Interpretation Response #PI-79-036 ([Shell Pipe Line Corporation] [R. E. Speckmann])
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Response Publish Date:
Company Name: Shell Pipe Line Corporation
Individual Name: R. E. Speckmann
Location State: TX Country: US
View the Interpretation Document
Response text:
Mr. R. E. Speckmann, Manager
Regulations and Maintenance Standards
Shell Pipe Line Corporation
P.O. Box 2648
Houston, Tx 77001
Dear Mr. Speckmann:
Your letter of June 19, 1979, requested a finding under 49 CFR 195.260(e) that valves are not justified at certain water crossings in your planned installation of the 48-inch diameter LOCAP crude oil pipeline between the Louisiana Offshore Oil Port (LOOP) terminal at Clovelly, Louisiana, and the existing input terminal to the Capline system at St. James, Louisiana.
In your letter, you stated that the LOCAP pipeline begins at LOOP's Clovelly, Louisiana, underground storage dome in Section 32, T18S, R22E, LaFourche Parish, and extends in a northerly direction across marshes, numerous bayous, swamps, the Intracoastal Waterway, and some farmland to the Capline Pipeline St. James Terminal located in Section 56, T12S, R16E, St. James Parish, Louisiana. Conditions along the LOCAP pipeline route are such that approximately 85 percent of the pipeline will be installed in marsh and swamp areas
using weight coating for stability. The pipeline will be welded together and floated in a ditch excavated through these areas. The pipeline will be submerged, and the floatation ditch will be
backfilled to cover the pipeline. Brackish and fresh water will exist at various times of the year over most of the length of the new pipeline.
You indicated that precise compliance with §195.260(e) would result in the placement of what the Shell Pipe Line Corporation (SPLC) considers to be an impractical number of valves. Instead you proposed to place valves at initiating and delivery terminals, near Highway 3199 and near Highway 20, and on each side of the Intracoastal Waterway. The valves at the initiating and delivery terminals and on each side of the Intracoastal Waterway will be remotely operable from the Capline St. James Control Center. Further, you also proposed to install two means to detect leaks, as discussed hereafter.
In the evaluation of your request, this Office considered the following factors as relevant to whether justification exists for not installing valves as required:
- Effectiveness of Proposed Leak Detection and Shutdown System
We found your plans for automated leak detection with alarms and remotely controlled block valves and shutdown pumps at Clovelly Station to be an effective, integrated set of alternative measures which will assure a level of safety far exceeding that attainable by literal adherence to §195.260(e). Your first method, a dynamic computer model of the pipeline, will provide rapid response to suddenly occurring leaks. I believe this model will read telemetered pressures and flow rates from Clovelly and St. James. Utilizing hydraulic surge theory, the model will calculate and compare calculated and telemetered hydraulic variables. Computerized computations will ascertain the divergence between real and calculated values and send appropriate alarms to the oil movements controller if a leak is indicated.
The proposed second method of leak detection by comparison of input and delivery volumes will be read into a computer line balance program and compared at periodic intervals. If a discrepancy exists between the adjusted input and output volumes exceeding a preset limit, the proposed leak detection alarm will be signalled to the oil movements controller, who will be able to shut down the pumps at Clovelly Station and isolate the pipeline by means of remotely controlled block valves at initiating and delivery terminals and on each side of the Intracoastal Waterway. Your proposed leak detection and shutdown appear to be safe and surpass the safety provided if shutdown capabilities were limited to manually controlled valves placed as required by §195.260(e). Even if these remotely controlled valves failed to close in the event of a pipeline rupture, the response time required to manually close them should be no greater than the response time necessary to close any manually operated valves under §195.260(e).
- Threat to the Integrity of the Pipeline at the Planned Water Crossings
The waterways to be crossed other than the Intracoastal Waterway are all less than 10 feet deep and most are less than 7 feet deep. Flow rates are so low that erosion of the pipeline cover is highly unlikely. Marine traffic consists of light, shallow draft boats and an occasional flat-bottomed barge, none of which can be expected to damage the pipeline within its 5-foot, filled trench by direct contact or dragging anchor. For these reasons, we conclude that the probability of pipeline rupture at these water crossings is not appreciably greater than that for the remainder of the pipeline.
- Drainage from Line after Shutdown
Placement of valves on either side of the water crossing is to limit line drainage into the waterway after shutdown in the event of rupture at a crossing. In your proposed valving plan locations, Drawing No. SK-0146 showing pipeline water crossings, even though a valve is not near a crossing, very little oil is expected to escape from any line rupture that might occur at the crossing after shutdown occurs and all dynamic effects cease. The maximum grade elevation variation along the pipeline is limited to approximately 15 feet. The elevation at Clovelly Dome is 0 feet to -1 foot, and at the St. James Terminal, the elevation is approximately +14 feet at the delivery manifold. Eighty percent of the pipeline will be installed in marsh and swamp areas using weight coating for stability. It is reasonable to postulate for practical purposes that the line will lie mostly beneath the water level and that after shutdown, water pressure will confine most of the line fill to the pipeline except for small amounts displaced by the differential in density between oil and water.
Therefore, in consideration of the above information and conclusions, the Materials Transportation Bureau finds that valves and a leak detection system installed and operated as proposed in you letter of June 19, 1979, will provide an acceptable level of public safety and that placement of valves on each side of every water crossing, other than the Intracoastal Waterway, along the LOCAP pipeline is not justified.
Sincerely,
Cesar De Leon
Associate Director for
Pipeline Safety Regulation
Materials Transportation Bureau