Subsea Tie-in

[Nottingham]

Dear all

In order to make a tie-in to the exising subsea pipeline, it seems for me the best way is to employ the hot-tapping in case the system shutdowm is not permitted. But if it is permitted for a certain period, does anyone has any idea what method should be applied in term of engineering, cost effectiveness and also for future matainence accessibility. Your help will be very appreciated.

Thank You Very Much

 

[cedric]

type of application (connection), water depth, size of the pipeline, environmental conditions?

 

[narenr]

Hottap would be the best option. Costly yet good solution would be hyperbarbic welding for the tie-in if shutdown permits. Simple soulution would be flanged tie-in if shutdown, flanges and flushing/drying etc is acceptable. These are general recommendations when no details are avialable. Obviously the detail engineering would provide a good soulution for subsea tie-in which are routine.

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.

 

[cedric]

Nottingham,

Contact IPSCO (UK) ltd.,

http://www.hottaps.com

If you provide me an email address, I can give you the contact number and email address of someone I know in IPSCO, who could give you all info required (technical, price...).

cedric

 

[krpandian]

If shut down is permitted for a limited period then I would suggest mechanical connectors and flanged tee. Mechanical connectors will avoid the subsea welding and very easy to install and align.
We have replaced a portion of subsea pipeline (10&quot using mechanical connectors. We completed the hole operation with a help supply vessel and divers.

 

[munari]

SHIFTING PIPELINE ANALYSIS
General Approach

M.Munari
Engineering
Central Sumatra Gas Project
PT Perusahaan Gas Negara (Persero)


Bla-Bla-Bla

This paper is to describe the pipeline shifting where shifting the existing laid not exactly route per design on the seabed or trenching. The case exists due to some factors such:
1. Receiving GPS (Geographic Positioning Station) on the barge is poor.
2. Design route not same with trenching design.
3. No fairly coordination on the site
4. Not proper trenching (above, bottom, width)
5. Barge works under extreme conditions

Purpose
This paper is describing a situation of shifting pipeline procedure without cutting off at end the pipeline.
The pipeline that lay on wrong route shall lift 4 meter of the touchdown and shall shift 4 meter maximum of initial point.
Potential Factors

The below are list of some potential factors to be considered:
• Easy to be done
• Lifetime of working is short
• Risk to damage
• Constraints not free (fixed)
• Stress at each ends increase
• Tend to create the torque
• More cheaply cost than other methods
• Un-conventional Method
• Highly Percentage system mode of failure (SMOF)

Disadvantages
• No Recommend Standardizations
• Un-conventional Method
• No assurance
• Risk to damage
• Constraints not free (fixed)
• Stress at each ends increase
• Tend to create the torque
• Highly Percentage system mode of failure (SMOF)

Advantages
• Easy to be done
• More cheaply cost than others


Design Basis
The pipeline installed with refers to DnV 2000 Standardization (OF-S101).

A. Designed Pipeline Data
Outside Diameter (OD) : 0.7112 meter
Thickness (t) : 0.0127 meter
Inside Diameter (ID) : 0.6858 meter
Grade : API 5L X 65
Density (s) : 7850 Kg/m3
Yield Strength (S) : 65000 Psi (448 N/mm2)
Tensile Strength (T) : 77042.41 Psi (531 N/mm2)
S/T Ratio : 0.84
Modulus of Elasticity (E) : 1.94 x 105 N/mm2
: 29000000 Psi
Linear Coefficient Tensile Strength (t) : 2.97 x 10-4 mm/mmoC


Procedure Working

Step by Step
• Set up barge on location
• Diver inspection (to observe backfill materials on the shifting location, pipe position in relation to trenching)
• Inserting sling around pipe at lifting points (4 points with interval 20 meters) with diver, if necessary using air jet compressor.
• Lowering wire from davits to joint onto sling
• Lifting pipe to y-axis direction with 4 davits (refer to Lifting Schedule) up to max. 4 meter (interval lifting 0.5 meter)
• Shifting pipe to x-axis direction with no lifting (interval 1 meter, max distance 4 meters). Barge shall move by foot-print of anchoring system.
• Lowering pipe y-axis direction with 4 davits (refer to Lifting Schedule) up to max. 4 meter (interval lowering 0.5 meter) on to trenching.
• Post-shifting survey to make sure that pipeline already on right position.
• Report

 

[brindavan22]

If Shutdown for a short period is allowed try out with Smart Flange / quick connect flange . This would be the cost effective one. If you are looking at Hot tap this would take time for you to get in touch with different parties as none of the hot tap companies have their own diving teams so a sort of co-ordination between the supplier and the installation contractor is reqd. If you go with Smart flange it is a fairly easy way!!

 

[MechanicOlet]

We've done pipeline leak repair 24" with water depth 72m. We're using Smart plug to isolate the system, install spool with flange connection and leaktest using kamos test. FIrst time in the world with 2 nos of smart plug double module and pipelifting bothside. All hot work done at surface... Cool huh...

Field Engineer,
TL Offshore Sdn. Bhd,
Malaysia.