COOLING WATER INJECTION SKIDS BASED ON GE STUDY-HABSHAN

HOT TAP CALCULATION

COMPANY : ABU DHABI GAS INDUSTRIES LTD (GASCO)

EPC CONTRACTOR : BABCOCK BORSIG SERVICE

ENGINEERING : TEBODIN MIDDLE EAST LTD

CONSULTANT

This page is a record of all revisions of this document . All previous issues are hereby superseded and are to be destroyed .

Rev Date Reason for issues Prepared by Checked by Approved by

A 04-04-2011 Issued for comments GDE SSS PVPApproved for construction

Notes :

1. Revisions are denoted as follows: (a) By a vertical line in the left-hand margin against the revised text .(b) By a triangle symbol for graphics, the revision number being denoted within the symbol.

Revision symbols are positioned adjacent to the revision.

PARAGRAPH REVISED THIS ISSUEPara No. Para No. Para No. Para No.

Table of Contents

1. INTRODUCTION2. SCOPE3. DEFINITION AND ABBERVIATIONS

3.1 Definitions4. REFERENCE DOCUMENTS

4.1 Codes and standarads 4.2 Project Specific Document 4.3 Company DGS

5. HOT TAP LIMITATION5.1 Process Fluid5.2 Pipe Material

ANNEXURE-A : 6” X 1/2" HOT-TAP (WT-6.8MM)

6. INTRODUCTION

7. MAXIMUM TEMPERATURE OF THE PIPE WALL

8. TEMPERATURE DERATING METHOD

9. VELOCITY CONSIDERATIONS

10. LOADING

11. CONFIGURATION REQUIREMENTS11.1 General 11.2 Area Replacement

12. STRENGTH TEST PRESSURE

13. CONCLUSION AND RECOMMENDATION

ATTACHMENT-1 : PIPING LAYOUT

ATTACHMENT-2 : UT REPORT

ATTACHMENT-3: WELDING PROCEDURE SPECIFICATIONS PARAMETERS 23ATTACHMENT-3: WELDING TEMPERATURE OF PIPE WALL 24ATTACHMENT-3: HOT TAP SAFE TEST PRESSURE RATIO 25

1. INTRODUCTION

Abu Dhabi Gas Industries Ltd. (GASCO) owns and operates Habshan Plant Located in theIn the western region of the emirate of Abu Dhabi which is situated 150 Kms south of AbuDhabi city. The plant elevation is 64 meters of jebel Dhanna Datum and approx. 25kilometers from the coast. Habshan cooling water system is divided into three units,Namely Habshan-0; 1 & 2.

GASCO- Habshan has been facing the problem of brass tube failure in lube oil coolers & carbon steel tube failures in water chillers and in order out the problem , a study was carried out by GE.

As a recommendation from GE study, GASCO intends three chemical injection packages for each cooling water expansion drum 66-V-501 located in Habshan-0, and 66-V-701 located in Habshan –II . These packages are corrosion inhibitor injection package, Biocide injection package and Oil dispersant injection package .

GASCO awarded the project to M/s Babcock Borsig Service on EPC basis to meet the objective of this project.

M/s. Babcock Borsig Service has awarded detail engineering part of the project to Tebodin middle east Ltd.(TME) as a subcontractor to Babcock.

2. SCOPE

Under this project six (6) hot tapping connections are required as tabulated below. The hot tap shall be carried out based on approved document “Method Statement for Hot Tapping”(HBT/E-040449-MS-1300-009). The calculation enclosed in appendix-A is applicable to TP-03, TP-04 & TP-05, Where the actual wall thickness of the run pipe (6” NPS) is 6.8mm as measured by UT.For TP-09,TP-10 & TP-11 same calculations are applicable , since the wall thickness is 6.9mm as measured by UT and all other parameters are identical.

Table-1

Tie-in Hot Tap Service Header(Existing)Line no Branch (new) Line noTP-03 6”X1/2” Cooling water 66-3501-L-6” 66-xxxx-CH-1/2”-13450-NTP-04 6”X1/2” Cooling water 66-3501-L-6” 66-xxxx-CH-1/2”-13450-NTP-05 6”X1/2” Cooling water 66-3501-L-6” 66-xxxx-CH-1/2”-13450-N

TP-09 6”X1/2” Cooling water 66-0709-CWS-6” 66-xxxx-CH-1/2”-13450-NTP-10 6”X1/2” Cooling water 66-0709-CWS-6” 66-xxxx-CH-1/2”-13450-NTP-11 6”X1/2” Cooling water 66-0709-CWS-6” 66-xxxx-CH-1/2”-13450-N

This report gives the outline for hot tap design calculations to arrive the maximum operating pressure and other design guidelines to be considered while carrying out hot tapping works on the operating cooling water lines.

The Design calculation for hot tapping shall be include the following considerations:

● Process Data / Limitations

● Pipe Data / welding suitability

● Pressure, Temperature and Velocity considerations

● Loading

3. DEFINITIONS AND ABBREVIATIONS

3.1 Definitions

COMPANY Abu Dhabi Gas Industries ltd (GASCO)

PURCHASER/EPC/ BABCOCK BORSIG SERVICE

CONTRACTOR

ENGINEERING TEBODIN MIDDLE EAST LTD (TME)

CONSULTANT

VENDOR VENDOR of Equipment, including Sub-vendors(s) appointed by

VENDOR to carry out part or all the work

4. REFERENCE DOCUMENTS4.1 Codes and Standards

ASME B31.3 - Process pipingASME Sec VIII - Boiler and pressure Vessel CodeDEP 31.38.60.10-Gen - Hot-Tapping on pipelines, Piping and equipment

4.2 Project Specific Document

HBT/E-0400449-MS-1300-009 - Method Statement for Hot Tapping 02-A0-xxxx - Utility Flow Diagram UNIT-66 cooling water System02-A0-xxxx - Piping Plan Area 60-22

4.3 Company DGS

DGS-1300-100 - Design General Specification for piping Tie-ins

HBT/E-SP-XXX - Piping Material Specification

5. HOT TAP LIMITATION

5.1 Process Fluid

According to DGS-1300-100 Section 8.3.2. Hot tapping shall only be performed under the following conditions:

● The contained process fluids shall remain stable when subjected to the high metal Temperature during welding

● The process fluids remain stable when it comes in contact with air during drilling and Perforation operations

● There shall be no decomposition or chemical reaction between components of the Contained fluid (explosive, ignition, exothermic reaction)

● There shall be no chemical reaction between the fluid and the hot contained wall (Burning, stress, corrosion, embrittlement).

These requirements lead to a number of situations in which welding operations are prohibited on equipment which contains:

• Mixtures of gases or vapours within their flammable range or which may become flammable as a result of heat input in welding operations

• Substances which may undergo reaction or decomposition leading to dangerous increase in pressure. Explosion or attack on metal. In this context, attention is drawn to the possibility that under certain conditions of concentration, temperature and pressure, acetylene and other unsaturated hydrocarbons may decompose explosively, initiated by a welding hot spot

• Oxygen-enriched atmospheres in the presence of hydrocarbons which may be present either in the atmosphere or deposited on the interior surface of equipment or pipe

• Compressed air in the presence of hydrocarbons which may be present either in the air or deposited on interior surfaces of equipment or pipe

• Gaseous mixtures in which the partial pressure of hydrogen exceeds 700kPa(g), except where evidence from tests has demonstrated that this can be done safely .

In addition, welding operation is prohibited on piping which contains hazardous subs conditions, as listed below. If any of these substances are known to be present within the piping , even in small quantities, investigations should be made on the stability of the fluid at the pipe wall temperature. The relevant substances/conditions included:

• Acetylene

• Acetonitrile

• Butadiene

• Caustic soda

• Chlorine

• Compressed air (Pressure is excess of 3000 kPa(g))

• Ethylene

• Ethylene oxide

• Rich/lean DEAIMEA

• HP steam (pressure in excess of 329 kg/cm2 g)

• Hydrogen

• Hydrogen sulphide

• Hydrofluoric acid

• Oxygen

• Propane

• Propane oxide

• Sulphuric acid

• Toxic substances

Conditions:

• Vacuum conditions

• Dissolved hydrogen in the pipe wall (e.g. due to service history)

• Pyrophoric scale deposits

Note:

1. The above list is not exhaustive, but gives an indication only.

2. The fluid under consideration is Cooling Water and does not involve any of the above Substances.

3. Vacuum conditions are not envisaged during welding.

5.2 Pipe Material

Fitting and branch material shall be of a type and grade compatible with the material of the run-pipe

to be hot-tapped.

Hot-Tap welding should not normally be performed on materials which require post-weld heat

treatment (PWHT). However, if stress relieving or post-weld heat treatment is required, a specialist

shall be consulted to access whether it is in fact feasible to make the specific hot-tapping operation

with post-weld heat treatment. (Stress-relieving may be required when a material is susceptible to

stress corrosion cracking and post-weld heat treatment may be specified by the design code when

the wall thickness is greater than a certain limit).

Welding operations shall not be performed if the actual wall thickness of the run-pipe, as determined

by ultrasonic testing, is less than 4.8mm.

Welding shall not be performed on lined, clad or special internally coated pipe.

ANNEXURE-A: 6" X 112" HOT-TAP (WT-6.8MM)

6. INTRODUCTION

The following design data of the existing 6" cooling water line (66-3501-L-6") has been considered

for hot tap design calculation at TP-03. The tie- in location is at the area 60-22(Refer attachment-1) .

Pipe Material - API 5L Gr.B

Service - Cooling Water

Wall Thickness (H) - 6.8 mm (Refer attachment-2)

MAOP (Max. Al lowable Operating Pressure) - 6 bar g

MNOP (Max. Normal Operating Pressure) - 6 bar g

Expected arrival Pressure at Tie-in point - 6 bar g (To be confirmed by COMPANY)

Max. Design Temperature - 87 °C

Max. Operating Temperature - 45 °C

7. MAXIMUM TEMPERATURE OF THE PIPE WALL

The maximum temperature of the inside of the pipe wall attained during welding may be derived from the actual wall thickness of the pipe (ta) and the expected heat input (HI) from the following equation:

HI = K V * A SWhere:

HI = heat input (Joules per mm)

K = net facto( = 0.85 for butt welds, and = 0.57 (=213 x 0.85) for fillet welds.

v = voltage (volts)

A = current (amperes)

S = travel speed (mm/s)

For a specific hot-tap. the permitted ranges of voltages. current and welding speed are defined in the Welding Procedure Specification (WPSl or method statement. The actual or mid-range valves can be considered.

The heat input during the Root pass, 1 st butterin9 and 2nd buttering are calculated using the current , voltage and travel speed values derived from the WPS parameter provided by CONTRACTOR (Refer attachment-3) and are tabulaled below in Table-A1 :

HI = K V*A SHI = 0.57 22.5*90 1.76

HI = 659.57 J/mm

Table-A1: Heat Input for NPS 6" X 1/2" Hot Tap

Pass Current Voltage(V) Travel speed(mm/s)

RA heat input (j/mm)

1) Root Pass 90 22.5 1.75 659.572) Buttering 90 22.5 1.75 659.573) Buttering 90 22.5 1.75 659.57

From the heat input vs wall thickness graph. The welding temperature of the pipe wall (i.e. The maximum temperature of the inside of the pipe wall attained during welding) is determined for the preheat case with initial pipe wall temperature of 25 °C. (Refer Attachment-4 of this document which is a copy of Appendix-12 of OGS-1300-OO1).

The actual run pipe (ON 6' existing header) wall thickness is 6.8 mm. As confirmed by UT (Refer attachment-2). From the graph in attachment-4, the inner pipe wall temperatures, the penetration depths, reduced wall thicknesses during the critical welding passes are calculated and tabulated below in Table-A2 :

Table-A2

Pass Max.inner wall temperature(oc)

Penetration depth`u’ (mm) Reduced wall thickness `t’ (mm)

Post pass thickness *

(mm)1) Root Pass 420 1.61 5.19 8.82) Buttering 350 1.30 5.50 10.83) Buttering 272 1.08 5.72 12.8

• Assume conservative estimate of 2mm thickness each pass.

As per Section 6.3.3.3 of DGS·1300·100, for general safety reasons:

1) During the hot tap welding, the pressure of fluid inside the run pipe shall not exceed the maximum allowable pressure. The maximum allowable pressure during welding operation is calculated by the Temperature Derating Method.

2) At any time during the hot tap operation, the pressure of fluid inside the run pipe shall not exceed the maximum working pressure of the hot tap equipment. The maximum normal operating pressure (MNOP) of the Cooling water line is 6 bar (g) (To be confirmed by COMPANY). Thus the hot tap equipment rating should be higher than 6 bar (g).

8 . TEMPERATURE DERATING METHOD

The allowable pressure is given by the equation:

P = 2t SEWT (as per ASME B31 .3) (D-2tY) Where

P = Max. Allowable operating pressure during welding operation in N/mm2

S = 137.89 N/mm2 for API5L Gr.B@8rC

D = Outside diameter of the run pipe = 168.28 mm

w = Weld joint strength reduction factor = 1.00 (at temp. 510 D C and below)

y = Coefficient from table 304.1.1 of ASME 831 .3 = 0.4

t = Reduced wall thickness, (H-u) = 5.19 mm

E = Quality Factor from Table A-1A or A-l 8 of ASME 831 .3 = 1.00

T = Temperature Derating Factor is 0.634 (Refer DGS-1300-100, Sec 8.3.3.3, Table-l)

p = 2 x 5.1 9 x 137.89 x 1.00 x 1.00 x 0.634 168.28 - (2 x 5.1 9 x 0.4)

= 5.53 N/mm2

= 55.3 bar (9) > 6 bar (g)

Hence calculated maximum allowable operating pressure is 55.3 bar (g) whereas the expected arrival pressure at the hot tap point is 6 bar (g)

"THE OPERATING PRESSURE OF THE EXISTING MAIN PIPE IS ACCEPT A8LE FOR HOT TAPPING OPERATION".

9. VELOCITY CONSIDERATIONS

The suggested maximum and minimum velocity for liquid flow is 1.75 m/sec and 0.5 m/s respectively.

Max. Flow Rate, Q = AV

Q= π x (d 1) 2 x V4

Where, di = inside diameter of 6" run pipe = 0.1547 m

V= 1.75 m1sec

Q = 3.14x(0.1547)2 x1 .75 = 0.0329 ml/s = 118.44 ml /h 4

Min. Flow Rate. Q = AV

Q= π x (d 1) 2 x V4

Where, di = inside diameter of 6" run pipe = 0.1547 m

v = 0.5 m/sec

Q= 3.14x(O.1547)2 xO.5 = O. 0094m3/s = 33.84m3/h 4

The flow corresponding to the minimum velocity of O.5m/sec shall at least be maintained during hot lapping. COMPANY shall ensure the minimum velocity of 0.5 m/sec (0 = 33.84 m3 /h) during welding.

10. LOADING

The hot-tap branch will be installed at 900 to the axis of the run pipe. The hot lap machine shall be properly and adequately supported such that weight of the hot-tap isolation valve and the drilling unit (hot-tap machine) etc. shall not cause any twisting of the run pipe. Also the operation shall be such as not to cause any buckling of the pipe wall at the base of the branch.

11 . CONFIGURATION REQUIREMENTS

11.1 General

Care shall be taken during hot tapping to ensure the following:

• The separation of the attachment fillet welds from existing circumferential welds shall be at least one run pipe diameter (i.e. 6" or 168.3 mm) and in no case shall be less than 150 mm.

• Interference with the longitudinal weld seam of the run pipe shall be avoided

• The chosen location in the run pipe shall be checked and verified as suitable for the hot tap connect ion, taking into consideration factors such as diameter and ovality, remaining (existing) pipe wall thickness, internal I external corrosion, defects in the pipe wall like internal deposits, soundness of adjacent welds, weld seam locations etc.

11.2 Area Replacement

A run pipe having a branch connection is weakend by the opening made in it. The branch connection must reinforce the opening and restore the original strength of the run pipe. 11 is the intent of this document that these integrally reinforced branch outlet fitting and the deposited weld metal used to attach the fitting to run pipes contain all the reinforcement required by the applicable piping codes without the addiction of saddles or pads.

As the proposed hoi tap is 6" x 1/2" socklet , area replacement calculation are not required in this

case.

12. STRENGTH TEST PRESSURE

The general testing procedures to be followed shall be:

1. The hot-tap valve before installing on the branch shall be body and leak tested as per the direction of the company.

2. Testing of the branch connection, with the valve installed and in the open position. to demonstrate leak tightness and strength. Duration should be at least 30 minutes.

3. Leak testing of the drilling machine mounted on the valve (with valve closed) for duration of 5 minutes.

The hot tap valve shall have a pressure test applied to the seats and body. During the test, this pressure acts as an external pressure on the run pipe. In order to avoid buckling of run pipe. as per c1ause 8.8 .1 of DGS-13~loo. for set on branch connections, the strength test pressure shall be as per Appendices 15 of DGS-1300-1 00.

PT = Test pressure in the branch pipe

PA = Actual Pressure in the run pipe = 6 bar g (To be confirmed by COMPANY)

F = Ratio of actual operating stress level in the wall of the run pipe to the material Specific minimum yield strength (SMYS)

S = Stress Value

S = [ P (D-2tY) ] /2tEW

S = [ 6x (168.28-2x 6.8 x 0 .4) ] / (2 x 6.8 x 1.0x 1.0)

= 71.84 bar (g)

= 1042 psi

F = 1042/35000 = 0.0297

It is assumed that F = 0.5 for more conservative result.

0= Outside diameter of the run pipe = 168.28 mm

d = Out Side diameter of the branch pipe = 21 .34 mm

t = Actual thickness of the run pipe = 6.8 mm

As per Appendix 15 of DGS-1300-100 (copy enclosed as Attachment -5) for .

d / D=0.13

D/ t = 24.75

F = 0.5

PT I PA = 1.625

Hence PT = 1.625 x 6 = 9.75 bar (g)

This pressure the run pipe can withstand without buckling. Hence the test pressure for the branch connection shall not exceed 9.75 bar (g).

13. CONCLUSION AND RECOMMENDATION

• The tabulated values of voltage. current and travel speed listed in Table-A 1 are provided by the CONTRACTOR and shall be maintained during the welding of the branch fitting.

• Flow rate during the welding shall be Q = 33.84 ml/h to maintain minimum velocity of 0.5m/sec

• The Maximum test pressure for the branch connect ion shall be 9.75 bar (g) and the testing medium shall be water.

• Before starting the hot lap operation the CONTRACTOR shall f ill the hot tap procedure check list (Appendix 17 of DGS-1300-1OO) and shall get approval from COMPANY.

• For General Safety Precaution for hot lap the CONTRACTOR shall refer to Section 7.4 of DGS-1300-100

• The document includes only one set of calculation for the HOT -TAP operation and shall be applicable for all six (6) connections (Refer Table-1). Since the calculation parameters are identical.