Home Compressor suggestions
- Thread starter spectrum
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
cool_hardware52
Contributor
Yup, marginally harder on the pump and potentially really bad the air quality.
Sustained load=badder
From a wear perspective I completely agree. From a filtration perspective the higher the setting for the priority valve the longer the dwell time in the filter tower(s)
Tobin
Lobzilla
Contributor
Many auto drains use a NO pilot actuated solenoid that is driven by an electrical solenoid. 2nd stage output is usually enough to drive the HP pilot actuated drains.
If this sounds like greek think about buying a kit.
Tobin
I fully understand the concept; but where can I get the valve components for an auto-drain? 5000 psi components is not exactly 'local hardware store' stuff.
rcontrera
Contributor
Lobzilla
Contributor
The former. I can get the low pressure solenoid from fleabay.
I have a Walter Kidde 4.2CFM compressor that has a 4th stage unloader controlled by oil pressure. Another possibility would be to move the unloader to the coalescer drain, plug the oil pressure port at the pump, and control the relocated unloader electro-pneumatically. Since the whole mixing and filling unit will be run by an embedded controller, unloading and draining can be combined in one valve. The only question is how well the unloader will take the watery condensate.
Last edited:
frogman62
Contributor
Stop. Two issues are important.
If the unloader valve is on the outlet of the 4th stage with a direct line from the oil pump to the unloader. You CAN close the oil line and COMPLETELY REMOVE the unloader valve.
The unloader valve CAN NOT be used by just pluging the oil line and the drain opening in the unloader valve as the body will not fail completely from the air pressure of the compressor.
IF you remove the unloader valve completely and relocate it to the drain connection for your moisture trap, you CAN use a low pressure air source (125 psi) to control the unloader valve (open or close) The unloader valve will drain the moisture trap until the pressure in the moisture drain reaches about 200 psi and then the 125 psi acting on the unloader piston will reclose.
You will require a check valve between the filter and the moisture drain to keep the filter volume from flowing back into the moisture trap.
If you need more information you can call me
Jim Shelden
316-992-0505
If the unloader valve is on the outlet of the 4th stage with a direct line from the oil pump to the unloader. You CAN close the oil line and COMPLETELY REMOVE the unloader valve.
The unloader valve CAN NOT be used by just pluging the oil line and the drain opening in the unloader valve as the body will not fail completely from the air pressure of the compressor.
IF you remove the unloader valve completely and relocate it to the drain connection for your moisture trap, you CAN use a low pressure air source (125 psi) to control the unloader valve (open or close) The unloader valve will drain the moisture trap until the pressure in the moisture drain reaches about 200 psi and then the 125 psi acting on the unloader piston will reclose.
You will require a check valve between the filter and the moisture drain to keep the filter volume from flowing back into the moisture trap.
If you need more information you can call me
Jim Shelden
316-992-0505
frogman62
Contributor
"From a wear perspective I completely agree. From a filtration perspective the higher the setting for the priority valve the longer the dwell time in the filter tower(s)
Tobin"
Tobin, I have a question?? How can you increase the dwell time once the priority valve opens and allows the air to flow through the filter? Once it is open the flow is just as fast as if you had no priority valve . The higher pressure certainly improves the moisture condensation but what does that have to do with dwell time?
Jim Shelden
Tobin"
Tobin, I have a question?? How can you increase the dwell time once the priority valve opens and allows the air to flow through the filter? Once it is open the flow is just as fast as if you had no priority valve . The higher pressure certainly improves the moisture condensation but what does that have to do with dwell time?
Jim Shelden
Goferrin99
Registered
Tobin, I have a question?? How can you increase the dwell time once the priority valve opens and allows the air to flow through the filter? Once it is open the flow is just as fast as if you had no priority valve . The higher pressure certainly improves the moisture condensation but what does that have to do with dwell time?
Jim Shelden[/QUOTE]
Jim,
Dwell time is a function of compressor output, pressure and filter volume. In a normal system the only variable is pressure and as pressure rises, dwell time increases.
For the system to reduce dwell time at higher pressure additional output would have to be added
Eg if a system is 200 ltr per min, PV crack at 100 Bar and filter capacity 10 ltrs:
At PV crack, 100 Bar, flow of compressed gas will be 2.0 ltrs per min and dwell will be 5 mins
At 200 Bar, flow of compressed gas will be 1.0 ltrs per min and dwell will be 10 mins
For dwell to drop below 10 mins at 200 bar would require either compressor output to increase above 200 ltrs per min or the filter volume to reduce. None of which would happen in a standard system.
Trust this helps.
Apologies for the simplistic explanation - I'm well aware of your experience and contribution to the Board
Jim Shelden[/QUOTE]
Jim,
Dwell time is a function of compressor output, pressure and filter volume. In a normal system the only variable is pressure and as pressure rises, dwell time increases.
For the system to reduce dwell time at higher pressure additional output would have to be added
Eg if a system is 200 ltr per min, PV crack at 100 Bar and filter capacity 10 ltrs:
At PV crack, 100 Bar, flow of compressed gas will be 2.0 ltrs per min and dwell will be 5 mins
At 200 Bar, flow of compressed gas will be 1.0 ltrs per min and dwell will be 10 mins
For dwell to drop below 10 mins at 200 bar would require either compressor output to increase above 200 ltrs per min or the filter volume to reduce. None of which would happen in a standard system.
Trust this helps.
Apologies for the simplistic explanation - I'm well aware of your experience and contribution to the Board
frogman62
Contributor
I understand your explanation but the question I still have is related to the delivered air flow. At 100PSI the flow from the compressor is 4.3 CFM. As the pressure goes up to 4000PSI, the flow from the compressor is only slightly reduces to 4.1 CFM. With no PV installed the air flow is 4.3 CFM and with a PV installed the flow is still 4.3 CFM -- So how can the dwell time be extended when the air flow has not changed I am still filling an 80 cubic tank in 20 minutes with or without a PV. Are you telling me that dwell time has no relationship to air flow. Maybe I do not understand dwell time.
I have had this question for several years and still don't have a good understanding.
I know the PV increases the moisture condensation efficiency
Jim Shelden
I have had this question for several years and still don't have a good understanding.
I know the PV increases the moisture condensation efficiency
Jim Shelden
Zodiacdiverdave
Contributor
- Messages
- 422
- Reaction score
- 72
- Location
- The North Atlantic, Canada
- # of dives
- I just don't log dives
About the best way to explane how the PV/PMV/Backpressure valve increases the effiecance of the purification process is this.
Water, oil and other liquid contaminents are basicly incompressable unlike the gas. As the pressure in a gas is increased the water and other liquids and rung out of the air just like when you ring out a wet towel. With the gas though the liquid molicules will combine with one another and form water droplets that are more easily traped by the molicular sieve.
The PV also provides early positive pressure to hold the floating piston against the piston guide.
ZDD
Water, oil and other liquid contaminents are basicly incompressable unlike the gas. As the pressure in a gas is increased the water and other liquids and rung out of the air just like when you ring out a wet towel. With the gas though the liquid molicules will combine with one another and form water droplets that are more easily traped by the molicular sieve.
The PV also provides early positive pressure to hold the floating piston against the piston guide.
ZDD
Similar threads
