3. EJECUCIÓN POR PRIORIDADES
3.4. EJE 4: DESARROLLO SOSTENIBLE LOCAL Y URBANO
Pipeline control in a batched products pipeline involves scheduling to transport differ- ent shipper nominated volumes of crude, products, and NGLs from designated injec- tion locations to designated delivery points, while maintaining the quality and quantity of the product.
Batching information is critical to the success of scheduling because it influences pipeline operation (Figure 5-24). Batch information provides a means for:
Determining the accuracy of the schedule ·
Identifying the baseline, or starting point, for scheduling new operations ·
Pipeline system operational requirements ·
Three major components of liquid pipeline operation are: Nominations (supply control, pipeline supply scheduling) ·
System operation (operations scheduling, pipeline control [products receipt, ·
pumps and tankage/storage operation, product delivery]) Inventory accounting.
·
A high level scheduling process cycle for a pipeline network transporting multiple products is shown in Figure 5-25. The process involves nominations, data review and input from schedulers to develop a cycle plan, a batch plan, and system schedule. This scheduling information is then distributed to shippers, terminals, schedulers, third par- ties, and pipeline controllers to keep everyone with an interest in product movements abreast of the schedule. The process usually allows schedulers to schedule up to 45 to 60 days in advance, and to modify that schedule as required.
Nominations: Shipper nominations involves receiving and processing all Notice
of Shipments (typically volume, type of commodity/product, injection and delivery points), performing system line balance calculations on all originating lines and deter- mining the system capacity adequacy to transport all products.
Generally, if adequate capacity exists, pipeline companies commence the trans- portation scheduling process. However, if adequate capacity does not exist, the follow- ing apportionment procedure is performed:
TAbLE 5-8. Minimum batch size Fuel
Minimum batch, m3
Year 2000 Year 2005 Year 2010
Diesel/Jet A-1 12968.50 12285.50 11704.00 Diesel/regular gasoline 25028.00 23795.00 22669.00 Regular/unleaded gasoline 22543.00 21433.00 20418.00 Unleaded/premium gasoline 7331.00 6969.67 6640.00 Premium gasoline/diesel 24417.00 23214.00 22115.000
TAbLE 5-9. interface between regular and unleaded gasoline (year 2000 volume)
Item 0–75km From Dist#2 (km 26) 75–100km 100–135km 135–150km 150–175km
Blended Viscosity cs 0.794 0.794 0.794 0.794 0.794 0.794 Reynolds Number (Re) 456,206 456,206 965,715 965,715 481,561 481,534 Critical Reynolds # (Rec) 54,701 54,701 67,271 67,271 54,701 54,701 Interface Length, LC, km 0.5397 0.31777 0.32427 0.38368 0.24006 0.30992 Interface Volume m3 61.50 36.21 58.50 69.22 27.36 35.32
Pipeline Operation and Batching n 263
Perform feeder pipeline nominations verification ·
Apportionment calculations to determine the percentage of apportionment by ·
line
Notify each shipper of the maximum allowable by shipper and by line ·
Receive from the shipper the adjusted/apportioned nominated volumes, i.e., ·
revised Notice of Shipments Commence scheduling process ·
Figure 5-23. Interface volume growth and tracking between diesel and Jet A-1
Ratability: Defined as the even distribution of batches carried by the pipeline
according to the shipper, the commodity type, the volume and the destination. The purpose is to help ensure that all shippers have equal access to the pipeline. It is also considered to be a measure of the ability of a pipeline to deliver a scheduled batch to its delivery point within a defined window of its originally scheduled date and time.
Capacity calculations: Several factors determine how pipelines are scheduled
Design capacity · Sustainable capacity · Operating capacity · Expected capacity ·
Proration/capacity matching/apportionment: If nominated quantities exceed
available capacity within any pipeline segment, the industry uses proration rules/ apportionment, to determine maximum total nomination by segment.
The purpose is to pinpoint areas of the pipeline where potential bottlenecks will occur. It involves calculating net pumping requirement, which is the total volume of commodity that a pipeline must pump every day of the month through each section of pipe in order to meet the product shipment volumes. Usually, all product shipments are totaled to determine capacity requirement/availability.
At the same time, schedulers determine each shipper’s minimum inventory level and maximum inventory level by product and location. These levels are necessary to ensure that all shippers share the responsibility for maintaining the working volume in the bottoms of the tanks based on each shipper share of the total nominated movements for that product. At the same time, each shipper is able to utilize the working storage capacity in proportion to their nominations. When overcapacity volume is determined, proration/apportionment is the process used to reduce the net pumping volume tendered for a section of pipeline. This apportionment or proration is calculated as follows:
Pipeline Operation and Batching n 265 Apportionment = (1 – ECV/NTV) ´ 100
where
NTV = net tendered volume ECV = expected capacity volume
Overcapacity occurs when the net pumping requirement exceeds the volume that a pipeline section is capable of moving for a given nomination period.
Pipeline supply scheduling: involves the following:
Receiving information for products to be shipped ·
Schedule batch movements downstream ·
Follow-through scheduling ·
Issue all schedules as segment fills are completed ·
Issue injection and delivery schedules ·
For all shippers, connecting carriers and delivery locations:
Schedule updates and communication for current and subsequent periods ·
Maintain system throughputs by pipeline segments ·
Direct contact with all shippers and connecting carriers ·
A typical planning schedule involving batch nominations and scheduling events is shown in Figure 5-26. The following provides a general sequential list of scheduling process involving nominations, batch planning and movements.
Notification of shippers for monthly nominations
Proration or apportionment if nominated quantities exceeds available capacity within ·
any pipeline section, to determine shipper’s maximum total nomination by segment. Determination (by schedulers) of each shipper's minimum inventory level and ·
maximum inventory level by product and location.
Communication of prorated deliverability and inventory to Shipper. ·
Designation by the Shipper which products are required to be cut back to meet the pro- ·
rated deliverability and inventory requirements by resubmitting new nominations. Generation of a preliminary cycle plan for, and communications of plan to all parties ·
Provision of comments by Shippers ·
Revision of cycle plan and communication to Shippers ·
Completion of the cycle and batch plans by pipeline schedulers. ·
Completion of slug/batch train plan. ·
Communication of the Planning Schedule to the shippers and all interested parties ·
Obtaining the connecting carrier schedules and communicating the Working ·
Schedule to the pipeline operations group.
Generating modified schedules and issue short-term movement orders as ·
required.
Determining and communicating the status of Shippers nominations/batches ·
Factors that influence batch scheduling are: Reductions in supply
·
Increases in supply ·
Delivery pattern changes ·
Third-party impacts ·
Line upsets ·
Scheduled and unscheduled maintenance · Tankage/storage requirements · Facility limitations · Refinery/delivery upsets ·
It is normal practice that once times have been assigned to batch injections and deliveries, schedules are sent to the
Shippers ·
Connecting pipelines/carriers ·
Injection and delivery sites on the pipeline ·
Refineries/delivery locations ·
Shipper schedules include information about All batches that the shipper owns
·
All injections of volumes tendered ·
All deliveries for both the current tender period and previous tender periods ·
In today’s technological environment shippers can electronically submit via the Internet:
Monthly forecasts ·
Monthly nominations ·
Pipeline Operation and Batching n 267 Batch changes
·
Batch trades and swaps ·
Further details on the batch scheduling and shipper information system including a web-based system such as T4 are detailed by Yoon et al. [3].