Subsea Control Module

Quick Links to Information Below

• Overview of the Subsea Control Module
• Mechanical Overview of the Subsea Control Module
• Electronics Overview of the Subsea Control Module
• Subsea Control Module Standard Functions/Features
• External Overview of the Subsea Control Module
• SEM Standard Functions
• ROV Control Module Tree Mounted Base
• ROV Control Module API 17H Mounting Base
• Subsea Diver Installable Control Module & Mounted Base
• Subsea Control Module on Test Stand
• Subsea Control Module Design Criteria

PDF Documents

• Subsea Control Systems
• Subsea Control Systems - Spanish Version

Overview of the Subsea Control Module

eP’s electro-hydraulic multiplex subsea control system is a modular design concept incorporating well proven technology and qualified components to minimize both CAPEX and OPEX costs.

An integrated system provides the requisite monitoring, control, and shutdown functions by means of multiplexed electro-hydraulic control, using communications on power between a surface master control station (MCS) and subsea control module (SCM) via a composite services umbilical and appropriate subsea distribution unit(s).

Communications between surface and subsea are by means of a ‘Lonworks’ power line carrier. Communications can be adapted to suit comms on power, twisted pair, or fiber optic dependent on configuration.

The system is designed for deployment and intervention by means of a remotely operated vehicle (ROV), assisted guideline and guidelineless running tool, available for rental with ROV assistance in very deep water, featuring a simple sliding plate design locking down mechanism; however a similar module is used for diver installation.

The subsea electronics module (SEM) is surface removable and replaceable without the need to disturb the module’s hydraulics chamber.

Electric and hydraulic connections are made using low-force connectors mounted on the base of the unit, which connect when the unit is locked into place.

Mechanical Overview of the Subsea Control Module

The SCM housing will be filled with dielectric fluid prior to installation and is pressure compensated to safeguard against over or under pressurization.

The SCM housing is fabricated from structural steel manufactured to BS EN 10 025 Grade Fe430C or Fe510 D1/D2 and finish painted to our standard subsea paint specification. All hydraulic and electric couplings are manufactured out of a minimum of 316 stainless steel or better.

The hydraulic system consists of self latching solenoid operated shear seal directional control valves mounted on a stainless steel block manifold, with single or dual hydraulic supplies dependent on client’s specifications. Electrically held-open valves can also be mounted in this unit for emergency shutdown (ESD) system functionality if required.

Individual high pressure (HP) and low pressure (LP) hydraulic supply filters are mounted within the control module maintaining fluid cleanliness specifications.

Both hydraulic supplies have pressure transducers to indicate system pressure within the control module.

The tree valve hydraulic actuator “inferred status” is sensed by individual pressure transducers, integral to the directional control valves, which relay the function line pressures to topside, where they may be displayed on the master control station (MCS) screen and made available to the distributed control system (DCS)/platform control system.

An accumulator can be accommodated within the control module to help prevent pressure drop during valve operations on large step outs, alternatively separate subsea accumulator modules can be provided to maintain local pressure levels.

Electronics Overview of the Subsea Control Module

The subsea electronics are enclosed in a 1-atmosphere dry nitrogen purged housing located within the main SCM housing, with proprietary penetrators allowing connection to the SCM. Within the SEM housing ambient temperature and pressure are continually monitored, and an alarm may be sent to the MCS should abnormal conditions arise.

The SCM incorporates dual 230-Vac @ 50 Hz power supplies and uses a super-imposed high frequency carrier on each power line, using the Lonworks network communications protocol, enabling control and monitoring via either or both power/comm lines.

The SEM will operate using twisted pair communication line and separate power supply or power line carrier as described earlier, the latter will reduce umbilical costs and also provides performance benefits.

The subsea electronic control and communication system is based around the neuron 3150 processor chip, with the surface being PC/PLC based. Responses from the surface or subsea units are propagated back to the PCS via a Modbus® compliant serial channel from the MCS. The SEM also runs diagnostics showing the state of all power supplies and communications. Bad communications are detected and rejected to prevent incorrect data causing unpredictable actions.

Diagnostic tools and displays are available to the operators via the topside MCS.

Subsea Control Module Standard Functions/Features

• Four HP hydraulic outputs
• Twenty-two LP hydraulic outputs
• Dual HP hydraulic inputs via shuttle valve
• Dual LP hydraulic inputs via shuttle valve
• HP ESD valve
• LP ESD valve
• Directly mounted digital control valves to single manifold block
• HP and LP vents to sea or closed loop returns

External Overview of the Subsea Control Module

• Carbon steel fabricated housing, painted to standard subsea paint specification
• Installation and intervention by ROV assisted running tool or diver onto mounting base
• Dielectric fluid filled pressure compensated housing and atmospheric SEM housing
• Designed for use up to 3000-m of water
• 1.5-atmosphere nitrogen filled electronics housing with pressure and temperature monitoring
• Dual HP and LP supplies, incorporating individual hydraulic supply line filters with B3 = 200 rated elements
• Control of hydraulic valve actuators by stainless steel body, sheer seal type solenoid valves
• Earth strap for bonding and low resistance connection to the module mounting base on the manifold cathodic protection system
• Connection points legibly identified by proprietary laminated nameplates
• Stand alone sacrificial anodes for cathodic protection will be provided based on isolation for six months on the seabed
• Two outgoing electro-hydraulic ROV/diver stabplates both mounted on SCM mounting base

SEM Standard Functions

• Standard unit has single SEM (dule SEM optional)
• Fully dual redundant power supplies
• Housekeeping functions
• SEM internal pressure
• SEM internal tempreature

ROV Installable Subsea Control Module on Tree Mounted Base

ROV Deployable Subsea Control Module on API 17H Mounting Base

Subsea Diver Installable Control Module & Mounted Base

Subsea Control Module on Test Stand

The test stand (shown without enclosure panels) is designed for onshore/offshore testing and commissioning or for use on vessel prior to deployment of the SCM. The stand is a fully integrated unit consisting of hydraulic power unit, pumps, filters, tree valve actuator simulators, and self contained controls computer panel.

Subsea Control Module Design Criteria