FAQs (frequently asked questions) About The Sag Correction System

How deep of a sag will the system remove?

Customers have commonly removed sags that were 3 and 4 inches deep. Most customers say the majority of sags they encounter are less than 2 inches deep.The maximum amount of sag that can be removed may vary with the job conditions. In some instances the pipe raises relatively easy all of the way and other times the pipe may get progressively more difficult to raise as it is lifted up.

At what depths of bury will will the sag machine still work?

The depth of the pipe does not appear to be a big issue. It has been used successfully at depths exceeding 30 feet deep. One customer reported removing a sag in an 8 inch line that was 45 feet deep.

How large of diameter pipe can the machine be used on?

The sag machine comes equiped for 8 inch pipe. We build adapters for 10 and 12 inch pipe. Sags in 12 inch pipe can be slow and difficult to remove.

Sags on larger diameter pipe are harder to remove. In order to remove a sag, the machine has to bend the pipe. Larger pipes have more strength and are more difficult to bend within the span of the sag machine. In addition, larger diameter pipe bends in a longer radius, so more length has to be lifted at the same time and as this length increases, it gets farther from the vibrator.

What is the success rate of the sag correction system?

The success rates vary with the customer and their job conditions. It is important that the pipe is surrounded with a granular material (crushed rock or sand) and the material is saturated with water or water is added as shown in the detail on the web site.

The sag machine usually works very well where the pipe is deep and the water table is above the top of the pipe. Most customers report success rates of 90 to 100 percent in these conditions with 8 inch and 10 inch diameter pipe.

The machine also has a high success rate in dry conditions where water is injected and the granular pipe zone material contains fines.

Where water is injected in dry conditions and the pipe zone material is coarse or the fines are screened out, the success results are more mixed. We think this could be from the material being too free draining in proportion to the amount of water that was applied and that not enough water was retained.

Where the machine has been used in dry conditions without adding water, the results have usually been poor. In most cases the machine will not work dry, although some customers have reported examples where they had success in dry conditions. Most experienced users tell us that if they do not see results immediately, they start injecting water.

Water helps lubricate the pipe zone material to flow underneath the pipe. Also, water helps transfer the vibration out into the surrounding material. In dry conditions we have seen the pipe lift, but go back down when the lift pressure was released.

There may be conditions specific to certain sites that affect the results. Feel free to call us to discuss your site conditions.

How long does it take to remove a sag?

This will vary with different conditions. Most experienced users tell us that it takes them about a half of a day to set up and remove a typical minor sag.

When assembling the machine sections inside a manhole it may be necessary to chip out part of the channel, to allow the sections to align and bolt together. This may take more time if it is not done in advance.

Can I turn the machine upside down and push down humps in the pipe?

No. The machine does not work upside down. It would be necessary to feather out the belly on the upstream side of the hump.

What types of pipe will the machine work on?

The pipe must be flexible so the machine can arch it up at the sag. Most of the feedback we have received was on 3034 PVC. One customer successfully removed a sag in a 10 inch C-900 PVC pipe. The machine will not work on ductile iron or rigid pipe.

What else will I need besides the sag correction system to remove a sag?

You will need a 75 CFM or larger air compressor, a 3/4 inch minimum diameter air hose, and our air swivel, oiler & filter assembly. You will also need a separate 3/8 inch air hose to activate the lift mechanism. It is possible to pull the machine and hoses by hand, but it is too much work for most people unless the sag is close to the manhole. We recommend using a light duty winch or pulling device to move the machine with rollers or pulleys at each end of the pipe. A pull back line should be attached in case the machine gets stuck. A TV camera will be necessary unless the sag is near a manhole.

Do you offer any on-site training?

We don't think any special training is necessary. Most customers have been doing fine by following the instructions. We can answer any questions by phone if they arise. Like learning to operate any other equipment, one should go slow and careful until they have some experience.

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