Pointers on blowing a pull string through conduit

[JDOFMEMI]

Maybe the smiley face did not show up? I wasn't trying to rain on the parade, just trying to give a different perspective for times when it is a larger project.

Maybe I should have added that I am a fan of using what you have, especially on a smaller project. For a larger project, the ease and savings of having the right tools far surpasses the small cost of the items I mentioned.

If time is not an issue, anything mentioned above will get it done, but for a larger job it really pays to have the tools. Especially in a multiple duct bank run. Stack 5 or 6 conduits in a racking system and you would go crazy trying to keep all the rope ends sorted out if you are doing it one stick at a time.

 

[95zIV]

Leave it to a professional to stifle everybody's creative energy....

Everybody here has bypassed the best solution for "blowing" a string through a pipe,

Just run a pipe to Minnesota and let Gramps have a go at it, he's got enough hot air to make short work of the job.

 

[Scrub Puller]

Yair...slightly off topic but one occasion I had the need to get 150 feet of extension cord beneath a fairly low set house...my wife inserted bull terrier with cord attached to chain collar and I yelled Pig! Pig! on the other side. Worked well.

Cheers.

 

[digger242j]

Maybe the smiley face did not show up? I wasn't trying to rain on the parade, just trying to give a different perspective for times when it is a larger project.

That's why I included the winking smiley. It's just that you were the first guy to mention the 100% professional method and specify the professional grade equipment. My inner wise-ass couldn't resist the temptation.

 

[CRAFT]

...my wife inserted bull terrier with cord ............ attached to chain collar............

BOY am I glad you didn't forget to add "attached to chain collar" ...... for a split second you had me visioning "inserted bull terrier with cord" ...wow that was close ....LOL

 

[JDOFMEMI]

Hearing Scrub's story of the terrier gets me to wondering what was used before the air compressor method, and why the tool used is called a "mouse"??? Maybe a big cheese ball at one end of the pipe??

 

[buckfever]

If it's a big job I agree JD but when it comes to small jobs i perfer to use the same gaug I use to pick my women. Fast, Cheap, and easy. (don't tell my wife I said that)

 

[john1066]

I took a mercy football cut biting half and put an eye Bolt in it. Then I made a stopper for the end of the pipe out of a toilet plunger and some 1" steel pipe with a ball valve to hookup to the compressor. It will do 300 foot runs in about 25 seconds

 

[DGODGR]

CM,
X2 for what JD has described. I would add a couple things as well. When using a parachute (what JD dedscribed as a rubber mouse) in the diameter pipes you have described you will need a fairly high CFM compressor. The one in the garage will not due. Any name brand (I/R; Sulair; Atlas Copco; etc) with around 185 CFM will work well. These are trailer mounted and can be found at most any rental yard if you don't own one (as I'm sure you know). I'm sure that you will have to "prove your duct" by running the mandrell (also as JD secribed so well). Instead of using the multiple lines and processes that JD describes I suggest that you only do it once. You should be provided a pull rope spec. for each utility. Back in the day it was 1/4" for electric (they would just use it to pull in their own hemp pulling ropes), 3/8" for telephone, and whatever for C-TV (they were always regarded as "bottom feeders"). We always used the yellow poly braded rope (also known as "pump rope") and the extra always proved invaluable for a multitude of tasks. Take a small piece of rope and tie the mandrell right behind the parachute. Then tie the pull rope to the back of the mandrell. This way you prove the duct and install the pull rope in one step.
I did dry utilities for over 10 years and can add much more to this if warranted. Since I went back and re-read the first post I think that the "profesional" method would not really be cost effective. That is unless you already own a 185 CFM compressor or can rent one for a 1/2 day (if rental yard is very close to job) or if you have someone who will allow you to rent one "of off the hour meter" instead of by the day. Since you only have (2) conduits I would probably say your best bet would be the "crescent wrench" method suggested by Stumpjumper. Do not be concerned with the rope getting glued to the pipe. You probably will still have to prove the duct (though you have not confirmed that) but that can be done manually as well and must be performed after installation and backfill is completed. I have more to offer but would like more info such as bedding/encasement- if any, pipe thickness (SDR, SCH 40, DB100), and compaction requirements and methods, before I know what to suggest.
On Edit: The rope with the increment marks (usually by the foot) that JD described is called "mule tape". Wether it, or the poly rope, will be required all depends on the specs that each particular utility employs.

 

[CM1995]

Thanks for the comments.:thumbsup We got the job, confirmed last Friday. There are two components to this project, the conduit installation and moving 8K yards of stockpile onsite to fill a temp retention pond - nice dirt work for a change and really the reason why we bid the conduit.:cool2

I had a phone conversation with the Power Co Engineer and he seemed very knowledgeable and willing to work around our schedule. He specifically told me a couple of times on the phone that he lives in the area and we all know what that means - he has an excuse to leave the office at 1PM, stop by the project for a drive-by and a "that looks great" as he is heading home...but I digress.

The Power Co Engineer assigned to the project is the one that inspects your conduit, trench depth, etc prior to backfilling. If you backfill before he/she inspects it, then you are digging it up. On the shorter runs in the past I have not had to prove the line or install pull rope.

DGODGR, heres more specs for the job:

Both conduits SCH 40 - 4" and 5"
Pre-cast concrete pull boxes with metal lids - the lids are the most expensive component of this project
8 - 45 degree sweeps per box for future conduits
The specs only call for a pull string to installed, no pull rope - confirmed by Engineer
There is no spec on the backfill, as it is run in the utility easement
Of course the 3 road cuts will be tamped stone backfill with an asphalt patch
4-6" of crush stone under pull boxes
Pull boxes must be within +/-4" of final grade, I prefer +4", you can always add a little more dirt

I included 2 days of compressor rental in the bid as this being the first time actually doing this ourselves, I didn't want to be too skinny on the rental amount - time and cost wise. Good thing is I have an old high school friend of mine that is the manager at one of the local rental houses, so I get good rates. I didn't think my Honda powered IR on the service truck would do the job...

We will be crossing a gravity and force main sewer, storm drain and water and running parallel with the gas. There is no phone/communication on that side of the road as we are installing the first run from the ROW to the first two lots. When I spoke with the Power Co Engineer I told him there was a discrepancy in the routing of the power conduit with the water valves, not that big of a problem as there is an adjacent 5' utility easement they can use.

Project is due to start the end of this month or the first week in April.

 

[DGODGR]

Thanks for the comments.:thumbsup We got the job, confirmed last Friday. There are two components to this project, the conduit installation and moving 8K yards of stockpile onsite to fill a temp retention pond - nice dirt work for a change and really the reason why we bid the conduit.:cool2

I had a phone conversation with the Power Co Engineer and he seemed very knowledgeable and willing to work around our schedule. He specifically told me a couple of times on the phone that he lives in the area and we all know what that means - he has an excuse to leave the office at 1PM, stop by the project for a drive-by and a "that looks great" as he is heading home...but I digress.

The Power Co Engineer assigned to the project is the one that inspects your conduit, trench depth, etc prior to backfilling. If you backfill before he/she inspects it, then you are digging it up. On the shorter runs in the past I have not had to prove the line or install pull rope.

DGODGR, heres more specs for the job:

Both conduits SCH 40 - 4" and 5"
Pre-cast concrete pull boxes with metal lids - the lids are the most expensive component of this project
8 - 45 degree sweeps per box for future conduits
The specs only call for a pull string to installed, no pull rope - confirmed by Engineer
There is no spec on the backfill, as it is run in the utility easement
Of course the 3 road cuts will be tamped stone backfill with an asphalt patch
4-6" of crush stone under pull boxes
Pull boxes must be within +/-4" of final grade, I prefer +4", you can always add a little more dirt

I included 2 days of compressor rental in the bid as this being the first time actually doing this ourselves, I didn't want to be too skinny on the rental amount - time and cost wise. Good thing is I have an old high school friend of mine that is the manager at one of the local rental houses, so I get good rates. I didn't think my Honda powered IR on the service truck would do the job...

We will be crossing a gravity and force main sewer, storm drain and water and running parallel with the gas. There is no phone/communication on that side of the road as we are installing the first run from the ROW to the first two lots. When I spoke with the Power Co Engineer I told him there was a discrepancy in the routing of the power conduit with the water valves, not that big of a problem as there is an adjacent 5' utility easement they can use.

Project is due to start the end of this month or the first week in April.

Congradulations on getting the work. Hopefully the engineer will be in a great mood when you see him. He should be if he's going home early. I get your point here but I suggest that you count your blessings on that one.
SCH 40 PVC is pretty tough so I think you won't need to do much to prevent crushing/distortion of the pipe. I have never installed 5" conduit, at least in a pair or more, without at least semi-encasement being required. That size pipe will fit a big wire. Big wire=big voltage. Anyway, depending on your soil and cover depth you may want to haunch the pipe before B/F. This is a good practice for the street crossings as you will have to begin compactive effort much closer to the pipe to avoid settlement later on. I assume 30"-36" of cover and that you are just going to tire roll, after B/F, with your 420 or a loader on the sections out of the streets. The down side of this pipe will be weight of 20' joints (for the 5" anyway) and it's resistance to deflection (you said that you will have to avoid other utilities). I would suggest that you talk to your supplier about obtaining some 22-1/2 degree segments, or bends, (better than the 45s because you can use them in more situations as they can be combined to make a few different degree bends) in the radius specified by the utility (usually no sharper than a 48" radius). These will allow you to make bends where necessary. Be aware that many utilities will require concrete encasement, around the inside of a radius (especially with direct buried conduit-meaning conduit that is not encased) because the friction of the rope, against the side of the conduit wall, can burn a hole through the conduit when they are pulling the cable into the conduit. The concrete will act as back-up to ensure that the integrity of the conduit (for shape but not water resistance) will remain through-out the pull. Without it the pull rope may get caught in the cut and would require locating and excavation to retrieve and repair. Many times it can also damage the pulled cable and that gets expensive fast. You did not mention any slopes or grade. Laying conduit on steep grades has it's own set of challenges. Let me know if you need me to elaborate.
I am not sure I agree with the logic of the 45s you mentioned. I assume they will have you install now so that someone will not have to grout them at the future install date. Someone will have to enter the pull box regardless (and the system will have to be placed in a "no-test" status for safety) when pulling in the new line. Surley it does not matter what I think about that anyway so I digress. I assume you will have to grout the holes in the ends of the boxes (maybe around the necking, or grade rings too). I recommend non-shrinking grout but I figure that they will have a spec for that too. The use of a "peanut grinder" or die grinder (pnuematic), with a bituminous cutting wheel, can be used to clean things up if they are installed in too eratic of a termination point (inspectors tend to like things neat and clean). If the P/Bs are the same that I have installed (3'x 5'; 4' x 6') I recommend that you take caution when handling the lids. I am thinking of a 2 pc "swing-up from center to open" with locking hinges and spring assist type. Be cautious as they are heavy and can remove fingers and/or kill if they close on someone who is in the hole. You are on track with the height on the P/B lids. No way would I put them below grade as that just turns them into water receptacles. If they are going to be placed in pavement (asphalt or concrete) let me know and I will offer suggestions for setting precise heights.

 

[digger242j]

Just coincidentally, the electric company was on site today, pulling wire through conduits recently installed by a subcontractor to the sitework contractor, so I asked them how they do it.

They had a portable generator, and a shop vac. They used the shop vac to suck a light nylon pull string through, and used that to pull a 1/4" braided rope through, which they then used to pull the wire. I asked the guy specifically about a mouse, and he said that the trouble with them is that if the conduit isn't perfect, they'll get hung up. He also said that it's particularly prone to happening if they've heated the conduit to make a bend. I guess our local power company doesn't have the same standards as the one you work for, DGODGR.

Anyway, I asked what they use instead of the mouse, and when they guy pointed it out to me, I just had to laugh. There, on top of the shop vac, was a wadded up plastic bag...

 

[buckfever]

We've used the plastic bag for years. Never worry about guys loseing them and its easy to find a plastic bag or shrink rap out on the job. As for pulling a manderel, the only thing around here that requiers that is sanitary line. Never seen a electric checked for round.

 

[wnydirtguy]

What I have done in the past is drill a small hole in a 90 and feed the pull string through. then make a nice ball out of a plastic bag and tie the string around it tight. then put the bag in the pipe and slide the 90 onto it. then have it sized down so I can hook the compressor right to it. put the air to it and watch it pop out the other end. It doesn't hurt to blow the pipe out before running the string. I have ran into problems when I dont first blow out the pipe and there is stuff in it. just make sure no one is near the other end.
On the last sewer job we just hooked the pull string for the pig to a bucket and sent it on its way. Did it with an 8 and 12 inch sewer. made it the whole 300 ft no problems. Just a heads up don't hear your hard hat while blowing down a 12 inch. When it falls off your head it gets sucked in real fast. Not fun trying to get out when it ends up 30 ft down the pipe.
Good luck!!

 

[CM1995]

Congradulations on getting the work. Hopefully the engineer will be in a great mood when you see him. He should be if he's going home early. I get your point here but I suggest that you count your blessings on that one.
SCH 40 PVC is pretty tough so I think you won't need to do much to prevent crushing/distortion of the pipe. I have never installed 5" conduit, at least in a pair or more, without at least semi-encasement being required. That size pipe will fit a big wire. Big wire=big voltage. Anyway, depending on your soil and cover depth you may want to haunch the pipe before B/F. This is a good practice for the street crossings as you will have to begin compactive effort much closer to the pipe to avoid settlement later on. I assume 30"-36" of cover and that you are just going to tire roll, after B/F, with your 420 or a loader on the sections out of the streets. The down side of this pipe will be weight of 20' joints (for the 5" anyway) and it's resistance to deflection (you said that you will have to avoid other utilities). I would suggest that you talk to your supplier about obtaining some 22-1/2 degree segments, or bends, (better than the 45s because you can use them in more situations as they can be combined to make a few different degree bends) in the radius specified by the utility (usually no sharper than a 48" radius). These will allow you to make bends where necessary. Be aware that many utilities will require concrete encasement, around the inside of a radius (especially with direct buried conduit-meaning conduit that is not encased) because the friction of the rope, against the side of the conduit wall, can burn a hole through the conduit when they are pulling the cable into the conduit. The concrete will act as back-up to ensure that the integrity of the conduit (for shape but not water resistance) will remain through-out the pull. Without it the pull rope may get caught in the cut and would require locating and excavation to retrieve and repair. Many times it can also damage the pulled cable and that gets expensive fast. You did not mention any slopes or grade. Laying conduit on steep grades has it's own set of challenges. Let me know if you need me to elaborate.

The specs don't call for any encasement but I do understand the logic. The soil type is a silty clay with sandstone fragments (nothing large 3-4"), good material to work with and it's not virgin soil. The route for the conduit is flat, adjacent to an existing street in a commercial development. Backfill outside the road crossings will be basic push in the trench and tire roll. It's in an easement, adjacent to the curb so nothing will be built over it in the future. I'll bed the pipe with stone in the road crossings and then backfill the first 8" or so with 3/4 crush and start the compaction lift. I like 3/4 crush for road crossings since it compacts well and doesn't settle once compacted.

I included 8 - 22.5 degree bends that wasn't on the plans because I anticipated we would need them to go around existing obstructions. There are 90 degree sweeps that turn up where the new pole will be placed to tie into the overhead service.

I am not sure I agree with the logic of the 45s you mentioned. I assume they will have you install now so that someone will not have to grout them at the future install date. Someone will have to enter the pull box regardless (and the system will have to be placed in a "no-test" status for safety) when pulling in the new line. Surley it does not matter what I think about that anyway so I digress. I assume you will have to grout the holes in the ends of the boxes (maybe around the necking, or grade rings too). I recommend non-shrinking grout but I figure that they will have a spec for that too. The use of a "peanut grinder" or die grinder (pnuematic), with a bituminous cutting wheel, can be used to clean things up if they are installed in too eratic of a termination point (inspectors tend to like things neat and clean). If the P/Bs are the same that I have installed (3'x 5'; 4' x 6') I recommend that you take caution when handling the lids. I am thinking of a 2 pc "swing-up from center to open" with locking hinges and spring assist type. Be cautious as they are heavy and can remove fingers and/or kill if they close on someone who is in the hole. You are on track with the height on the P/B lids. No way would I put them below grade as that just turns them into water receptacles. If they are going to be placed in pavement (asphalt or concrete) let me know and I will offer suggestions for setting precise heights.

I don't agree with the logic of the 45's either but that's what the Engineer wants.:beatsme They are for future services as this line will provide underground for 6 or 7 commercial lots. The PB's have knock outs for 5" conduit and will be 4'x6'. Thank you for the advice on the lids as I don't have specific knowledge of installing them. They are the two piece swing up from center type. What would be your suggestion in installing the lids? At our disposal we have skids, PC78, 420D and a Gradall forklift (although I don't want to mobilize it to the site just to set lids). I will also have my 953C there to do the dirt work but I don't see how it would be of any help, as the lids aren't heavy enough to warrant that much lifting power.

Thank you for your time and knowledge!

 

[CM1995]

Just a heads up don't hear your hard hat while blowing down a 12 inch. When it falls off your head it gets sucked in real fast. Not fun trying to get out when it ends up 30 ft down the pipe.
Good luck!!

I got a chuckle out of that one because I can see myself doing something like that! Hmmm, now how are we going to get my hard hat out of that pipe? I have a big ol' noggin' so my hard hat won't fit in this 5" pipe.

 

[DGODGR]

digger242j,
The work I did was in S. California. For electric we would bid to So Cal Edison, and the Dept of Water and Power for the city of Los Angeles. They, however, were not the only ones that required us to prove the conduit. General Telephone (GTE), Pacific Bell, AT&T (all telephone companies), and even private firms, like AmGen, would require it. This was almost always off-site infrastructure work. Most of it was in the street and/or in the public right-of-way. I can't speak about your electric company but if, as you put it, the mouse (I think you meant mandrell as mouse is the term used for the little wadd of plastic bags or foam that you vaccum or blow through the pipe) gets stuck that's not nearly as inconvienient as getting the wire stuck, or maybe damaging it and not knowing until it is energized. The whole point is that you are trying to ensure that the wire fits. Maybe your guys oversize the conduit so proving it is not so critical. BTW the Shop-Vac will probably work. I'm just not sure if it would suck enough volume to work on such a large conduit as 5" over 300'. I use it a lot on smaller conduit. I've used plastic shopping bags (with and without rags inside), rags held to shape by duct tape, and even potato chip bags (the least effective method). Since we are discussing "McGuiver" methods...Have you ever seen anyone cut PVC pipe with string? It can be done in a pinch and, in some situations, it is the best way.

 

[DGODGR]

The specs don't call for any encasement but I do understand the logic. The soil type is a silty clay with sandstone fragments (nothing large 3-4"), good material to work with and it's not virgin soil. The route for the conduit is flat, adjacent to an existing street in a commercial development. Backfill outside the road crossings will be basic push in the trench and tire roll. It's in an easement, adjacent to the curb so nothing will be built over it in the future. I'll bed the pipe with stone in the road crossings and then backfill the first 8" or so with 3/4 crush and start the compaction lift. I like 3/4 crush for road crossings since it compacts well and doesn't settle once compacted.
I would be a bit concerned about the sandstone chunks if they are that big. Hand bedding, or at least baby sitting the backfill, may be required.

I included 8 - 22.5 degree bends that wasn't on the plans because I anticipated we would need them to go around existing obstructions. There are 90 degree sweeps that turn up where the new pole will be placed to tie into the overhead service.
It sounds like you are on top of things. In my experience the 5" sweeps (we always had fiberglass or galvenised steel 90s-I assume because they are exposed to light and resist burning through better than PVC) are a major PITA. They were always less than 90 degrees, were 5' radius (so you had to be pretty deep for them to fit right), and had shallow couplings. We fought each and every one.



I don't agree with the logic of the 45's either but that's what the Engineer wants.:beatsme They are for future services as this line will provide underground for 6 or 7 commercial lots. The PB's have knock outs for 5" conduit and will be 4'x6'. Thank you for the advice on the lids as I don't have specific knowledge of installing them. They are the two piece swing up from center type. What would be your suggestion in installing the lids? At our disposal we have skids, PC78, 420D and a Gradall forklift (although I don't want to mobilize it to the site just to set lids). I will also have my 953C there to do the dirt work but I don't see how it would be of any help, as the lids aren't heavy enough to warrant that much lifting power.
If it were me I would use the 420 or the 78. It all depends on how close you satge the lids and how much room you have to move around. You will need a special sling to keep it balanced level. The one we installed were set up for a 4pt lift. You had to have a special "knuckle" to get the sling to hook onto the lifting lugs. Without them you might be able to use the fork lift but, as you said before, they are expensive so probably not the best method.
Thank you for your time and knowledge!

Here are my three charachters to meet the minimum.

 

[Drc]

We make a parachute out of tie wire and plastic, tie it to pull string or a ball of baler twine blow it through with a 185 compressor. Other methods may fail if you're blowing through fibreglass sweeps (they have a constriction in the slip coupler) or have water in the conduits.

 

[DGODGR]

We make a parachute out of tie wire and plastic, tie it to pull string or a ball of baler twine blow it through with a 185 compressor. Other methods may fail if you're blowing through fibreglass sweeps (they have a constriction in the slip coupler) or have water in the conduits.

I've never had trouble with the regular parachutes making it through the sweeps. The mandrel had to be run to the base of the sweep and then pulled back (it won't fit through). Enough water, in the conduit, can be a bit tough. Usually, with a 185 CFM compressor, it just makes a fountain at the other end. Place the green horns at the receiving end and we all get a good laugh!