Detail Design, Supply, Erection and commissioning of

Close Loop Corrosion Test Rig (CLCTR)

1. Preamble

Corrosion of sea water carrying pipelines is an important issue, particularly for oil drilling industries.

One way to control chloride assisted corrosion of such pipelines is by reducing the O2 level <20 ppb

in water during pressurized sea water injection. However, sometimes oxygen level shoots up and

may reach as high as 2000 to 5000 ppb which may cause premature service failure. The expected

life of such pipes is ~15 years; the failures, however, have been observed only after 4-10 years of

service due to corrosion. It is thus important to understand the influence of O2 contents varying

from 20-1000 ppb on the extent of corrosion of steel and to investigate the critical oxygen level in

order to avoid pitting/ crevice corrosion. Such critical O2 concentration would be different for steel

differing in the alloying constituents and need detailed experimentation under the close cycle loop

system where flow rate and oxygen can be controlled and maintained during experiment. Corrosion

evaluation of the steel under the influence of varied O2 concentration and flow rate using coupon

exposure, open circuit potential measurements, and other electrochemical methods can be

performed using suitably fabricated loop. Such studies are possible with high quality closed loop

system which is capable of isolating the environmental elements, particularly, oxygen from entering

the water/ solution inside the loop. Oxygen concentration to the level of 20 ppb is strictly needed to

be maintained by such loop, which is the prime target for proposed equipment. The other aids such

as inert gas flow and chemical doses of oxygen scavenger shall also be provided to the water

inside the loop to bring down the oxygen concentration.

2. Objective

Fabrication of a closed loop corrosion test rig from stainless steel(316L) pipes

leaving no sites for oxygen entry into the system (One Unit)

The loop shall be equipped with the online accurate measurement of oxygen (within ppb level or

10-5000ppb) and water flow measuring system. As envisaged, the fabricated test rig (CLCTR) shall

be suitable for saline/ marine water and continued in operation for 1-90 days in each campaign to

study the corrosion behaviour of different steel alloys under influence of O2 contents in water

varying from 20-1000 ppb.

3. Description of the system

The proposed CLCTR is primarily a air tight close loop system suitable for handling saline/ marine

water with a provision to regulate the desired flow of water into the system and also to control

Oxygen contents in water varying from 20-1000 ppb. The sample (i.e. the coupon) under study will

be kept within the sample holding rig. The water with controlled level of Oxygen will be allowed to

flow at desired flow rate through the sample holding rig. Refer the attached Drg.

No.NML/ENG/ONGC/GA-01.

The CLCTR will comprise of the following major components:

i) Water Tank

ii) Water pumping system

iii) Test Rigs

(a) Sample holding Rig

(b) Electrode Probe holding Rig

iv) Oxygen Scavenging system

v) Oxygen measuring sensor

vi) Vacuum pumping system

vii) Argon purging system

viii) Instrumentation and control

ix) Pipeline and valves

x) Flow meter

xi) Civil foundations and Steel structures

xii) Computer

The description and broad specification of the components are detailed below:

S. No. Description Qty

1. Water tank:

This SS 316L tank will hold 3.5 % NaCl water solution, as

representative of sea water, to be circulated through the corrosion

Test Rig. Approximate capacity of the tank will be about 500 litres.

The tank id designed to hold a submersible type pump on its head to

be placed on the top of tank. Various ports are to be provided in the

tank as per scheme attached. Working pressure of water tank may be

considered as 1.5 bar.

1 no

2. Water pumping system:

A Submersible Pump of suitable materials capable for handling

marine water at a rate of 315 litres/minute. This is to be supplied for

circulation of water media at adjustable and predetermined rate

(maximum 200 litres/minute) across the rig loop and to be maintained

during the campaign. This pump shall be placed within the water tank.

The operating pressure may be at about 1.5 bar. The pump shall be

supplied with all associated motor, other electrical and of continuous

duty.

1 no

3.(a) Sample holding Rig:

4 nos of steel sample/ coupon of the size 5mm thick x 40mm x 100

mm need to be put in the rig for desired exposure time and flow rate.

Tentative rig size will be of 2”NB pipe 3 mm thick x 450 mm long.

These 4 nos of samples/ coupons are to places in the rig so that the

water flow in this rig is least obstructed. The sample should not touch

each other and the walls of the holding Rig. The test rig shall be

made of SS 316L while Teflon may be used as separator for

positioning of sample and to avoid the contact between samples.

Sample holder shall have flanged connections at both the ends with

provision of viton seal to prevent entry of atmospheric oxygen/gas.

2 nos

Schematic sketch of the Rig is enclosed

3.(b) Electrode Probe holding Rig:

This rig will hold 3 electrodes required to measure the potential of

alloy steel specimens with reference to reference electrode and other

probes (by using specimen mount). This rig is required to be

connected with the sample holding rig in series/parallel operation.

Tentative size of the rig will be about 2.0” NB pipe about 450 mm long

with adequate placing of 3 different types of probe electrodes (to be

supplied by CSIR-NML). Material of this rig shall be SS 316L.

Schematic sketch of the Rig is enclosed.

2 nos

4. Oxygen Scavenging system

Dosing tank: This tank of suitable material will hold the chemical

reagent required to control the dissolved Oxygen content in the

circulating water. Suitable line to be provided with control valve for

dosing reagent to the water tank in required qty and rate.

Approximate capacity of the dosing tank will be 20 litres. Material of

construction should be SS316L. The scavenging of Oxygen will be in

Argon atmosphere. This tank should be designed for 1.5 bar

pressure.

1 no

5. Vacuum pumping system

A rotary vacuum pump of suitable capacity (Pfeiffer, Edwards, Varian,

Leybold) is to be provided to evacuate the system before start the

process. The pump should be able to evacuate the system to a

vacuum level of 10-2 mbar in about 30 mins. This system shall be

complete with pump, motor, Fore-line trap and all associated

electrical and control and pipings.

1 no

6. Argon purging system

Argon will be purged into the system after evacuation as well as

during the campaign period. Suitable accessories like regulator, main

header gas line and valve to be provided. The system shall be

suitable to accommodate 3 nos. of Argon gas cylinders at a time.

Material of construction should be SS316L.

1 no

7. Instrumentation and control

7.(a) Water Flow meter:

Non contact type (magnetic) flow meter to be provided for measuring

and recording flow data through the rig. Flow meter should be made

of suitable material to avoid any effect on the performance in

corrosive media under long continuous operation (36 months). Flow

data is to be acquired for research purpose and therefore

arrangement may be provided for its acquisition and storage. Flow

meter measuring range (approx 50L/min to 300L/min)

2 nos

7.(b) Dissolve oxygen sensor:

Oxygen probe with digital display will be provided (Mettler-Toledo

2 nos

make:27050XXX-M800-1CH/IP6970i-120/AK9-5M). Data is required

to be recorded for research purpose so adequate data acquisition

system should be provided with the sensor.

7.(c) Level indicator:

Suitable non contact type level indicator with alarm to be provided to

monitor the water level in the tank.

1no

7.(d) Pressure guage:

Suitable pressure gauge (bourdon type) shall be provided at places

indicated in the attached drawing.

3 nos.

7.(e) Pirani Gauge:

Suitable pirani gauge shall be provided at place indicated in the

attached drawing.

1 no.

8. Pipeline and valves:

Rig pipe lines and accessories: Suitable 1.5” NB SS 316 pipe line to

be provided to circulate the media water from tank to sample holding

rig and back to the tank. The pipe line will be supplied with required

nos of valve to control the media flow and for other maintenance

purposes. Flanged connections will be provided at various junctions

wherever required. Other joints which are not required to be

dismantled during operation may be welded. Pipe line should be

gas/air tight to avoid any ingress of atmospheric Oxygen to the

circulating water media. Drawing is attached.

1 Set

9. Civil foundations and Steel structures:

All the pipelines, rigs, etc. shall be properly fixed/ mounted on a

stable and rigid steel structure. Necessary civil foundation shall also

be provided by the vendor? Where ever required.

1 set

10 Computer for data storage with latest specification of reputed make

(hp/Dell) with following broad specifications to be provided. The

computer should be equipped to acquire data from the test rig

(Dissolved Oxygen, Flow rate) for the test period.

Processor- Intel i7-2600 3rd generation or better

RAM 4 GB or more

Hard disk 1TB or more

LED display minimum 21”

And with required ports

The PC should be loaded with genuine Operating system (Windows

10 Professional)

2

4. Design Philosophy:

The equipment under consideration is for testing corrosion of samples in the environment of

marine water (3.5% Na solution with ~ 0 turbidity).

a. Test rig size will be kept of 2” NB for holding samples and 2” NB for placing various electrodes / potentiostat (3 types). Length of the rigs will be about 1m and the rigs will be replaceable type (i.e. with flanged end connections).

b. Flow rate in the sample test rig is required to provide flow speed at 1m/s. c. Both the rigs will generally be operated in series. Generally the flow will be from sample

rig to potentiostat rig side i.e. from 1.5” NB rig to 2’ NB rig. However provision need to be kept for operating them in parallel also.

d. The system will be leak proof to maintain dissolved O2 level below 20 ppb. Preferably all the joints/ components/ material in the rig equipment will be leak proof to avoid air ingress during the test. All flanged joints will be provided ‘O’ rings suitable for working in the marine water environment. Additional 50 nos. of such ‘O’ rings shall be supplied as an accessories.

e. In general, material of construction of components will be SS 316/316L/ PTFE corrosion resistant material for such application.

f. Water tank will preferably be cylindrical with dished ends (will depend on the pump shape and size). Exact size and shape will be decided after pump selection and keeping in view that the pump should be submersed minimum 6” at minimum working level condition and the tank should be able to accommodate all the water of the rig system.

g. System pressure should be slightly above the atmospheric pressure during the operation at all points in the system to avoid ingress of air into the system. However the system to be designed considering operating pressure is 1.5 bar.

h. 1 no. flow meter (magnetic type to measure the flow in the test rigs) and 1 no. dissolved O2 sensor will be provided in the system with digital display. One sensor may be provided as spare.

i. Level indicator (non contact type) will be provided with relays to control the system at High Level and Low Level.

j. Online data acquisition of dissolved O2 and flow rate through test rig is required. k. Venting points are to be provided at suitable location to avoid air/ argon lock in the

system. l. Proper drain points to be provided in the tank and in the line to flush all the water. m. In general all flow lines will be of 1.5” diameter. n. Provision to be kept for cleaning of the tank through manhole.

5. Working Philosophy: 5.1 The system will be evacuated to a level of 10-2 mbar. 5.2 Purging of Argon into the system to bring back the system to slightly higher than

atmospheric pressure. 5.3 Pouring of media water to the tank. 5.4 Killing of dissolve O2 by dosing the chemical to the water. 5.5 Switching On the pump, O2 level monitoring and activation of the flow through sample rigs

after attainment of required O2 level. 5.6 Operating the system little above the atmospheric pressure under argon atmosphere.

6. Vendor Scope of the work

Detail designing based on the scheme provided by the CSIR-NML and fabrication of CLCTR as

described above. The drawings are to be presented by the vendor at CSIR-NML which

subsequently shall be vetted by the CSIR-NML before fabrication of the CLCTR.

Supply, erection and commissioning of the CLCTR at CSIR-NML

Operating manual of each component along with the entire loop

Demonstration of parameters such as water flow rate uninterruptedly, achieving low and high

oxygen level

Online measurability of oxygen and electrochemical workstation

Pre despatch inspection at the sites of vendor by CSIR-NML.

One week operational training to CSIR-NML staff

Supply of all accessories/ consumables like O-ring, sealing, fastener and Teflon bush for

holding electrodes (50nos)

Warranty for three years on fabricated parts and one year on brought out parts. Vendor will

have to do minor modifications in the fabricated parts if required.

7. CSIR-NML Scope

To provide space along with the electric power points and water supply source as per the

requirement given by vendor at single point. The vendor has to get the system connected from

this point with the isolation switches/ valves.

Sectional

view of pipe

Eiectrod Gripper/

Coupen Holder Ring

Ring Spacer

at both the end

COUPEN

COUPEN

100.0

40.0

5.0

450.00 aprox

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2.5'

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Pipe-3 thk(aprox)

Teflon Replaceable

Electdrod Plug

Tightening Screw

Electrod

Electrod

Wire Ø3 mm aprox

Electdrod

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Platinum/Steel Disk

450.00

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