega Item#FLDN3502G recommended)
• Gas cylinder with regulator (Nitrogen recommended)
• Soapy water with small plastic pipettes

When our students enter the workforce, there is a strong chance that they will need to work with fluid delivery systems and pipelines. When students enter our chemical engineering teaching lab, they are greeted by several such systems, and they are often intimidated by them and do not have a sense of what they would need to do to make these setups. To offer students an opportunity to explore building such systems, a three-week long series of hands on activities, culminating in a laboratory experiment to create from scratch, build, and test a gas delivery system was developed.

There are several key objectives to this activity, divided among the 3 days for this activity:

• Day 1: Learn About Different Fittings

Begin the lab session with a lecture discussion on the different types of fittings, and use YouTube videos and live demonstrations of how to measure objects using Vernier calipers. Then, break students into pairs of 2 and give them calipers, 21 different fittings and 6 pieces of tubing and pipes to identify. In the assignment memo, Table 1 is provided for the students to use to fill in information about all of their fittings. Each partner is asked to measure the size of each fitting’s connections, and some of the fittings have 1 side while others have up to 4 sides. As a team, they need to agree on the type of fitting, material of the fitting, whether a fitting is male, female, or both, and if this is a pipe or tube fitting. They also need to consider the purchase costs for these fittings.

Day 1 Deliverable: Completed Table 1 and navigate the Swagelok website to determine the part number and cost for any seven of the 21 fittings they studied. We later discuss in class how when designing fluid systems, they need to consider costs and think creatively, with multiple design considerations, to determine the most ideal assembly.

• Day 2: Learn How to Assemble Fittings and Tubing

Begin day 2 with a lecture and demonstration on how to apply Teflon tape properly to a male pipe fitting. Then in teams of 2, students take turns applying Teflon tape to the male pipe fitting, and then they use wrenches to tighten their Teflon tape wrapped male pipe fitting into the female pipe fitting. This activity involves showing students how to properly use wrenches and discussing how many wrench turns need to be used to connect those two fittings. Next, demonstrate how to cut and bend copper tubing. In pairs, students are given a tubing cutter and a long piece of copper tubing, and they are asked to cut off a specific length of copper tubing, making sure to deburr the newly cut piece of tubing. Students at this time will also bend a piece of tubing to create a 90-degree bend. Students need to be coached to make this bend with the tubing benders slowly so as to not reduce the inside diameter of the tubing. Monitor all of the students as they are cutting and bending to offer pointers, and inspect their final piece of tubing before we move onto the last part of this session. This last part begins with a demonstration as to how to permanently attach a nut and ferrule to a piece of copper tubing, and then each student attaches a nut and ferrule to one side of a piece of tubing. Thereby each pair of students creates a functional piece of tubing, and by the end of Day 2, several pieces of useable tubing for the last day’s activities have been acquired. At the end of this session, students are shown what equipment (gas tank, rotameter, pressure gauge, valve, tee, and various pieces of tubing and adapters) they will have access to during Day 3 to construct a gas delivery system to transport nitrogen gas from a gas cylinder into a separate gas storage tank.

Day 2 Deliverable: Students needed to complete some short answer questions on a worksheet directed at the skills they completed that day to reflect on what they have learned – for example, why did we apply Teflon tape in a clockwise direction? How is a gas tight connection made with compression fittings?

• Day 3: Learn How to Design and Assemble a Functioning Gas Delivery System

Begin class by combining the student pairs from last week into teams of 4 (ie combine two pairs to make a team of 4). Then, students have time as teams to think creatively to decide how to assemble the fittings, tubing, and equipment that they have been given to transport nitrogen gas from a gas cylinder into their separate gas storage tank. They must consider different design options, considering safety, functionality, and ease of assembly. Confirm that the students' design will work before giving them approval to start constructing their systems. Watch the students to make sure that they are using wrenches properly, applying Teflon tape when needed, and not overtightening fittings. When students believe they have assembled all system components, review their setups before allowing students to pressurize their systems for the leak test. Next, students leak test their system for 10 minutes. Their actual experiments should take ~2 minutes, so a short leak test was acceptable. If a group saw a pressure drop in their system during the leak test, they were required to perform a bubble test on the system to identify the leaking connection. Then the group would depressurize their system, tighten that connection, and perform another leak test until pressure in the system remained constant. Finally, groups collected pressure and volumetric flow data over time while depressurizing their system at least three times such that they had a total of at least 3 experiments where the time it took to depressurize their system at a constant flow rate was within 10% of each run. Their final challenge is to determine a way to use this data to accurately calculate the volume of the reactor. Simply multiplying volume flow rate by time will not take into account the changing pressure in the system, therefore they need to do research and review topics from previous courses to develop a calculation technique. 

Day 3 Deliverable: Individual technical memo that reported on their reactor volume approximation with error analysis.