Hydraulic HIPPS

HIPPS Development Project

This presentation describes the Energy Equipment Corporation Hydraulic HIPPS control development project, and gives:

Brief background information about Energy Equipment Corporation and the Hydraulic HIPPS concept.How it works.Reliability. The advantages of the system.Project status & objectives.

Background to the HIPPS Project.

Energy Equipment Corporation are US based manufacturers of valves, actuators and chokes, used mainly within the oil industry.Founded in 1986 the company has grown steadily and turnover during 2006 is expected to exceed $40Million.The EEC hydraulic Subsea HIPPS is one of several development projects currently in progress.EEC took the decision to develop a hydraulic subseaHIPPS for several reasons….

Background to the HIPPS Project.

EEC were confident that a simple, more cost effective and potentially more reliable system of HIPPS control could be developed, based on the same mechnical principles as their Line Pressure Operated Valve.In addition, the situation in the GoM, with the MMS slow to approve HIPPS using programmable electronic controls, it seems there may be good reasons for developing an alternative control arrangement. In essence, our objective was to design a control arrangement similar to that used with the EEC Line Pressure Operated Valve, but for a safety critical subseaapplication.Our concept resulted from bringing together this technology and placing it into the context of existing subsea systems.

General Project ObjectivesImprove/enhance current HIPPS technology.Reduce the need for project specific HIPPS design.Reduce the reliance upon E/E/PE features within the system design.

Why?A different approach to provide diverse control means within a layered system, i.e. one system controlled using programmable electronics, and one with no safety critical E/E/PE controls. To create a simple solution…..IEC states “These systems are usually complex, making it impossible in practice to fully determine every failure mode or test all possible behaviour”

The EEC HIPPS Control ConceptThe key to this concept is a ‘differential pilot pressure dump valve’ operated using the PCS LP or HP system supply pressure as a ‘reference’.There need be no specific relationship between the system supply pressure used and the required HIPPS trip pressure.

SCMHIPPS Valve

The key to this design is the differential pilot pressure dump valve.

Reference pressure direct from the HPU. (HP or LP)Vent

Pressure transfer barrier

Differential Pilot Pressure Dump Valve Pressure ‘A’

Pressure ‘B’

Pressure ‘C’

Vent Line

HIPPS Valve

Fig. 1. The Differential Pilot Pressure Dump Valve is configured for specific applications, i.e. the relationship between the opposing pilot piston areas, and the ability to change this relationship during the system design stage is used to determine the way in which the valve operates. In the example above, Pressure ‘C’ can be lower than Pressure ‘A’ but because ‘Pilot 1’ piston has a smaller area than ‘Pilot 2’, Pressure ‘C’ will apply sufficient force to the main stage piston, to move the valve to the vent position. This means that Pressure ‘A’ need have no specific relationship to Pressure ‘C’,

Pilot 1.

Pilot 2.

Example (HP) For this example, the PCS HP system supply pressure is

690 bar. The design pressure of the pipeline to be protected is

207 bar. With a safety margin, the HIPPS trip pressure is

specified at 200 bar.The ‘close’ pilot piston is 20mm in diameter and

therefore has an area of 314.16 mm²690÷200 = 3.450Therefore 3.450 X 314.16 = required ‘open’ pilot piston area of 1083.85 mm² (37.15 mm dia), to make the dump valve open when the ‘open’ pilot is exposed to more than 200 bar.

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SCMThe HIPPS unit takes a hydraulic

reference pressure, directly from the controls distribution system

Configuration.The pressure reference source can be either HP or LP. Local demand for fluid within the system will result in system pressure reduction for periods of time.A pressure stabilisation means will be included in the system, to prevent the changes in pressure from triggering a HIPPS valve shut down.The HP system can be used as a source and the need for any pressure stabilisation will be unlikely. A pressure transfer barrier (sealed metal diaphragm design) is required. Consideration must be given to the additional force required to ‘drive’ the PTB when calculating piston areas.

Pressure ConverterThe pressure transfer barrier is better described as a pressure converter.

It uses the pressure from the pipeline to create a force.

The force acts upon the dump valve main stage piston, via a pushrod.

Metal-to-metal sealing coupling

The dump valve is bolted to

this surface

Push rod end

Pressure Converter

In this view, pipeline pressure is below HIPPS ‘trip’ pressure.

The piston / diaphragm / pushrod, are therefore in the retracted position

Pressure from pipeline

Pressure Converter

In this view, pipeline pressure has increased to above the HIPPS ‘trip’ pressure.

The piston and diaphragm have moved, and the pushrod is extended.

To prevent damage to the diaphragm from over pressure, the top surface of the diaphragm matches the top surface inside the diaphragm chamber.

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

The EEC HIPPS uses a hydraulic control system.

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

The Differential Pilot Pressure Dump Valve

forms the basis of this system

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

The dump valve is configured to use

any available control system supply pressure

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

Pressure from the HP

supply applies a

force to the closing pilot

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

Pressure from the pipeline

applies an opposing

force to the opening pilot

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

The required pilot piston diameters are each calculated at

the design stage, to achieve the required HIPPS trip pressure.

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

In this example:

The HIPPS will use 10,000 PSI, from the control system HP hydraulic supply

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

To provide a pipeline HIPPS

‘Trip Pressure’ of 2,750 PSI

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

10,000 PSI is supplied to a 20mm

diameter closing pilot piston

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

When the pipeline pressure increases, and the 38.14mm diameter opening

pilot piston is exposed to 2,750

PSI

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

The opposing forces, to close or open the dump valve become

equal.

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

So, when the pressure in the

pipeline exceeds 2,750

PSI

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

The force applied to the opening pilot

increases

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

This exceeds the closing force and pushes the dump valve to the open

position.

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

The HIPPS valve actuator starts to

vent

SCMHPU

DSV

Controls Umbilical Containing HP and

LP Supplies

Flow from tree

In the closed position, the HIPPS valve now

provides protection for the pipeline section downstream of the

HIPPS

Significant Issues

Subsea test and calibration.

Susceptibility to supply pressure fluctuation triggering ESD.

Supply Pressure Fluctuation

The supply (reference) pressure, now passes through a device we call a supply pressure stabiliser (SPS) prior to reaching the dump valve closing pilot.

The SPS provides pressure ‘damping’, preventing short term pressure fluctuations from reaching the HIPPS Controls.

Subsea Test and Calibration

During a meeting in December 2005 with the MMS in Houston, their concerns relating to how the system would be tested were discussed. A proposed method of system testing was presented to the MMS in March 2006. The proposal was reviewed against a list of requirements originally set out by the MMS in December 2005, and judged to be satisfactory.

Subsea Test and Calibration

In the example presented to the MMS, the section of pipeline between the PWV upstream of the HIPPS, and a pipeline test isolation valve downstream of two HIPPS valves, could be pressurised via a chemical line. With the PWV closed and the pipeline test isolation valve closed, pressure is gradually increased until a HIPPS valve ESD is triggered.The pressure required to trigger the ESD is monitored using pressure transducers positioned alongside the HIPPS valves, on the pipeline.In addition to the pipeline pressure and the control system hydraulic supply pressure, six events are monitored/recorded during the test. They are the two HIPPS valve closures and four dump valve closures. (four because they are dual redundant, two on each HIPPS valve actuator)Position indicators are used to monitor HIPPS and dump valve positions during the tests.

Subsea Test and Calibration

The additional up stream and downstream system valve tests can be carried out by pressurising the pipeline, again via the chemical line, and isolating pressure within the required section for a specific valve test. These tests will also use pressure transducers positioned at the HIPPS to monitor pressure.In a layered system where the hydraulic HIPPS control is working along side a programmable electronic HIPPS control, the pressure transducers used during testing will be the same as those used to supply the data on which the 2oo3 voting is based. However, although this instrumentation is used during testing, no data from instrumentation forms any part of the ESD decision making process within the hydraulic HIPPS.

Reliability

An evaluation of the HIPPS design has been carried out by Risktec, risk analysts specialising in SIL assessment.

They provided a preliminary reliability statement, concluding that the EEC HIPPS will be capable of meeting the requirements for a SIL 3 protection system. A copy of the report can be made available on request.

Advantages

Fully compatible with existing production control systems.

Will provide a strong ‘contrast’ to E/E/PE based controls when used within a layered system.

Significantly reduced project specific design and qualification…..hence lower costs and reduced timescales

Design Focus

The new part of this system, and therefore the focus of qualification testing, will be the pressure converter and the dump valve.As many field proven parts as possible will be used in the system.The pressure converter/diaphragm is a new design.An interface block, linking the pressure converter to an existing small bore valve is a new design.The small bore valve/actuator will have minor modifications made, to allow the actuator to link up with the adaptor, and also to minimise travel from the open to the closed position.

Significant Issues The stem is extended/modified to

allow a pulling (opening) force to be

applied

The gate is reversed and the through bore within the gate and seats is machined as

a slot, to reduce travel (currently to

0.37”) from the closed to the open

This slide shows a sectional view of the 1” bore LB Bentley valve

selected for use as the basis for the dump valve and briefly

describes the required modifications

Push rod from pipeline diaphragm applies pulling

force to stem

The pulling force applied to stem moves the gate

to the open position

Top of the LB Bentley valve

actuator

The Diaphragm to Dump Valve Adaptor

Configuration

Closing hydraulic Supply

HIPPS Dump Vent

Dump valve

HIPPS valve/ actuator

Dump valve position indicator

Dump valve actuator

Dump valve 90° push rod to stem arrangement

‘T’ to two parallel HIPPS controls

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2 1/16” flanged diaphragm housing

Design Decisions

The width of the slot through the seat/gate assembly within the dump valve may be changed, to provide the required speed of HIPPS pipeline valve closure. Currently the flow area is around 5 X that of a controls DCV.

Whether to include a facility for a ‘bolt-on’ arrangement (shown in the next slide) to accommodate SCMMB and SCM on EEC HIPPS skid. A provision for installation of the instrumentation necessary for a PES control will be made.

HIPPS Layered System

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SPS

….

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HIPPS control module and mounting base

Hydraulic HIPPS