1.0 Scope

This specification defines the minimum requirements to cover the procurement of an electro hydraulic installation and workover control system (IWOCS) that should be used to install and function the subsea tree.

2.0 General Requirements

2.1 Main Installation/Workover Functions

The IWOCS should provide for the control of all installation and major workover operations including running and retrieving the subsea tree.

2.2 Functions

IWOCS functions should facilitate running of the subsea tree and operation and troubleshooting of the subsea control pod.  The IWOCS umbilical should have a minimum of two spare control hoses and wire pairs capable of serving the highest expected service pressure and electrical requirement of the system.  The IWOCS umbilical should also have three (3) chemical injection hoses with specifications the same as the production control line jumpers.

2.3 System Pressure Ratings

Well Flow Stream Components

All components in contact with well bore and annulus fluids should be rated to a working pressure of 5000 psi.

Hydraulic Components

All hydraulic components in the control system, except where higher pressure rating is specified, should be rated to 3000 psi working pressure.


All subsea components should be designed to operate at a water depth of 4,500 feet subsea.

2.4 Tubing and Connection Numbering System

A consistent numbering system should be used throughout the entire control system.  It will apply to the tree valves, production control system, installation/workover control system and all interface connections.  This system should apply to all hydraulic and pneumatic tubing and connections.  Control system and tree hardware suppliers should work with Buyer to develop a consistent scheme prior to the start of detailed design.

2.5 Subsea Component Requirements

Subsea components of the installation/workover control system should be designed for long term reliability, easy maintenance, and to be serviceable for a 25 year life.  All subsea components should be fabricated of stainless steel or material resistant to corrosion by seawater and salt laden offshore atmosphere.

2.6 Surface Component Requirements

Surface equipment should be designed for easy maintenance with adequate access to all frequently replaced parts such as filter elements, lubricators, regulators, drains, motors, pumps and instruments.  All components should be fabricated with suitable material for harsh offshore environment.  Aluminum, if used, should be copper free.  All fasteners should be stainless steel.  All electrical equipment and interconnections should be suitable for operation in a Class 1, Division II, Group D hazardous area.

2.7 Tubing and Fittings

All hydraulic tubing in the workover/utility system should be made of a stainless steel alloy suitable for extended exposure to sea water and moist salt laden air encountered in offshore operations.  Specific requirements for tubing and hose fittings are:

  • All hydraulic fittings should be stainless steel.
  • All hydraulic tube fittings should be stainless steel flareless type.
  • All hydraulic hose fittings should be stainless steel JIC 37° type.

2.8 System Cleanliness

All hydraulic circuits of surface and subsea deliverable equipment, including test equipment, should be flushed and cleaned with appropriate hydraulic fluid to NAS 1638, January 1968, Class 6 specification, prior to system integration testing and packing for shipment.

2.9 Control Fluid

Marston Bentley Oceanic HW525 (or equal) should be used as control fluid.  This fluid should be used during all testing, flushing, and commissioning of the system.


3.1 General

The IWOCS should provide a stand-alone capability to monitor and control the subsea and surface equipment.  It should provide, where practical, automatic safety related sequenced shutdowns, regardless of the operator control point.

The IWOCS should be based on proven industry standard PC hardware architecture.  The IWOCS for the Subject Field should be configured as a single PC controlled system with a VDU and keyboard/mouse. Power to the IWOCS should be provided from an uninterruptible power supply (UPS) capable of operating the subsea control pods and IWOCS in the event of host facility power loss.  This unit should operate continuously on line and provide bumpless transfer of power.  The system should be robust enough to stay operable in offshore rig environments with a high level of reliability. The main functions of the IWOCS should be as follows:

  • Generate digital commands in response to operator inputs and transmit them to the subsea equipment via the IWOC umbilical.
  • Interpret digital signals received from the subsea equipment via the IWOCS control umbilical and present the information to the operator.
  • System logic and programming for ESD scenarios will be developed jointly by Buyer and Supplier.
  • Execute certain pre-programmed control and/or monitoring sequences in response to operator inputs.
  • The system should continuously monitor the tree gauges, the downhole gauges, and the internal subsea control pod monitoring points.  The system should notify the operator of any out of limit values.
  • Display the status of all tree and pod functions including valves, gauges, pressure transducers and sensors.
  • Display the status of all alarms (i.e., display the status of monitored parameters that are outside their normal range and that the operator has acknowledged them).
  • Record activities and events, and produce hard copy data as directed.
  • Interface with the portable electronic test equipment for testing and diagnostic purposes.
  • Display the following as a minimum:
    • Alarm list
    • Sequences list
    • Project specific report call-up
    • Pressure profile trends
    • Fast trends (live data)
    • Data base tag browser (search facilities)

3.2 Hardware Configuration

The IWOCS configuration should be easily maintainable and upgradable.  HPU pressure gauges, regulators, and control valves required for operation of the system should be mounted on a panel in the IWOCS room.  A standard Microsoft Windows compatible color desktop or laptop computer should be used to control the system.

A freestanding printer should be provided to produce hard copy of alarms, events, logs, and VDU screen displays.  The printer should have as a minimum the following basic specification:

  • Type                      Laser or Buyer approved alternative
  • Page Style           Individual page with automatic feed
  • Interface             Serial RS-232
  • Page width         8-1/2” x 11” or 14” (Letter or A4) paper

3.3 Uninterruptible Power Supply (UPS)

The UPS should provide conditioned power to the system.  Non-gassing battery power should be used as required to maintain the power supply within the IWOCS power input specification.  It should also provide back-up power to the subsea control pods and installation / workover for a minimum of 40 minutes normal system operation.  The UPS should be mounted in the installation / workover control room.

3.4 ESD Protocol

Emergency Shut-In

The system should respond to a RIG ESD by closing valves in an ordered sequence.  Closing sequences should be defined during detailed system design.  Buyer should approve the ESD protocol.

4.0 HPU Assembly

4.1 General

A skid mounted installation / workover control unit assembly with integral control station and hydraulic power system should be provided.

Construction and Painting

The skid should be constructed of steel and coated per manufacturer's in-house coating system, subject to approval by Buyer QA/QC or Corrosion engineer.  All non-stainless steel surfaces including bottom of the skid and inside of enclosures should be coated.


Provision for 4-point lift with appropriate pad eyes on the top of the skid should be provided per API 17D.  The unit should be pre-slung with certified and tagged slings.


Provisions to protect all mechanical parts, panels and function handles from damages during shipping and handling should be provided.

4.2 Hydraulic Power Control Panel

The hydraulic power control panel should provide control and indication of status of the hydraulic power system.  Design features of the panel should be as follows:

  • Gauges should be provided for regulated pressures of the main and SCSSV supply circuit.  Individual gauges should be mounted on each accumulator.
  • Hydraulic regulators should be panel mounted.
  • Level indication for the fluid reservoir should be provided on the panel.

4.3 Utilities and Services

Provision for the following utilities/services hookups should be made:

  • Air:  100 PSI min. air supply will be provided to the skid from the rig air system.
  • Power:  240 VAC, 1 Ph, 60 Hz.

4.4 Hydraulic Power System

The hydraulic power system should provide regulated 1500-PSI fluid for tree control functions and a maximum pressure of 3,000 psi.  The hydraulic power system should provide regulated 7500-PSI fluid for the SCSSV.  Construction features of the hydraulic power system should be as follows:

  • Fluid Reservoir - The hydraulic fluid reservoir should have a single fluid compartment.  The reservoir should be constructed of stainless steel including all covers, fittings, fluid inlets and outlets, flanges, breather and cap, nuts and bolts.  All screws should have drilled and tapped holes when used on the reservoir tank - no nuts should be used unless they are welded in place.
    • Manhole(s) with covers should be provided on top of the reservoir, large enough to facilitate proper clean-out of the interior.  Bottom of the reservoir should be sloped to one corner with a valve drain installed on the bottom at that corner.  The reservoir may be raised from the floor of the HPU to accommodate this.
    • A level sight glass with drain and clean-out provision should be provided.  Each sight glass should be adequately protected against breakage.  A sampling valve should be provided for the fluid in the reservoir.
  • Piping Materials - All air and fluid pipe and tubing should be stainless steel.  All outlet bulkhead fittings for connection to control lines should be stainless steel.
  • Hydraulic Pumps - Four (4) air powered hydraulic pumps should be provided; one high pressure, one low pressure, one high-pressure back up and one low-pressure back up.  Air pumps should be sized to provide optimum accumulator recharge time consistent with tree function fluid demands.  Pumps should be capable of pressuring the system from ambient to full rated working pressure in 10 minutes or less.  Each pump should be equipped with a check valve and isolation valve that would facilitate maintenance and change out of pumps without bleeding down the system.
  • Accumulators - Accumulator banks should be provided for the 1500-PSI and 7500-PSI circuits.  The number and size of accumulators should be selected to provide two complete operations of all tree functions (from full charge) with all pumps inoperable.  Each accumulator should have an isolation valve to enable the removal of an accumulator for service without de-pressurizing the hydraulic power system fluid supply circuits.
  • Filters - Filters should be provided in all air and hydraulic fluid circuits.  Hydraulic fluid filters should be provided at inlets to the hydraulic pumps and upstream of all hydraulic regulators.  The size of filter elements should be selected such that hydraulic fluid will meet the NAS 1638 class 6 cleanliness requirements.
  • Pressure Gauges - Pressure gauges provided in the HPU should be solid front, liquid filled safety gauges.  Normal operating range should be between 1/2 to 2/3 of full scale of the gauges.  Pressure gauges should be provided for but not limited to:
    • suction and discharge of all hydraulic pumps
    • accumulator manifolds
    • all pressure switch and transmitter connection points
    • upstream and downstream of all regulators
    • upstream and downstream of all filters
    • regulated pressure for main and SCSSV supplies
    • air supply pressure
  • Name Tags - All gauges and regulators should be labeled with appropriate engraved nametags.  Names will be consistent with functions on the production control system.  Where tags are used, they should be held in place with stainless steel screws or stainless steel wire.
  • Flow Meters - Flow meters with bypass and block and bleed valves should be provided for the tree control function supply circuit.  The meters should be sized to provide accurate readings for the minimum and maximum anticipated flow.  Total flow rate with reset should be displayed on the tree control panel.
  • Relief Valves - Relief valves should be provided with capacity to relieve the full pumping rate of the pump(s) in the circuit.  Pressure relief valves should be installed between the pumps and first isolation valve on the discharge line to prevent accidental pressuring to the pump discharge side.  Relief valves should be set to release at no greater than 110% of the system operating pressure.
  • Utility Hydraulic Output - An extra valved outlet should be provided for the 1500-PSI regulated supply.  A 1/2" JIC 37° male connector with cap should be used.
  • Valved Outlets - Two valved outlets, one up to 7,500 psi should be provided to allow connections for charting and testing the tree, SCSSV lines, operate the hydraulic wellhead connector and tubing hanger and running tools.  The system should incorporate maximum flexibility for testing and commissioning work and utilize, as far as practical, industry accepted standard equipment such as fittings, gauges, pumps and motors.

5.0 Bundle Assemblies

5.1 Connection Plate Assemblies

Supplier should supply all surface connection plate assemblies.  The connection plates should be fabricated of carbon steel with an epoxy finish.

Connector Guidance and Makeup

Guide pins should be designed and asymmetrically placed to prevent misconnection of hoses.  The guide pins should be designed to engage the mating plate before hydraulic connectors are mated and to carry the weight of the connection plate.  Final make-up may be affected using over-center latches or bolts.

Long Over - Travel Hydraulic Connectors

Long over - travel hydraulic connectors should be used to ensure all connectors are mated properly.  Connector design should ensure that any shut-off poppets are fully open on both connector halves following make-up.  National coupler design should be used unless otherwise approved by Buyer.

5.2 Control Bundles


The installation/workover hose bundle should be designed for the appropriate water depth with an overall protective thermoplastic jacket, designed and manufactured in accordance with API Specification 17E.  Armoring should be considered only if the water depth necessitates the requirement.

Installation/Workover Umbilical Hoses

The installation/workover umbilical hose bundle should be made up with the necessary individual hose and wire sizes and design pressures to facilitate installation and testing of the tree.  The utility umbilical should have a minimum of two spare hydraulic lines and electrical cores capable of serving the highest expected service pressure or electrical requirements of the system.  This requirement should be consistent with the tree design.

Hydraulic Connections

Individual hose connectors should be 316 stainless steel, 37° JIC rated at 3000 PSI.

Electrical Connections

Electrical connections if any will be of robust design for offshore environments and the subsea connection should be wet-mateable and designed for installation by a work class ROV.  Surface connections will be enclosed in weatherproof fixtures meeting the appropriate electrical codes. 


The subsea end of the installation/workover umbilical will be terminated with a connection plate with hydraulic and / or electric connectors for hook-up to the appropriate interface on the subsea tree or control system.

A means to terminate the umbilical into ROV deployable and connectable end fitting(s) is required using API Specification 17D or 17H  ROV interfaces.  The umbilical termination will be adaptable for deployment on a downline and pipe as specified by Buyer.

The umbilical termination will be designed to be deployed through a moonpool on Buyer specified pipe and wire and have interfaces to mount on a Buyer specified BOP/LMRP or be freestanding on the sea bed with field installable parts.

The subsea umbilical electrical termination should be field serviceable and replaceable and be of similar design to the connection at the subsea equipment.  As much as possible, the design should be of a nature to minimize the number of spare parts required to maintain in inventory.

There will be provisions in the umbilical termination to allow for disconnect of the marine riser package from the BOP without damaging the umbilical terminations.  As much as possible this disconnect should take place automatically without extra operations required at the surface prior to unlatching the marine riser package.

ROV interfaces must be robust and self-aligning such that, as much as possible, the particular ROV operators skill is negated.  The goal is to minimize installation time and reduce wear and tear concerns on the equipment.

Supplier will work with Buyer to verify installation requirements and ensure the umbilical termination design meets the requirements of the installation vessel and auxiliary equipment as described in this specification.

Strain Reliefs

Strain reliefs and bend restrictors should be provided on each end of the umbilicals, integrated to the connection plates, to prevent over stressing and kinking of the hose bundles.

5.3 Jumper Hose Bundles

A jumper hose bundle should be provided to connect the hydraulic power unit to the powered umbilical reel assembly.  The configuration of the jumper hose should be the same as each umbilical.


Each bundle should be 200 feet long with an overall protective thermoplastic jacket.  No armoring is required.


Both ends of each jumper bundle should be terminated at a connection plate assembly with quick disconnects.

Strain Relief

A strain relief and bend restrictor should be provided at the ends of each bundle, integrated to the connection plate to prevent over stressing and kinking of the hose bundle.


A means to conveniently handle and store jumper hoses should be provided.

5.4 Installation/Workover Hydraulic Umbilical Riser Clamps

Suitable clamps or straps should be provided to secure the installation/workover umbilical to wire rope and pipe as specified by Buyer during tree installation and completion.  Design should be of an industry-proven type for reliability and ease of use.  Sufficient clamps should be supplied such that one clamp every 25 feet can be installed.  Completely Non metallic clamps which are designed to be positively buoyant in a seawater environment should be used during installation of the tubing hanger utilizing a production riser (tubing hanger running string) as specified by Buyer.

5.5 Umbilical Sheaves

Two sheaves should be supplied for routing the installation/workover umbilical from the reel assembly to the installation/workover pipe or wire as specified by Buyer beneath the rig floor.  The sheave should be designed to allow insertion and removal of the umbilical while installed, and should provide a bend radius greater than the minimum working bend radius of the installation/workover umbilical.  Optional jockey sheaves will be sourced which can support the installation/workover umbilical at intervals between the reel location and the main turndown sheave.

Smaller or single roll jockey sheaves are required to lift the umbilical from the deck to prevent damage to the umbilical during deployment and recovery.  This sheave should be removable or installable with the umbilical paid out with single point lifting capabilities.

6.0 Hose Reel Assemblies

6.1 General

One air powered steel hose reel assembly should be provided for the installation/workover control line bundle.

6.2 Drive Motor

The air powered motor should be capable of variable speed up to 90 ft/minute at 100 PSI air supply.  The system should prevent the air powered motors from slipping.

6.3 Air Powered Brakes

On loss of air pressure, the brakes should fail in the lock-up position and should be capable of supporting a minimum of 100 feet of control line in air while filled with control fluid.  A mechanical locking pin should be provided to prevent the reel from turning once the jumper hose is connected to the hose reel.  The locking pin and its anchors should be capable of supporting all of hose (100 feet in the air plus water depth and air gap) when filled with control fluid.

6.4 Capacity

The hose reel should be sized to accommodate water depth plus air gap and reel excess for spooling and recovery.

6.5 Connection Plate Assemblies

A connection plate assembly should be provided on the installation/workover reel for connection to the jumper hose bundle.  A protective cover should be provided for the connection plate assembly during transportation and for storage.

7.0 Test Equipment and Procedures

Test equipment should be provided to perform component test, factory acceptance tests, factory integration tests, control system/tree hardware integration tests, on-site pre-installation tests and subsequent maintenance and troubleshooting tests.  All test equipment should be furnished with mounting hardware and fittings for connection or mating to the equipment to be tested.  The test equipment should include:

  • Manifold test blocks with blanking plugs for testing all plate or manifold mounted components, which cannot readily be connected for testing with tube or hose fittings.
  • An independent skid mounted test pump for use in commissioning and testing equipment while the main IWOCS HPU is occupied with equipment installed subsea.  The test pump should have a minimum of two independent, regulated, circuits for low-pressure (<3000 psi) high volume application and a high pressure circuit for testing up to 7,500 psi.

All jumper hoses, fittings, and adapters for connecting the hydraulic supplies, test stands, and test pieces should be provided.  Vendor should supply a complete set of jumper hoses, fittings and adapters to allow the factory and integration tests to be performed on site during installation.  Supplies should eventually be stored onshore at Buyer discretion for use in testing and commissioning or later workovers.

Supplier should work with Buyer to plan the tests required and make diagrams of test set-ups.  The diagrams should show all equipment to be tested, test equipment and all connections, fittings, adapters, jumpers, portable pump units, etc., such that the equipment and materials will be available at the test sites.

8.0 Tools

Two complete sets of any special tools required to work on all components should be provided.  Two sets of tools required to install all common size hose fittings should also be provided, including all dies and pushers for steel and stainless fittings and a hydraulic swaging tool.

All hand and power tools and supplies for Supplier representatives to reasonably install and maintain Supplier supplied equipment should be provided and maintained or replaced as necessary during the course of the project at no additional cost to the Buyer.  Where Buyer supplied tools or supplies are required they will be backcharged to Supplier at cost plus %15.  Notwithstanding this clause, Supplier should provide sufficient back up tools to provide reasonable coverage during the project and with due consideration for the remoteness and difficulty in re-stocking in this area.

Supplier should provide a minimum of (2) ETU’s, laptop computers, printers, software and test lines for each system.  In addition each ETU and laptop system should be supplied with individual UPS units complete with spare fuses and components

9.0 Workshop / Spares Storage

A workshop or cabin with air conditioning will be provided for storage of tools and equipment and for working on Supplier supplied equipment as required.  The workshop should be wired for 220V, 60hz, 1phase power supply and have sufficient interior lighting for a working environment. All electrical equipment and interconnections should be suitable for operation in a Class 1, Division II, Group D hazardous area.

A portable spares storage facility will be supplied which has provisions for electrical lighting and shelves suitable for storage of spares and consumables to be utilized during the course of the project. All electrical equipment and interconnections should be suitable for operation in a Class 1, Division II, Group D hazardous area.