A major Texas midstream operator was preparing to commission a new 36-inch transmission line, 64 miles long, designed to carry an average of 17 million standard cubic feet per hour at 850 psig. Before the line could carry odorized gas to downstream customers, the interior of the pipe had to be conditioned. Fresh steel reacts with mercaptan. Mill scale, rust, and the inherent reactivity of new pipe surfaces would strip odorant from the gas stream and produce odorant readings at the downstream end well below the regulatory detectability standard.
Rushing the line into service without conditioning was not an option. The operator needed a pickling strategy that would saturate the reactive sites along the full 64 miles, stabilize odorant consumption at a predictable rate, and produce the documentation a regulator would expect to see at audit.
Approach
MRR designed an online pickling operation built around elevated upstream odorant injection and continuous monitoring at the downstream end. Six temporary odorizers were staged at the front of the pipeline, set to inject at concentrations several times the operator’s normal target. The elevated rate provided the headroom needed to overcome reactive losses along the full 64-mile length while still delivering odorized gas to the downstream connection.
Flow measurement on a transmission line of this size required equipment that could be installed without breaching the pipe. MRR deployed ultrasonic clamp-on flowmeters at the upstream injection point, providing accurate flow data for proportional odorant control without any modification to the line itself. Solar-powered flow controls allowed the temporary odorizers to operate in the remote sections of the route without tying into utility power.
Monitoring at the downstream end tracked odorant concentration in real time over the full 10-week operation. As the pipe interior conditioned and reactive losses dropped, the upstream injection rate was reduced in stages. The operation concluded when the downstream concentration tracked the upstream concentration within an acceptable margin and held there.
Outcome
The line was successfully conditioned over 10 weeks of continuous operation. Approximately 5,500 gallons of Scentinel E odorant was consumed during pickling — the volume required to saturate the reactive surface area of 64 miles of fresh steel pipe at this diameter. At the end of the operation, the pipeline transitioned to normal service with stable odorant consumption and downstream readings within the operator's approved detectability specification from the first day of commercial operation.
The documentation produced through the operation — upstream and downstream concentrations, equipment settings, flow data, daily logs — became part of the line's commissioning file, giving the operator a documented record to support regulatory review.
MRR runs pickling operations across pipe sizes from distribution laterals to large transmission lines. The 64-mile Texas line sits at the upper end of that range; a 4-inch lateral commissioning operation runs on the same principles at a fraction of the duration.
