Pipeline Exposure

An integrity dig is an examination, and the excavation is part of it

The purpose of this hole is evidence. Somebody is going to write down what the pipe looked like, what the coating was doing, what the wall measured and whether the feature an inline tool reported is what the tool thought it was. Every one of those findings is only as honest as the condition the pipe arrives in. A tooth mark added during excavation contaminates the assessment, because now the coating damage in the photograph has two possible authors and the one the report needs is the ground. That is why operators write non-destructive excavation into the procedure rather than leaving it to preference. Water erodes soil and flows around the barrel, so the disbondment, the holiday, the corrosion cell and the mill scar all get handed over exactly as the years left them. This is the reason the excavation contractor on an integrity dig is a technical participant rather than a machine rental.

Coating is evidence before it is protection

On an operating line the coating is the first thing the inspector reads. Where it is disbonded, where water has been sitting under it, whether the cathodic protection has been reaching what is beneath it, how the mainline coating and the field joint coating have aged differently: that story explains the corrosion the wall measurements are about to quantify. Different systems behave differently in the ground and in the hole. Coal tar on older line, fusion bonded epoxy on newer, tape wrap at field joints, and shrink sleeves that have their own well known failure habits at the overlap. Each responds differently to water pressure and to a wand that sits still, which is why the tip spreads energy rather than concentrating it and the operator keeps standoff and keeps moving. A coating survey with a holiday detector usually follows the dig, and a hole that added its own defects makes that survey argue with itself.

Verifying what the inline tool called

The dig exists because a tool run flagged something, and the field examination has to confirm, correct or dismiss the call. That is a comparison, so the excavation has to make the comparison possible. The feature has a reported length, a reported orientation on the clock and a reported distance from a reference weld, and the exposure needs enough pipe on both sides of it that the technician can find the reference, work the full extent of the area of interest and then keep going far enough to be confident nothing was missed at the edges. Features arrive in clusters more often than the sheet suggests. The barrel has to be reachable at every clock position, top, sides and bottom, because external corrosion prefers the bottom of the pipe where water sits and that is the hardest place to get a probe. A hole sized to expose the top of the line has confirmed almost nothing at considerable expense.

A bell hole a technician can actually work a probe in

Dimensions on an integrity dig are set by the examination, not by the pipe. There has to be room to swing around the barrel and to get under it for a full circumferential sweep, room to hold a probe at whatever angle the procedure specifies, and room for a grinder or a blast setup where the surface preparation calls for one. If the finding turns into a repair, a composite wrap or a full encirclement sleeve needs more clearance again, and it needs it around the whole pipe rather than over the top of it. Depth pushes all of that into a shoring conversation, since anything a person enters gets sloped, benched or shored for the soil it is in, with a ladder and a way out. Groundwater is the other constant. The table sits high across most of this state and a right of way through drained wetland ground produces water continuously, so a pump and a sump in the corner of the hole is normal, and a dry surface is a precondition for most of the techniques that are about to be used on it.

What the operator is going to ask before you are on their right of way

Integrity work brings paperwork before it brings shovels, and the answers exist here ahead of the ask. The tankers are ours and the drivers are ours, every one holding a CDL, with the fleet running under USDOT 4547071, active. The company is bonded and insured, family owned, first responder owned and operated, with a master plumber on staff and the phone answered at any hour of any day of the year. Spoil from a right of way dig is a regulated stream and it leaves in the tank under our haulers permit to a facility permitted to receive it, documented, which matters because the generator of that waste is the operator rather than us. Excavation travels statewide for pipeline work, further than we go for local service work, so send the milepost and the scope rather than assuming the county line is a boundary.

Worth knowing

Size the hole to the examination rather than to the flag on the dig sheet. Send the procedure, the reported feature length and orientation, and what the inspector needs to reach, including the bottom of the barrel. Reopening a right of way dig because the excavation ended where the feature did is an entirely avoidable day.