Post on 21-Mar-2018
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
4
5
°
2.5'
Ø
1
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1.5'N
B
Flange 6thk
30.0
10.0
10.0
1
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5
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1
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Pipe-3 thk(aprox)
Teflon Replaceable
Electdrod Plug
Tightening Screw
Electrod
Electrod
Wire Ø3 mm aprox
Electdrod
Port
Platinum/Steel Disk
450.00
1.5
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50.00
50.00
4
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