Practical Approach to Transform Aged Onshore Un-Piggable Pipelines into Piggable Pipelines

Mr. Ahmed Hashem Makram Presenter Mr. Ahmed Hashem Makram HOT Engineering & Construction Company. Kuwait. Abstract Since the first transport pipeline was built in the late 19th century, many oil and gas pipelines have been constructed and nowadays they are considered as un-piggable.

It is estimated that at least one third of all oil and gas pipelines around the world are considered non-piggable for one reason or another. There is growing tendency in the market to look into the integrity of these pipelines.

From operators’ point of view, continue operating un-piggable pipelines without assessing their real condition constitute immense pressure to ensure the safe operation and to minimize the impact on environment.

According to the availability of information considering costs, environment impacts and risks involved, operators’ recommendations and decisions are different:

Some decided to build new pipeline systems and demolish the existing.

Some decided to use newly developed ILI tools that can negotiate un-piggable pipelines.

Some decided to rehabilitate the lines and transform them into piggable pipelines.

Some decided to accept the current situation and do remedial actions as required.

The objective of this paper is to explain the methodology of safe and cost effective method to transform un-piggable pipeline systems into piggable. This operation has been developed for safely pigging, de-oiling and demolishing of existing aged pipelines in Kuwait.

7th Pipeline Technology Conference 2012

The main obstacles were as follows:

Short radius 1.5D bends.

Multi-diameter pipelines.

The lines have never been pigged before.

Risk of existing metal parts and waxes inside the lines

Un-known valves conditions.

Un-barred Tees.

Non availability of Pig Launcher/Receivers.

PRACTICAL APPROACH TO TRANSFORM AGED ONSHORE UN-PIGGABLE PIPELINES INTO PIGGABLE PIPELINES

1. Background:

Kuwait Oil Company (KOC) is one of the leading crude oil producing Companies in the Middle East. KOC, as part of its program to upgrade its exporting facilities, decided to Demolish and remove 9 Crude Oil Filling Lines and replace by new pipeline system under Contract No. 33851. The project had 2 Portions: Portion 1: The scope of Portion 1 was the Engineering, Procurement and Construction of new filling pipeline system connecting the Central Mixing Manifold to the South Tank Farm and North Tank Farm sizes (30”, 34”, 36” & 48”). Portion 2: The scope of Portion 2 was the Demolition of existing pipelines system. The demolition work started one month after successful commissioning of the new pipelines system. The demolition scope included demolitions of pipelines with sizes (16”, 22”, 30”, 34”, 36”, 42” & 48”) with lengths vary from 1.0 kilometer to 10 kilometers for each. South Korea’s Daelim Industrial Company was the selected main contractor. HOT Engineering & Construction Co. had been selected by Daelim/KOC for the execution of the Pipelines Civil & Mechanical scopes in Portions 1 & 2. 2. Paper Objective and Main Ideas:

The objective of this paper is to explain the methodology of safe and cost effective method to transform un-piggable pipeline into piggable pipeline. This operation has been developed for safely pigging, de-oiling and demolishing of the existing pipelines system in Portion 2.

The same method can be adopted to transform any un-piggable pipeline into piggable pipeline by removing the obstacles that prevent performing pigging operation. Consequently, the Client can carry out full assessment of the pipeline condition by intelligent pigging that may constitute considerable savings by extending the operating life of the line.

3. History of the “Filling Pipelines” system:

The filling pipelines were installed since more than 40 years. The pipelines were having no pigging facilities. The surveillance inspection reports showed very low thickness in some areas at the ends of the pipelines, external corrosion mostly at bottom sides and disbanding of coating at various locations. Oil leaks had been observed in the pipelines at North Tank Farm area and repaired by changing the corroded pipes.

4. HOT Engineering Objectives during performing the Demolition Scope:

Performing the demolition work with the safest possible manner.

Avoid any oil spillage and/or soil contamination.

Perform the work within the construction schedule and budget.

To reach these objectives, HOT Engineering decided to perform de-oiling by pigging to ensure full, and controlled de-oiling of the pipelines system; consequently, safe demolition operation. A detailed method statement had been developed to ensure reaching the above goals.

5. Developing of Demolition Method Statement:

a. Site Surveying and Collecting Data:

Surveying the site, verifying the demolition drawings and marking at site the locations of valves, orifice flanges, branches, bends, reducers, etc.

Identifying the positive isolation points and the proposed locations for the temporary hot tapping points required to be executed on the existing lines for draining purpose at particular locations.

The following data has been collected/verified for each of the existing pipelines:

Pipeline elevation at different locations especially at start & end points.

Comparing the P&ID and available drawings with the actual situation at site.

Pipeline Inspection report.

Identification & marking of Pipeline Isolation and de-oiling Points.

b. Data Analysis:

From the collected data, we found the followings:

I. Pipelines’ elevation at North Tank Farm area NTF (End Point) is higher than the pipelines’ elevation at Central Mixing Manifold CMM (Start Point) by ~19.0 Mt. in 10KM length which allow for performing bulk de-oiling by gravity.

A B

Elev. Differance

II. Main obstacles/risks that prevent pipelines de-oiling using pigging are:

All bends are short radius of 1.5D.

Some lines are Multi-Diameters as reducers are encountered in the pipeline route.

Risk of existing metal parts and waxes inside the lines.

Un-known valves conditions (full or reduced bore, partially closed..etc).

All Tee branches are “Un-barred Tees”.

Non- availability of Pig Launcher/Receivers.

Orifice Flanges are encountered in the pipeline route.

c. Method Statement Details:

i. Bulk De-oiling by gravity:

Bulk de-oiling was performed from the lowest point in the line near to CMM area. The main purpose of the bulk de-oiling is to transfer the maximum quantity of oil from the line by gravity to prepare for starting the required modification works.

After bulk de-oiling, the line was not fully de-oiled as considerable oil quantity was entrapped in areas like A & B because of the changes in pipeline elevation along its route.

Figure 1: Areas of remaining oil inside the line after bulk de-oiling by gravity

ii. Transforming the Aged Un-piggable Pipeline into Piggable Pipeline:

The main idea is to remove the obstacles mentioned in clause 5.b.ii that prevent pigging the pipeline as explained in Figure 2-1:

Figure 2-1: Schematic diagram for existing pipeline

Figure 2-1 describes schematic diagram for existing pipeline. The pipeline is not

piggable because of the following reasons:

There is no pig L/R at points “A & F”.

Valve at point “B” might be reduced bore or partially closed.

Unbarred tee branch at point “C”.

Reducer at point “D”.

1.5D bends at points “A, E, & F”.

Orifice flange at point “O”.

Figure 2-2: Locations for hot tapping points

Figure 2-2 describes schematic diagram for the locations of 6” hot tapping points

performed on the existing line. The hot tapping points executed at the following

locations:

At point “A” for removal of remaining oil before starting cold cutting, welding of flange and installation of pig launcher.

At point “B” for removal of residual oil before removal of the existing valve to check its condition and replace it, if necessary.

At point “D” for removal of residual oil to start cold cutting, welding of flanges and installation of pig launcher &receiver.

At point “F” for removal of remaining oil to start cold cutting, welding of flange and installation of pig receiver.

At point “O” for removal of remaining oil and replacement of orifice flange by spacer ring.

Figure 2-3: schematic diagram for the pipeline after modification

Figure 2-3 describes schematic diagram for the pipeline after completion of required

modifications to transform it from un-piggable pipeline to piggable pipeline:

At point “A” pig launcher had been installed.

At point “B” the existing valve had been replaced by pub piece.

At point “O” orifice flange had been replaced by spacer ring.

At point “D” 2.0 numbers pig launcher & receiver had been installed.

At point “F” pig receiver had been installed.

Referring to Figure 2-3, pig propelled by Nitrogen and launched from point “A” to “D1”

and removed oil can be transferred to section (D2-F).

And then, the same above procedure repeated to launch a pig from point “D2” to “F”.

Removed oil transferred to existing service by suitable De-oiling Pump.

6. Actual work execution and challenges faced the construction team:

a. Hot Tapping:

During execution, HOT’s construction team faced difficulties in performing the hot

tapping works before de-commissioning of the old system. Therefore, HOT suggested

using fabricated clamp branch instead of welding the branch directly to the line. Our

suggestion got approved.

Figure 3.1: Testing of Fabricated Clamp branch before Hot Tapping

Figure 3.2: Performing Hot Tapping through the fabricated clamp branch

We used the same technique when we found that the pipe wall thickness is not suitable

to perform welding works at the hot tapping point.

b. Bulk De-oiling:

The hot tapping was performed at the lowest point in the line to prepare for bulk de-

oiling.

Figure 4.1

Arrangement of temporary line for de-oiling.

Figure 4.2: Piping arrangements for de-oiling.

Figure 4.3: Preparing the De-oiling Pump.

c. Solving problem of passing Pig through 1.5D Bends and Un-barred Tees:

Many ideas were negotiated and discussed with the pigs’ manufacturer, “Pipeline

Engineering UK” to select the most suitable pig design.

PE recommended using specially designed medium density foam pigs that can pass

through the 1.5D bends and having length of 2.15D to be able to pass through the un-

barred tees without stuck according to the design below.

.

Figure 5: Details of Extra Length Foam Pig

d. Installation of Pig Launcher/Receiver

The steps are as follows:

Installation of 6” Hot Tapping Point

Suck the residual oil from the line through the hot tap point by vacuum tanker or

diaphragm pump.

Cut the line by cold cutting means.

Install gas plug to provide save welding environment

Weld fabricated flanges at both sides

Install the Pig Launcher

Installation of 6” Hot Tapping Point

Figure 6.1: Performing Hot Tapping

Cold Cutting started after sucking the residual oil from the Hot tapping point

Figure 6.2: Cold Cutting

Welding of flange to the existing line

Figure 6.3: Welding of flange to the existing line

Welding of flanges completed

Figure 6.4: Flanges welded to the existing line

Temporary Pig Launcher Installed

Figure 6.5: Temporary Pig Launcher Installed

e. Pigging the line to complete the de-oiling & cleaning processes:

The steps are as follows:

Insert the pig inside the pig launcher.

Launch the pig using Nitrogen Gas.

Transfer the oil from the pig launcher to the existing facilities directly by temporary

line. De-oiling pump can be used as required.

Receiving the pig at the pig receiver.

Remove the pig, sludge and any objects were inside the line.

Temporary de-oiling Line from Pig Receiver to existing facilities

Figure 7.1: Temporary De-oiling Line connected to existing facilities

Temporary De-oiling Line connected to the existing facilities

Figure 7.2: Temporary De-oiling Line

Pig Launcher Area

Figure 7.3: Pig Launcher Area

Receiving the Pig at the Pig Receiver

Figure 7.4: Pig Receiving Area

De-oiling completed and Pig received at the Pig receiver. Crew is dismantilling the blind

flange to remove the Pig from the Pig Receiver

Figure 7.5: Dismantling of Pig Receiver blind flange

Pig received at the Pig receiver. Sludge and wooden pieces received in front of the Pig

Figure 7.6: Pig Received

Completion of pigging, de-oiling and cleaning processes and removal of the pig.

Figure 7.7: Removal of the pig from the pig receiver

7. Conclusions:

Hot Engineering & Construction Company combined a group of activities and developed a safely working methodology for pigging and cleaning aged un-piggable pipelines. This technique was developed for the de-oiling and demolishing of the existing pipelines system in Portion 2 in Contract No. 33851 for Kuwait Oil Company.

The same method can be adopted to transform any un-piggable pipeline into piggable pipeline and allow the pipeline owner performing full assessment of the pipeline condition by intelligent pigs that may constitute considerable savings by extending the operating life of the pipeline.