NEW CONSTRUCTION ERA REFLECTED IN EAST TEXAS LPG PIPELINE

April 2, 1990
T. J. Mittler Texas Eastman Co. Longview, Tex. Installation of 240 miles of 6, 10, and 12-in. LPG pipelines from Mont Belvieu to Tyler, Tex., has provided greater feedstock-supply flexibility to Texas Eastman Co.'s petrochemical plant in Longview, Tex. The project, which took place over 18 months, included tie-ins with metering at four Mont Belvieu suppliers. The new 10 and 12-in. pipelines now transport propane while the new and existing parts of a 6-in. pipeline transport propylene.
T. J. Mittler
Texas Eastman Co.
Longview, Tex.

Installation of 240 miles of 6, 10, and 12-in. LPG pipelines from Mont Belvieu to Tyler, Tex., has provided greater feedstock-supply flexibility to Texas Eastman Co.'s petrochemical plant in Longview, Tex.

The project, which took place over 18 months, included tie-ins with metering at four Mont Belvieu suppliers. The new 10 and 12-in. pipelines now transport propane while the new and existing parts of a 6-in. pipeline transport propylene.

SUPPLIES NEEDED

Texas Eastman Co., a division of Eastman Kodak Co., operates a petrochemical plant in Longview that manufactures more than 40 different chemicals and plastics.

The Longview plant was started in 1950 with plentiful LPG feedstock (ethane and propane) from the East Texas oil field. As the plant expanded and the East Texas field production diminished, additional feedstock supplies were needed.

In the early 1960s, a 6-in. pipeline was built from the Phillips Clemens Dome terminal, 60 miles southwest of Houston, to Texas Eastman's salt-dome storage facility in Tyler, 35 miles west of the Longview plant. Three pipelines linked the Longview plant and the Tyler storage facility.

Two additional Houston-area suppliers were later connected to the 6-in. line via a pipeline built by Mustang Pipeline Co., a common-carrier pipeline that is a wholly owned subsidiary of Eastman Kodak.

As additional quantities of feedstock were needed, three 600-hp booster pumps were added along the 6-in. pipeline.

By the mid-1980s, Texas Eastman's feedstock supply system was stretched to the maximum. Up to 70 trucks and 5 railroad cars of propane, representing 20% of the plant's feedstock requirements, were being unloaded every day. Unloading 23,000 trucks per year, decreasing East Texas supplies, and planned plant expansions required additional pipeline capacity. A new polypropylene plant required purchased propylene in addition to the LPG feedstock.

The Mont Belvieu saltdome storage area was determined to provide the best source of both propylene and LPG feedstock. This pipeline project was justified based on freight and labor savings over truck and rail transportation, improved safety, competitive procurement, supply security and a good variety in feedstock types.

DESIGN, ROUTE SELECTION

Texas Eastman contracted with Williams Bros. Engineering Co., Tulsa, to provide engineering, procurement, surveying, right-of-way services, and construction inspection for the project. Texas Eastman staffed the project with two full-time engineers and an electrical/instrument engineer who worked on the project part time. The engineering design was done in Tulsa.

Texas Eastman provided the conceptual design including flow sheets, preliminary routing, and a written scope of work. This effort started in May 1987 and the original schedule called for completion in March 1989. This schedule was improved by 5 months.

Another group of Texas Eastman purchasing personnel worked in parallel with engineering to identify and select the suppliers for the LPG feedstock and propylene at Mont Belvieu. These negotiations required more time than expected and delayed final design for the routing, tie-ins, and checkmeters at Mont Belvieu.

The final design provided a 10-in. propane line and a 6-in. propylene line from Mont Belvieu to Conroe, northwest of Houston. These 43-mile long lines were built by Mustang Pipeline Co. The existing 6-in. pipeline from Conroe to Tyler was to be converted to propylene.

A new 150-mile, 12-in. pipeline between Conroe and Tyler would transport the propane feedstock received from the 10-in. Mustang pipeline and the existing 6-in. pipeline from Clemens Dome.

The route for the 12-in. pipeline between Conroe and Tyler was parallel to the existing 6-in. pipeline that had multiple line rights for 80% of the easements. The route for the dual Mustang pipelines was selected based on driving reconnaissance and review of U.S. Geological Service (USGS) topographic maps,

Fig. 1 shows the dual 6 and 10-in. lines being lowered near Mont Belvieu.

The route search centered on existing corridors for other pipelines and power lines; virgin right-of-way on the fringes of Houston was out of the question. The good news was that there was no lack of pipeline and power-line corridors in this area.

An existing pipeline known as the Santa Fe Pipeline, now owned by Koch Industries Inc., crossed Texas Eastman's existing pipeline near Conroe and terminated at Mont Belvieu. This route was selected as the most direct route from Mont Belvieu to Conroe.

Santa Fe provided its alignment sheets as a reference. This 43-mile route included about 20 miles parallel to a dual high-voltage powerline right-of-way operated by Gulf States Utilities. GSU was cooperative in providing maps and agreeing to joint occupancy of its right-of-way in congested areas.

With the route selected, Texas Eastman released an order for aerial photography in July. Hazy Texas Gulf Coast weather delayed completion of aerial photography until early September.

Route surveying was started along the existing 6-in. pipeline when enough abstracting information was available to obtain landowner permission. The alignment and depth of the existing pipeline and a preliminary alignment for the new pipeline were staked.

Typical alignment was for the new 12-in. pipeline to be 15 ft from the 6-in. pipeline. Where conflicts limited the working space, the new line was located as close as 5 ft from the existing line.

Numerous interferences and encroachments were identified. Several subdivisions used the right-of-way as a "natural" boundary either as a rear lot line or as a street; one house was found to be 6 ft over the existing pipeline. The most congested areas were identified for reroutes.

As survey notes and abstracting data were received in the Tulsa office, the alignment sheet drafting was started. Numerous abstracting questions were raised in Tulsa as the drafters pieced together the puzzle.

After several months of unresolved questions, it became apparent there was a communication problem between the Tulsa office and the two field offices. A drafter was added in each field office to assist in resolving abstracting questions and also to prepare plats.

The route surveying and alignment-sheet mapping for the dual Mustang pipelines were not quite as straightforward because new easements were being acquired. The existing Santa Fe Pipeline was generally on the south side of the overhead power lines.

Texas Eastman started out to acquire its easements outside of the Santa Fe Pipeline. In several places, the route jumped inside the power-line right-of-way because of existing houses or other interferences. Texas Eastman tried to work closely with landowners to meet their preferences for routing.

Other detailed design activities included valve stations, scraper traps, the scada system, piping at the junction of five pipelines at Conroe, and checkmeter facilities at Mont Belvieu.

Engineering personnel in Tulsa performed studies, prepared specifications and calculations, quoted and prepared requisitions for all items to be purchased, and prepared the construction contract documents.

CASING, PIPE DESIGN

Texas Eastman's limited pipeline experience and proposed federal regulations prompted several design studies. Casing problems, in particular cathodic-protection shorts, are a common operating problem. Many companies have chosen to eliminate casing, although some authorities, especially railroads, still require casing.

Texas Eastman's operating personnel were reluctant to eliminate casing because it provides some mechanical protection from "backhoe bites" especially in ditches adjacent to roads. Several methods of protection were considered, with the final decision being to use concrete-coated pipe in all road crossings.

For railroads and one county that required casing, Texas Eastman used the concrete-coated pipe inside the casing to provide continuous insulation.

The line pipe was designed for ANSI-600 service, 1,480 psig. There was some regulatory discussion about the reliability of ERW (electric-resistance welded) pipe, but it was finally concluded that nearly all pipelines were still being built with ERW pipe, and Texas Eastman had 30 years' operating experience without weld-seam problems.

All pipe was specified to be triple random lengths with a minimum average of 57 ft and a minimum of 0.250-in. W.T. It was determined that normal welding procedures could be used for pipe strengths up to X56.

Using the liquid pipeline design factor of 0.72, an operating pressure of 1,480 psig, and a yield strength of 52,000 psi led to a calculation of 0.255-in. W.T. for the 12-in. pipeline. The minimum of 0.250-in. W.T. for the 10-in. pipeline and X52 steel provided a slightly better factor of safety.

Proposed DOT rules included requiring LPG pipelines to be designed for class locations similar to gas pipelines. Texas Eastman chose to provide heavier wall thickness in populated areas with the gas-pipeline class descriptions as a guideline.

Texas Eastman provided two heavier wall thicknesses for the 10-in. and 12-in. pipe corresponding to Classes 2 and 3 design factors of 0.6 and 0.5, respectively. A higher yield strength was used for the two heavy-wall, 12-in. design conditions.

A minimum design factor of 0.6 was used for all road crossings. The design resulted in the pipe sizes shown in Table 1. Texas Eastman's existing 6-in. pipeline was 0.219-in. W.T., grade X46, which provided a design factor of 0.48.

The company's success with this design and the conservative design factor led to the decision to use the same design for the new 6-in. pipeline.

The inquiry for 19,000 tons of pipe generated considerable interest. Bid requests were issued to all major U.S. mills and several Japanese trading companies. Although the Japanese submitted the lowest prices, they would not commit to the total quantity required.

The lowest domestic bid was offered by Mannesmann for pipe manufactured at the former U.S. Steel mill in Provo, Utah, which had just been restarted by Geneva Basic Industries. The selection of this mill to manufacture the pipe required an extensive investigation of the mill's capabilities and the soundness of the company.

After lengthy negotiations regarding terms and conditions, warranty, shipping, and the manufacturing schedule, the pipe order was awarded to Mannesmann for pipe to be manufactured by Geneva Basic Industries.

COATING, VALVE DESIGN

Pipe coating provides a wide range of choices. Texas Eastman's most recent pipeline work in 1981 used YG-III two-layer tape manufactured by Polyken. This coating performed well during construction and in operation during the 8 years.

Fusion bonded epoxy (FBE) appears to be a good coating but frequent formula changes and improvements and several reported cases of disbandment made this coating appear to still be in the development stage.

Extruded polyethylene was rated to be equal in performance to the YG-111 tape coating. The company has a small amount of extruded polyethylene coating on the 6-in. pipeline that had performed well for 28 years.

Texas Eastman's bid specification allowed both YG-111 tape and extruded polyethylene, both 50 mils thick. Encoat, Pearland, Tex., was selected to provide extruded polyethylene coating for all of the pipe. Compression Coat, Conroe, applied the concrete coating for road crossings and water crossings with a portable plant in Encoat's yard.

All pipe was coated and stockpiled in Encoat's yard and loaded on stringing trucks during construction.

Several factors related to main line block valves were studied: type, manual vs. automatic, aboveground vs. underground, and spacing.

Previously, Texas Eastman had installed trunnion-mounted ball valves on an 8-in. pipeline and decided this was the best choice based on compactness compared to gate valves, ease of actuation and mounting of automatic actuators, and cost.

The company's existing 6-in. pipeline had been retrofitted with Shafer hydraulic actuators set to close at low line pressure but there were no scada facilities at most of the valves. This system caused problems with false trips that resulted in frantic searches for the closed valve.

There was also a question of how quickly the valves would close if a leak occurred.

A design for the new lines was selected that provided scada-controlled valve actuators to isolate the pipelines into segments ranging from 6 to 45 miles. Manual valves were provided at a maximum spacing of 10 miles with several sections in populated areas and at major water crossings as close as 3 miles.

Texas Eastman's existing pipelines all had aboveground valves but many companies used in-line, underground valves. One major reason for considering the buried valves was the line sizes: While not as large as many gas lines, the 12-in. aboveground valves begin to be large enough to require special support and access facilities.

Texas Eastman estimated lower installation costs because of elimination of bends and supports. Improved safety was expected by keeping all product-containing facilities underground.

The main line valves were installed underground; a few disadvantages became apparent: The ball valves were provided with screwed piping to extend emergency sealant and cavity drain connections aboveground and some of this piping had minor leaks during testing and in two locations after startup. There is also a general desire by operating personnel to see what they are operating.

PIPE BENDS, TIE-INS

Texas Eastman provided 300 factory bends for sharp changes in alignment greater than 30. Several problems arose, including late determination of what was required, availability of pipe to match the line-pipe specification, timely delivery to the coating yard and subsequent coating, and finally making the ditch match the bends.

The conclusion was that it would have been much better to utilize field bends wherever possible.

Many people think building a pipeline is as simple as drawing a line from Point A to Point B. The design of the dual Mustang pipelines was made difficult because each line had two "A's" that were not identified until late in the design phase. Supply contracts were delayed over 6 months from the original schedule.

Texas Eastman worked with engineering representatives of the four suppliers to coordinate tie-ins, checkmeter designs, pipeline routing, telephone, power, procurement, tie-ins, and construction. The company had different splits of responsibility for design, procurement, and construction for each of the four suppliers, ranging from complete design and construction by the supplier or by Texas Eastman.

The company worked with suppliers to coordinate the design of their custody transfer meters and its checkmeters. The typical meter system included a turbine meter with temperature and pressure compensation provided by a flow computer, a densitometer, and a composite sampler.

SCADA, SPEC DESIGN

This project included a new scada system including replacing 17 existing remote terminal units (RTU's). The software and hardware were provided by Hydril Co., Houston, based on a detailed specification prepared by Williams Bros.

Dual DEC Microvax II computers were provided in Longview. In addition to the existing RTU's, 10 new RTU's were provided for the four Mont Belvieu checkmeters, automated main line valve stations, and new checkmeters in Tyler and Longview.

Several alternate communication methods were investigated and the company decided to continue its leased-lines system. The existing network was split into three geographic zones with individual trunk lines to improve reliability.

One of the largest coordination challenges was working with AT&T and seven different local telephone companies. The communication quality has been good since start-up.

A separate part of the scada system is a leak-detection system designed by Scientific Software Intercomp, Houston.

Start-up of this system was delayed by low computer capacity and has not been tested yet.

A critical part of the design work is preparation of the construction specifications. Williams Bros. had an accumulation of specifications that had been used for a long time. Some of the terminology and technology were outdated.

Texas Eastman had experienced a similar problem with its last project (1981) and had rewritten a similar set of old specifications. The company worked with Williams Bros. to prepare a complete set of specifications.

Gone are the days when a contractor can accurately anticipate and bid when every section ends with "or as directed by engineer."

RIGHTS-OF-WAY

Right-of-way acquisition and permits were a major effort for this project.

Field activities were started immediately with the knowledge that it would be a challenge to complete prior to the start of construction. Several obstacles included: no permanent Texas Eastman or Mustang right-of-way staffs, several late condemnations, government bureaucracies, and the endangered red-cockaded woodpecker.

Two field offices were established, one in Crockett, Tex., to cover the north 110 miles of the Texas Eastman line and one in Conroe to cover the south 40 miles of the Texas Eastman line and the dual Mustang lines. Right-of-way staffing was 2040 people.

Numerous supervisory and agent changes, some unqualified personnel, and too few clerical personnel in the beginning added to the complexity of the acquisition program.

The Texas Eastman route work was similar to a new route because no title work had been done since the original acquisition 28 years before. The original files were used as a starting point for title abstracting. Numerous residential subdivisions and other rural sales resulted in about 700 tracts, twice as many as in 1961. The basic approach was to secure an acknowledgment of multiple line rights where those rights existed. Texas Eastman offered and paid the market value for new right-of-way although most of the multiple right easements provided for $1/rod for additional lines.

The company purchased 25 ft of temporary work space from most landowners to provide a total working width of 75 ft. Acquisition along this route went fairly well with the usual few holdouts and hard-to-locate undivided interests.

The Mustang right-of-way progressed with the same sequence of abstracting and acquisition. "Windshield" appraisals were used to establish land values and set payment limits based on land use. Because Mustang's right-of-way was adjacent to other existing easements, most landowners were receptive.

Several large corporate owners and farmers were difficult to deal with and usually involved attorneys from both sides. Texas Eastman was unable to settle 5 tracts out of a total of 300 and were required to use Mustang's right of eminent domain.

Government permits presented another major challenge in spite of early contacts and applications. Major agencies included the USDA-National Forest, Corps of Engineers, Trinity River Authority, and Texas Parks & Wildlife Department.

Environmental studies included a vegetative analysis, numerous reports on the red-cockaded woodpecker, and several archeological studies. Originally, permit work was coordinated in the field offices by a right-of-way permit agent. It quickly became obvious that the major permits needed special handling, and the responsibility was transferred to the project engineer in the Tulsa office.

NATIONAL FORESTS

The Texas Eastman route parallel to the existing pipeline crossed 12 miles of the Davy Crockett and Sam Houston National Forests. There were three different district rangers responsible for the areas crossed.

Early contacts with the three districts indicated no particular problem. They were interested in the amount of timber to be cut and with making sure the right-of-way was repaired.

Texas Eastman soon found, however, that it was caught in the middle of a federal suit filed by the Sierra Club, the Wilderness Society, and the Texas Committee on Natural Resources against the USDA-National Forests. These groups were trying to protect the red-cockaded woodpecker, an endangered species, by limiting timber cutting within certain distances of known woodpecker colonies.

The company's problem was having its permit request put on hold while the court case was pending; this didn't fit the construction schedule.

Hearings were held from February through April 1988. With construction scheduled to start in June, Texas Eastman was anxious to settle this permit and its potential restrictions. What was expected was restricted clearing within about 1,200 ft of colony trees.

Construction was started June 6 with about a 3-week lead time before it reached National Forest property. Unfortunately, the permit was not settled at this time.

The judge issued his ruling June 17, but the rangers refused to issue the permit until government attorneys could review the decision and establish procedures to satisfy the ruling.

Final restrictions prohibited clearing within 1,400 ft of a colony, required selective clearing to save old growth pine trees (100 years old) within 1,200 m, and imposed restrictive working hours.

These restrictions required Forest Service personnel to identify colonies, no clearing limits, and old growth trees to be saved. When this task was completed, the company learned that the Forest Service had to do an appraisal of the timber to be cleared in order to process a timber-sales contract. With this last paperwork processed, Texas Eastman was finally released to begin construction in the National Forests.

There were eight areas of restricted clearing that required the new 12-in. pipeline to be installed 5 ft from the existing pipeline in a 30-ft right-of-way.

The National Forest permits also required an archaeological study. A consulting firm used published data about the area and a site investigation to identify possible cultural resources.

Four sites were checked by shovel tests up to 3 ft deep with one site indicating a potential to produce pertinent information based on pottery fragments recovered. Because the site had been disturbed by the original pipeline, the permit was issued to cross the site if the consulting archaeologist was on site during excavation. The procedure was followed, and no artifacts were discovered.

CORPS, PARKS

A Corps of Engineers permit was required for crossings of the Neches River and Lake Livingston/Trinity River. Again, the Corps was glad to have several months of lead time which managed to be used up by a disagreement between the Corps and the Texas Parks & Wildlife Department over jurisdiction and responsibility for protection of bottomland hardwoods.

The permit for the Lake Livingston crossing was finally issued 3 days after construction had begun.

The Trinity River Authority (TRA) also has jurisdiction over Lake Livingston. The permits from the TRA were obtained without difficulty.

The proposed Mustang route crossed the future Lake Houston State Park, and the Texas Eastman route crossed an unusually shaped state park--the Texas State Railroad. These two parks required approval of the Texas Parks & Wildlife Department.

The challenge with these permits was to submit the required information and get on the agenda for a board meeting, scheduled only six times a year. Once again, the long lead time was used up.

The Texas Parks & Wildlife Department also administers the Sand, Shell, Gravel, and Marl Program that requires a permit when river and stream beds are excavated, usually commercially to sell those products. Although not controversial, these permits required public notice in local newspapers before the permits could be issued.

Routine permits included eight railroad crossings, nine county commissioners' courts, the state highway department, a county airport, and two crossings of the Coastal Industrial Water Authority canals.

CONSTRUCTION

Construction bids were solicited from ten contractors with the job split into three spreads. The bid analysis indicated the best option was two spreads by one contractor, Michael Curran & Associates, Houston.

Major subcontractors were Laney Inc. for road boring, Harcro for drilled crossings, Parkhill Pipe Services Co. for stringing, Phillips & Jordan Inc. and Northern Clearing for clearing, Continental Dredging Inc. for the lake crossing, and Milbar HydroTest for testing,

Longview Inspection Industries Inc. was contracted directly to provide 100% radiographic inspection.

INSPECTION

Texas Eastman and Williams Bros. Engineering provided significant inspection staffing during the construction. One engineer worked with an experienced drafter on the south spread while another engineer and one of Texas Eastman's plant construction inspectors worked on the north spread.

These were available to make quick decisions, interpret specifications, audit craft inspectors, and report progress to management. Williams Bros. personnel included a field manager who had been on the job since the beginning of right-of-way and surveying work, a "super" chief inspector responsible for both spreads, a chief inspector for each spread, and up to 25 craft inspectors on each spread.

Texas Eastman's requirement to have an inspector with every excavation activity adjacent to the existing pipeline resulted in several extra inspectors. The heavy inspection staffing was very helpful to keep up with the fast-paced construction progress.

The main line construction spreads operated with normal crews sequenced as follows: clearing, grading, ditching, stringing, bending, welding, coating, lowering in, backfill, and clean-up. Each crew averaged 9,000-12,000 ft/day with the welding crews frequently getting 200 welds/day.

Most construction activities were straightforward and will not be discussed. Several special construction features will be reviewed.

The drought of 1988 provided excellent construction conditions and very few days were lost due to rain during the 4 months of major construction.

PIPE MAGNETISM, CROSSINGS

A routine inspection of the pipe by the contractor before stringing indicated high magnetism levels that could affect welding. Random testing of all sizes and wall thicknesses indicated this was a widespread problem with magnetism levels up to 100 gauss.

Due to the imminent start of stringing, a decision was made to degauss all of the pipe at the coating yard. Although no standard was found, the literature and experience indicated a level below 20 gauss was needed for successful welding.

Vetco Services Inc. was hired to degauss the pipe, which actually is a realignment of magnetic forces, using a lance-type unit. The different pipe sizes and wall thicknesses were handled in the sequence they were needed for stringing.

A detailed study indicated the most likely sources of magnetism was the pipe mill. The pipe specification did not have a maximum gauss level and resulted in a negotiated settlement with the manufacturer.

Directionally drilled crossings were used for the San Jacinto River (Fig. 2) and Luce Bayou on the Mustang dual lines. Each crossing was approximately 1,000 ft long.

A single hole was bored, and the 6-in. and 10-in. lines were pulled together. The accuracy of this proven technology was good with only minor adjustments of the pilot holes to hit the target exit points.

Another special construction area was the 12,000-ft crossing of Lake Livingston with the 12-in. Texas Eastman line. The original 6-in. pipeline was built before the lake. Alternate routes for the new line to go around the lake would have required extensive new right-of-way and increase the length of the line.

The design provided a 50-ft offset from the existing line for the seven water crossings that ranged in width from 500 to 3,100 ft. The deepest water was 60 ft in the Trinity River channel. All crossings were dredged with barge-mounted draglines to provide 5 ft of cover (Fig. 3). All pipe was concrete coated.

SPECIAL CONDITIONS

Special precautions were taken for the 150 miles of 12 in. built parallel to Texas Eastman's existing 6-in. pipeline. The company required the contractor to bellhole the existing pipeline every 500 ft to verify alignment and depth. This was done ahead of grading.

The bellholes were backfilled and a 2 x 2-in. stake was left over the line with the depth noted which provided a record during the entire construction sequence. The existing pipeline was hit one time by a backhoe excavating for a boring pit during the first two weeks. The safety procedures to be followed were re-emphasized and no other accidents occurred.

The dual Mustang pipelines paralleled a 138-kv overhead power line for 20 miles. The clearing crew had several incidents of dropping trees on the power lines. A safety meeting was held after the first incident but the crews using D-9's with cutter blades generally refused to change their procedures and dropped several more trees on the power lines.

The utility company was cooperative and even shut off the power line until the clearing was completed. Fortunately no injuries resulted from this activity.

The Mustang pipelines also paralleled an existing 12-in. LPG pipeline owned by Santa Fe (Koch). Texas Eastman's was typically 25 ft from this line although it crossed it many times. This 43 miles was successfully excavated without incident.

One significant problem was settlement of extra work claims. Without going into details, the contractor performed extra work related to right-of-way restrictions with both sides thinking the contract provided a clear method to handle payment. Unfortunately there was not enough prior communication with the contractor to define the method of extra payment.

The lesson here is to address extra work before it begins and agree exactly how the extra costs will be computed.

Several other contracts were handled at the same time as the main line construction.

An electrical contractor, Amber Inc., installed scada facilities for most of the pipeline route. Troy Construction installed a new checkmeter at Phillips' Clemens Dome terminal. Michael Curran also was awarded the contract for the checkmeters, tie-ins, and pipeline work at Mont Belvieu.

TESTING

Hydrostatic testing provides the final proof of successful construction. The new lines were broken into test lengths between 20 and 30 miles with most limited by elevation differences.

In spite of detailed calculations to compare temperature and pressure variances, acceptance of most tests seemed to require a judgment based on inexact information.

One section of 12 in. failed at around 1,000 psig. The leak was located by repeated cutting in half of the test section and walking of the right-of-way. No surface water showed up until after 10 days of pumping water into the leaking section. The leak was determined to be a mill defect.

One of the most unusual experiences was the difficulty in running a brush pig through the new 6-in. pipeline which was split into two 20-mile sections. It ultimately required a cup pig and more than 150 psig of air pressure to remove a bushel of internal longitudinal weld skarf.

No one on the job had ever seen this before and it was hard to believe that the weld skarf could have remained in the pipe from the mill in Utah after railroad transportation to Houston, handling for coating, degaussing, stringing, and swabbing prior to welding. As luck would have it, there was weld skarf in both halves of the pipeline.

After final testing, the lines were dewatered by conventional methods of multiple trains of foam pigs. After dewatering, a caliper pig was run to provide an indication of internal pipe condition. No defects were found.

The pipelines were left with a 50-psig nitrogen purge; no special dehydrating was required.

START-UP

Start-up of the 10-in. and 12-in. LPG feedstock system was coordinated by Texas Eastman's operating department.

Prefilling procedures included final valve checks, installation of temporary flares at several locations, and final checkout of the new metering equipment. Start-up teams were set-up for two 12-hr shifts and included engineers, pipeline operators, and maintenance contractor.

Communication was provided by hand-held radio/telephones that provided excellent coordination. The start-up was based at the Mont Belvieu checkmeter station.

The fill plan was to launch a supercast cup pig and then a hollow poly-pig with a transmitter.

It was planned to leap-frog two receivers for the transmitter between valve stations. The target fill speed was 5 mph.

The receiver signals were missed at the first two stations but product was detected with a portable combustible gas detector. Use of the transmitter pig was abandoned after the 43-mile section of 10-in. pipeline was filled.

Fill progress was monitored with the gas detectors and listening for the pigs to pass the valve stations. Fill progress closely matched the metered volume of input.

The supercast pig maintained a good interface between the nitrogen and propane.

The propane pressure behind the pig was near the vapor pressure. When the pigs were received in Tyler at the north end of the 12-in. pipeline, the flow was routed through a flare to vent off any residual nitrogen.

A clean product stream was obtained within a few minutes and the line was valved-in. Line fill at Mont Belvieu packed the line above vapor pressure to assure the line was full of liquid. The fill pigs were received in Tyler at the end of 193 miles of new pipeline 68 hr after starting the filling.

The propylene pipeline system was started-up in a similar way after the existing 6-in. pipeline was tested and tied-in.

Copyright 1990 Oil & Gas Journal. All Rights Reserved.