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Locating underground conduit
I know this is slightly off topic, but since I am intending to run some RF cable in the conduit, and since there are a lot of intelligent hams on this group, I will proceed anyway: Last year at the beginning of construction of a new house I buried about 50 feet of 3/4" Sched. 40 PVD between the house and a location on the property perimeter. Now that I am ready to use it, I can not locate the perimeter end.... it is somewhere in about a 10' area, and the end curves up to probably about a foot underground. The ground is nearly pure sand, and is well landscaped now to the point that I do not want to randomly dig it up. The end terminated in an elbow curving up and is well duct taped shut. Can anyone suggest a method or equipment I might use to locate that far end? Tnx. Ed K7AAT |
Locating underground conduit
Ed wrote:
I know this is slightly off topic, but since I am intending to run some RF cable in the conduit, and since there are a lot of intelligent hams on this group, I will proceed anyway: Last year at the beginning of construction of a new house I buried about 50 feet of 3/4" Sched. 40 PVD between the house and a location on the property perimeter. Now that I am ready to use it, I can not locate the perimeter end.... it is somewhere in about a 10' area, and the end curves up to probably about a foot underground. The ground is nearly pure sand, and is well landscaped now to the point that I do not want to randomly dig it up. The end terminated in an elbow curving up and is well duct taped shut. Can anyone suggest a method or equipment I might use to locate that far end? Tnx. Ed K7AAT Ed; Run a metal snake into the conduit then get a metal detector and sweep the area for the conduit. If this doesn't work there are wire tracing detectors that might do the job. You hook the transmitter to the snake and sweep with the detector. If all fails you might try a metal probe. Stick the probe into the ground and feel for the conduit. Or dig up a couple of feet of conduit. Note the direction it is going then move in that direction and dig a small trench where you thing the conduit is. One of these methods should work. If all fails install new conduit. Dave WD9BDZ |
Locating underground conduit
A suggestion for other folks who will be burying a conduit: Take a bunch
of pictures before the trench is filled. It's good to include distances to some fixed reference points -- you can write them with a marker on big pieces of paper laid on the ground to get them in the picture. I haven't yet used the pictures I took of mine, but I sure have made a lot of use of the pictures I took of the uncovered walls of a home addition, showing the locations of all the studs and wiring. Roy Lewallen, W7EL |
Locating underground conduit
Andy suggests:
Couple a garden hose to the end you can find and run water into the PVC.... Go to the area surrounding the buried end and look for the sandy ground to be wet...... Andy W4OAH |
Locating underground conduit
"Ed" wrote in message . 192.196... I know this is slightly off topic, but since I am intending to run some RF cable in the conduit, and since there are a lot of intelligent hams on this group, I will proceed anyway: Last year at the beginning of construction of a new house I buried about 50 feet of 3/4" Sched. 40 PVD between the house and a location on the property perimeter. Now that I am ready to use it, I can not locate the perimeter end.... it is somewhere in about a 10' area, and the end curves up to probably about a foot underground. The ground is nearly pure sand, and is well landscaped now to the point that I do not want to randomly dig it up. The end terminated in an elbow curving up and is well duct taped shut. Can anyone suggest a method or equipment I might use to locate that far end? Tnx. Ed K7AAT Stab an antenna rod down until you find it. |
Locating underground conduit
On Oct 15, 1:17*am, Ed wrote:
* *I know this is slightly off topic, *but since I am intending to run some RF cable in the conduit, *and since there are a lot of intelligent hams on this group, *I will proceed anyway: * *Last year at the beginning of construction of a new house I buried about 50 feet of *3/4" Sched. 40 PVD between the house and a location on the property perimeter. * Now that I am ready to use it, *I can not locate the perimeter end.... it is somewhere in about a 10' area, and the end curves up to probably about a foot underground. * * The ground is nearly pure sand, and is well landscaped now to the point that I do not want to randomly dig it up. * * The end terminated in an elbow curving up and is well duct taped shut. * * Can anyone suggest a method or equipment I might use to locate that far end? * * Tnx. * *Ed * K7AAT Ive done this to locate wires in walls, might work for wires in ground. Make a buzzer form a relay by attaching the NC contacts in series with the coil and battery. Connect it to a wire running through the conduit making sure the wire is not connected to power. The buzzer will generate enough hash you can pick it up on a pocket AM rx. Jimmie |
Locating underground conduit
On 15 Oct 2008 05:17:22 GMT, Ed
wrote: Last year at the beginning of construction of a new house I buried about 50 feet of 3/4" Sched. 40 PVD between the house and a location on the property perimeter. Now that I am ready to use it, I can not locate the perimeter end.... it is somewhere in about a 10' area, and the end curves up to probably about a foot underground. If there is a wire in the conduit, just rent a "cable finder" from the local rental yard. It's a low frequency transmitter and receiver combination. If you have access to one end of the pipe, just shove a metal "snake" into the pipe to provide a suitable conductor. The ground is nearly pure sand, and is well landscaped now to the point that I do not want to randomly dig it up. That should be easy. Dry sand doesn't attenuate the signal much. Wet sand is another story. The end terminated in an elbow curving up and is well duct taped shut. Ummm... I think you'll find that the duct tape has dried out by now and that your pipe is full of water and sand. Can anyone suggest a method or equipment I might use to locate that far end? The cable finder is the right way. Ground penetrating radar will work but is messy. You can pressurize the conduit with an air compressor. That should blow off what remains of the duct tape. Use your ears or a stethescope to listen for the noise through the sand. If the end is just below the surface, it should make a nice blow hole. Be prepared to clean the sand out of your uncleable buried elbow. If you think the pipe is clear, drop a small loudspeaker down the other end and play rock music with a heavy bass beat. You should be able hear that 50ft away. Use a stethescope. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Locating underground conduit
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Locating underground conduit
AndyS wrote in news:58eba0a6-8107-40dc-85e9-
: Andy suggests: Couple a garden hose to the end you can find and run water into the PVC.... Go to the area surrounding the buried end and look for the sandy ground to be wet...... Andy W4OAH That's an excellent idea.... but I really hate water in my electrical conduits.... I'll use that as a last resort. Thanks. Ed |
Locating underground conduit
"JB" wrote in
: "Ed" wrote in message . 192.196... I know this is slightly off topic, but since I am intending to run some RF cable in the conduit, and since there are a lot of intelligent hams on this group, I will proceed anyway: Last year at the beginning of construction of a new house I buried about 50 feet of 3/4" Sched. 40 PVD between the house and a location on the property perimeter. Now that I am ready to use it, I can not locate the perimeter end.... it is somewhere in about a 10' area, and the end curves up to probably about a foot underground. The ground is nearly pure sand, and is well landscaped now to the point that I do not want to randomly dig it up. The end terminated in an elbow curving up and is well duct taped shut. Can anyone suggest a method or equipment I might use to locate that far end? Tnx. Ed K7AAT Stab an antenna rod down until you find it. A definate consideration.... since the ground is sand. If the antenna rod doesn't just bend around the conduit... may just work. Tnx. Ed |
Locating underground conduit
Run a metal snake into the conduit then get a metal detector and sweep the area for the conduit. If this doesn't work there are wire tracing detectors that might do the job. You hook the transmitter to the snake and sweep with the detector. If all fails you might try a metal probe. Stick the probe into the ground and feel for the conduit. Or dig up a couple of feet of conduit. Note the direction it is going then move in that direction and dig a small trench where you thing the conduit is. One of these methods should work. If all fails install new conduit. Dave WD9BDZ Dave, your idea above, plus some comments from others has made me realize that this is the way I should proceed, for my first attempt. I do have a Service Monitor. I'll simply run my snake into the empty pvc conduit until it hits the end ( duct tape ) and connect an RF signal to it, then using a small HT, track the signal down to the end. My thanks to all for other ideas presented here, too. Ed K7AAT |
Locating underground conduit
"Ed" wrote in message . 192.196... AndyS wrote in news:58eba0a6-8107-40dc-85e9- : Andy suggests: Couple a garden hose to the end you can find and run water into the PVC.... Go to the area surrounding the buried end and look for the sandy ground to be wet...... Andy W4OAH That's an excellent idea.... but I really hate water in my electrical conduits.... I'll use that as a last resort. Thanks. Ed Hi Ed Have you considered the use of a wad of towel pulled thru the conduit to dry it after using water to locate the burried end? Compressed air could be used in place of the water. The air excaping from the burried end shouild be easily detected. Jerry KD6JDJ |
Locating underground conduit
Jerry wrote:
That's an excellent idea.... but I really hate water in my electrical conduits.... I'll use that as a last resort. Thanks. Ed When in doubt, couple ways the Pros do it: 1) Run a Metalic Snake thru it, and hook to a (Low Power RF , or a Fairly high power A.F. source-- follow the snake (above ground with an inductive sampler ( or rf receiver)) to the end - use a cable marker (Paint) to follow the duct if needed to find an intermediate point , then repeat agan if necessary. 2) for those that have access to a "THUMPER", can do the same Apply high level of sound to the PVC, and use a listening device to follow the noise, in the ground. Works for locating buried cables for utilities- should work for you! Jim NN7K |
Locating underground conduit
"Jim-NN7K" . wrote in message ... Jerry wrote: That's an excellent idea.... but I really hate water in my electrical conduits.... I'll use that as a last resort. Thanks. Ed When in doubt, couple ways the Pros do it: 1) Run a Metalic Snake thru it, and hook to a (Low Power RF , or a Fairly high power A.F. source-- follow the snake (above ground with an inductive sampler ( or rf receiver)) to the end - use a cable marker (Paint) to follow the duct if needed to find an intermediate point , then repeat agan if necessary. 2) for those that have access to a "THUMPER", can do the same Apply high level of sound to the PVC, and use a listening device to follow the noise, in the ground. Works for locating buried cables for utilities- should work for you! Jim NN7K What an interesting thread! How about one of those 'stage' smoke machines pumped into the open end? VK5JE |
Locating underground conduit
Ed wrote:
I know this is slightly off topic, but since I am intending to run some RF cable in the conduit, and since there are a lot of intelligent hams on this group, I will proceed anyway: Last year at the beginning of construction of a new house I buried about 50 feet of 3/4" Sched. 40 PVD between the house and a location on the property perimeter. Now that I am ready to use it, I can not locate the perimeter end.... it is somewhere in about a 10' area, and the end curves up to probably about a foot underground. The ground is nearly pure sand, and is well landscaped now to the point that I do not want to randomly dig it up. The end terminated in an elbow curving up and is well duct taped shut. Can anyone suggest a method or equipment I might use to locate that far end? Tnx. Ed K7AAT Another simple way - the old Native American waiting for a train method. Push the fish tape all the way until it stops. Person 1 keeps ramming the fish tape and person 2 puts ear to ground near far end and listens for it. Needs no batteries or smoke. Nix the water. I like the compressed air trick, Just don't look directly at the conduit end . . -- "From spongecake to satellites, it's gotta be Krebstar" |
Locating underground conduit
Another simple way - the old Native American waiting for a train method. Push the fish tape all the way until it stops. Person 1 keeps ramming the fish tape and person 2 puts ear to ground near far end and listens for it. Needs no batteries or smoke. I like that! I will try it before bothering to hook up an RF source to the fish tape! Ed K7AAT |
Locating underground conduit
How about one of those 'stage' smoke machines pumped into the open end? VK5JE That's a good one, too, but in my case, I KNOW that I duct taped the end of the conduit in such a manner that it is truly air tight... even possibly under pressure. Thanks anyway. Ed |
Locating underground conduit
On Wed, 15 Oct 2008 20:58:55 -0700, Cable Shill
wrote: Another simple way - the old Native American waiting for a train method. Push the fish tape all the way until it stops. Person 1 keeps ramming the fish tape and person 2 puts ear to ground near far end and listens for it. Needs no batteries or smoke. Nix the water. I like the compressed air trick, Just don't look directly at the conduit end . . Well, how about combining the two methods? Find some flex lawn drip irrigation tubing. Attach a bosons whistle to the end and shove it through the pipe. Add compressed air and it should scream like a banshee. That should be easy to hear through the sand. Maybe the duct tape will act as a diaphragm. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Locating underground conduit
Ed wrote:
Run a metal snake into the conduit then get a metal detector and sweep the area for the conduit. If this doesn't work there are wire tracing detectors that might do the job. You hook the transmitter to the snake and sweep with the detector. If all fails you might try a metal probe. Stick the probe into the ground and feel for the conduit. Or dig up a couple of feet of conduit. Note the direction it is going then move in that direction and dig a small trench where you thing the conduit is. One of these methods should work. If all fails install new conduit. Dave WD9BDZ Dave, your idea above, plus some comments from others has made me realize that this is the way I should proceed, for my first attempt. I do have a Service Monitor. I'll simply run my snake into the empty pvc conduit until it hits the end ( duct tape ) and connect an RF signal to it, then using a small HT, track the signal down to the end. My thanks to all for other ideas presented here, too. Ed K7AAT Ed; Thanks for the compliment. I wish you luck and envy you for your acreage for antenna's. My lot here in St. Louis is something like 40 feet by 120 feet with the house in the center. I do have some trees along the back alley that I have wire hanging from. Works but not optimal. Let us know how everything works out. Dave WD9BDZ |
Locating underground conduit
Plumbers power snake for sewers... Rent it at the rent it shop... It
will auger up through that duct tape and sand like it is tissue paper... denny/ k8do |
Locating underground conduit
On Thu, 16 Oct 2008 06:36:34 -0700 (PDT), Denny
wrote: Plumbers power snake for sewers... Rent it at the rent it shop... It will auger up through that duct tape and sand like it is tissue paper... denny/ k8do Ummm.... this is through 3/4" schedule 40 PVC with at least two right angles. The augers I've seen are for much larger sewer drain pipe and will not fit inside 3/4" PVC. Anything that can drill through sand can probably also do some real damage to the PVC. A much smaller diameter "snake" is probably safer. With only 1ft of sand to push through, a solid "tape" type electricians snake can be pushed through by hand. The only down side is that the pipe will fill with sand when the duct tape is breached, so cleanup may be a problem. If dry sand, a small hose on the end of a vacuum cleaner should work. Incidentally, the frequencies used by commerical cable finders are 815Hz, 8Khz, and 82KHz at 2-3 watts. http://www.rycominstruments.com/3-8879-Cable-Utility-Locator.asp However, that's good for 15 ft depth and many miles of cable. Higher frequencies will probably work for 1ft of sand and only 100ft of wire. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Locating underground conduit
Ummm.... this is through 3/4" schedule 40 PVC with at least two right
angles. The augers I've seen are for much larger sewer drain pipe and will not fit inside 3/4" PVC. Anything that can drill through sand Ouch! Unless you are trying to fish a phone line, you (might/might not/want) WILL dig it all up and go to 2" with 45 degree bends and bevel the inside edges. Once above ground you can break out to pull boxes. You have my sympathy. |
Locating underground conduit
"Ed" wrote in message . 192.196... How about one of those 'stage' smoke machines pumped into the open end? VK5JE That's a good one, too, but in my case, I KNOW that I duct taped the end of the conduit in such a manner that it is truly air tight... even possibly under pressure. Thanks anyway. Ed Hi Ed Will the taped end will not leak with 80 PSI air in the conduit? Jerry KD6JDJ |
Locating underground conduit
On Thu, 16 Oct 2008 16:37:22 GMT, "JB" wrote:
Ummm.... this is through 3/4" schedule 40 PVC with at least two right angles. The augers I've seen are for much larger sewer drain pipe and will not fit inside 3/4" PVC. Anything that can drill through sand Ouch! Unless you are trying to fish a phone line, you (might/might not/want) WILL dig it all up and go to 2" with 45 degree bends and bevel the inside edges. Once above ground you can break out to pull boxes. You have my sympathy. Thanks for the sympathy but it's not my conduit or problem. The plumbing belongs to Ed, K6AAT. Question: What's the difference between conduit and plumbing? Answer: Plumbing holds water. Otherwise, they're the same. I'm not sure what might be going inside a 3/4" conduit, but if it's for a tower, it's way too small. The original question does not indicate what manner of wiring goes inside. With 3/4", you can get perhaps one run of LMR400 plus some flat rotator cable and you're full. Hard to tell from here. It's also possible to place a diplexer (or triplexer) at both ends of the single coax run for splitting out HF, VHF, and UHF. I've done that when running multiple coax cables was impossible. http://www.rfparts.com/diamond/Product_Catalog/plexers.html It's been a long time since I've done any tower construction, but for commercial installs, I never used buried coax runs. AC power for the tower lights were in 3" steel threaded conduit (not EMT), but the coax was all above ground. That shortened the coax runs about 25ft which was well worth the effort. Incidentally, a good trick is to *NOT* lay the conduit perfectly horizontally plumb. Put one end lower than the other so that water well drain into that end. Shove a PEX sprinkler line down to the low point of pipe and pump out the water once a year. I prefer pressurized conduit, but a water sump works fairly well. I discovered, the hard way, why using steel pipe instead of PVC was a good idea. With everything underground, the obvious parking location for the crane, cherry picker, or propane truck was directly on top of the buried PVC. After a few cracked pipes, I decided that steel was a good idea. I like to pressurize the conduit slightly to keep the water out. It's really not necessary as most coax will survive when immersed. However, everyone re-uses coax, which has cuts in the outer jacket, and which might not be fully waterproof. A pressure gauge, bicycle valve, bicycle pump, some putty, and a few PSI are good enough. I almost forgot.... a slow death to the installer that shoved a coax barrel splice down a stuffed conduit, thus insuring that all subsequent coax runs will jam up against the coax connectors. Also, this is what happens when a monopole tower is stuffed full of coax cables, and some idiot decides to enlarge the hole with a cutting torch. http://802.11junk.com/jeffl/pics/drivel/slides/monopoleBurn.html http://odessaoffice.com/wireless/priceless.jpg -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Locating underground conduit
On Thu, 16 Oct 2008 17:17:05 GMT, "Jerry"
wrote: Will the taped end will not leak with 80 PSI air in the conduit? Jerry KD6JDJ Well, if it does leak, the sand above the duct tape will dribble down into the 3/4" conduit creating a rather awkward clean up exercise. That's why conduit runs usually terminate above the ground, not below. The trick is to find the conduit end without blowing off the seal. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Locating underground conduit
"Jeff Liebermann" wrote in message ... On Thu, 16 Oct 2008 17:17:05 GMT, "Jerry" wrote: Will the taped end will not leak with 80 PSI air in the conduit? Jerry KD6JDJ Well, if it does leak, the sand above the duct tape will dribble down into the 3/4" conduit creating a rather awkward clean up exercise. That's why conduit runs usually terminate above the ground, not below. The trick is to find the conduit end without blowing off the seal. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 Hi Jeff It may be of little interest to the OP, but the sand might have difficulty leaking back into a conduit with air blowing out of it. In addition, the air might leak from a small rupture below the oipen end of the conduit. The OP may have no access to compressed air anyway. Jerry KD6JDJ |
Locating underground conduit
On Thu, 16 Oct 2008 20:31:56 GMT, "Jerry"
wrote: "Jeff Liebermann" wrote in message .. . On Thu, 16 Oct 2008 17:17:05 GMT, "Jerry" wrote: Will the taped end will not leak with 80 PSI air in the conduit? Jerry KD6JDJ Well, if it does leak, the sand above the duct tape will dribble down into the 3/4" conduit creating a rather awkward clean up exercise. That's why conduit runs usually terminate above the ground, not below. The trick is to find the conduit end without blowing off the seal. Hi Jeff It may be of little interest to the OP, but the sand might have difficulty leaking back into a conduit with air blowing out of it. In addition, the air might leak from a small rupture below the oipen end of the conduit. The OP may have no access to compressed air anyway. Jerry KD6JDJ Welcome to rec.radio.amateur.antenna.physics Ok, let's do the math. Dry sand weighs 100 lb/cubic-foot. There's about 1 ft of sand above the end of the 3/4" conduit. The weight action is roughly conical, so the volume of sand involved is (my guess) about: 100 lbs/ft^3 * 1/3 = 33 lbs of sand. All that it acting on a 3/4" diameter pipe, with a cross sectional area of about: Pi * 0.75" = 2.4 in^2 Therefore, the pressure exerted by the sand is: 33 lbs / 2.4 in^2 = 14 PSI So, if he can pressurize the pipe to more than 14 PSI, he can lift the column of sand sufficiently to keep it from dribbling into the pipe. Of course, it's not that simple. Laminar air flow, pressure gradients across the conduit, and the effects of the duct tape will ruin my simplistic guesswork. Worse, the back pressure created by the immovable column of sand will force some sand particles into the conduit around the edges with the "reflected" air pressure. In the middle of the conduit, the air flow is all out of the conduit, but near the edges, it could easily be the other direction. I'm also assuming that the sand is a perfect air seal, which it's not. To prevent all this from happening, the minimum air pressure should be about twice the 14 PSI, which is easily achievable with an air compressor, but not a vacuum cleaner. I'm also trying to imagine how the process will work. I see an air compressor pumping madly away as the neighbors kids furiously dig around the resultant sand volcano, as sand rapidly refills the conical hole. In my never humble opinion, there's no way to prevent sand from dropping into the conduit if the duct tape seal is broken before excavating the end of the conduit. Once the sand is in the conduit, just blowing air through the pipe isn't going to magically elevate the sand particles 1ft or more in the air. The air does not have sufficient mass to convey enough momentum to move the sand particles, much less eject them vertically. For that, one needs a denser medium, such as water. Shoving a plunger through might work, but it's equally likely to jam sand particles into the PVC conduit walls. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Locating underground conduit
On Thu, 16 Oct 2008 13:57:44 -0700, Jeff Liebermann
wrote: Worse, the back pressure created by the immovable column of sand will force some sand particles into the conduit around the edges with the "reflected" air pressure. H E R E S Y Reflected waves do NOT have power in them - or so goes the catechism. This new and dangerous introduction of a side topic can only lead to endless debate about the superposition phase properties of sand in vacua (particel theories inhabiting the crevices in the science of Equal Librium) 73's Richard Clark, KB7QHC |
Locating underground conduit
"Jeff Liebermann" wrote in message ... On Thu, 16 Oct 2008 20:31:56 GMT, "Jerry" wrote: "Jeff Liebermann" wrote in message . .. On Thu, 16 Oct 2008 17:17:05 GMT, "Jerry" wrote: Will the taped end will not leak with 80 PSI air in the conduit? Jerry KD6JDJ Well, if it does leak, the sand above the duct tape will dribble down into the 3/4" conduit creating a rather awkward clean up exercise. That's why conduit runs usually terminate above the ground, not below. The trick is to find the conduit end without blowing off the seal. Hi Jeff It may be of little interest to the OP, but the sand might have difficulty leaking back into a conduit with air blowing out of it. In addition, the air might leak from a small rupture below the oipen end of the conduit. The OP may have no access to compressed air anyway. Jerry KD6JDJ Welcome to rec.radio.amateur.antenna.physics Ok, let's do the math. Dry sand weighs 100 lb/cubic-foot. There's about 1 ft of sand above the end of the 3/4" conduit. The weight action is roughly conical, so the volume of sand involved is (my guess) about: 100 lbs/ft^3 * 1/3 = 33 lbs of sand. All that it acting on a 3/4" diameter pipe, with a cross sectional area of about: Pi * 0.75" = 2.4 in^2 Therefore, the pressure exerted by the sand is: 33 lbs / 2.4 in^2 = 14 PSI So, if he can pressurize the pipe to more than 14 PSI, he can lift the column of sand sufficiently to keep it from dribbling into the pipe. Of course, it's not that simple. Laminar air flow, pressure gradients across the conduit, and the effects of the duct tape will ruin my simplistic guesswork. Worse, the back pressure created by the immovable column of sand will force some sand particles into the conduit around the edges with the "reflected" air pressure. In the middle of the conduit, the air flow is all out of the conduit, but near the edges, it could easily be the other direction. I'm also assuming that the sand is a perfect air seal, which it's not. To prevent all this from happening, the minimum air pressure should be about twice the 14 PSI, which is easily achievable with an air compressor, but not a vacuum cleaner. I'm also trying to imagine how the process will work. I see an air compressor pumping madly away as the neighbors kids furiously dig around the resultant sand volcano, as sand rapidly refills the conical hole. In my never humble opinion, there's no way to prevent sand from dropping into the conduit if the duct tape seal is broken before excavating the end of the conduit. Once the sand is in the conduit, just blowing air through the pipe isn't going to magically elevate the sand particles 1ft or more in the air. The air does not have sufficient mass to convey enough momentum to move the sand particles, much less eject them vertically. For that, one needs a denser medium, such as water. Shoving a plunger through might work, but it's equally likely to jam sand particles into the PVC conduit walls. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 Wow, Jeff, you are a really smart guy. It sure is nice to know that you are able to analyze this sand over conduit problem so thoroughly. Heck, I thought the air would blow out thru the sand. I didnt even consider the sand above the air leak to be immovable. I thought the air would find a path to leak out somewhere between the tape and the conduit. I hadnt thought about using neighbor kids. Why would you consider using kids for this project? I'll assume you wont recommend the OP use water or air to locate the far end of his conduit. Jerry KD6JDJ |
Locating underground conduit
On Thu, 16 Oct 2008 14:19:05 -0700, Richard Clark
wrote: On Thu, 16 Oct 2008 13:57:44 -0700, Jeff Liebermann wrote: Worse, the back pressure created by the immovable column of sand will force some sand particles into the conduit around the edges with the "reflected" air pressure. H E R E S Y Hershey Bar (Chocolate Rules). Besides, following the orthodoxy lacks entertainment value. Reflected waves do NOT have power in them - or so goes the catechism. This new and dangerous introduction of a side topic can only lead to endless debate about the superposition phase properties of sand in vacua (particel theories inhabiting the crevices in the science of Equal Librium) Yeah, but I like playing in the sand. Try this experiment next time you have an air compressor and nozzle handy. Find a cardboard, plastic or metal tube at least 3 ft long. A vacuum cleaner extension pipe will suffice. Plug up the other end with whatever is handy. Blow air into the center of the tube. Run your fingers around the edges of the tube and note which way the air is flowing. That's what will happen if the compressed air is not sufficient to blow 30 lbs of sand into the air. The air and the sand will flow back into the pipe in the opposite direction as the compressed air. 73's Richard Clark, KB7QHC -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Locating underground conduit
On Thu, 16 Oct 2008 22:04:20 GMT, "Jerry"
wrote: Wow, Jeff, you are a really smart guy. It sure is nice to know that you are able to analyze this sand over conduit problem so thoroughly. Nope. My guesswork is far from exact. Close enough. Heck, I thought the air would blow out thru the sand. I didnt even consider the sand above the air leak to be immovable. It is immovable, until it moves. That's the real problem. We can consider the sand to be a solid plug until it starts to break up. As soon as that happens, it leaks like a sieve. As soon as it starts leaking, the air pressure available for lifting the sand is dissipated, resulting in the collapse of the sand pile. Think of it like a real volcano. As soon as the volcano stops erupting and belching gasses, the eruption column of airborne rock collapses, heads for the ground, and creates a messy pyroplastic flow. I thought the air would find a path to leak out somewhere between the tape and the conduit. There's plenty of opportunities for air leaks. If the PVC joints aren't glued, the air pressure will probably separate the lengths of PVC pipe. I hadnt thought about using neighbor kids. Anyone that uses 3/4" PVC for antenna conduit, and then buries and loses one end, is certainly not a professional underground construction contractor. He certainly isn't going to use high prices professional union ditch diggers. The cheapest alternative are the neighbors kids. I currently have a horde of them working on removing the blackberries from my hillside. It may take months and result in a few non-fatal injuries, but it's still cheaper than hiring a landscape contractor. Also, more fun to watch. Why would you consider using kids for this project? They work cheaply. They're familiar with playing in the sand using shovels and pails. Just tell them it's kinda like at the beach. They also bounce instead of break at a young age, which makes them suitable for dangerous tasks. I'll assume you wont recommend the OP use water or air to locate the far end of his conduit. I posted some serious recommendations in previous rants. I like dropping a boson's whistle down the pipe at the end of a small diameter air hose. Apply air pressure and it should be hear through a foot of sand. If not, it will surely scare the gophers, which might be useful. Jerry KD6JDJ -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Locating underground conduit
On Thu, 16 Oct 2008 21:53:20 -0700, Jeff Liebermann
wrote: Plug up the other end with whatever is handy. Blow air into the center of the tube. Run your fingers around the edges of the tube and note which way the air is flowing. That's what will happen if the compressed air is not sufficient to blow 30 lbs of sand into the air. The air and the sand will flow back into the pipe in the opposite direction as the compressed air. Hi Jeff, Well, it's been a coon's age since I've seen vacuum cleaners that would let me attach to their exhaust - so that's out. As for driving compressed air into a short (or open). I've done that, but not for sand excavation. Rather, I've used what was commercially called the "vortex effect" which separates the two air current flows you allude to above to create a hot stream and a chilled stream of air. (Elevated or depressed from the average of the inlet temperature.) I used this for cooling electronics in a paper mill. Not particularly efficient, but compressed air was available, and the VorTec nozzle was a quick and easy solution to their NEMA enclosures. See: http://www.vortec.com/support_casestudies.php or https://secure.vortec.com/store_prod...tID=9&prodID=6 This, and some of my fluidic applications constitute a specialized niche in alternative logic systems. Notably, they all work off principles of reflected power that demonstrate palpable examples. 73's Richard Clark, KB7QHC |
Locating underground conduit
Richard Clark wrote:
Well, it's been a coon's age since I've seen vacuum cleaners that would let me attach to their exhaust - so that's out. Have you ever heard of a shop vacuum? Usually only available at highly specialized stores such as Walmart. -- Jim Pennino Remove .spam.sux to reply. |
Locating underground conduit
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Locating underground conduit
On Oct 15, 2:28*am, Roy Lewallen wrote:
A suggestion for other folks who will be burying a conduit: Take a bunch of pictures before the trench is filled. It's good to include distances to some fixed reference points -- you can write them with a marker on big pieces of paper laid on the ground to get them in the picture. I haven't yet used the pictures I took of mine, but I sure have made a lot of use of the pictures I took of the uncovered walls of a home addition, showing the locations of all the studs and wiring. Roy Lewallen, W7EL We always do this at work and lately started doing GPS surveys of new buried cables marking GPS and survey data on the pictures, This comes in real handy when you are paying for 4 guys and a rented backhoe to stand around and wait for you to find a cable, Jimmie |
Locating underground conduit
On Thu, 16 Oct 2008 22:26:10 -0700, Richard Clark
wrote: Well, it's been a coon's age since I've seen vacuum cleaners that would let me attach to their exhaust - so that's out. The problem with vacuum cleaners is that they all suck. I have an ancient Electrolux and a Shop Vac that both have usable exhaust ports. I also have a Hoover upright and a Hoover cannister in the office that do not. Y'er right that it's a vanishing breed. However, you re-read what I scribbled, you might notice that I suggested that one use the air compressor to pressurize the 3/4" PVC pipe. That's because the average vacuum cleaner can barely generate more than a few PSI. They also leak badly. If you're trying to lift a column of sand or demonstrate backpressure, it's much easier with a proper air compressor. As for driving compressed air into a short (or open). I've done that, but not for sand excavation. I have. The clumsy backhoe operator (me) once dropped a load of dirt on top of the steel 3" conduit end during construction. I'm also the idiot that forgot to shove a protective rag into the conduit end. I spent the next two days trying to figure out how to get the dirt out of the pipe. I eventually fabricated a cylinder shaped rubber plug with an eyebolt down the center, dumped some water into the conduit, and dragged the plug through the pipe with a winch. It took about 5 passes for the water to come out clear. I then pumped out the remaining water, dragged a sponge through the pipe a few dozen times, and then let evaporation do the final cleanup. Compressed air was attempted just for fun, but it was obvious that it wasn't going to lift the dirt out of the pipe. Rather, I've used what was commercially called the "vortex effect" which separates the two air current flows you allude to above to create a hot stream and a chilled stream of air. (Elevated or depressed from the average of the inlet temperature.) I used this for cooling electronics in a paper mill. Not particularly efficient, but compressed air was available, and the VorTec nozzle was a quick and easy solution to their NEMA enclosures. See: http://www.vortec.com/support_casestudies.php or https://secure.vortec.com/store_prod...tID=9&prodID=6 Nice. I built several out of the original Amateur Scientist book (which I still have on my bookshelf) in the early 1960's. It worked amazingly well. Much later, I built one out of PVC pipe, which melted. Now I know why they're made out of metal. Never mind the inefficiency. It's the noise they make that drives me nuts. At one point, we had 4 of them in series, with 4 assorted air compressors pumping about 4 SCFM into each, and got it down to about -100C. We started with a group of about 10 lab students, and ended up with a crowd of about 100 nosey students wondering why someone was trying to operate a jet engine on campus. This, and some of my fluidic applications constitute a specialized niche in alternative logic systems. Notably, they all work off principles of reflected power that demonstrate palpable examples. I'll pass. I don't believe in logic any more. Everything can be explained in terms of politics, psychology, and conspriacies. Logic is obsolete. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Locating underground conduit
On Fri, 17 Oct 2008 06:02:04 -0700, Jeff Liebermann
wrote: However, you re-read what I scribbled, you might notice that I suggested that one use the air compressor to pressurize the 3/4" PVC pipe. Hi Jeff, I was responding to the broad assortment of methods which included what was the closest option for me of a vacuum cleaner. That's because the average vacuum cleaner can barely generate more than a few PSI. They also leak badly. If you're trying to lift a column of sand or demonstrate backpressure, it's much easier with a proper air compressor. No doubt and no argument. At one point in my career, I found myself with a dead weight tester, calibrating a pressure gauge to 10,000 PSI when the coupling line spit sending a fine spray of pressurized oil past my face. Took me half an hour to shake off the thought of it hitting me square. As for driving compressed air into a short (or open). I've done that, but not for sand excavation. I have. The clumsy backhoe operator (me) once dropped a load of dirt on top of the steel 3" conduit end during construction. I'm also the idiot that forgot to shove a protective rag into the conduit end. I spent the next two days trying to figure out how to get the dirt out of the pipe. I eventually fabricated a cylinder shaped rubber plug with an eyebolt down the center, dumped some water into the conduit, and dragged the plug through the pipe with a winch. It took about 5 passes for the water to come out clear. I then pumped out the remaining water, dragged a sponge through the pipe a few dozen times, and then let evaporation do the final cleanup. Compressed air was attempted just for fun, but it was obvious that it wasn't going to lift the dirt out of the pipe. I've done that too. For a summer of my youth (when dinosaurs ruled the earth) I would plunge down a manhole with a tethered ball. I'd plug it into the downhill side, clamber out, and fill the manhole with water. Then go to the next manhole, clamber down and dig out all the muck that had been plunged ahead of the tether ball. Repeat for weeks. Substituting one central phrase of "Apocalypse Now": "The aroma of it all! The AROMA of it all!" I'll pass. I don't believe in logic any more. Everything can be explained in terms of politics, psychology, and conspriacies. Logic is obsolete. Last night I went to a reception for Joseph Stiglitz where he mentioned being a liberal too much (he was apologizing to the group at that point) and I drew him aside to comment that he had no need to explain his bias as this was the first time in our political history when we had two candidates BOTH running against the administration AND the Republican Party. We laughed at that logic. 73's Richard Clark, KB7QHC |
Locating underground conduit
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Locating underground conduit
On Fri, 17 Oct 2008 09:19:00 -0700, Richard Clark
wrote: At one point in my career, I found myself with a dead weight tester, calibrating a pressure gauge to 10,000 PSI when the coupling line spit sending a fine spray of pressurized oil past my face. Took me half an hour to shake off the thought of it hitting me square. Ouch. At that pressure, the first few drops of oil will give you an instant tattoo. An acquaintance recently had that happen to him. He's now recovering from the skin grafts and laser ablative cleanup. The closest I came to that was getting a hydraulic fluid shower while riding as an operator inside a Rose Float (in about 1968). The floats animation was run by a pony engine and hydraulic pumps. The coupling directly over me started to leak. After 2 hours in the float lumbering through Pasadena, I arrived thoroughly soaked. http://802.11junk.com/jeffl/pics/jeffl/slides/RoseFloat01.html That's me testing the chair position (which was arc welded in place so it had to be perfect). My feet are resting on top of the electrical animation switching panel. For a summer of my youth (when dinosaurs ruled the earth) I would plunge down a manhole with a tethered ball. I'd plug it into the downhill side, clamber out, and fill the manhole with water. Then go to the next manhole, clamber down and dig out all the muck that had been plunged ahead of the tether ball. Repeat for weeks. Well, I missed such fun when I was younger. I worked for the same monopoly. While you were playing in the muck, I was "re-enforcing" 100 pair bundles and working in the battery room. Substituting one central phrase of "Apocalypse Now": "The aroma of it all! The AROMA of it all!" These days, the installers doing FTTS (Fiber Through the Sewers) have all the fun. Instead of summer interns, the dirty work is done by a robot which installs a SAM (sewer access module): http://www.kate-pmo.ch/pages/en/fast.html Despite the robotics and improved handling, the packets delivered still seem to smell of effluvia. ... as this was the first time in our political history when we had two candidates BOTH running against the administration AND the Republican Party. We laughed at that logic. Chuckle. Very true. Worse, the "real" agendas of both parties are almost identical. I noticed that both parties are also against the status quo (which is generally considered awful). That makes me wonder just what they are in favor of actually doing. I would prefer they do absolutely nothing and let the economy fix itself, but that's too much to hope for. Let the lesser evil win in Nov and never mind trying to decode their logic. I should feel guilty for encouraging this off topic discussion, complete with topic drift, but I don't. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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