Pipeline Test

7/29/2019 Pipeline Test

1/17

Out-of-straightness detection,

assessment, and monitoring, using

the SAAM pipeline-inspection tool

The Pipeline Pigging, Integrity Assessment,and Repair Conference

Holiday Inn Select Hotel

Houston, Texas

February 6-8, 2001

Organized by

Clarion Technical Conferencesand

Pipes & Pipelines International

and supported by the

Pigging Products & Services Association

by Gordon Short1 and Patrick Ogunjimi2

1RST Edinburgh, UK2Brass Exploration, Isleworth, UK


2/17

3 The Pipeline Pigging and Integrity Conference, February, 2001

Proceedings of the 2001 Pipeline Pigging, Integrity Assessment, and Repair Conference, Houston, USA.

Copyright 2001 by Clarion Technical Conferences, Pipes & Pipelines International andthe author(s). Allrights reserved. This document may not be reproduced in any form without permission from the copyright owners.

Out-of-straightness detection, assessment,

and monitoring, using the SAAM

pipeline-inspection tool

RST PROJECTS Ltds SAAM Pipeline Inspection tool represents the state of the art in

low cost pipeline inspection and monitoring technology. The tooling has been

designed for use on-board standard bidi and cup pigs. The SAAM tooling has a number

of capabilities, however; one of the most important uses is in the detection, assessment

and monitoring of pipeline Out-Of-Straightness problems. This paper examines how

SAAM can be used to detect pipeline Out-Of-Straightness and presents results ofexperimental work carried out in test facilities. Consideration is also given to field

applications with a case study of the 12" Oil Export Pipeline in the Abana Field offshore

Nigeria, owned and operated by Moni Pulo Limited and Brass Exploration, being

presented.

Introduction

Determining the presence and severity of pipeline Out-Of-Straightness (OOS) has been a

problem which has challenged pipeline engineers since the very first lines were laid. Even the early

Roman engineers were concerned with pipeline straightness. These engineers invested consider-able time and effort in carrying out detailed route surveys to ensure that the natural gradients of

the land were used to best effect when transporting water under gravity from the well to the user.

Obviously the slightest OOS during the construction could compromise this aim.

In modern hydrocarbon pipelines the presence of pipeline OOS presents a more dramatic

problem. An oil or gas pipeline with a severe change in bend radius can have abnormally high

bending stresses which can cause the pipeline to exceed its elastic limit, potentially leading to


3/17

4Out-of-straightness detection

failure. When combined with other factors (such as torsion and internal pressure), it represents an

extremely difficult problem for the engineer to assess. Clearly when making this assessment

knowing the precise shape the pipeline takes is of vital importance.

The shape of a pipeline is a complex interaction between the pipeline itself (its physical properties

such as stiffness) and its surrounding environment. For example, a pipeline which crosses a region

of soft sand, will acquire a very different profile to a similar pipeline which is laid on firm soil. Having

a precise knowledge of pipeline position is often not sufficient to determine its integrity. Having

information on pipeline motion and changes in profile is of equal or greater importance.

The consequences of failing to detect and rectify pipeline OOS can be dramatic. On its ownexcessive bending can lead to failure with the pipeline exceeding its elastic limit. Unsupported

pipelines can be a hazard for others, potentially leading to accidents [1].

It is clear that detecting, assessing and monitoring the shape of a pipeline can be of critical

importance to ensuring that a line is operated safely.

This paper presents the results of work carried out by RST Projects Limited into pipeline OOS.

It focuses on the use of the SAAM pipeline inspection tool, presenting examples of its actual use in

the field. It should be noted that the theory underlying how OOS detection tools (such as SAAM)

operate could become an exercise in applied mathematics. This paper, however, does not dwell

heavily on the theory but rather chooses to focus on its applications.

Background

Many pipelines suffer from OOS. For example, buried onshore pipelines which cross areas of

subsidence can become unsupported. From the surface this may not be obvious. However, when the

pipeline is excavated the extent of the problem can be found. Similarly, subsea pipelines can suffer

from what is known as scouring. This results in the material beneath the pipeline being progres-

sively washed away. When this happens the pipeline can again be left unsupported, forming a free-

span. This can become a local stress point for the pipeline. It can also be a source of other problems,

such as trawl gear becoming snagged under the pipe [1].

A further factor which leads to pipeline OOS has been the development of high temperature

(usually smaller diameter) pipelines. These lines operate at elevated temperatures and can suffer

from excessive thermal expansion. This means that they can pop upwards and form what is known

as an Upheaval Buckle. Severe buckles can result in permanent plastic deformation of the pipeline.OOS can be a very real problem for the pipeline operator. On occasions the first indication of the

problem may be a pipeline failure or an incident involving a third party. As a result the ability to

detect, assess and monitor pipeline OOS is seen as being an important part of the pipeline asset

management process.

Existing technology

Traditional approaches to determining pipeline OOS can be described as being hit or miss. Many

pipeline operators rely solely on the use of external visual inspections (or the equivalent for subsea

pipelines) to determine when a pipeline OOS problem exists.External surveys only provide limited information on the profile of the pipeline. Visual surveys,

for example, can provide no meaningful information for a pipeline which is buried. They can also be

very time consuming and there may also be question marks over their accuracy. This often means

that a pipeline operator who finds an OOS problem then looks for an alternative means of profiling

the feature. ROVs and Side Scan Sonars can go some way to providing this information for subsea

pipelines, but their resolution and accuracy are often inadequate for subsequent data analysis

requirements.

A second approach involves the use of Internal tools. The approach here has been to use gyro

systems, or Inertial Navigation Units [2,3]. These instruments tend to be borrowed from the military

or aviation industries. The acceleration data produced is double integrated to give a profile. This


4/17


double integration is a major source of systematic error, and over the distances of interest, this

procedure can easily swamp the signal of interest. This means that the calculated profile needs to

be compared with known reference points at regular intervals along the length of pipeline. Probably

the best known example of this type of tool is the BJ Geopig.

It is reasonable to conclude that existing OOS technology can be difficult and relatively expensive

to deploy and often their accuracy brings into question the validity of any post survey data analysis

used to assess the condition of a pipeline.

The SAAM approach

The approach developed by RST is fundamentally different to other existing techniques. The

SAAM tool is a package which can be fitted to existing pipeline cleaning and gauging pigs, rather

than being a special standalone inspection pig (Figure 1). This means that any existing cleaning or

gauging pig can be used to acquire OOS data.

Over the past 2 years there have been a number of papers published by RST which details the

theory of the SAAM inspection tool [4,5,6,7]. In summary it can be described as:

using the dynamic response of a cleaning or gauging pig to the presence of a feature within

a pipeline as a measure of that feature

In effect the behaviour of a cleaning pig is monitored and changes used to identify features

present within the pipeline. This can be extended to give a complete inspection capability (Figure

2).

The above principle can be applied to the presence of pipeline OOS. This is possible because

SAAM monitors changes in the angular position of the pig. Sensors onboard the unit provide pitch

and angular velocity data. To date only systems with the pitch sensors have been used operationally

to give 2 dimensional profiling of a pipeline. It is this 2-D approach which is discussed in detail in

this paper. The use of the angular velocity sensors (gyros) is a new innovation recently introduced

by RST to provide a basic 3-D capability and is discussed only briefly towards the end of the paper.

Although not intended to be a justification of the mathematical basis of SAAM, it is important

to appreciate in general terms the underlying theory. To do this, consider a pipeline in 2 dimensions

with a change in the vertical position of the line (Figure 3). When a pig travels along this line itschange in vertical position (y) can be expressed by the following equation:

y = V sint (1)

where V is the velocity of the pig along the axis of the pipeline, q is the angle of pitch of the pig relative

to the horizontal and t is the interval in time. In fact this equation can be simplified as V can be

expressed as:

V = L/t (2)

where DL is the incremental distance travelled along the axis of the pipeline in the period t. Also,

where the angle of pitch is measured directly using a gravitational accelerometer then the sinvalue

in (1) can be directly replaced by the measured value from this instrument a. Substituting these

into (1) simplifies the expression to:

y = a L (3)

This is the governing equation used by RST in determining the vertical profile of a pipeline. A

simple numerical integration technique can then be used to give the shape of the feature.

In order to use this equation it is necessary to have the following data:


5/17


1. The angle of pitch of the pig (a).

2. The distance travelled (L) between each data point.

The angle of pitch (a) is measured using a gravitational accelerometer. This is a device which is

in effect a membrane with a mass supported in the middle. When the pig tilts the mass exerts more

force on the membrane which then results in a change in the voltage. This change in voltage is then

a direct measure of the angle of pitch. The angle itself is automatically resolved into its gravitational

(vertical) component meaning that it is in fact the sinq value.

The second value used in (3) is the distance travelled in the incremental timet. t is set to equalthe sample rate used by the SAAM unit. Typically for SAAM L is of the order of 5-10cm. L is

actually calculated from the known distance between two points, such as girth welds, divided by the

sample rate of the tool.

Using these two values the localised vertical profile of the pipeline can be determined.

Sources of error

In common with other OOS tools the main limitation with SAAM is its accuracy. The are many

potential sources of error associated with this type of technology. The most common are discussed

below.

Pipe joint length

Standard pipe joints are specified at 12.2m (40ft). In reality a wide range of factors will combine

to give a spread of lengths covering a range of a metre or so. Typically this means that every pipe

joint can have an implicit error of the order of +/-0.5m, which equates to about 4% of the length.

Where this is not accounted for it will feed directly into an equivalent error in the generated vertical

profile. However, this error can be dramatically reduced using techniques developed by RST, where

differences in pipe spool length can be clearly identified. Furthermore, where a detailed pipe tally

is available (or can be obtained from field measurements) it can be effectively eliminated as a source

of error. It should be noted that an error in pipe joint length does NOT change the calculated

minimum bend radii as the error applies in proportion to both the vertical and horizontal distances.

Discussion of how SAAM detects girth welds and from this derives pig velocity and pipe joint lengthis given in [4,5,6].

Pig attitude

Any change in the attitude of a pig travelling through an OOS feature will result in a significant

error in the measured profile. The most likely changes in pig attitude are pitch and rotation. Pitch

problems tend to be associated with the presence of in-line debris, such as wax. Where this is present

it tends to be found locally and only in certain types of pipelines. Where necessary it can be

minimised by pre-cleaning the line. The second type of attitude error is to do with pig rotation. As

it is not possible to position a SAAM unit in a pig body precisely co-linear with the axis of the pipeline,

then any rotation over a short distance of the line can give a signature similar to that of an OOS

problem. From RSTs experience this has never been observed and RST believes that if pig rotationdoes occur in straight pipe sections then its period is far greater than that which would affect the

quality of a typical OOS feature. This is supported by the preliminary results of the 3-D SAAM tool,

discussed towards the end of the paper.

Impact loading

Any significant impact will be detected by the accelerometer used to measure the angle of tilt of

the pipeline. Impacts result from the pig coming into contact with some obstruction within the

pipeline. The severity of this impact will mainly depend upon on three factors, pig speed, size of the

obstruction and line diameter. Generally, the faster the pig, the smaller the diameter and the more


6/17


severe the obstruction, then the greater the measured impact. From experience it has been found

that in-line features such as girth welds will not normally cause an impact with a corresponding

change in linear velocity, but will instead show up as vibration [4,5]. However, where the pipeline

suffers from, for example a dent then this will be detected. Techniques have been developed by RST

for handling impacts.

Lateral pipe displacement

Probably the single most significant error associated with the 2-D SAAM method, is the impact

of any lateral displacement of the pipeline. In effect should the pipeline be offset at an angle to the

vertical then this will compromise the results of the survey. The accelerometer used to measure the

angle of tilt will only measure the vertical component. When this is combined with a rotation of the

pipeline it will under estimate the true change in alignment. The measured value understates the

true value by the Cosine of the angle of rotation. From experience RST has found that small rotations

of the order of 5 from the vertical do not generate any significant error, and up to 10 the results

are generally acceptable. Values greater than this have to be taken on a case by case basis. The error

which results causes the SAAM method to understate the minimum bend radii and overstate the

length of the feature, in effect making the feature longer and shallower.

In practice there is no easy way to determine from the SAAM data whether the pipeline OOS is

vertical or offset at some angle. Again, from experience it has been found possible to determine if

this has occurred by comparing the calculated SAAM horizontal distance over the length of afeature, with true measured distances (say taken from a GPS). Where the SAAM distance is

significantly longer then this would suggest that the OOS feature is actually offset as some angle,

rather than being vertical. It is this limitation with the 2-D method that is one of the drivers behind

the development of the 3-D capability discussed later in this paper.

It should be noted that any change in horizontal direction of the pipeline that is not associated

with rotation, such as horizontal bend, will NOT directly effect the calculated vertical profile.

Reference points

The SAAM profiling technique relies upon having known local reference points (start and end

points) which relate the pipeline to the real world. In the case of the 2-D SAAM method accurate

vertical distances are required, whether these are above or below sea level. Where pipeline

movement is the main concern an agreed reference level can be taken and used for all subsequentanalysis and so changes in the pipeline shape will be clearly recognisable and consistent relative to

the chosen fixed point. In this case the need for accurate reference points can be avoided.

Drift and integration error

Measuring devices such as accelerometers and gyros are well know to suffer from drift. This can

be very significant if not understood and handled. The instrument used on SAAM has been selected

so that this has the minimum impact. Under test, this instrument has been shown to have a

negligible drift over a period of days (typical for a survey). It was also found that drift cannot be

measured over the time taken to transit typical OOS features. This is very important because the

process of integration compounds any drift error, and those detection methods that require a double

integration further exaggerate this problem. SAAM only requires a single integration. In addition

the time step Dt (which equates to the sample rate of the SAAM unit) has been selected by testing

to minimise this error. The combination of the selected instrument, the single integration process

and selected sample rate have all but eliminated drift and integration errors over typical OOS

features using SAAM.


7/17


Validation

With any new measurement technique it is vital to validate and prove the methodology. The use

of SAAM to determine pipeline OOS is no different. The validation carried out by RST has taken 2

forms. Firstly, the use of loop tests and secondly, field trials.

Loop tests

RST has carried out extensive loop trials over the past 5 years. These trials have had a variety

of aims, from basic research purposes, to fault finding, through to specific OOS tests. In addition RST

has adopted a policy of loop testing all of its SAAM units prior to shipping them into the field. As

a result a very large database of information has been developed. At the time of writing this paper

RST has over 1400 sets of individual loop data. In the vast majority of cases the SAAM unit involved

has been deployed with the capability of measuring pipeline tilt and often they have been run

through test sections with a known change in vertical profile.

Analysis of this loop data has been carried out in order to assess and validate the capabilities of

the SAAM tooling at measuring pipeline OOS. An example of part of this assessment is shown on

Figure 4. In this case the test section of the flow loop is approximately 35m long with a change in

elevation of 1.45m. The start and end points are at the same elevation and the distance between the

pipe flanges is known. The data is taken from pigs with disks that had different amounts of wear.

In this case 37 loops of data from the one test are presented. All of the data were found to be within+/-7.5cm of the known vertical value.

Field trials

Testing was carried out in pipelines within known OOS features. These pipelines were selected

on the basis of being relative stable with little or no pipeline movement expected. The results of these

trials confirmed the capabilities of SAAM. It was found that for all of the test cases the vertical OOS

could be classified within +/-0.09% of the horizontal distance travelled and that an accuracy of +/-

0.05% was achievable in 80% of the cases. This is comparable with other mapping tools [2,3].

It was also possible to compare some of the SAAM generated data with other data. An example

of this is given in Figure 5. This shows that there is a relatively good tie-in between the SAAM data

and that acquired from a Remotely Operated Vehicle (ROV), and where there are significantlydivergences the error has subsequently been tracked down to limitations with the ROV data rather

than with SAAM.

Case study

Abana 12-in oil-export pipeline, Nigeria

So far the paper has concentrated on detailing the overall theory, testing and validation of the

SAAM measuring technique. This part of the paper now focuses on the application of the technology

with a case study of the Abana 12 Oil Export pipeline, offshore Nigeria being presented.

Field description

The Abana field is located in block OPL230 offshore Nigeria. Moni Pulo Limited, an indigenous

Nigeria oil company, is the majority interest holder in the Block. Brass Exploration is a wholly

owned subsidiary of Baker Hughes E & P Solutions and is technical partner to Moni Pulo Limited

on block OPL230.

Installed in 1998 the Abana Field comprises the Abana West Facility, Abana East Facility, the

Abana Water Injection Facility and a 12 oil export pipeline. The layout of the field is shown on

Figure 6, and can be summarised as follows. Abana West is connected to Abana East by an 8 oil


8/17


flowline, an 8 test line, a 4 gas flowline and a 4test flowline. Production is delivered through these

lines to Abana East. The product is treated at Abana East on a floating production facility and is then

exported via a 12, 40km oil pipeline to a third party platform. Injection water is supplied to the

Water Injection Facility from Abana East via an 8" line.

In partnership with Moni Pulo Ltd, Brass Exploration were responsible for the construction of

the facilities and are now responsible for day to day operation of the field including the 12 oil export

pipeline.

Application

Of particular concern to Brass Exploration is the stability of the 12 oil export pipeline from field.

Clearly, this is of strategic importance as it is the sole export route. When constructed the line was

trenched and covered with an unknown quantity of silt. The stability of this line is complicated by

the fact that it was laid in an estuary effectively at right angles to the current. The currents in this

estuary are known to be very strong, ranging from 3 4 knots in the spring, to 8 10 knots during

the rainy season. It was feared that these currents could cause erosion of the seabed around the

pipeline causing it to change shape. In particular it was felt that the line may become unsupported

in places, causing it to sag and become over-stressed. Brass wanted to know what the status of the

line was post construction, whether there were any locations where the pipeline was bending

excessively and then to monitor its shape at regular intervals to assess whether it was in fact

changing.

Proposed solution

RST were approach by Brass with a view of using SAAM as the routine monitoring tool. After

much discussion it was concluded that SAAM could be used to monitor both the 8 flowline and the

main 12 oil export pipeline. At that time RST could only operate SAAM down to 10 and as such

the unit needed to be re-engineered in order to be deployed successfully in the 8 lines. This aspect

of the development is discussed elsewhere [8].

Schedule

The project KOd in August 1998 and the development of the special SAAM system was completed

during December of the same year. RST supplied the SAAM unit, carrier pigs for the 8 and 12 linesand operator training for Brass personnel. In common with all of RSTs systems, the system supplied

to Brass was designed to be deployed within a cleaning pig. The pig supplied was designed by RST,

but was in effect a standard BIDI type pig (Figure 7) with its body cavity specially modified in order

to house the SAAM system. The first survey using the tooling was carried out during July 1999.

Survey

The results of the first survey provided good quality data to benchmark the line. From this a

number of features were identified as being significant and were profiled. It was found that none

of these exceed the expected limits for features in a pipeline of this size. For each the profile, location

and minimum radius of curvature were determined. An example is given in Figure 8. In this case

the raw data (angle of tilt and vibration) are shown along with the profiled feature. In addition

composite strip maps were produced over the entire length of the line. These were developed using

specified reference points along the length of the line.

The second survey was carried out on the 13th October 1999. It had been timed to follow the rainy

season in order that the effects of this could be evaluated. The SAAM unit was again deployed on

board the supplied BIDI cleaning pig. The results of the survey were very revealing. Firstly it was

evident that large sections of the line were very different to the previous survey. When analysed this

indicated that the pipeline had moved, much in the same way that sand waves can cause pipelines

to move in the desert.

Of more interest was the behaviour of the pipeline at the locations that had previously been found

to give the most severe changes in pipeline inclination. Surprisingly, it was found that these


9/17


locations had changed least. Indeed on closer examination it was found that some of these showed

no significant change from the benchmarked profile. This was both re-assuring as it confirmed that

the most severe bend radii were not getting worse, whilst confusing in that it seemed to be counter

to what would have been expected. On reflection it is now believed that these more severe features

are probably related to some real feature on the seabed, such as a rock. These act as pivot causing

the pipeline shape to change severely. However, at the same time they are believed to act as an

anchor, in that they are not moving and hence the shape of the pipeline in their vicinity is also

effectively anchored. Analysis of the data from a third survey is expected to be completed early in

Q1 2001, which it is hoped will provide yet further information on these features.

Other applications

The case study presented has discussed only one of the potential applications for the SAAM OOS

technology. However, there are clearly more depending upon the design and operation of different

pipeline systems. One proven use of the technology has been in the detection and assessment of

Upheaval Buckles. This is primarily a problem with some subsea flowlines. Upheaval Buckles come

about as a result of temperature effects causing a pipeline to change length (grow). With the line

fixed at either end then the growth in its length will have to be relieved in some other way. Often

this occurs where there is a slight vertical kink in the line. This will act as the source of the bucklewith the pipeline tending to pop upwards.

These resulting buckles do represent significant problems for the pipeline operator. The

deformation of the pipeline can in worst cases become plastic. In other cases they can interfere with

third parties (fishing boats trawl gear). SAAM can be deployed to inspect lines for Upheaval Buckles.

Figure 9 shows the result of one such survey. In this case a buckle was found and sized in a buried

subsea flowline. It is interesting to note that the feature exhibits the expected classic shape, with

slight downwards dips at either end.

A further potential application for the technology is in the detection of pipeline free-spans.

Although the technology cannot provide confirmation of a void around the pipeline, it can be used

as part of a monitoring programme to determine if the shape of a pipeline has changed (sagged)

providing evidence that the pipeline may have become un-supported.

Future developments

3-D capability

The paper so far has presented work associated with the 2-D SAAM OOS method. This has shown

the capabilities of the developed technology, discussed potential benefits and illustrated some the

applications. However, clearly there are limitations with this approach and it is apparent that a 3-

D version would be advantageous. There are many different reasons for this, including:

1. The elimination of lateral displacement errors associated with the 2-D method.

2. Provide unambiguous evidence of the presence and size of in-line horizontal andinclined bends.

3. Allow lateral buckling problems to be handled.

4. Provide a means of develop 3-D models of inaccessible pipeline features.

The ability to develop this 3-D method has been a long stated goal for RST. To achieve this RST

has been working on combining data from angular velocity sensors (gyros) with the existing vertical

profiling data. This is being done as part of a new upgraded version of the SAAM tooling.

This work has recently reached a significant milestone with the completion of a series of loop tests

using the first prototype tool. Details of this new SAAM unit are not being released that this stage,


10/17


however, the tooling will have all of the capabilities of current SAAM tooling, along with new sensors

and substantial upgrades in terms of range and size (miniaturisation).

At the time of writing this paper it is too early to draw many firm conclusions regarding the 3-

D capability of this new tooling. However, some preliminary results are included for interest. These

results have been acquired using 10" bidi pigs, deployed in RSTs in-house pigging test facility. The

facility is arranged in a never-ending form with 4 off 5D, 90 horizontal bends, located two at either

end of the facility, details of which are given in Figure 10.

The test pigs have been deployed at a range of velocities between 0.7m/s and 1.1m/s. Some of the

preliminary results of these tests are presented in Figure 11. This figure gives output from 2 angularvelocity sensors mounted at right angles to each other. A total of 70 laps around the test loops have

been included. These show a regular response as the pig passes around each bend. When resolved

it would appear that the measured response is consistent with a change in angular position of 90.

The results of this are shown in Figure 11.

What is also interesting here is that as a result of the way the sensors have been arranged they

can also detect the effective rotation of the pig in the test loop. It would appear that the pig rotates

on average about 9 per bend. This can be seen as the overall wave like response of the data over

the 70 laps of the test. Also, the data would appear to show that there is effectively no rotation in

the straight pipe sections. On closer examination it can be seen that the pig rotation is consistent,

but slightly quicker in approximately half of laps when compared with the rest. It is believed that

this is caused by the pig being slightly out of balance with a small added mass on one side, which

causes it to rotate when acted on by gravity.

At this stage no formal assessment has been carried out on the 3-D prototype, however, the

preliminary results are encouraging. It is anticipated that this assessment will be carried out during

Q1 2001 with the first field trials likely to follow soon thereafter.

Pipeline mapping

The SAAM 2-D method was not developed with the intention of providing an overall mapping

capability. Instead it was intended to give localised information for pipeline OOS purposes only.

However, even with this data it has been found to be possible, given certain supporting information

to develop basic strip maps. Clearly the development of the 3-D capability would be a major step

forward with an obvious extension being the development of overall pipeline routing maps.

Furthermore, it should also be possible to link the internal data acquired from the SAAM unit with

data from pipeline markers, hence giving another means of cross-referencing locations along thelength of the line.

Conclusions

Detecting, assessing and monitoring OOS is clearly an important aspect of pipeline mainte-

nance. The development of a pipeline cleaning pig based internal inspection tool, with the benefits

associated with ease of deployment and minimal risk, is believed to represent a major contribution

towards the successful management of OOS problems. The SAAM Pipeline Inspection tool is

believed to be the first commercially available product specifically design for use on-board standard

cleaning pigs.

SAAM has been shown to offer a viable, cost effective alternative to traditional methods of

determining OOS. Details of the 2-D method have been presented and discussed. Of particular

importance has been the approach to error handling and the accuracy of the tooling. A clear

understanding has been presented regarding how these errors arise and how they are managed

within acceptable limits.

The case study presented and the other applications discussed, have illustrated the different

roles in which SAAM can be used. It has been shown how it can be used to acquire pipeline OOS data

associated with a known problem, such as an Upheaval Buckle, thereby enabling the client to make

informed decisions regarding the remedial strategy. The Abana case study, on the other hand, has

shown how the tooling can be incorporated within an on-going maintenance programme in order to


11/17


locate and monitor parts of the pipeline which may be changing and becoming increasingly out of

straight.

The development of a 3-D version of the tooling is becoming an ever increasing possibility with

the successful completion of the first series of tests using the most recent version of SAAM. These

tests have shown that the tooling can be used to determine changes in the horizontal plane and work

is progressing in developing the limits of this technology in order that it can be released during 2001.

In conclusion, the detection of pipeline OOS using the SAAM Pipeline Inspection tool is one of

the most proven uses of the technology. The ability to perform this role using a cleaning pig as the

carrier tool is seen as being a major step forward. Combined its relatively modest cost, the use ofSAAM as part of a routine condition monitoring programme for pipeline OOS detection, assessment

and monitoring has now been shown to be a reality.

References

1 Marine Accident Investigation Board. Report of Inspectors Inquiry into the Loss of the Fishing Vessel

Westhaven AH190. April 1998.

2 Kirkvik R, Clouston S, Czyz Dr. J; Pipeline Out of Straightness and Depth of Burial Measurements Using

an Inertial Geometry Intelligent Pig; OPT 1999.

3 Czyz Dr. J, Falk J; The Use of the Geopig for Prevention of Pipeline Failures in Environmentally Sensitive

Areas; Pipeline Pigging Integrity Assessment and Repair Conference, Houston February 2000.4 Short G, Hak J, Smith Dr. G; Low Cost Smart Pigging Comes of Age; Pipeline Integrity Assessment and

Repair Conference, Houston February 2000.

5 Short G, Fletcher M; The Role of Smart Cleaning Pigs In Pipeline Rehabilitation and Repair; Pipeline

Rehabilitation and Maintenance Conference, Prague September 2000.

6 Russell D, Snodgrass B, Smith Dr. G.; The Smart Acquisition Analysis Module for Pipeline Inspection;

ISOPE 2000, Seattle, May 2000.

7 Smith Dr. G, Short G, Russell D, Owens E; Testing Instrumentation for the Identification of Wax In

Hydrocarbon Pipelines; ISOPE 2000, Seattle, May 2000.

8 Russell D, Ogunjimi P; Measurement of Pig Behaviour Provides Low Cost Solution to Monitoring Pipeline

Geometry; Oil and Gas Journal, May 2000.


12/17


Figure 1. SAAM in a bidi pig.

)LJXUH6$$0,QVSH.WLRQ&DSDELOLW\


13/17


)LJXUH3LSHOLQH6.KHPDWL.

)LJXUH7HVW/RRS'DWD


14/17


)LJXUH&RPSDULVRQ%HWZHHQ6$$0DQG529'DWD

)LJXUH$EDQD)LHOG/D\RXW


15/17


)LJXUH5DZ'DWDDQG*HQHUDWHG3URILOH

)LJXUH$EDQD&DUULHU3LJ


16/17


)LJXUH3URILOHRIDQ8SKHDYDO%X.NOH

)LJXUH3KRWRRI5677HVW)D.LOLW\


17/17


)LJXUH''DWD/DSV

)LJXUH+RUL]RQWDO'LVSOD.HPHQW$URXQG5677HVW5LJ

Documents

Pipeline Test