Sleeper footing foundation ( corroded reinforcing bars during internal Visual inspection) 2

[121974don]

Any recommendation with regards to sleeper footing foundation with Pipes ( Functional ) on top of it.My preliminary assessment when we exposed one of the support footing foundation is that there are some developing cracks on the surface of the concrete and the reinforcing bars are corroded. the span of the support is 7.5 meters , depth of footing is 400 mm x 1500 mm. Also, the concrete pedestal attached to the footing ( 950mm x 400 mm) is also deteriorated. the problem is that Pipes (loads) are already functioning and if the operation will be stopped, it will be a big impact to costing.....can it be retrofit????Your ideas are welcome...

 

[Ron]

Why is the problem occurring? Do you have high chlorides in the concrete? Do you have high sulphates in the soil? Is it old?

Don't know how to fix until you know why!!

 

[SlideRuleEra]

As Ron has stated, more details will be helpful.

Find out when the next "scheduled plant outage" will take place. It could be many months, even over a year away. At some time there will be a "scheduled outage" for maintenance, repairs, equipment modifications, etc. That is the time for replacement of the foundations / pedestals. Typically, the plans for the replacements will be prepared before the outage and all preparations ready (say, having a Contractor on notice, and certain materials on hand) so that work can begin as soon as the outage starts. The consequences for a plant to have an "unscheduled outage" can be very high, and operations will not do it except for VERY good reasons.

Evidence that the pipe line must be shutdown would be major leakage, especially if the pipe contents are toxic, at high pressure or temperature, etc. - just minor leakage of say, cooling water, is not enough of a problem.

Be prepared to perform minor pipeline support and bracing (probably with heavy timber), to keep the system on-line. In addition to pipeline operating conditions, find out as much as you can:

Type of pipe - steel, ductile iron, concrete, etc.
Type of pipe joints - welded, bell-spigot, bolted flange, etc.
Pipe covering, if any - insulation (calcium silicate, fiberglass, mineral wool, ***asbestos***, etc.) also any sheet metal covering (lagging) covering the insulation.

This information will be helpful to plan for temporary repairs. Other than the above steps, sit back and wait - plant operations (usually) are more important than manageable structural defects.

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[121974don]

Hi Ron and slide Rule,

The soil or environmental condition is Highly sulfated.I tried to asked when it was constructed to have my assessment most likely satisfiable but nobody has the idea.Most likely the structure is around 25 years and cast in situ. The depth of footing is 400 mm + 950 mm Pedestal, the backfilled is around 750 mm so that you can see the pedestal protruding at 600 mm.

We do the surveillance within our discretion especially major defects are observed aside from Plant assessment schedule.we had 50 sleeper foundations in that area and spaced @ 6000 mm apart.Nowhere to shut down the plant as it is critical and it is distribution area.As per my investigation, it can be replaced or repair, retrofit at random schedules only in order not to prolong operation activities.

The Pipeline is carrying Diesel and kerosene.Timber is not allowed in the company standard even for Temporary support even steel support to hold the pipeline that are distributed in 7500 mm will not be accepted as a measure to pursue civil activities except as i said earlier that it can be done at a random schedule only or one at a time approach.

Thank you for participating with your good ideas.

 

[dik]

Have you undertaken any lab testing of the concrete? Any idea of how long? and what the earlier concrete strength was?

Dik

 

[121974don]

No testing yet as our department is only for external visual inspection. The concrete design is 4000 psi.Though that is my next recommendation as a Sr. Inspector, we have some limitation in our scope of work. Obviously ., I already recommended that the structure are to be replaced and that is definite as per my judgment even without Laboratory test ie. hammer testing, Coring test or any integrity test that will give the definite answer. The operation needs another approached aside from the replacement because of Financial Constraints in oil and gas ...and the quantity is very huge... 50 Sleeper foundation...

 

[121974don]

To Mr. Dik,

You mean the span length? that is 7.5 meters

 

[SlideRuleEra]

The operation needs another approached aside from the replacement...

Now I understand.

To repair with the pipeline in operation, look into removing bad concrete using hydrodemolition. This will leave the corroded rebar in place, but remove the corrosion so that new concrete can bond with the rebar.

Use shotcrete to replace the concrete. This will NOT restore the sleepers, but may slow down deterioration to extend their useful life.

This is a temporary repair you can discuss with management, get pricing for the work, and let management decide if temporary repair is worth the cost. Many times management just needs proof that spending much money for a permanent fix is better than spending some money for a temporary repair. Give management the information... just quietly standby, answer any questions, and let them decide.

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[121974don]

Hi SlideRuleEra,

Thanks for your great idea!!! I will stand in the same thoughts you have...yes probably considering that today all around the world are in the state of crisis, Any management will opt to have the same opinion until the recovery period $$$$$.Thank You very much...

Regards,

 

[Ron]

Good idea SRE. Consider using at least Type II cement in the shotcrete

 

[SlideRuleEra]

121974don - You are welcome.

Ron - Thank you.

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[dik]

I don't know the interaction, but, Type 5 (Sulphate Resistant) is contraindicated for exposure to Chloride. If any exposure to Chlorides and Sulphates, then you might consider using normal Portland cement with 25-30% fly ash. If severe sulphate attack, then, I'd avoid Type 2 cement. If no chlorides, I'd go directly to Type 5, or normal with flyash.

Dik

 

[121974don]

Based on our reference standard if the Water-soluble Sulfate (SO4) in Soil, Percent by Mass is 0.2 ≤ SO4 < 2.00 or Dissolved Sulfate (SO4) in Water, ppm2 is 1500 ≤ SO4 < 10,000 wherein the case here falls under this category,then we categorized it by Exposure S1 : if; Fc' 28 mpa then cement type shall be Type 2 or 5, reinforcing steel is uncoated.