RESEARCH REPORT 492 - Health and Safety Executive · breathing performance of an ‘Octopus’...

HSE Health & Safety

Executive

Standard unmanned testing procedures for open-circuit

‘Octopus’ systems

Prepared by QinetiQ Ltd for the Health and Safety Executive 2006

RESEARCH REPORT 492

HSE Health & Safety

Executive

Standard unmanned testing procedures for open-circuit

‘Octopus’ systems

A S Fisher T G Anthony

R J Gould S D Samways

QinetiQ Ltd Fort Road

Alverstoke Gosport

Hampshire PO12 2DU

Self-Contained Underwater Breathing Apparatus (SCUBA) often use an ‘Octopus’ system as an alternative air supply. QinetiQ at Alverstoke were contracted by the Health and Safety Executive (Contract 6253) to identify appropriate simple (single breathing machine) test procedures for ‘Octopus’ systems. A single breathing machine, in conjunction with a constant flow from the first stage regulator, was able to represent the breathing performance of an ‘Octopus’ SCUBA system obtained by dual in-phase breathing machines. A test procedure is proposed that uses a constant flow equivalent to the root mean square of the peak flow (ie ventilation rate * 0.707 * π * pressure (bar)). The proposed procedure should be considered for inclusion in future diving apparatus standards including the next revision of BS EN 250. Tests re-confirmed the recommendation that ‘Octopus’ systems should be based on high performance (possibly higher cost) first stage regulators.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.

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First published 2006

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3

Executive Summary When using Self-Contained Underwater Breathing Apparatus (SCUBA) it is recommended that divers use an appropriate alternative breathing gas source/secondary life support system. ‘Octopus’ systems are often used to fulfil or support this requirement.

Following growing concerns over the use of ‘Octopus’ systems and incidents involving them, on behalf of the Health and Safety Executive (HSE), QinetiQ at Alverstoke conducted a review and unmanned breathing performance testing of six ‘Octopus’ systems and made initial safety recommendations for their operational use (http://www.hse.gov.uk/research/rrhtm/rr341.htm).

It was recommended that ‘Appropriate test procedures and acceptance criteria should be identified for ‘Octopus’ systems, and proposed for inclusion in future diving apparatus standards including the next revision of BS EN 250.’

QinetiQ Sea Division, Submarine Escape and Diving Systems at Alverstoke were contracted by the HSE, Contract 6253, to identify appropriate procedures that may be considered as a simple, low cost adjunct to existing BS EN 250 tests.

Three of the original six ‘Octopus’ systems were used for this study and represented the full range of expected performance. Initial tests showed that the performance of the ‘Octopus’ systems may be improved by increasing the volume of the intermediate pressure system.

The original testing identified that the greatest demand, and associated degradation in performance, occurred when both ‘Octopus’ valves were breathed in-phase. To replace a breathing machine with a constant flow, at the depth (pressure) of the diver, the flow rate was expected to be between an equivalent of the ventilation rate (i.e. Ventilation rate * pressure (bar), l·min-1) and the peak gas flow during sinusoidal breathing (i.e. Ventilation rate * π * pressure (bar), l·min-1).

Testing identified that a single breathing machine, in conjunction with an appropriate constant flow from the first stage regulator, was able to represent the breathing performance of an ‘Octopus’ SCUBA system obtained by dual in-phase breathing machines.

A flow of gas, equivalent to peak flow during sinusoidal breathing (i.e. Ventilation rate * π * pressure (bar)) proved more severe than in-phase breathing, but was able to discriminate the same BS EN 250 pass/fail results. Analysis indicates that the root mean square (rms) of the peak flow (i.e. Ventilation rate * 0.707 * π * pressure (bar)) would be an appropriate constant flow rate.

A single breathing machine test procedure is proposed for open-circuit ‘Octopus’ systems and for inclusion in future diving apparatus standards including the next revision of BS EN 250.

Tests conducted for this study, including those from the severe high constant flow tests, re-confirm the recommendation that ‘Octopus’ systems should be based on high performance (possibly higher cost) first stage regulators.

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List of contents 1 Introduction 6

1.1 Background 6 1.2 Apparatus selection 6

2 Procedures 9 2.1 Principle of single breathing machine test procedure 9 2.2 General 9 2.3 Breathing performance 10 2.3.1 Generic test conditions 10 2.3.2 Dual breathing machine testing 10 2.3.3 Constant flow configuration - dual breathing machine testing 11 2.3.4 Constant flow configuration - single machine testing with additional

constant flow 12 2.4 Pass/fail criteria 13

3 Results 15 3.1 Results presentation scheme 15 3.1.1 Pass/fail summary tables 15 3.1.2 Work of breathing bar charts 16 3.2 Breathing performance results 17 3.2.1 Summary tables 17 3.2.2 Detailed results Phase 1 and Phase 2 dual breathing machine

comparison (Annex A) 17 3.2.3 Detailed results Phase 2 constant flow configuration (Annex B) 19 3.2.4 Matched constant flow pressure-volume loops 19

4 Discussion 20 4.1 Phase 1 and Phase 2 dual breathing machine configuration tests 20 4.2 Constant flow configuration tests 20 4.2.1 Dual breathing machine tests 20 4.2.2 Out-of-phase breathing performance 21 4.2.3 Low constant flow tests 21 4.2.4 High constant flow tests 22 4.2.5 Matched in-phase breathing performance 23 4.2.6 Root mean square (rms) 24 4.3 ‘Octopus’ system performance 25

5 Proposed standard un-manned test procedure for open-circuit ‘Octopus’ systems 26 5.1 Test configuration 26 5.2 Test procedure 26

5

6 Conclusions 27 7 Recommendations 28 8 References 29 A Breathing performance data 30 B Breathing performance data 42 C Example pressure-volume loops 48

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1 Introduction

1.1 Background

For safety reasons when using Self-Contained Underwater Breathing Apparatus (SCUBA) it is recommended that divers use an appropriate alternative breathing gas source/secondary life support system [1, 2, 3, 4]. It is common practice within recreational diving agencies and during some commercial diving activities to use an ‘Octopus’ system to fulfil or support this requirement. A SCUBA ‘Octopus’ system consists of a first stage regulator connected to a ‘primary’ second stage demand valve and a ‘secondary’ second stage demand valve, the ‘Octopus’. The ‘Octopus’ provides a back up demand valve in cases of primary demand valve failure and may also act as an alternative air source (AAS) for the diving ‘Buddy’. An AAS does not require the ‘Donor’ diver to remove their own primary demand valve when supplying air to a ‘Buddy’ diver who has experienced regulator failure or an out of air situation.

The current European standard for open-circuit compressed air breathing apparatus, BS EN 250 [5] specifies the performance requirement of a single demand valve, first stage regulator combination. This, however, gives no indication as to how an ‘Octopus’ (two demand valves, single first stage regulator combination) might perform.

Following growing concerns over the use of ‘Octopus’ systems and incidents involving them [6, 7], on behalf of the Health and Safety Executive (HSE), QinetiQ at Alverstoke conducted a review and unmanned breathing performance testing of six ‘Octopus’ systems [8]. The breathing performance testing used two breathing machines submitting the ‘Octopus’ systems to both ‘out-of-phase’ (one diver inhaling as the other exhales) and ‘in-phase’ (both divers inhaling at the same time) breathing patterns. The report on the testing highlighted several concerns with the performance of ‘Octopus’ systems and made initial safety recommendations for their operational use. It was also recommended that ‘Appropriate test procedures and acceptance criteria should be identified for ‘Octopus’ systems, and proposed for inclusion in future diving apparatus standards including the next revision of BS EN 250’.

To identify an appropriate test procedure the HSE contracted the QinetiQ Sea Division, Submarine Escape and Diving Systems at Alverstoke (Contract number 6253) to identify a simple, low cost adjunct to existing BS EN 250 tests. The procedures to be such that test houses would be able to evaluate ‘Octopus’ systems using a single unmanned breathing machine and that they may be proposed for inclusion in the next revision of BS EN 250.

This report presents the development and testing of a new method of evaluating breathing performance of ‘Octopus’ systems using a single breathing machine in conjunction with a constant flow from the first stage regulator.

1.2 Apparatus selection

The original breathing performance evaluation of ‘Octopus’ demand regulators was conducted on the six systems outlined in Table 1-1 [8]; the evaluation identified that the worst case performance occurred at high ventilation rates, depths greater than 30 m and when the systems were being breathed in-phase.

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System Identification Number

First Stage and Primary Demand Valve

Secondary ‘Octopus’ Demand Valve

Justification

1 Supplier A Supplier A

System 1 was a high cost, high performance option assembled as per supplier’s recommendations.

2 Supplier A Supplier B

System 2 envisages the assembly of a high performance option utilising a low cost regulator as an ‘Octopus’.

3 Supplier A Supplier C BCD Combination unit

System 3 was a high cost, streamlined option assembled as per supplier’s recommendations.

4 Supplier B Supplier B

System 4 was a low cost, low performance option assembled as per supplier’s recommendations.

5 Supplier B Supplier D Used

System 5 envisages the assembly of a low performance option utilising a well used older model regulator as an ‘Octopus’.

6 Supplier B Supplier C BCD Combination unit

System 6 was a low cost, streamlined option assembled as per supplier’s recommendations.

Table 1-1: ‘Octopus’ systems from original evaluation [8]

Due to logistical constraints it was decided to investigate a standard unmanned test procedure using only three of the original six systems, and that the test conditions would be those known to demonstrate the ‘Octopus’ systems performance issues of concern.

The three systems chosen encompassed the full range of expected performance. Table 1-2 identifies the systems used, together with the justification for selection.

The systems were purchased new for the original evaluation and at that time had only limited use in fresh water. Subsequent to the original evaluation they were thoroughly cleaned, dried and stored in ideal conditions (nominally 20 °C, dry and protected from exposure to light) for 28 months before being used for the tests conducted for this study. To prevent any major changes in performance and to have the best chance of the systems performing as per the original study, they were tested straight from storage without undergoing any maintenance procedure.

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System Identification Number

First Stage and Primary Demand Valve

Secondary ‘Octopus’ Demand Valve

Justification

1 Supplier A Supplier A

System 1 was selected as a high performance system that was expected to comfortably pass all test conditions.

4 Supplier B Supplier B

System 4 was selected as a mid range performance system with acute failures associated with in-phase breathing at the selected test depths and ventilation rates.

6 Supplier B Supplier C BCD Combination unit

System 6 was selected as a low performing unit expected to fail with in-phase breathing at the selected test depths and ventilation rates.

Table 1-2: Systems selected for evaluation of standard unmanned test procedure

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2 Procedures

2.1 Principle of single breathing machine test procedure

The original QinetiQ breathing performance evaluation of ‘Octopus’ demand regulators was conducted using two breathing machines to simultaneously breathe both the primary and the ‘Octopus’ demand valves [8]. Both breathing machines provided a sinusoidal breathing waveform that was synchronised to be either in-phase (both divers inhaling at the same time – i.e. worst case) or out-of-phase (one diver inhaling as the other exhales). Although the testing reported from the original study was useful in defining the performance of ‘Octopus’ systems, it is not practical as a routine testing procedure that may be included in a standard for open-circuit breathing apparatus (e.g. BS EN 250).

To develop a test procedure using a single breathing machine, the principle employed was to replace one of the breathing machines with a constant flow from the first stage regulator; the test procedure then being a constant flow coupled with a breathing machine breathing either the primary or the ‘Octopus’ regulator as required.

The original testing identified that the greatest demand, and associated degradation in performance, occurred when both machines were breathing in-phase. To replace a machine with a constant flow it is reasonable to expect the flow rate to be between the following extremes:

• Low constant flow: A constant flow of gas equivalent to the ventilation rate (V, l·min-1) of the breathing machine at the depth of the test (D, bar).

Flow rate = V * D

Low constant flow was anticipated as placing a respiratory demand, upon the first stage regulator, in the order of two divers breathing out-of-phase. It represents the minimum demand upon a first stage regulator.

• High constant flow: A constant flow of gas equivalent to the peak gas flow that is created by a breathing machine with a sinusoidal breathing waveform at the depth of the test (D, bar). For a sinusoid the peak flow is the ventilation rate (V, l·min-1) multiplied by Pi (π).

Flow rate = V * π * D

High constant flow was anticipated as placing a respiratory demand, upon the first stage regulator, slightly greater than two divers breathing in-phase. It represents the maximum demand upon the first stage regulator.

2.2 General

Unmanned evaluation was conducted at QinetiQ Alverstoke using two hyperbaric breathing machines and associated equipment within the Life Support Systems Laboratory (LSSL). This laboratory is able to evaluate the apparatus in a range of simulated environments and operational conditions. All monitoring was carried out using calibrated instrumentation and software that give results in real time [9].

Three different units for pressure are used extensively in this report. It is common to use metres to describe the pressure a diver is exposed to; i.e. depth below the water surface. Gas supply pressures are measured in bar. Any other pressures mentioned have been quoted in the S.I. unit of Pascal (Pa). Throughout the work carried out to produce this report it has been assumed that a pressure change of

10

100 kilo Pascal (kPa) = 1 bar = 10 m (assuming a density of seawater of 1.01972 at 4 ° Celsius (C)) and that the air pressure at sea level = 0 m = 101.3 kPa (one standard atmosphere).

Some data from the original testing, detailed in the previous QinetiQ report on ‘Octopus’ systems [8], has been included in this report for comparative purposes. These data are referred to as ‘Phase 1’ data.

Data obtained from the testing conducted specifically for this study is referred to as ‘Phase 2’ data.

2.3 Breathing performance

2.3.1 Generic test conditions

The systems were evaluated for compliance with elements of BS EN 250 Respiratory equipment - Requirements, testing, marking [5] and the Norwegian Petroleum Directorate/Department of Energy (NPD/DEn) guidelines [10] for underwater breathing apparatus.

The systems were rigged in the vertical attitude, immersed in fresh water at a regulated temperature of 5 °C and evaluated at simulated depths of 30, 40 and 50 m. A temperature of 5 °C was used for logistical reasons, compatibility with the tests conducted for Phase 1 and as a generic cold water challenge; it should be noted that a formal cold water test as per BS EN 250 should be conducted in the temperature range 1 to 4 °C.

Air complying with BS EN 12021:1999 [11] was supplied to the apparatus, at a nominal pressure of 50 bar.

Where present, the Dial-a-Breath settings of demand valves were placed in mid-positions. Venturi levers/pre-dive controls were set as per supplier’s recommendations.

Breathing performance was assessed at the nominal ventilation rates shown in Table 2-1.

Ventilation rate

(l·min-1)

Tidal volume

(litres)

Breaths per

Minute

40.0 2.0 20

62.5 2.5 25

75.0 3.0 25

90.0 3.0 30

Table 2-1: Ventilation rates

2.3.2 Dual breathing machine testing

To identify any change in performance from the original Phase 1 test data, the three selected ‘Octopus’ systems were subjected to both in- and out-of-phase two breathing machine tests. The tests were conducted using an equipment configuration identical to that used during the previous period of evaluation and as detailed in the QinetiQ report [8]. A restricted set of test conditions were used, that were known to identify where degradation in performance may occur. i.e:

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Test depths: 30, 40 and 50 m

Ventilation rates: 40.0, 62.5, 75.0 and 90 l·min-1

Supply pressure: 50 bar

The breathing performance of the regulators was assessed with each of the second stage demand valves (primary and ‘Octopus’) attached to a dedicated breathing machine configured for synchronous control. Operating the breathing machines ‘in-phase’ simulated maximum demand as both divers inhale and exhale at exactly the same time and rate. Conversely, operating the machines ‘out-of-phase’ simulated minimum demand as one diver inhales whilst the other exhales. Both machines were set to the same ventilation rate.

This data is referred to as ‘Phase 2’ dual breathing machine data.

2.3.3 Constant flow configuration - dual breathing machine testing

Following the Phase 1/Phase 2 dual breathing machine comparative testing, the ‘Octopus’ systems configuration was modified to allow breathing air to be vented to atmosphere from the first stage regulator, via an intermediate pressure (IP) hose. This flow could be controlled with a rising stem valve and was recorded using a Coriolis flow meter. A Rotameter flow meter was also attached to the outlet to provide additional monitoring and to assess the use of a simple (compared to the Coriolis meter) method of recording flow. See Figure 2-1.

n.b. – Not to scale

Figure 2-1: Diagrammatic representation of constant flow breathing performance evaluation system

As this test configuration introduced an additional 226 ml to the volume of the intermediate pressure part of the demand valve; additional dual breathing machine testing was performed to allow a direct comparison with the single breathing machine constant flow testing.

Rotameter flow meter

Coriolis flow meter

123. 4

Pressure vessel

Rising stem valve

First stage regulator

Breathing machines Demand valves

12

This data is referred to as ‘Phase 2’ Constant flow configuration - dual breathing machine data.

2.3.4 Constant flow configuration - single machine testing with additional constant flow

Using the test configuration illustrated in Figure 2-1, two protocols were used for constant flow tests:

• Low and high constant flow tests: A flow rate, as indicated by the Coriolis meter was set as shown in Table 2-2. Simulated breathing was then initiated using the breathing machine attached to the demand valve under test. Although the constant flow rate was reduced by the simulated breathing the flow was not re-adjusted. Inhale and exhale respiratory pressures were recorded throughout the breathing cycle and work of breathing was calculated.

• Matched constant flow tests: Simulated breathing was initiated using the breathing machine attached to the demand valve under test. The constant flow was adjusted until the work of breathing (J·l-1) of the demand valve was the same as that observed during the constant flow configuration - dual breathing machine in-phase evaluation. The simulated breathing was then stopped and the matched constant flow recorded.

This data is referred to as ‘Phase 2’ Constant flow configuration – high and low flow data.

Low constant flow

(litres STP)

High constant flow

(litres STP)

Depth (m) Depth (m) Ventilation rate

(l·min-1 ATP)

30 40 50 30 40 50

40.0 160 200 240 503 628 754

62.5 250 313 375 785 982 1178

75.0 300 375 450 942 1178 1414

90.0 360 450 540 1131 1414 1696 Ambient Temperature and Pressure (ATP), Standard Temperature and Pressure (STP)

Table 2-2: Set constant flow rates

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2.4 Pass/fail criteria

The pass/fail criteria adopted for this evaluation encompass both the current European Standard BS EN 250 [5] and the NPD/DEn guidelines published in 1991 [10].

BS EN 250 specifies limits for breathing performance at a ventilation rate of 62.5 l·min-1 and at a depth of 50 m. The specific limit of BS EN 250 is derived from the maximum limit of the NPD/DEn guidelines.

The NPD/DEn guidelines for breathing performance of diving apparatus include testing at ventilation rates from 15.0 to 90.0 l·min-1 Body Temperature Pressure Saturated (BTPS) and are applicable to any selected depth.

Due to logistical constraints and in order to overcome the Ambient Temperature Pressure (ATP) and BTPS differences of the two systems and standardise output for this evaluation all data has been recorded, presented and analysed as ATP in accordance with BS EN 250.

The results obtained at a ventilation rate of 62.5 (±5 %) l·min-1 at 50 m were compared directly with the requirements of BS EN 250.

The data obtained at additional ventilation rates and depths were analysed along side BS EN 250 data using the pass/fail criteria for work of breathing shown in Figure 2-2 and for respiratory pressure in Figure 2-3.

The pass/fail limit lines for both work of breathing and respiratory pressure have been extended to provide physiologically relevant guidance at ventilation rates up to 90 l·min-1. This results in a pass/fail limit line for work of breathing of 4.1 J·l-1 at 90 l·min-1, as opposed to the 5.0 J·l-1 limit in the NPD/DEn guidelines.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 10 20 30 40 50 60 70 80 90 100

Ventilation rate (l.min -1

ATP)

Wo

rk o

f b

rea

thin

g (

jou

les

.lit

re-1)

Example Pass

Example FailPass/Fail

BS EN 250 Pass/Fail 50 m

Fail @ 75 l.min-1

(off scale) No data @ 90 l.min-1

(anticipated fail)

Figure 2-2: Pass/fail criteria work of breathing

Data points falling below the dotted red line in Figure 2-2 were deemed to have passed, those above to have failed. Anticipated failures are indicated by dashed areas.

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-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

0 10 20 30 40 50 60 70 80 90 100


ATP)

Resp

irato

ry P

ressu

re (

kP

a)

Example Pass

Example Fail

Pass/Fail

BS EN 250 Pass/Fail 50 m

Fail @ 75 l.min-1

(off scale) No data @ 90 l.min-1

(anticipated fail)

Figure 2-3: Pass/fail criteria respiratory pressure

(Example shows inhalation respiratory pressure only)

Data points falling above the dotted red line in Figure 2-3 were deemed to have passed, those below to have failed. Anticipated failures are indicated by dashed areas.

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3 Results

3.1 Results presentation scheme

3.1.1 Pass/fail summary tables

In order to simplify the presentation and comprehension of the available data, summary tables have been used. Examples of summary tables using the nominal data presented in Figures 2-2 and 2-3 are shown in Table 3-1 and Table 3-2.

Depth (m) 50

Nominal ventilation rate (l·min-1 ATP)

Demand valve

Supply pressure (bar)

40.0

62.5

75.0

90.0

Example 50

D P

Example 50

Example 50

Pass WoB< 0.5 J·l-1 at 0 l·min-1- 4.1 J·l-1at 90.0 l.min-1

Fail WoB> 0.5 J·l-1 at 0 l·min-1- 4.1 J·l-1 at 90.0 l.min-1

No data (Anticipated Fail - see text)

Table 3-1: Example summary table for work of breathing

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Depth (m) 50

Nominal ventilation rate (l.min-1 ATP)

Demand valve

Supply pressure (bar)

40.0

62.5

75.0

90.0

Example 50

D P

Example 50

Example 50

Pass Respiratory Pressure < 2.5 kPa

Fail Respiratory Pressure > 2.5 kPa

No data (Anticipated Fail - see text)

Table 3-2: Example summary table for respiratory pressure

A pink box in summary tables indicates a ventilation rate where it was anticipated that obtaining data would result in a breathing performance failure that would risk damage to the test apparatus and preclude further evaluation.

3.1.2 Work of breathing bar charts

Work of breathing bar charts have been used to aid the rapid comparison between systems and different evaluation parameters. An example work of breathing bar chart using the nominal data presented in Figure 2-2 is shown in Figure 3-1.

System example - 50 bar - 50 m

0.0

1.0

2.0

3.0

4.0

5.0

40.0 62.5 75.0 90.0Nominal ventilation rate

(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Example

Example

Example

Pass/Fail limit

7.9

Figure 3-1: Example work of breathing bar chart

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3.2 Breathing performance results

3.2.1 Summary tables

The BS EN 250 pass/fail results for the four configurations tested are summarised in Table 3-3.

3.2.2 Detailed results Phase 1 and Phase 2 dual breathing machine comparison (Annex A)

The detailed results comparing the Phase 1 and Phase 2 dual breathing machine data are presented in Annex A. Table 3-4 indicates the pass fail summary tables for work of breathing and respiratory pressures.

Phase 1 Phase 2

Work of breathing

Respiratory pressures

Work of breathing


System 1 Table: A-1 Table: A-2 Table: A-3 Table: A-4



Table 3-4: Pass/fail summary tables in Annex A

The work of breathing data is also presented in bar chart form to compare trends in breathing performance, Table 3-5.

Phase 1 Phase 2

Work of breathing

30 m

Work of breathing

40 m

Work of breathing

50 m

Work of breathing

30 m

Work of breathing

40 m

Work of breathing

50 m

System 1 Figure: A-1

Figure: A-2

Figure: A-3

Figure: A-4

Figure: A-5

Figure: A-6


Figure: A-8

Figure: A-9

Figure: A-10

Figure: A-11

Figure: A-12


Figure: A-14

Figure: A-15

Figure: A-16

Figure: A-17

Figure: A-18

Table 3-5: Work of breathing bar graphs in Annex A

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Phase 1, Phase 2, Phase 2, Phase 2, Dual breathing machines Dual breathing machines Constant flow configuration Constant flow configuration

(using dual breathing machines) (low and high constant flows)

Table 3-3: Pass/fail summary BS EN 250 criteria

Depth (m) 50

Nominal ventilation rate (l·min-1

ATP)

Demand valve

Supply pressure

(bar)

62.5

62.5

62.5

System

1 4 6

Primary 50

Octopus 50

Primary

(out-of-phase) 50 Octopus (out-of-phase) 50

Primary (in-phase) 50

Octopus (in-phase) 50

Depth (m) 50


ATP)

Demand valve

Supply pressure

(bar)

62.5

62.5

62.5

System

1 4 6

Primary 50

Octopus 50

Primary




Depth (m) 50


ATP)

Demand valve

Supply pressure

(bar)

62.5

62.5

62.5

System

1 4 6

Primary 50

Octopus 50

Primary




Depth (m) 50


ATP)

Demand valve

Supply pressure

(bar)

62.5

62.5

62.5

System

1 4 6

Primary 50

Octopus 50

Primary

(low flow) 50

Octopus (low flow)

50

Primary (high flow)

50 Octopus

(high flow) 50

Pass BS EN 250 breathing performance recommendations

Fail BS EN 250 breathing performance recommendations

No data (Anticipated Fail - see text) No data

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3.2.3 Detailed results Phase 2 constant flow configuration (Annex B)

The detailed results comparing the constant flow configuration, dual breathing machine and constant low and high flow data are presented in Annex B. Table 3-6 indicates the pass fail summary tables for work of breathing and respiratory pressures.

Phase 2 – Constant Flow

Work of breathing


System 1 Table: B-1 Table: B-2



Table 3-6: Pass/fail summary tables in Annex B

The work of breathing data is also presented in bar chart form to compare trends in breathing performance, Table 3-7.

Phase 2 – Constant Flow

Work of breathing

30 m

Work of breathing

40 m

Work of breathing

50 m

System 1 Figure: B-1

Figure: B-2

Figure: B-3


Figure: B-5

Figure: B-6


Figure: B-8

Figure: B-9

Table 3-7: Work of breathing bar graphs in Annex B

3.2.4 Matched constant flow pressure-volume loops

Example pressure-volume loops illustrating the characteristics of each demand valve alone, in-phase and simulated in-phase with a matched constant flow are presented in Annex C. The pressure-volume loops for each system in Annex C are identified in Table 3-8.

Primary ‘Octopus’

System 1 Figure: C-1 Figure: C-2



Table 3-8: Example pressure-volume loops in Annex C

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4 Discussion

4.1 Phase 1 and Phase 2 dual breathing machine configuration tests

The tests conducted for this report (Phase 2) were undertaken 28 months after the previous evaluation (Phase 1).

When the data, obtained under identical test conditions from the two periods of testing (Tables A-1 to A12 and Figures A-1 to A-18), was examined, no appreciable change in overall performance was observed, although some minor variations in performance were identified. This is supported by no change in the outcome of the BS EN 250 pass/fail results as presented in Table 3-3 (comparison of Phase 1 and Phase 2 dual breathing machines).

As no appreciable degradation in performance of the three ‘Octopus’ systems had occurred, and their performance reflected the selection justification presented in Table 1-2, these systems were used for the investigation of simplified test procedures.

4.2 Constant flow configuration tests

4.2.1 Dual breathing machine tests

When configured for constant flow tests there was a slight improvement in recorded performance of the low performance/cost first stage regulator ‘Octopus’ systems when compared to the performance without the constant flow pipe work (e.g. comparison of data for System 4, Tables A-7 and A-8 with Tables B-3 and B-4 respectively and for System 6, Tables A-11 and A-12 with B-5 and B-6 respectively). No change in performance with the constant flow pipe work was observed with the high performance/cost regulator, System 1.

The improved performance of the low performance/cost first stage regulator systems may be explained by the increase in volume of the intermediate pressure system. The pipe work associated with the constant flow configuration included an additional intermediate pressure hose, chamber penetration, adapter and external 19 mm bore hose to the rising stem valve. The total internal volume of this pipe work, determined by measuring water capacity, was 226 ml. An increase in the volume of the intermediate pressure system provides a buffer (capacitance effect) for the peak gas flow during inhalation, thus reducing the flow requirement of the first stage regulator with an associated increase in breathing performance.

As the comparative data obtained for single valve performance, dual valve performance and constant flow performance, was acquired using the same constant flow test configuration, the slight improvement in absolute breathing performance was not of concern against the objective of identifying a single breathing machine standard test procedure.

However, when defining the conditions for a standard test procedure, it is recommended that the additional intermediate system volume imposed by a constant flow test configuration should be kept as small as possible. Examination of the test system used for these tests indicated that a specifically designed and pragmatic test configuration may be achieved by a volume not exceeding 200 ml.

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4.2.2 Out-of-phase breathing performance

The work conducted for the Phase 1 trials identified that the worst case ‘Octopus’ system performance occurred when two divers were breathing in-phase and that out-of-phase breathing performance was similar to that when either the primary or ‘Octopus’ valves were tested singly. Examination of the data from the tests for this report (Tables A-1 to A-12 and Figures A-1 to A-18) confirms this observation.

Similarly when tested with the constant flow configuration, it was identified that out-of-phase breathing performance was consistently the same as single demand valve performance in the systems tested (see example in Figure 4-1).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 10 20 30 40 50 60 70 80 90 100 110


ATP)

Wo

rk o

f b

rea

thin

g (

jou

les

.lit

re-1)

Single valve only

Out of phase

Pass/Fail

Figure 4-1: Example of identical out-of-phase/single demand valve performance (System 4, ‘Octopus’, 50 m)

Out-of-phase breathing performance has not been identified as a limiting factor for operational ‘Octopus’ performance [8]. It has also been shown that it may be predicted by assessment of single demand valve performance. Accordingly, out-of-phase performance was not considered for the development of a simple single breathing machine test procedure.

4.2.3 Low constant flow tests

It was anticipated that a single breathing machine combined with the low constant flow (equivalent to V * D; i.e. average flow) would be equivalent to two divers breathing out-of-phase. Typically, the breathing performance obtained was slightly worse than that obtained from a single demand valve alone or out-of-phase two demand valve performance but appreciably better than in-phase performance (see example in Figure 4-2). As with out-of-phase dual breathing machine performance the single breathing machine/low constant flow performance proved inappropriate to discriminate useful failure points of breathing performance in the systems tested. Low constant flow was therefore not considered for the development of a standard test procedure.

22

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 10 20 30 40 50 60 70 80 90 100 110


ATP)

Wo

rk o

f b

rea

thin

g (

jou

les

.lit

re-1)

Single valve only

Out of phase

Low flow

In phase

Pass/Fail

Figure 4-2: Example of intermediate low flow breathing performance (System 6, ‘Octopus’ 40 m)

4.2.4 High constant flow tests

It was shown (Tables B-1 to B-6 and Figures B-1 to B-9) that both the dual breathing machine in-phase testing and the high constant flow (equivalent to V * π * D; i.e. peak flow) were both able to identify shortfalls in performance of ‘Octopus’ systems. It is also apparent, (Table 3-3) that when compared to the BS EN 250 requirement, the high flow test was also able to discriminate the same level of pass/fail as the in-phase dual breathing machine test.

It was expected that the high constant flow test condition would be a worse case situation and would provide a test procedure that would be more severe than two divers breathing in-phase. Detailed examination of the test data (Tables B-3 to B-6 and Figures B-4 to B-9) confirms this. Representative data (Figure 4-3), illustrates the severity of the constant flow test.

The high constant flow tests have demonstrated that a simple single breathing machine test associated with a constant flow may be used to identify the performance of ‘Octopus’ systems and to identify when shortfalls in performance may occur.

Accordingly, it is recommended that a single breathing machine linked with an appropriate constant flow be considered as a standard un-manned test procedure for open-circuit ‘Octopus’ systems.

23

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 10 20 30 40 50 60 70 80 90 100 110


ATP)

Wo

rk o

f b

rea

thin

g (

jou

les

.lit

re-1)

Low flow

In phase

High flow

Pass/Fail

Figure 4-3: Example, severity of testing using high constant flows (System 6, ‘Octopus’ 40 m)

4.2.5 Matched in-phase breathing performance

To attempt to identify an appropriate constant flow rate for a standard test procedure, matched in-phase breathing performance evaluations were conducted. Matching of the breathing pressure-volume loops proved challenging but, to a first approximation it was achieved, producing loops with both similar peak values and shapes to those generated using the dual breathing machine configuration, as illustrated in Annex C Figures C-1 to C-6.

The matched flow breathing loops (Annex C) reinforce the principle that a constant flow test procedure may be used to test ‘Octopus’ systems. However, there was no consistent indication of a relationship between the constant flow established and the matched breathing performance that would allow repeatable simulation of in-phase breathing performance. The problem is illustrated in Figure 4-4.

The problem with the matched flow technique may be understood when considering the matched loops for System 1 (Figure C-1 and C-2). As the pressure-volume loop is unaffected by the flow rate, it is not possible to identify an appropriate flow rate by matching the loops.

24

0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

1600.0

1800.0

0 10 20 30 40 50 60 70 80 90 100 110


ATP)

Co

ns

tan

t fl

ow

ra

te (

l.m

in

-1)

Low flow

Simulated in phase

High flow

Figure 4-4: Example of no correlation between flow and simulated in-phase breathing (System 6, ‘Octopus’ 30 m)

4.2.6 Root mean square (rms)

Although the declared high constant flow (V * π * D) could be used as a standard un-manned test procedure, it is unnecessarily severe and a reduced rate would be more appropriate. As illustrated above, matching the pressure-volume loops did not produce an acceptable solution to the required flow rate. Accordingly an alternative approach was required.

It is common in sinusoidal alternating current electrical systems to use the concept of root mean square (rms) to give a value for the average power [12]. Providing a breathing machine is producing a sinusoidal flow rate with time, it would also be appropriate to apply the rms concept to give the average flow. The rms average flow rate for a sinusoidal breathing pattern would then be:

Flow rate (rms) = 0.707 * V * π * D

Limited data was available to illustrate this concept (See figure 4-5) and for logistical reasons additional testing could not be conducted; should further test data become available it may be necessary to revise this approach. However, rms is an accepted physical analysis of a sinusoidal system and is proposed as an appropriate constant flow rate for use in conjunction with a single sinusoidal breathing machine to overcome the undue severity of the high constant flow rate (V * π * D).

25

0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

1600.0

1800.0

0 10 20 30 40 50 60 70 80 90 100 110


ATP)

Co

ns

tan

t fl

ow

ra

te (

l.m

in

-1)

Low flow

Simulated in phase

High flow

rms

Figure 4-5: Illustrative rms correlation with simulated in-phase breathing (System 6, primary 30 m)

4.3 ‘Octopus’ system performance

Throughout all the tests conducted, including the severe high constant flow configuration, the performance of System 1, the high performance/cost system, (Tables A-1 to A-4 and B-1 to B-2, Figures A-1 to A-6, and B-1 to B-3) remained comfortably within recognised performance criteria. This confirms the recommendation from the previous QinetiQ report [8] that ‘Octopus’ systems should be based on high performance (possibly higher cost) first stage regulators.

26

5 Proposed standard un-manned test procedure for open-circuit ‘Octopus’ systems

5.1 Test configuration

The system configuration would be similar to that used for the tests conducted for this report (Figure 2-1), although only a single breathing machine and demand valve are required. In addition, although an accurate ‘Coriolis’ flow meter was used in tandem with a conventional ‘floating bob’ Rotameter style flow meter, experience gained throughout these tests indicates that only a Rotameter would be required.

The volume of the intermediate pressure system pipe work should be minimised and not exceed 200 ml.

It is proposed that the standard test procedure use a supply pressure of 50 bar and is conducted at the maximum test depth of 50 m (6.0 bar), as per BS EN 250.

5.2 Test procedure

Testing should be conducted using the breathing machine settings and constant flow rates identified in Table 5-1.

Tidal volume

(litres ATP)

Breathing rate

(breaths per minute

Ventilation rate

(l·min-1 ATP)

Constant flow

(litres STP)

1.5 10 15.0 200

1.5 15 22.5 300

2.0 20 40.0 530

2.5 25 62.5 830

3.0 25 75.0 1000

3.0 30 90.0 1200 Ambient Temperature and Pressure (ATP), Standard Temperature and Pressure (STP)

Table 5-1: Breathing machine ventilation rates and constant flow rates

Testing should be conducted according to the following procedure:

• Set constant flow rate; • Initiate simulated breathing using a single breathing machine attached

to the demand valve under test; • During the simulated breathing the flow rate shall not be adjusted; • Inhale and exhale respiratory pressures to be recorded throughout the

breathing cycle and work or power of breathing calculated.

The recorded and calculated results may then be compared with a recognised standard for breathing performance.

27

6 Conclusions The breathing performance of an open-circuit demand regulator may be improved by an increase in the volume of the intermediate pressure system.

When constructing a single breathing machine with constant flow from the first stage regulator test system, the intermediate pressure system volume should not be increased by more than 200 ml.

A single breathing machine, in conjunction with an appropriate constant flow from the first stage regulator, was able to represent the breathing performance of an ‘Octopus’ SCUBA system obtained by dual in-phase breathing machines.

Simulation of breathing performance with a single breathing machine and constant flow from the first stage regulator was able, to a first approximation, to reproduce a demand valve dual in-phase breathing pressure-volume loop in respect of peak respiratory values and work of breathing.

A high constant flow of gas, equivalent to peak flow during sinusoidal breathing (i.e. Ventilation rate * π * pressure (bar)), proved more severe than in-phase breathing, but was able to discriminate the same BS EN 250 pass/fail results.

Attempts to establish a consistent constant flow of breathing gas that would allow exact simulation of in-phase breathing performance proved unsuccessful. However, analysis indicates that the root mean square (rms) of the peak flow (i.e. Ventilation rate * 0.707 * π * pressure (bar)) would be an appropriate constant flow rate.

The tests conducted for this study, including those from the severe high constant flow tests, confirm the recommendation from the previous QinetiQ report [8] that ‘Octopus’ systems should be based on high performance (possibly higher cost) first stage regulators.

28

7 Recommendations A test procedure using a single breathing machine linked with a constant flow from the first stage regulator may be used as a simple test for open-circuit SCUBA ‘Octopus’ systems.

The test procedure proposed in Section 5 of this report should be used for open-circuit ‘Octopus’ systems and for inclusion in future diving apparatus standards including the next revision of BS EN 250.

Further data should be obtained to confirm, or identify an alternative to, the root mean square (rms) of the peak flow (i.e. Ventilation rate * 0.707 * π * pressure (bar)) as the ideal constant flow rate for single breathing machine testing of ‘Octopus’ systems.

‘Octopus’ systems should be based on a high performance (possibly higher cost) first stage regulator.

29

8 References [1] The Diving at Work Regulations 1997. SI 1997/2776. ISBN 0 11 065170 7 [2] Recreational diving projects. The Diving at Work Regulations 1997. Approved

Code of Practice L105. HSE Books. 1998. ISBN 0 7176 1496 4. [3] Media diving projects. The Diving at Work Regulations 1997. Approved Code

of Practice L106. HSE Books. 1998. ISBN 0 7176 1497 2. [4] Scientific and archaeological diving projects. The Diving at Work Regulations

1997. Approved Code of Practice L107. HSE Books. 1998. ISBN 0 7176 1498 0.

[5] BS EN 250: 2000. Respiratory equipment – Open-circuit self-contained

compressed air diving apparatus – Requirements, testing, marking. [6] British Sub-Aqua Club Technical Services. NDC Diving Incidents Report

(02/202, 144). 2002. [7] British Sub-Aqua Club Technical Services. NDC Diving Incidents Report

(03/225, 139, 075). 2003. [8] Anthony, T.G, Fisher, A.S. and Gould, R.J. ‘Breathing performance of

‘Octopus’ demand regulator systems’. HSE Research Report 341, 2005. ISBN 0 7176 6106 6. http://www.hse.gov.uk/research/rrhtm/rr341.htm

[9] Life Support Systems Laboratory Handbook.

QinetiQ/D&TS/CHS/MP0600277/1.0:Annex B. [10] Norwegian Petroleum Directorate/Department of Energy. Guidelines for

evaluation of breathing apparatus for use in manned underwater operations in the petroleum activities. 1991. ISBN 82-7257-308-3.

[11] BS EN 12021:1999. Respiratory protective devices. Compressed air for

breathing apparatus.

[12] Halliday, D., Renick, R. and Merrill, J. Fundamentals of Physics 3rd Edition extended. John Wiley & Sons, New York. 1988. ISBN 0-471-63736-X.

30

A Breathing performance data Phase 1 Data.

Depth (m)

30 40 50 Nominal ventilation rate (l·min-1 ATP) Demand

valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50

Primary (out of phase) 50 Octopus

(out of phase) 50

Primary (in phase)

50 Octopus (in phase)

50

Pass WoB< 0.5 J/l at 0 l·min-1- 4.0 J/l at 90 l·min-1 Fail WoB> 0.5 J/l at 0 l·min-1- 4.0 J/l at 90 l·min-1 No data (Anticipated Fail - see text)

Table A-1: Summary table for work of breathing. System 1

Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50

Primary (out of phase)

50 Octopus

(out of phase) 50

Primary (in phase) 50

Octopus (in phase) 50

Pass Respiratory Pressure < 2.5 kPa Fail Respiratory Pressure > 2.5 kPa No data (Anticipated Fail - see text)

Table A-2: Summary table for respiratory pressure. System 1

31

Phase 2 Data. Dual breathing machine configuration.

Depth (m) 30 40 50 Nominal ventilation rate (l·min-1 ATP) Demand

valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


(out of phase) 50

Primary (in phase)


50



Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


50 Octopus

(out of phase) 50





32

Phase 1 Data

System 1 - 50 bar - 30 m

0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)Primary only

Primary out ofphasePrimary inphaseOcto only

Octo out ofphaseOcto in phase

Pass/Fail limit

Figure A-1: 30 m work of breathing data. System 1


0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit


33

Phase 2 Data. Dual breathing machine configuration


0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)Primary only



Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit


34

Phase 1 Data


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


(out of phase) 50

Primary (in phase)


50

Pass WoB< 0.5 J/l at 0 l·min-1- 4.0 J/l at 90 l·min-1 Fail WoB> 0.5 J/l at 0 l·min-1- 4.0 J/l at 90 l·min-1 No data (Anticipated Fail - see text) No data


Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


50 Octopus

(out of phase) 50



Pass Respiratory Pressure < 2.5 kPa Fail Respiratory Pressure > 2.5 kPa No data (Anticipated Fail - see text) No data


35


Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


(out of phase) 50

Primary (in phase)


50



Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


50 Octopus

(out of phase) 50





36

Phase 1 Data


0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit

6.80



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit

5.595.578.1


37



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit

11.58 7.55



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit

5.0211.48 15.0618.355.92


38

Phase 1 Data

Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


(out of phase) 50

Primary (in phase)


50



Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


50 Octopus

(out of phase) 50





39


Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


(out of phase) 50

Primary (in phase)


50



Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50


50 Octopus

(out of phase) 50





40

Phase 1 Data


0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)Primary only



Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit

5.57


41



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)Primary only



Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only



Pass/Fail limit

5.57


42

B Breathing performance data Phase 2 Data. Constant flow configuration

Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50



Primary (high flow)

50 Octopus (high flow)

50


Table B-1: Summary table for work of breathing. System 1


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50



Primary (high flow)


50


Table B-2: Summary table for respiratory pressure. System 1

43

Phase 2 Data. Constant flow configuration


0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)Primary only

Primary inphasePrimary highflowOcto only

Octo in phase

Octo high flow

Pass/Fail limit

Figure B-1: 30 m work of breathing data. System 1


0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only


Octo in phase

Octo high flow

Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only


Octo in phase

Octo high flow

Pass/Fail limit


44


Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50



Primary (high flow)


50




valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50



Primary (high flow)


50



45



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)Primary only


Octo in phase

Octo high flow

Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only


Octo in phase

Octo high flow

Pass/Fail limit

5.4



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only


Octo in phase

Octo high flow

Pass/Fail limit

7.53 5.9


46


Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50



Primary (high flow)


50



Depth (m)


valve Supply

pressure (bar)

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

40.0

62.5

75.0

90.0

Primary

50

Octopus 50



Primary (high flow)


50



47



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only


Octo in phase

Octo high flow

Pass/Fail limit



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only


Octo in phase

Octo high flow

Pass/Fail limit

7.91



0.0

1.0

2.0

3.0

4.0

5.0


(l .min-1 ATP)

Wor

k of

bre

athi

ng(J

/l)

Primary only


Octo in phase

Octo high flow

Pass/Fail limit

7.75


48

C Example pressure-volume loops

Figure C-1: System 1, Primary only, Primary in-phase, Primary simulated in-phase

Figure C-2: System 1, ‘Octopus’ only, ‘Octopus’ in-phase, ‘Octopus’ simulated in-phase

49


Figure C-4: System 4, ‘Octopus’ only, ‘Octopus’ in-phase, ‘Octopus’ simulated in-phase

50


Figure C-6: System 6, ‘Octopus’ only, Octopus in-phase, Octopus simulated in-phase

Printed and published by the Health and Safety ExecutiveC30 1/98

Published by the Health and Safety Executive09/06

RR 492

RESEARCH REPORT 492 - Health and Safety Executive · breathing performance of an ‘Octopus’...

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