Pengenalan Sistem Elektrik Rev (2)

8/11/2019 Pengenalan Sistem Elektrik Rev (2)

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Pengenalan Sistem Elektrik,

Instalasi dan Hazardous Areapada MODU (Mobile OffshoreDrilling Unit)

Oleh:

Pandhu A. Lakshana

Materi Tambahan untuk Kelas COGII IKBAL M. YOS Batam

Dengan Menggunakan Rujukan ABS RulesUntuk MODU


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Turbine Generator


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Main Switchboard - HV


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LV Switchboard


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HV and LV Switchboards


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HV and LV SwitchboardsA High Voltage Electrical system is defined as a system havingnominal voltage (phase to phase) exceeding 1 kV, but not to

exceed 15 kV. Onshore electrical classifications would considerthis as Medium Voltage

The selection of a high voltage system for ship service dependsfrom several factors and is in particular dictated by the required

generator outputs.

In general:

Low voltage system is suitable when the nominal output of eachgenerator is below 8000 kWHigh voltage system is suitable when the nominal output of eachgenerator is over 10000 kWBoth systems are suitable when the nominal output of each generator

is between 8000 and 10000 kW


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SAFETY FEATURE IN HV

SYSTEMHV switchgear & control-gear assemblies

Item LV Switchgear HV Switchgear

IP Degree forControl Room

IP22 IP32

Circuit Breaker orDisconnecting

Switch

Plug-in type isallowable

(Non-Withdrawable)

To be Withdrawable

MechanicalLocking Facility Not Applicable Applicable

Shutter forCircuit Breaker

Not Applicable Applicable

Comparison between LV and HV switchgear:


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SAFETY FEATURE IN HV

SYSTEMHV switchgear & control-gear assemblies (Contd

Comparison between LV and HV switchgear:Item LV Switchgear HV Switchgear

Earthing andShort Circuiting

FacilityNot Applicable Applicable

Earth FaultDetection

Not Applicable Applicable


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(a) Runs of cables:

Not to run through accommodation space

(b) Segregation of cables:

Segregation of HV cables operating at different voltageratings each other

Not to install HV cables inthesame cable tray for LV cables

SAFETY FEATURE IN HV SYSTEM

HV Cable installation

(c) Marking of cables:

Marking for Identification


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Single Line Diagram


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Single Line DiagramQuestions

- What is the difference between a Bus transfer feederand a Bus tie?

- Bus transfer feeder has 2 circuit breakers

connected and both switchboards are physicallysegregated by fire proof wall or partition

Bus transfer feeder connects 2 switchboardsseparated by Fire-proof wall / partition

Bus tie exists in the same cubical/ room


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Single Line Diagram

1. Only G1 CB trip

2. TB will trip, followed by G1 CB

3. Only CB of feeder will trip4. TB will trip, followed by G2 CB


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Single Line Diagram


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Single Line Diagram


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Single Line Diagram


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Single Line Diagram 3 split


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Single Line Diagram


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Single Line DiagramDiscussion

- How many thruster will be lost if Main SWBD 1 fails ?- Only one thruster

- If the SWBD 1 and SWBD 2 run in single bus andassuming no protection scheme on the SWBD, then a

short circuit is occurred on the bus, how manythrusters will be lost ?

- Three thrusters


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Single Line Diagram


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- From where the Switchboard HS1 is getting the supply ?

- Main Generator 1 and Main Generator 2

- Do the both GS on each Main Switchboard (HS1, HS2, HS3)required to run together ?

- No, bus tie feeders between switchboards can be closed to

make synchronization between generators and share theload

- What is the bus bar rating for Main Switchboard ?

- 11KV, 2000A, 60Hz, 31.5KA, 1 sec

- Compare to the incomer breaker, which one is bigger ? Why ?- Incomer breaker 1250A, bus bar rating is bigger. If there is aovercurrent exceeds the breaker rating, it is still safe for thebus bar because the nominal current rating is bigger than itsincomer


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- From Where Emergency Switchboard is getting the main supply?

- From Bus A and Bus C 690V Switchgears

- If the Main Switchboard HS1 is lost, can the vessel still perform

drilling operation ?- Yes, because drilling switchgears have three (3) independent

bus sections with NORMALLY OPEN breaker between thesections and each having supply from each 11KV MainSwitchgear sections via transformer feeders

- If there is a fire on Main Switchboard Room HS2. What will behappen on other SWBD (HS1 and HS3) ?

- Not affected. A60 partition bulkhead between switchgears areavailable and bus tie feeders between switchgears are

NORMALLY OPEN during normal operation


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- If all Main switchboard run in 4 splits mode, andSWBD MV2 is lost. Can the vessel perform drillingusing No.1 Drilling Drive Switchboard ?

- Can, interlock mechanism on the No.1 drilling drive

switchboard incoming breaker will be opened andclosed the breaker on No.2 drilling driveswitchboard. At the same time bus tie feederbetween the switchboards are closed

- If the Main Distribution & MCC LV3 is lost due to shortcircuit on the bus bar, can the operator operate theDrilling MCC2 ?

- No


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Hazardous Areas

Zone 0 in which an explosive air mixture iscontinuously present or present for long periods.

Zone 1 in which an explosive air mixture is likely tooccur in normal operation.

Zone 2 in which an explosive air mixture is not likelyto occur in normal operation and if occurs will existonly for a short period.

Non.HA none of the above.


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Hazardous Areas Enclosed Areas -a space bounded by decks

and bulkheads which may or may not havedoors, windows or other similar openings.

Semi Enclosed Locations - a location where adispersion of gas may not occur due to thepresence of structure.

Open Areas


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Hazardous AreasHazardous Areas Zone 0 Include: i) The internal spaces of closed tanks and pipes of the mud circulating system between the

welland the final degassing discharge, e.g., escape gas outlets,

ii) The internal spaces of closed pipes and tanks for oil and gas products, iii) Other spaces in which an oil-gas mixture is present, continuously or for long periods.

Hazardous Areas Zone 1 Include: i) Enclosed spaces containing any part of the mud circulating system that has an opening

into the spaces and is between the well and the final degassing discharge.

ii) Outdoor or semi-enclosed locations within 1.5 m (5 ft.) from the following: openings toequipment which is part of the mud system); any ventilation outlets from Zone 1 spaces;and any access to Zone 1 spaces.

iii) Pits, ducts or similar structures in locations which otherwise would be Zone 2 but whichare arranged so the dispersion of gas may not occur.

iv) Enclosed spaces or semi-enclosed locations that are below the drill floor and contain apossible source of release of gas such as the top of a drilling nipple.

v) Enclosed spaces that are on the drill floor and which are not separated by a solid floorfrom the spaces


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Hazardous Areas Zone 2 Include: i) Enclosed spaces which contain open sections of the mud circulating system from the

final degassing discharge to the mud pump suction connection at the mud pit.

ii) Outdoors locations within the boundaries of the drilling derrick up to a height of 3 m (10ft.) above the drill floor

iii) To the extent of their enclosure, semi-enclosed locations that are on the drill floor andwhich are not separated by a solid floor from the spaces).

iv) Semi-enclosed derricks to the extent of their enclosures above the drill floor or to aheight of 3 m (10 ft.) above the drill floor, whichever is greater.

v) Semi-enclosed locations below and contiguous with the drill floor and to the boundaries

of the derrick or to the extent of any enclosure which is liable to trap gases. vi) Outdoor locations below the drill floor and within a radius of 3 m (10 ft.) from a possible

source of release gas such as the top of a drilling nipple.

vii) The areas 1.5 m (5 ft.) beyond the Zone 1 areas specified in 4-1-3/3.3ii) and beyond thesemienclosed locations specified in 4-1-3/3.3iv).

viii) Outdoor locations within 1.5 m (5 ft.) of the boundaries of any ventilation outlet fromZone 2 spaces, or any access to Zone 2 spaces, except where 4-1-3/5.3 applies.

ix) (1995) Air lock spaces between Zone 1 and nonhazardous space, in accordance with 4-1-3/5.5i).

Paint Store is considered Hazardous Area

Hazardous Areas


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Hazardous AreasTypical equipment in Zone 0 and 1 Explosion proof: the enclosure withstands and explosion

inside and prevents propagation. Intrinsically safe ia & ib: an intrinsically safe barrier is

installed in a safe area to avoid sparks by limiting theenergy to the circuit in the hazardous area.


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Hazardous Areas Two Different Standards:

International Electrotechnical Commission

(IEC Series 79): Zone 0, 1, 2 National Electric Code (NEC Art 500):

Class I Div1, Div 2


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Class I Div 1: locations in which ignitable

concentration of flammable gas or vapors mayexit under normal operating conditions or suchconcentrations may exits frequently due torepairs, maintenance or leakage.

Class I Div 2: locations in which ignitableconcentration of flammable gas or vapors would

occur only as result of accident or breakdown ofsystems, or in which concentrations are normallyprevented by mechanical or natural ventilation.

Hazardous Areas

H d A


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Surveyor/ Inspector:

Equipment nameplate shows suitability foruse in hazardous area.

Hazardous Areas

What spaces are classified as

HAZARDOUS AREAS in a MODU? ForABS Rule

Drill Floor

Shale Shaker, Degasser, Desander, Desilter

Mud Tanks or Mud Pits


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Hazardous Areas What to look for in a nameplate on

equipment installed in hazardous area The Testing Labs name: CSA, UL or others

The Certificate No.

The Hazardous Area Marking


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Hazardous Areas .

Cert No.Testing Labs Name

Hazardous

Area

Marking


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Hazardous AreasWhats wrong with this nameplate?


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Hazardous Areas Nameplate IEC


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Hazardous Areas

However:

Zone 2 equipment Class I Div 2

Zone 1 equipment Zone 0 equipment Class I Div 1

There is NO equivalency between

Zone and Division!!!


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Hazardous Areas If an enclosure or room installed in hazardousareas, but equipment inside not been certified and

the box itself is not explosion-proof.

Purged Pressurized System.

positive pressure in relation to the surroundedatmosphere. (NPA 496 or IEC 79-2).e.g: drillersconsole.

Solution


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Hazardous Areas Ventilation is Hazardous Areas Ventilation inlets and outlets - Ventilation inlets be located in

nonhazardous areas. and completely separate from that for

nonhazardous areas. More critical less pressure flow from less to more

Number of air changes required for enclosed mud pits - Every twominutes.

Ducts passing though hazardous zones - Under pressure in to lesshazardous areas and at overpressure to more hazardous areas are to be rigidly constructed to avoid air leaks. Ventilation of non Harzardous zones - to be located in nonhazardous

area and overpressure in relation to the hazardous area.

Self closing doors are required between nonhazardous and hazardouszones


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Hazardous Areas


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Hazardous Areas


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Hazardous Areas


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Hazardous Areas Boilers and engines

Exhaust outlets outside the Hazardous area andfitted with non sparking devices

Air intakes at least 03 meters form Hazardousareas

Can not be installed in Zone 0

Can be installed in Zone 1 and 2 under specialconsideration


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Hazardous Areas All jacking or other elevating systems are to be

constructed and installed in accordance with

approved plans.

Jacking Trial - the completed hull up to the

limit of designed travel and then down again

Instrumentation - the controls for elevatingoperations.


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Hazardous AreasSpecial Considerations.

Electrical equipment in exterior locations andoperable after total shutdown needCERTIFICATION (at least Class I Div 2)

although may not be installed in a hazardousareas.

Rational: after a blow out, gas may present

throughout the platform, and the equipmentoperable is to be safe with presence of gas.


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Special Considerations

Brushless motors (and other similar

equipment) can be installed in Class I Div2(NEC 501.8B) with no hazardous areacertification, i.e. squirrel cage motors.

Requirement: Nameplate is to show the max surface T

(C) for the space heater. The exposed surface of thespace heater is not to be above 80 % of the ignition T(C) of the gas involved

Hazardous Areas


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Hazardous Area Case Study I In the drawing the area below the Drillfloor is

shown as totally enclosed with hazardousarea defined as Zone 2.


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Hazardous Area Case Study I As per ABS rules: Zone 1: Enclosed spaces or

semi-enclosed locations that are below thedrillfloor and contain possible source of releaseof gas such as the top of a drilling nipple.(Assumption - not adequately ventilated)

As per ABS rules : Zone 2: Semi-enclosedlocations below the drillfloor which are liable totrap gases. (Assumption not adequatelyventilated)

Hazardous Area Case Study I


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y



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Adequately Ventilated ?

Why ?

y



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API 505 6.6.2.4.7 partially enclosed area

are considered adequately ventilated:a)a building or area having a roof or ceiling withwalls comprising 50% or less vertical wall area

than the total wall area possible is consideredto be adequately ventilated (regardless of thetype of floor).

b)A building or area is considered to beadequately ventilated provided it has neither afloor (for example, the floor is grating) nor a

roof or ceiling.

y

Hazardous Area Case Study II


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Drillers Cabin modification:

Previously it was a shelter with the controls.

The client has added walls and roof to theshelter, including A/C system and ergonomiccontrols.

The new drillers cabin has been rated as

non-hazardous location.

The floor has some cables penetrations.



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What do we have to check?



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Acceptable ?



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What do we have to check?

Driller's Cabin Door Opening From Non-hazardous Location Towards aHazardous Location

1) The Driller's Cabin will be pressurized in accordance to NFPA 496(Chapter 5) or equivalent standard so that the interior of the Driller'sCabin is a non-hazardous location. NFPA 496 (Chapter 5.4) requiresthat the pressurization system is capable of maintaining a positivepressure of 25 Pa (0.1 in. water) with all openings closed and tomaintain a minimum outward air velocity of 60fpm (0.305m/sec) when

all openings are open. An alarm is to be fitted for low pressure in thecabin.

2) It is to be demonstrated that the door remains gas tight afterclosing on its own.

3) For units where ABS is issuing the MODU Code certificate thegovernment administration agreement is required.

Hazardous Area Case Study III


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Enclosed spaces containing any part of the mudcirculating system are considered Hazardous areas asper ABS MODU Rules.

However Mud laboratories on mobile offshore drilling rigsare not considered Hazardous spaces.

Why ?

Mud laboratories



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Drilling Mud System


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Why ?

1) The mud laboratory has no direct piping connection to the mudcirculating system.

2) A mechanical ventilation system providing at least six (6) air changesper hour is provided to the mud laboratory.

3) Mud samples taken for analysis are to be taken after the muddegassing process.

4) Mud samples are not to be stored in the mud laboratory.

5) Proper precautions (e.g., warning notice) are to be taken to insure thatthe ventilation system of the mud lab is always on when mud sampleanalysis is underway.

Exercise


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Electrical Installations LARGE: battery charger above 2Kw. Battery room:

The room is to have natural or mechanicalventilation, capable of changing the airevery 2 min or alternatively, to maintain the

gas level below the lower explosive limit(LEL).

Exhaust vent at the top of the room, and

the inlet vents near the floor.Trays for batteries are to be chocked withwood strips and each tray is to be fittedwith nonabsorbent insulating supports

HAZARDOUSAREA OR NOT

HAZADOUSAREA ?

It is classifiedas HAZARDOUS

AREA


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Special attention to UPS installed in

Air Conditioned Control Room. UPS must be certified for use in a control

room.

Hydrogen emission can add to beconsidered Hazardous Area.

Electrical Installations


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Electrical InstallationsSwitchboard Are to be located in a dry place so as to provide a clear working

space at the front of the switchboard and a clearance at the

rear

Safety-type Panels Dead front type panels are to be used where voltage to earth is

in excess of 50 volts DC / 50 volts AC Disconnecting Arrangements The disconnecting device is to be externally operated. If the disconnecting device is not within sight of both motor

and controller, or if it is consider far (based on class/regulation) from either, it is to be arranged for locking in theopen position.


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Electrical Installations Receptacles and Plugs of Different Ratings

Receptacles and plugs of different electricalratings are not to be interchangeable so 110

V can not fit 230 V


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Electrical InstallationsArmored cable: (zone 1).Bronze, tinned copper or aluminum braid,sometimes between the inner jacket and the outer sheath.

Rational: Protection against mechanical and physical damage.

Armored Cable

Armor

Sheath


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Armored cable must be grounded at each end.


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Armored cable must be grounded at each end.

Question : If the armored cable is notgrounded at each end, so what ???



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What happens if the armor is damaged?


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Need to be replaced ?

Why ?

How about if it installed in Hazardous Area ?



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Deck and Bulkhead Penetrations

Where cables pass through watertight, firetight or smoke-tightbulkheads or decks, the penetrations are to be made through the

use of approved stuffing tubes, transit devices or pourablematerials which will maintain the watertight, firetight or smoke-tight integrity of the bulkheads or decks

When cables pass through non-watertight bulkheads where thebearing surface is less than 6.4 mm (0.25 in.), the holes are to befitted with bushings having rounded edges and a bearing surfacefor the cable of at least 6.4 mm(0.25 in.) in length.

Where cables pass through deck beams or similar structural partscare is to be taken to eliminate sharp edges.

Where cable conduit pipe or equivalent is carried through decks orbulkheads, arrangements are to be made to maintain the integrityof the water or gas tightness of the structure.

Cables are not to pass through a collision bulkhead.



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High Voltage Cable Installation

In accommodation in enclosed transit system

Continuous (grounded) metal sheath or armour orcasing

Not to be in the same cable bunch, duct, pipe or boxas LV circuits

Separate junction boxes are to be used for each ofthe rated voltage levels exceeding 1 kV.

Same cable tray ok for different HV cables; but

observe clearance distances for the higher one



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Apply DC voltage:1.6(2.5Uo +2kV) for cables 1kV < Uo =3.6kV

For 15 minutes Dont forget to discharge the cable

Repeat insulation resistant test

Alternatively a full voltage test for 24 hours couldbe accepted if advised by cable manufacturer

Test After Installation and after insulation resistanttesting



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Operation After Shutdown

The following services are to be operable after an emergency shutdown:

Emergency lighting for half an hour

General alarm

Blow-out preventer control system

Public address system

Distress and safety radiocommunications

Note - Exterior locations - Zone 2 .

Fire Detection


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Early detection of fire is essential if fire damage is to be minimized

Fires may be detected by personnel observation or by automaticdevices

Where does ABS require fire detectors in a MODU?

Unmanned Machinery Space

Service Spaces Accommodation Spaces Smoke Detectors

Flame detectors

are to be used inaddition of otherfire detectors.

Flame detectors even

though are fast detectors,

they may give false alarms.

Rational

Gas Detection


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Gas indication panels areto be located at the drill floor

and control room.

Audible & visual alarm Location & concentration of gas

Where does ABS require GAS detectors in a MODU?

Cellar Deck

Drill Floor

Mud Pit Area

Shale Shaker Area

Other enclosed spaces containing open componentsof the mud circulation system

Gas Detectors in Production

F iliti


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FacilitiesFacilities Guide

Gas Detectors to be provided at fresh air inlets tonon-classified areas

Gas detectors is not required but recommended in

process areas Facility shutdown is required at high gas detection

If no gas detectors in- the process area, the

shutdown will be based on the gas detection atfresh air inlets


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Fire Detection Case Study


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Questions

Pengenalan Sistem Elektrik Rev (2)

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