Pourhead Design

Nozzle Testing

The Problem

Plants at Woodbridge facilities worldwide were reporting that many of the nozzles that can be found inside of a pourhead were not performing as expected. The back pressure that they were generating was out of spec and the jet was not straight causing cavitation and accelerated wear in the metal housings. The mixing process needs to be very precise in order to get the desired foam composition so it is clear why this unpredictable variance is an issue.

Solution

I was tasked with designing a test fixture to validate nozzles that were being produced at the machine shop before they get shipped to the plants. My design is a closed-loop system that pumps fluid through the nozzle. It contains a reservoir of plasticizer because it is of similar viscosity to the chemicals used in the plant. An inlet hose draws from the reservoir and feeds a pump and motor. The pump is a 1725 rpm, 5.5kW, 4.0GPM, piston pump that can generate up to 3000psi behind the smallest nozzle which had a 1mm orifice diameter. An outlet hose connects the pump to the nozzle holder. The nozzle holder is mounted to the top of a clear enclosure where the jet can be observed. The enclosure is then affixed to the top of the reservoir where the jet shoots into, thus closing the loop. The reservoir contains a baffle that prevents air bubbles produced by the jet from entering the pump inlet.

Equipment Used

• Pump and Motor
• Flow Meter - Recorded Data for Each Tested Nozzle
• Pressure Gauge - Recorded Data for Each Tested Nozzle
• Pressure Transducer - Cuts power to system if pressure spikes
• Baffle - Prevents air from entering pump inlet
• Nozzle Holder - Common component found in pourheads

Results

The fixture was used to validate 40 nozzles while I was at Woodbridge and continued to be in use after I left. I had to determine through testing what pressure and flow readings can be deemed acceptable. The test results are composed of a pressure and flow reading which are linearly proportional seen below. I made the standards for the nozzle certifications including the pressure, and flow measurements as well as a picture of the jet showing that it is straight.

Takeaways

This was great mechanical experience for me as I got to work with industrial equipment including high-pressure pumps, flow gauges, and machined components. I also utilized SolidWorks to build the assembly and get my parts fabricated at the machine shop. Lastly, I got to apply some knowledge from school including Bernoulli's equation to predict the pressure that the pump would be able to generate behind each nozzle size.

Slab Mixhead Design

This project stemmed from the need of a plant such that they wanted to have a custom pourhead that can pour a slab of foam continuously. Our department at Woodbridge was responsible for pourhead R&D projects, so it was our task to design and manufacture the assembly. I did a lot of work in SolidWorks to create the assembly while also researching seals that can be used.

Components

• Drive Shaft (Purple) - Rotates mixing shaft
• Drife Shaft Enclosure (Grey)
• Mechanical Seal
• Lubrication Housing (Yellow) - Distributes lubricant to the seal
• Mixing Chamber (Pink) - Inlet for chemicals
• Mixing Shaft (Green) - Coupled to drive shaft and stirs the chemicals inside the chemical housing
• Ball Bearings

The Seal

The most complex component of this assembly is the shaft seal because it is operating at both high RPM and high pressure which means the entire assembly will get quite hot as well. A pusher seal was selected as they are designed for high temperatures and aggressive chemicals. A pusher seal consists of a face seal that is coupled to the rotating shaft and there is pressure from the static side of the seal that is spring-loaded to maintain contact. This kind of seal requires lubrication so there is an O-ring along the ID of the seal to make sure the lubricant doesn't cause a leak as well.

Takeways

Industrial process equipment takes a long time to design, manufacture, and implement due to the high risk and high cost of development. During my four-month co-op we made great progress on the design and it will hopefully be in production soon. I learned about shaft and seal design as well as different machining processes that can be used to make this equipment. I also honed my SolidWorks skills further developing my mechanical experience.