500m/2000ft pipe inspection help :)

Moderator: Jeff Snyder

500m/2000ft pipe inspection help :)

Postby rovtom » Sun Mar 28, 2010 9:19 am

Hey guys,
I have been asked to do an internal pipe inspection. But unlike usual pipes that have access points along the length this one does not. Its 500m long :P which is around 2000ft. I just want people to confirm that the loss down the line to a proIII GTO through that length won't effect it enough to not go the whole way. I dont want to turn up to the job and go 350m and find it cant pull its own tether the rest of the way. HELP :D
User avatar
rovtom
Member
 
Posts: 30
Joined: Wed Jun 10, 2009 6:35 am
Location: UK

Re: 500m/2000ft pipe inspection help :)

Postby ncuwi » Mon Mar 29, 2010 6:45 am

Although I've never tried a VR ROV with a tether that long I suspect you're going to run into problems. The first issue you'll run into is "voltage drop". If you know the voltage (AFAIK VR's use a tether voltage of 48VDC), wire gauge (I'm guessing 18 AWG but don't know for sure) and distance, you can calculate the voltage drop ( check out the calculator at the bottom of this page: http://www.powerstream.com/Wire_Size.htm ). Assuming you don't want a voltage drop of more than 50-60% (I'm guessing) you can see what the maximum tether length will be. Perhaps someone at VR can provide the specifics, but I'm pretty sure it will be far short of 2,000 feet. I suspect that, for a situation such as this, you'd need to use on board battery power or a very high voltage system to provide power over the tether to the ROV.

Another possible issue is control communcations distance. Depending on what protocol the VR uses, it may not be able to reliably send a signal that far. A similar question came up recently and the answer was 1200 feet. That thread may prove helpful: viewtopic.php?f=4&t=469
ncuwi
Member
 
Posts: 32
Joined: Mon Feb 15, 2010 5:08 pm

Re: 500m/2000ft pipe inspection help :)

Postby tom_glebas » Mon Mar 29, 2010 9:24 am

The maximum usable VideoRay tether length depends on the model and is technically based on the ability to transmit communications and power.

The Phillips-based (processor) systems (Scout/Explorer/Pro/Pro II/Pro 3/Deep Blue) use CAN Bus for the communications protocol, which is limited to about 1200 feet. I say "about" 1200, because it depends on how many connections and how clean the connections are, etc., which can introduce noise and degrade the signal.

The power available at the ROV is dependent upon the tether type. Negative tether has the largest conductors and transmits the most power. Neutral tether uses smaller wires, and PPT uses the smallest. That is why we always recommend that negative is used for long tether runs. The Phillips-based models use 48 VDC in the tether. Again, the state of the tether and connections may affect the actual power drop by introducing additional resistance.

The Pro 4 communications protocol is RS-485, and we have tested it to 2000 feet. The Pro 4 also uses 74 VDC in the tether. Given the same length of tether, the Pro 4 has more power available at the ROV over the Phillips-based models.

One of our consultants reported that he used 1500 feet of tether to inspect a 1000 feet of pipe. I expect he'll be posting a report on this board soon.

Tom
tom_glebas
Member
 
Posts: 129
Joined: Mon Mar 07, 2005 12:31 pm

Re: 500m/2000ft pipe inspection help :)

Postby rovtom » Mon Mar 29, 2010 11:02 am

cheers Tom. I did wonder, I always hear story of people using various tether lengths. I used over 1000ft once but not on the horizontal. Using negative I would assume over distance is problematic as the drag is greater. There is always a balance I suppose.
User avatar
rovtom
Member
 
Posts: 30
Joined: Wed Jun 10, 2009 6:35 am
Location: UK

Re: 500m/2000ft pipe inspection help :)

Postby Jeff Snyder » Tue Mar 30, 2010 4:17 pm

For what it is worth, Tom, I, too, have been asked to do a few pipeline inspections in the 1500 to 2000 foot range. Scheduled for this summer. I'm going to take a shot at them with the Pro4 I should be receiving in the next few days. I'm assuming that the negative tether is going to be a drag, so I've got to come up with some kind of game plan to keep the tether clear. But I'll let you know (via email) if I come up with anything cool. In my case, I actually bid the work assuming that I would have the Pro4 and have it capable of 2000 feet.

Tom better be right... :evil: :D
Jeff Snyder
Member
 
Posts: 13
Joined: Wed Mar 10, 2010 8:22 pm
Location: Rhode Island, USA

Re: 500m/2000ft pipe inspection help :)

Postby ncuwi » Tue Mar 30, 2010 6:39 pm

Is it possible to add a battery pod to the Pro4? If so, that might help.
ncuwi
Member
 
Posts: 32
Joined: Mon Feb 15, 2010 5:08 pm

Re: 500m/2000ft pipe inspection help :)

Postby tom_glebas » Tue Mar 30, 2010 6:54 pm

We have had a Professional Performance Battery for the Deep Blue, but have since discontinued it. Theoretically, it could work - the battery provides power when the ROV needs it and the topside doesn't push enough down, and it charges when the ROV isn't using much power.

This approach is not on the VideoRay road map. We've demonstrated a prototype of the Pro 4 with a much higher tether voltage system, and are continuing to research that approach.

Tom
tom_glebas
Member
 
Posts: 129
Joined: Mon Mar 07, 2005 12:31 pm

Re: 500m/2000ft pipe inspection help :)

Postby rovtom » Wed Mar 31, 2010 4:08 am

I remember having a battery on a pro II in Bermuda, ah the good old days. Anyway the job fell through but stil good to know for future projects and prospective jobs. I will push the pro4 their way before I use the proIII if its long distance. Thanks Tom
User avatar
rovtom
Member
 
Posts: 30
Joined: Wed Jun 10, 2009 6:35 am
Location: UK

Re: 500m/2000ft pipe inspection help :)

Postby rovsteve » Mon May 03, 2010 12:56 am

I have used the VideoRay Pro 3 GTO for many culvert/pipe inspections over the past 3-5 years and the limit for the unit is between 750 feet to 1,000 feet. After that the video is B&W and can drop out at any time. The unit has very little power at these extreme distances to pull the tether. I have been lucky with several inspections where the water was moving in the correct direction and carried the GTO and tether toward my target. Power loss is the culpruit and VideoRay has not developed a solution. At one point they made and sold some Li-on battery packs which helped a bit but only provided minimal extra boost power for a few minutes.

The Pro 4 is a bit better and should be able to do 1,500-2,000 feet on a horizontal run. I have done seveal 1,150 foot runs with it recently and it had power to drag the tether and even run a BlueView multibeam sonar. I will be conducting a 2,000 foot inspection in a week or two with the Pro 4, this will be the ultimate test fvor this distance.

Technique is very important for successful long tether deployments. Entry into the culvert/pipe should be direct, head in, if you have to go in from above or the side then efforts to reduce drag on the edge of the culvert must be taken. Best is when the pipe is not fully flooded and you have some air space. If fully flooded, you must keep below the top 1 or 2 feet to keep from dragging on the surface of the pipe with the ROV or the tether. Normally, I try to keep moving and go the entire distance without stopping. One there I conduct the inspection on the way back as the the tether is being retrived. If at all possible I try to always try to enter the culvert/pipe from both ends, THat way I know I can do 1,000 feet each way, it;s a lot of extra effort but it gets the job done.

Good luck.

Steve

Good luck an
User avatar
rovsteve
Member
 
Posts: 21
Joined: Mon Mar 07, 2005 1:00 pm

Re: 500m/2000ft pipe inspection help :)

Postby Jeff Snyder » Fri May 14, 2010 10:43 pm

Hey Tom,

Just figured that I would dump in a quick update here. I've been in Florida on vacation, and I was supposed to do a few 1500-ft runs down here. My project has since been pushed to January, but Steve and I caught up and we've been doing some testing with the neutral tethers in parallel with the factory. The Pro4 system seems to be able to push the video and data up the tether - I had it connected to two 750-ft neutrals and one 250-ft neutral. Total distance, 1750-ft. I used a Honda 2000i generator to power the system so that I would have steady power without any "ramping" from the generator attempting to meet demand.

The hitch here is that I have not yet tested the tether-pulling capability...but using the neutral tether will definitely help, as will a few advanced engine room tweaks that the factory can describe.

Steve will likely have an update in the next few weeks, as it sounds like he will take a shot at that 2000-ft mark.
Jeff Snyder
Member
 
Posts: 13
Joined: Wed Mar 10, 2010 8:22 pm
Location: Rhode Island, USA

Re: 500m/2000ft pipe inspection help :)

Postby rovtom » Sat May 15, 2010 4:27 am

lol brilliant, goes to show where theres a will there is a way. Keep me posted. Otherwise youcould do three lengths in pararrel :lol:
User avatar
rovtom
Member
 
Posts: 30
Joined: Wed Jun 10, 2009 6:35 am
Location: UK


Return to Survey and Instrumentation

Who is online

Users browsing this forum: No registered users and 1 guest

cron