aarongough
Stainless
- Joined
- Oct 27, 2014
- Location
- Toronto, Canada
Hey all!
I want to build a small pressure casting system, the principle is you pour epoxy into a small mold then the whole thing goes inside a pressure chamber and air pressure is applied to crush any entrapped bubbles down to nothing.
This is a common thing to do, but pretty much all the 'pressure casting chambers' that you can buy online are not ASME coded, and I have heard some horror stories as they seem to be built 'just enough' which is obviously not ideal with pressure vessels...
Because the parts I need to cast are narrow and long they are a good fit inside 2-3" NPT pipe. I want to build a small chamber from pipe and fittings, with one end cap permanently attached and the other end screwed on and sealed with teflon tape so it can be opened and parts put inside...
My question: how do I build a system like this safely??? Here's a screenshot of the assembly as it stands in Fusion -
Currently the components are:
16" long 3" NPT Schedule 40 welded pipe - McMaster-Carr
Class 150 Iron 3" NPT Cap - McMaster-Carr
Class 150 Iron 3" NPT to 2" NPT reducer - McMaster-Carr
Class 150 Iron 2" NPT to 1/4" NPT bushing - McMaster-Carr
1/4" NPT Nipple - https://www.mcmaster.com/7727K131/
High pressure brass cross fitting - https://www.mcmaster.com/50785K233/
125 PSI Safety relief valve - https://www.mcmaster.com/5784T12-5784T124/
High pressure 1/4" NPT needle valve - https://www.mcmaster.com/7833K72/
1/4 NPT Industrial quick connect - https://www.mcmaster.com/6050T15/
The lowest rated component is rated to 150PSI... Working pressure for the vessel would be 120PSI with the safety relief valve set for 125PSI. The idea behind the needle valve is to allow filling and exhausting the chamber slowly to avoiding the flow of air disturbing the parts inside.
This is an area where I know enough to build something potentially dangerous, but not enough to be 100% sure that I'm doing everything right. So:
- Is the design as it stands unsafe for a 120PSI service pressure?
- What additional measures, if any, should I be taking?
- Would hydro testing to 150% of service pressure be a good idea? If so does the grease-gun hydro test work fine for this kind of thing?
Should I ditch the current design and upgrade to class 1000 or class 3000 components for the extra safety factor?? Should I just ditch the whole idea?
Any and all input appreciated. I bought all the components before realizing that I need to think/research deeper about this, but I'm fine with writing them off as useless if need be. I value my limbs & life more highly than the cost of a pipe fitting or two.
Thanks!
-Aaron
I want to build a small pressure casting system, the principle is you pour epoxy into a small mold then the whole thing goes inside a pressure chamber and air pressure is applied to crush any entrapped bubbles down to nothing.
This is a common thing to do, but pretty much all the 'pressure casting chambers' that you can buy online are not ASME coded, and I have heard some horror stories as they seem to be built 'just enough' which is obviously not ideal with pressure vessels...
Because the parts I need to cast are narrow and long they are a good fit inside 2-3" NPT pipe. I want to build a small chamber from pipe and fittings, with one end cap permanently attached and the other end screwed on and sealed with teflon tape so it can be opened and parts put inside...
My question: how do I build a system like this safely??? Here's a screenshot of the assembly as it stands in Fusion -
Currently the components are:
16" long 3" NPT Schedule 40 welded pipe - McMaster-Carr
Class 150 Iron 3" NPT Cap - McMaster-Carr
Class 150 Iron 3" NPT to 2" NPT reducer - McMaster-Carr
Class 150 Iron 2" NPT to 1/4" NPT bushing - McMaster-Carr
1/4" NPT Nipple - https://www.mcmaster.com/7727K131/
High pressure brass cross fitting - https://www.mcmaster.com/50785K233/
125 PSI Safety relief valve - https://www.mcmaster.com/5784T12-5784T124/
High pressure 1/4" NPT needle valve - https://www.mcmaster.com/7833K72/
1/4 NPT Industrial quick connect - https://www.mcmaster.com/6050T15/
The lowest rated component is rated to 150PSI... Working pressure for the vessel would be 120PSI with the safety relief valve set for 125PSI. The idea behind the needle valve is to allow filling and exhausting the chamber slowly to avoiding the flow of air disturbing the parts inside.
This is an area where I know enough to build something potentially dangerous, but not enough to be 100% sure that I'm doing everything right. So:
- Is the design as it stands unsafe for a 120PSI service pressure?
- What additional measures, if any, should I be taking?
- Would hydro testing to 150% of service pressure be a good idea? If so does the grease-gun hydro test work fine for this kind of thing?
Should I ditch the current design and upgrade to class 1000 or class 3000 components for the extra safety factor?? Should I just ditch the whole idea?
Any and all input appreciated. I bought all the components before realizing that I need to think/research deeper about this, but I'm fine with writing them off as useless if need be. I value my limbs & life more highly than the cost of a pipe fitting or two.
Thanks!
-Aaron