Tài liệu PIPELINE PIGGING TECHNOLOGY- P15 pdf

Test Report for lOin x lOin x lOin piggable wye fitting design test, HydroTech Project 1763H, January.. Test Report for lOin x lOin x lOin piggable wye fitting investigative test, HydroT

There were also five tests performed with a misaligning flange installed in

the transit spool The VetcoLog intelligent pig was tested once with a 5° offset

in the misaligning flange, and twice with a 10° offset The TDW dual-diameter

(14x10) scraper pig and the Knapp Polly Pig dual-diameter (14x10) gauging

pig were also tested once each, with a 10° offset

CONCLUSIONS

The test results showed that all of the pigs tested can pass through the

symmetric wye fitting geometry without problem and without damage to the

pig or the fitting Moreover, the successful passing of each type of pig was

demonstrated under a wide range of flowing conditions, i.e pig velocities and

flow conditions in the opposite inlet

The tests using air with the short, light pigs, such as the foam pigs and

spheres, show that concerns over stalling pigs with high by-pass potential can

be eliminated by simply undercutting the inside of the fitting For these types

of pigs, it is recommended that the ID of the fitting be enlarged to remove at

least one-half of the pig squeeze just prior to the crotch area This generally

amounts to approximately a 2-4% increase in the wye fitting ID in the

undercut region

The test results presented in this paper are exclusively for 10-in pigs and

for dual-diameter (14x10) pigs passing through a lOin x lOin x lOin piggable

wye Additional testing is required over a range of other sizes before the

results can be generalized for all sizes

There are a large number of pigs used routinely in pipeline construction

and production operations that have not been tested Therefore, additional

tests are recommended to extend the conclusions to other pigs Specifically

of interest are the other large, heavy, intelligent pigs, such as the British Gas

On Line Inspection pig and the Tubescope Linalog pig.

ACKNOWLEDGEMENTS

The authors wish to thank Transcontinental Gas Pipe Line Corporation,

HydroTech Systems, Inc, Conoco, Inc, and their joint interest owners in the

Jolliet Project, Oxy USA Inc, a subsidiary of the Occidental Petroleum Corp,

and the Four Star Oil and Gas Company, a subsidiary of Texaco Inc, for their

Pigging through YJiWngs

kind permission to publish the pig testing results

REFERENCES

1 L.A.Decker, 1989 Test Report for lOin x lOin x lOin piggable wye fitting

design test, HydroTech Project 1763H, January

2 LA.Decker, 1989 Test Report for lOin x lOin x lOin piggable wye fitting

investigative test, HydroTech Project 1763H, March

3 L.A.Decker, 1989 Test Report for lOin x lOin x lOin piggable wye fitting

operational test, HydroTech Project 1763H, May

4 L.A.Decker, 1990 Test Report for lOin x lOin x lOin piggable wye fitting

using gas (air), HydroTech Project 1978S, March

5 LA.Decker and W.S.Tillinghast, 1990 Development of a 10-in piggable

pipeline wye fitting for the Jolliet Project, Offshore Technology

Confer-ence, Paper no.OTC64l5

6 A.Ghielmetti and T.B.Schmitz, 1989 A case history: Agip Barbara lateral

pipeline installation, Offshore Technology Conference, Paper no.OTC6l01

7 B.R.Oyen, 1985 wye connection replaces offshore platform, Pipe Line

Industry, January.

8 W.S.Tillinghast, 1990 The deepwater pipeline system on Conoco's Jolliet

Project, Offshore Technology Conference, Paper no.OTC6403

PEAK PIGGING DIFF PRESS

PIG IN TRANSIT DESCRIPTION SPOOL(PSI)

Scraper Pig(Pig Train)

Knapp Foam Pig & TDW 29-40

Dual-Diameter(14X10)

Scraper Pig(Pig Train)

Sun Engineering Squeegee 37-42

0

2-10 N/A 6-25 11-37

1 Soluble sphere velocities based on flow rates.

Table 1 Summary of pigging results.

Pigging through Yfittings

.59 FPS (146 6PM) 92 FPS (214 GPM)

2 2 3 FPS (519 GPM) 2.31 FPS (567 GPM) 2.50 FPS (582 GPM) 2.60 FPS (606 GPM)

400-550 GPM

NO FLOW

300-450 GPM

NO FLOW

100-200 GPM

PEAK PIGGING DIFF PRES

IN

T-(PSI)

FLOW IN OPPOSITE SIDE

NO FLOW

400-550 GPM

NO FLOW

Table 3 Knapp Polly Pig foam pig (using water)

NO FLOW

Pigging through Yfittings

AVG VEL

(FLOW RATE)

.41 FPS (102 GPM) 63 FPS (145 GPM) 66 FPS (163 GPM) 74 FPS (173 GPM) 1.35 FPS (333 GPM) 1.73 FPS (425 GPM) 1.78 FPS (437 GPM) 2.08 FPS (484 GPM)

2 2 3 FPS (518 GPM) 2.40 FPS (559 GPM) 3.68 FPS (855 GPM) 6.90 FPS 1

(1,698 GPM)

PEAK PIGGING DIFF PRES

IN "T"

(PSI) 28

1 Pig also passed through Misaligning Flange with 10 degree offset.

Table 4 TDW dual-diameter (14 x 10) scraper pig (using water).

PEAK PIGGING DIFF PRES

IN T"

(PSI)

FLOW IN OPPOSITE SIDE

NO FLOW

NO FLOW

Table 5 Knapp foam pig and TDW dual-diameter (14 x 10) scraper

pig in a pig train (using water).

Pigging through Yfittings

PEAK PIGGING TRANSIT PEAK PIGGING

DIFF PRES SPOOL DIFF PRES FLOW IN

IN TRANSIT AVG VEL IN T" OPPOSITE

SPOOL(PSI) (FLOW RATE) (PSI) SIDE

Table 6 TDW 'Redskin' foam pig and dual-diameter (14 x 10)

scraper pig in a pig train (using water).

.82 FPS (191 6PM) 91 FPS (211 6PM) 1.49 FPS (346 6PM) 1.78 FPS (437 6PM) 2.08 FPS (485 6PM) 2.40 FPS (559 6PM) 5.18 FPS 1

(1,274 6PM)

PEAK PIGGING DIFF PRES

1 Pig also passed through Misaligning Flange with 10 degree offset.

Table 7 Knapp dual-diameter (14 x 10) gauging pig (using water).

Pigging through Y fittings

PEAK PIGGING DIFF PRES

IN T"

(PSI)

FLOW IN OPPOSITE SIDE

(636 GPM) 2.70 FPS (665 GPM) 3.11 FPS (764 GPM)

4 7 8 FPS 2

(1,176 GPM) 4.78 FPS 1

NO FLOW

NO FLOW

1 Pig also passed through Misaligning Flange with 5 degree offset.

2 Pig also passed through Misaligning Flange with 10 degree offset.

Table 8 Vetcolog intelligent pig (using water).

4.1 FPS (175 SCFM) 5.6 FPS (259 SCFM) 10.0 FPS (510 SCFM) 20.0 FPS (1,477 SCFM)

TOW 'Redskin'

PEAK PIGGING DIFF PRES

IN (PSI)

5.0 FPS (769 SCFM) 7.7 FPS (355 SCFM) 8.3 FPS (1,108 SCFM) 16.7 FPS (1,293 SCFM)

PEAK PIGGING DIFF PRES

IN

T-(PSDN/A

N/A

N/A

N/A

FLOW IN OPPOSITE SIDE

NO FLOW

2,107 SCFM

NO FLOW

NO FLOW

Table 10 S.U.N.Engineering 'squeegee' cup-type pig (using air).

Pigging through Yfittings

PEAK PIGGING DIFF PRES

IN (PSI)

T-FLOW IN OPPOSITE SIDE

10

10

4.50 FPS (184 SCFM) 6.30 FPS ( 7 6 9 SCFM) 10.0 FPS (1,539 SCFM) 20.0 FPS ( 1 , 6 4 3 SCFM)

PART 4 THE CONSEQUENCES OF INSPECTION

Interpretation of pig survey results

INTERPRETATION OF INTELLIGENT-PIG

SURVEY RESULTS INTRODUCTION

Recent years have seen a dramatic growth in the use of on-line inspection

technology for the revalidation of operational pipelines Much of this growth

can be attributed to the success of high-resolution inspection technology in

providing cost-effective solutions to a range of pipeline problems; the

extensive application of these advanced services has allowed pipeline

opera-tors to confirm their accuracy and value

As with all pigging operations, the technical details associated with the

in-field running of inspection tools is of great importance to both the inspection

contractor and the pipeline engineer, and adequate preparations in advance

of any in-field work are essential if expensive errors or delays are to be

avoided Ultimately, however, the provision of inspection data in a final

report is the sole objective of running an on-line inspection tool in a pipeline,

and the value of the entire exercise is determined only by the quality and

nature of the information contained in the report

This paper addresses a number of important aspects relating to British Gas'

inspection technology and to the eventual interpretation of data and

prepa-ration of inspection reports

ACQUISITION OF PIPELINE DATA

In most circumstances, pipelines are selected for on-line inspection on the

basis of some form of risk assessment This is usually related to considerations

for personnel safety and security of supply for gas pipelines, and with an

additional consideration for pollution in the case of liquid lines Although such

assessments are often of a qualitative nature, an increasing number of pipeline

operators are adopting formalized, quantitative schemes, which can be used

to great effect in ensuring that the most appropriate inspection, repair and

maintenance programmes are employed over the life of a pipeline

Once the decision has been made to perform an on-line inspection survey

of a pipeline, considerations of technical standard and cost become the focus

of attention The two factors are closely related, since the inspection phase

of a project cannot be financially divorced from the consequent costs of

remedial work and the subsequent costs of pipeline maintenance The

inspection service must, therefore, be regarded as an integral part of pipeline

maintenance, with the accuracy and repeatability of the service determining

the final out-turn of maintenance costs

Preparation

Before a pipeline is inspected, it is prudent to perform a detailed review

of its engineering records to gain early information about it's suitability for

on-line inspection This phase is usually complemented by extensive discussions

with the pipeline operator, and an on-site survey of the line by a British Gas

engineer Once it has been established that the pipeline is suitable for the

running of an inspection tool, the in-field operational phase can begin

In-field tool running

This phase comprises a series of operations, carried out in a specific order

to ensure the successful running of the inspection tool The first part entails

the running of cleaning and bore-proving pigs, to provide optimum

condi-tions for inspection; the second part involves the running of the inspection

tool itself

Extensive preparatory work ensures the timely execution of this part of

the service, together with specialized handling equipment to simplify the

insertion and extraction of pigs In addition, the detail of inspection tool

design provides a virtual guarantee that the tool will pass through the pipeline

without becoming stuck or damaged

Validation of survey data

Of particular importance in the field is the post-inspection validation of the

survey data, and this occurs following the withdrawal of the magnetic tape

store from the on-board tape recorder During the inspection operation, data

Interpretation of pig survey results

will have been processed digitally in real time, securely coded against errors,

and organized in a particular format for acceptance by the on-board tape

recorder Clearly, early validation of the data, to confirm the successful

operation of the system, is essential This is a complex task in view of the huge

quantities of data involved, and has demanded major developments in

microcomputer-based test equipment for its completion Following the

confirmation of a successful survey run, the magnetic tape, containing the

inspection data, is returned to the British Gas Computer Centre in England for

detailed analysis and interpretation

Interpretation of inspection data

At the On-Line Inspection Centre, the data recorded on tape during the

inspection run is replayed via a process-control type of computer on to

standard computer tapes, which can then be analysed using one of the

Centre's five main computers These machines reformat and reorganize the

data so that information from the various types of sensor is properly aligned

and correlated with positional data

The next process is to reject signals from normal, defect-free pipeline

fittings such as welds and bends Each fitting gives a particular shape of signal

which can be identified, checked and then eliminated If existing pipeline

maps resulting from previous inspection runs are available, these are also used

to verify and reject data Significant sensor data is then presented on an

electrostatic plotter, and interpreted by trained operators This form of

output allows many parallel sensor traces to be plotted and quickly analysed

Finally, a mathematical sizing model, used in conjunction with a computer

graphics terminal, is employed to obtain a direct estimate of the size and shape

of defects This system is complemented by a comparative sizing technique

based on an automatic search through a large library of known signals

Inspection data must be preserved for comparison with subsequent

inspection logs and as a historical record The scale and frequency of

inspection operations demand that data analysis must be a highly-automated

process The keys to rapid and reliable data analysis are defect sizing

capability, and the ability to recognize and classify automatically the signals

which characterize particular pipeline fittings When such a signal is

identi-fied, it is necessary to check that the fitting is not faulty in some way, for

example to check that a weld between sections of pipe has not become

corroded The integrity of each fitting must be verified, but the obvious

approach of comparing new signals with standard examples works only in a

limited number of cases

For instance, a good weld at one point in a pipeline can produce a very

different image from an equally-good weld at a different point on the same

pipeline More sophisticated techniques have had to be used

Possible faults are analysed using pattern-recognition and

image-process-ing techniques similar to those employed in medical scannimage-process-ing and satellite

imaging Such techniques, originally developed for purposes like enhancing

blurred photographs, or teaching computers to recognize particular words,

are equally relevant to the interpretation of pipeline inspection data Instead

of a blurred photograph, the on-line inspection device provides a record of

magnetic field variations in the pipeline; its sharpness is limited by the

response of sensors and electronics and the errors introduced during data

collection in the harsh conditions inside a pipeline

British Gas has modified and developed existing techniques to cope with

the problems posed by pipeline inspection The general approach has been

to measure various parameters to characterize a signal and then to use

statistical techniques to discriminate between significant and spurious data

Much depends on choosing the appropriate image parameters to measure

The experience of engineers who design and operate inspection vehicles has

proved invaluable for this purpose

The data-reduction techniques employed are designed to operate in a

cascade fashion, so that only the simplest operations are applied to the bulk

of the inspection data, more complex steps being reserved for later stages in

the analysis sequence Using various software tools, the operator may search

for particular types of feature, manipulate images on graphics terminals, and

test new signal-processing algorithms to identify any misclassification errors

These techniques have been developed at the On-Line Inspection Centre and

by leading consultancy organizations working under contract

The procedure may be modified when dealing with data from seamless

pipe in which the method of manufacture produces large variations in wall

thickness (often outside specified tolerance limits) over quite small areas of

pipe In addition, the amount of metal-working associated with the forging

process also produces significant variations in the material's magnetic

char-acteristics Such wall-thickness and magnetic variations are detected by

magnetic-flux leakage inspection vehicles, and can obscure or distort signals

from potential defects A special de-blurring process has been developed by

British Gas which enables the "natural" variation in response to be recognized

and eliminated without distorting the signals from metal-loss defects The end

product is corrected data which looks like that obtained from pipes

manufac-tured from controlled-rolled plate