Servomex 570a Oxygen Analyser Instruction Manual

GENERAL SAFETY INFORMATION Servomex Oxygen Analysers are sophisticated devices intended for use by qualified personnel only. It is necessary that this manual be read and understood by those who will install, use and maintain this equipment. Important Model B - Versions of the 570A analyser are certified by BASEEFA for use in certain hazardous areas, subject to the conditions laid down in the certificates at the rear of this manual. Certification can be recognised by the BASEEFA crown on the back panel of the analyser. 578A - Power supply units are for use with Model B analysers only, and are not suitable for use in hazardous areas.

WARNING ANY MODIFICATION TO THE ANALYSER WILL INVALIDATE BASEEFA APPROVAL

DESCRIPTION OF SAFETY TERMS IN THIS MANUAL DANGER -

Used when there is a possibility of serious personal injury or death.

WARNING -

Used when there is a possibility of personal injury.

CAUTION -

Used when there is a possibility of damage to the equipment.

NOTE -

Used to alert the user to pertinent facts and conditions.

I

NOTES The 570A portable paramagnetic oxygen analyser complies with the European Community “Electromagnetic Compatibility Directive” 89/336/EEC by the application of the following standards: EN50081-1: EN50082-1:

Emissions: Immunity:

Light Industrial Environment Light Industrial Environment

The 570A is certified for use in hazardous areas and is excluded from the scope of the European Community “Low Voltage Directive” 73/23/EEC. The 570A is CE marked for the European Community “Electromagnetic Compatibility Directive” 89/336/EEC only. It complies with the transitional arrangements of the European Community “ATEX Directive” 94/9/EC.

Oxygen USP Verification Measurements Analysers used for Oxygen USP verification, must be set up in accordance with Section 2.2.2(c) and calibrated and used in accordance with the relevant part of Section 3.3

II

LIST OF CONTENTS Section 1.

Page Description... 1.1 1.1 1.2 1.3 1.4

2.

Initial Set Up... 2.1 2.1 2.2 2.3

3.

General... 4.1 Recharging the rechargeable batteries... 4.2

Testing and Fault Diagnosis... 5.1 5.1 5.2

6.

Operational Precautions... 3.1 Operation... 3.4 Calibration... 3.4 Recorder Output... 3.5 Altitude Compensation... 3.5

Routine Maintenance 4.1 4.2

5.

Rechargeable Battery Pack... 2.1 Support Facilities... 2.1 Connections to Automatic Flow Control Device (AFCD)... 2.3

Operating and Calibration Instructions... 3.1 3.1 3.2 3.3 3.4 3.5

4.

General... 1.1 Principles of Operation... 1.2 Specifications... 1.4 Optional Extras... 1.7

General... 5.1 Test Procedure for a complete 570A... 5.2

Repair... 6.1 6.1 6.2 6.3 6.4. 6.5 6.6 6.7 6.8 6.9 6.10 6.11

General... 6.1 Replacement of a Fuse... 6.1 Replacement of a Filter... 6.2 Replacement of the 570A Circuit Board Assembly (570/935) . . . 6.2 Replacement of components on the front panel... 6.2 Replacement of rechargeable batteries... 6.5 Repair of the Automatic Flow Control Device... 6.5 Adjustment of the Automatic Flow Control Device... 6.7 Replacement of the Measuring Cell... 6.8 Replacement of the Zero Assembly... 6.11 Replacement of the 500A Printed Circuit Board (500 / 921)... 6.13

III

Section 7.

Page Parts List... 7.1 7.1

8.

Optional Extras... 8.1 8.1 8.2 8.3

9.

Introduction... 7.1

578A Power Supply... 8.1 Internal Sampling Pump... 8.2 Portable Flue Gas Sampling System (214/706)... 8.4

Appendix 1 - BASEEFA Certificates... 9.1

LIST OF FIGURES Figure... Page 1.1 1.2 1.3 2.1 2.2 3.1 5.1 5.2 5.3A 5.3B 6.1 6.2 6.3 6.4 6.5 6.6 8.1 8.2 8.3 8.4

Dumb-bell System... 1.2 Servomex Oxygen Cell... 1.2 Servomex Analyser Configuration... 1.3 570A Principal Dimensions and Controls... 2.4 Automatic Flow Control Device (AFCD) Section... 2.5 Graph for Adjusting Span AOT Resistor... 3.6 Internal View of the 500A Transducer... 5.1 Interconnection Diagram 570A Model B... 5.8 570A Digital Display Circuit Diagram (Sheet 1)... 5.9 570A Digital Display Circuit Diagram (Sheet 2)... 5.10 Exploded View of the 500A Transducer... 6.4 Automatic Flow Control Device (AFCD)... 6.6 Removing the Measuring Cell... 6.9 Orientation of the 500A Transducer fanning strip... 6.10 Zero Assembly Connections... 6.12 Sample Flow Diagram... 6.14 578 Power Supply Circuit Diagram... 8.3 Flue Gas System Circuit Diagram... 8.3 Installation Details Internal Pump... 8.6 Flue Gas System Schematic... 8.6 LIST OF TABLES

Table... Page 2.1 7.1

Effect of various Input Configurations... 2.3 Recommended Spares Lists, Model B Analyser... 7.2

IV

Section 1: Description 1.1

General

This manual describes the Servomex 570A portable Oxygen Analyser, used for determining the oxygen content of a gas sample in the range 0 to 100% O2. It is fully portable, being powered by rechargeable batteries. An optional power supply / recharging unit is available. The 570A has a digital liquid crystal display to indicate the oxygen reading. The 570 A analyser is BASEEFA approved, certificate number EX812155X, code EEX ib IIC T4. This approval also covers CENELEC standards EN50 014 and EN 50020. The analyser is supplied with a standard accessories kit comprising: 1 x Hand Aspirator 1 x Drying Tube 1 x 5mm Allen Key 1 x 3/32 “ Allen key 1 x Filter Elements 1 x 2.5mm Jack Plug 1.1.1 Analyser Variants A serial number label on the base of the analyser identifies the model number and its variants.

The model variant number is as follows for Model B analysers: Rechargeable Rechargeable + Internal Pump

712 713

1.1

1.2

Principles Of Operation

1.2.1

Analyser

The analyser measures the paramagnetic susceptibility of the sample gas by means of a proven magneto-dynamic type measuring cell. The paramagnetic susceptibility of oxygen is significantly greater than that of other common gases. Simply, this means that oxygen molecules are attracted much more strongly by a magnetic field than are molecules of other gases, most of which are slightly diamagnetic (repelled by a magnetic field). Magneto-dynamic oxygen analysers are based upon Faraday’s method of determining the magnetic force developed by a strong non-uniform field on a diamagnetic test body suspended in the sample gas. The test body of all measuring cells in Servomex oxygen analysers consists of two nitrogen filled quartz spheres arranged in the form of a dumb-bell as shown by figure 1.1 A single turn of fine platinum wire (the feedback coil) is secured in place around the dumb-bell. A rugged, taut band platinum ribbon suspension attached to the midpoint of the dumb-bell positions the dumb-bell in the strong non-uniform magnetic field between the specially shaped pole pieces of the permanent magnetic structure - see Figure 1.2.

Figure 1.1 Dumb-bell System The angular rotation of the dumb-bell is sensed by a light beam projected onto a mirror attached to the dumb-bell from which it is reflected onto a pair of photocells. See figure 1.3. The difference in the outputs from these photocells is fed to an amplifier whose output is zero when both photocells are illuminated equally.

Figure 1.2 Servomex Oxygen Cell

1.2

When a sample gas containing oxygen surrounds the dumb-bell, the oxygen molecules are attracted to the strongest part of the magnetic field, thus changing the forces acting on the dumb-bell, causing a displacement of the light beam across the photocells, which in turn results in a difference signal being sensed by the amplifier. The corresponding output of the amplifier is a current, proportional to the oxygen content of the sample, which is fed to the feedback coil of the measuring cell. This produces a magnetic field, which opposes the forces causing the dumb-bell to rotate. Thus the dumb-bell is retained in its original position. Since this current is proportional to the oxygen content of the gas sample, it is used to develop the output signals available from the analyser. This current feedback force balance design is resistant to mechanical shock and has outstanding accuracy and linearity. The paramagnetic susceptibility of oxygen varies inversely as the square of the absolute temperature, therefore, a temperature sensitive element in contact with the magnet / measuring cell assembly is included in the feedback current circuit to provide compensation for changes in analyser temperature. While this compensation is adequate to maintain the instrument accuracy over normal short fluctuations at ambient temperature, larger changes will require span adjustment.

Figure 1.3 Servomex Analyser Configuration 1.2.2

Sampling System

The sampling system of this analyser includes a combination filter / automatic flow control device (AFCD), which is designed to introduce the sample into the measuring cell within the proper range of flow rates (80 to 150cc / min of air) and to prevent the entrance of particles into the measuring cell. The sample gas enters the AFCD through one of the upper two ports. If the sample pressure is between 0 and 1/3 psig (0 to 2.3 kPa) all of the sample gas flows to the measuring cell via the upper port. The spring loaded ball valve begins to open at sample inlet pressures above 1/3psig (2.3kPa) thus by-passing the excess sample flow to vent. Selection of the inlet / outlet ports is based on the relative importance of the speed of response, ability to accommodate accidental introduction of condensate and whether or not the internal sample pump is fitted. (See section 2.3)

1.3

1.3

Specifications

1.3.1

Mechanical

Dimensions:

Width Height Length

150mm (6in) 190mm (7.5in) 305mm (12in)

Weight

6.5kg (14lb)

Inlet and outlet connection 6.5mm (0.25") OD tube. Push on 1.3.2

Environment

Operating temperature range 0 to 50°C (32 to 122°F) (BASEEFA Approval to 40°C) 1.3.3

Electrical Requirements

Powered by a rechargeable NiCad pack which is re-charged by the power supply. Rechargeable battery capacity between charges is 25hr approx. Or 12hr if a pump is fitted. The analyser will run continuously when the power supply is connected. WARNING NEVER USE THE 578A POWER SUPPLY IN A HAZARDOUS AREA

The 578A is BASEEFA approved for connection to model B analysers. BASEEFA certification of the analyser will be invalidated if the analyser is connected to any power supply other than the 578A. Range From 00.0% O2 to 100.0% O2. Readout / Output The readout is a 3½ digit 0.7 inch high liquid crystal display with a resolution of 0.1% O2 An output of 0-1 volt for 0-100% is available through a 2.5mm jack socket. Output impedance 1k ohm. Accuracy is ±0.1% oxygen.

1.4

Operating Controls Push button switches. On / Off Battery check, momentary action. Combined screwdriver or finger adjust on front panel for span. Screwdriver adjust on left hand side of case for zero. 1.3.4

Sample Requirements

Particle Size Less than 0.6 micron Dew Point 10°C (18°F) below minimum expected ambient temperature. Inlet Pressure Min 1/3psig (2.3kPa). Max. 10psig (70kPa). Inlet pressure change from 1/3psig to 10psig will cause a reading change of less than 0.1% O2. When the internal pump is fitted, the minimum inlet pressure is 25mm Hg suction and the maximum is 2psig (14kPa). Flow Control An automatic flow control device controls the cell flow to between 80 and 150cc/ min, with an inlet pressure of 1/3 psig (2.3 kPa) to 10 psig (70 kPa) The bypass flow will vary between 1 ½ litres / minute and 6 litres / minute approx for inlet pressure between 1/3 psig (2.3kPa) to 10 psig (70kPa) Inlet on front panel. Cell outlet and bypass outlet on back panel. A replaceable fibreglass type tubular filter is fitted on the back panel. Response Time The overall response time is less than 7.5 seconds with an inlet pressure of 10psig (70kPa)

1.5

Materials in contact with sample -Stainless steel 303 and 316 -Glass -Platinum -Epoxy Resin -P.T.F.E -Viton -Polypropylene Additionally when an internal pump is fitted: -Carbon -Resin 1.3.5

Certification

The model B instrument has been approved by BASEEFA for use in Zone 1 and 2 hazardous areas, where the ambient temperature is less than 40°C, and in hydrogen atmospheres. The certification also approves the analyser for use on a mixed hydrogen and oxygen gas sample. (Certification number EX812155X Code EEX ib IIC T4). See certificates at the rear of this manual for further information. 1.3.6

Accuracy

There are various effects that will influence the measuring activity of the analyser as follows. Effect of battery charge The reading will change by less than 0.05% O2 when the battery changes from full charge to end point (8.1 to 6.6V). Temperature Coefficient Effect at 0% O2, less than ±0.02% O2 /°C Effect on span: Less than ±0.2% full scale /°C Pressure Effect The oxygen reading will vary in direct proportion to barometric pressure. Repeatability Better than 0.1% O2. Linearity Better than 0.1% O2. 1.6

Effect of tilt (from Calibration attitude) Degrees of Tilt ±O2 Error (Max) ±O2 Error (Typical)

0 0 0

10 0.2 0.1

45 0.45 0.3

90 0.9 0.6

For best accuracy, the analyser should be calibrated at the angle of tilt at which it is to be read. Effect of External Magnetic Materials When magnetic materials are placed directly on the analyser case, the reading will alter by less than 0.1% O2. 1.4

Optional Extras (Refer also to Section 8 of this manual)

(i)

Internal Sampling Pump

The back panel can be fitted with an electrical pump which will enable sample gas to be drawn in automatically from ambient or slightly negative pressure atmospheres. Model B analysers fitted with the internal pump are BASEEFA certified. (ii)

Mains Power Supply

The power supply can be used to recharge the rechargeable battery. (iii)

Flue Gas Sampling System

This system permits the monitoring of the oxygen content of a flue gas sample either on a sot check basis or for carrying out boiler performance surveys.

WARNING Analysers modified to take the flue gas sampling system are not BASEEFA certified, even if the system is not connected.

1.7

NOTES

1.8

Section 2: Initial Set-Up 2.1

Rechargeable Battery Pack

Check the state of charge by pressing the On /Off switch to On. Press the battery check button (>6.5). The reading should be greater than 6.5. If the indication is less than 6.5 then the batteries need to be recharged. The Servomex Power Supply plugs into the jack socket on the back of the analyser, to charge the batteries and power the analyser at the same time. WARNING NEVER USE THE 578A POWER SUPPLY IN A HAZARDOUS AREA. 2.2

Support Facilities

The following utilities, gases, test equipment and tools must be available on site in order to maintain proper operation of the analyser. 2.2.1

Electricity Supply

If a 578A Power supply is used, a source of electric power, installed in accordance with local codes of practice, capable of supplying a nominal voltage of 100, 117 or 234V AC, 48 to 62 Hz, must be available at locations where the analyser is to be used or serviced. Regulation of this supply must be within ±15% of the nominal voltage if specified accuracy is to be maintained. 2.2.2

Calibration Gases

The following calibration gases must be available:(a) Oxygen-free Nitrogen - Zero Gas The minimum purity of this nitrogen must be 99.9% WARNING NITROGEN IS AN ASPHYXIANT AND MUST NOT BE USED IN CONFINED SPACES WITHOUT ADEQUATE VENTILATION. (b) Instrument Quality Air Instrument quality air meeting the requirements of ISA Standard S-7.3 - Dew Point Temperature 10 deg C (18 deg F) below the lowest expected ambient temperature. - Particle size - maximum; less than 3 micron. - Oil Vapour; below 1ppm.

2.1

WARNING NEVER USE THE ANALYSER TO MEASURE A GAS WITH A HIGH OXYGEN CONTENT FOLLOWING USE ON AIR WITH AN OIL VAPOUR CONTENT. THE OIL VAPOUR WILL CONTAMINATE THE TUBING AND MAY RESULT IN A FIRE ON CONTACT WITH HIGH OXYGEN LEVELS.

If instrument quality air is not available, dry bottled air or ambient air with hand aspirator and drying tube may be used.

CAUTION All gas cylinders used in conjunction with 570A Analysers must be fitted with a tank or cylinder mounted regulator whose delivery pressure can be limited to 10 psig (70 kPa) and an appropriate output pressure gauge. This will prevent serious over-pressuring of the analyser and resulting damage to the measuring cell. c) Certified Oxygen Cylinder A certified cylinder of high purity oxygen 99.2% minimum, for analyser span when verifying high purity oxygen. The cylinder must be fitted with either a pressure regulator with gauge or an adjustable litre flow regulator. use of high purity oxygen negates the requirement for instrument air in (b). 2.2.3

Test Equipment /Tools

The following test equipment and tools should be available to personnel responsible for maintenance and calibration of the analyser (a)

Test Equipment A volt, ohm, milliamp meter of impedance of at least 1,000 ohms per volt. A manometer to measure 12 inches (300 mm) water gauge.

(b)

Spanners

- Removing an installing a measuring cell requires the following open ended spanners:British Designation 3/16 Nom. (c)

Width across the Flats 0.445in

U.S Equivalent 7/16

Removing the case halves requires a 5mm hexagon key (supplied) Opening the cover to the 0 to 1 volt signal output requires a 3/32 “ hexagon key (supplied). Removing the span potentiometer knob requires a 1.5mm hexagon key.

2.2

(d)

Bubble flowmeter to adjust automatic flow control device.

(e)

A 4 ½ digit voltmeter to adjust the analogue to digital converter.

(f)

Silica gel for refilling drying tubes. WARNING USE ONLY THE BATTERY PACK SUPPLIED BY SERVOMEX. FITTING OF ALTERNATIVE BATTERIES INVALIDATES BASEEFA CERTIFICATION.

2.3

Connections to Automatic Flow Control Device (AFCD)

The selection of the sample / measuring cell connections to the automatic flow control device (AFCD) should be based on the relative importance of speed of response, ability to accommodate accidental introduction of condensate, and presence of internal sampling pump. Figure 2.2, shows the internal construction of the AFCD and also the fixed restrictions, A & B, used along with the spring loaded relief valve to control the flow to the measuring cell. The characteristics of the fixed restrictions for identifications purposes are as follows:- (Ref: Fig 2.2) Function

Bore mm (in)

Height of Hex Base mm (in)

A. Inlet

0.33 (0.013)

Short 3.1 (0.125)

B. To measuring Cell

0.63 (0.025)

Tall 6.2 (0.25)

The results obtained with the various configuration are given in Table 2.1. Table 2.1 Effect of Various Input Configurations Configuration

A (inlet)

B (to cell)

Flow rate (total l/min)

Time90% Response

1 Direct

M

T

6

11 sec

Minimal

2 Direct

T

M

6

5 sec

Soak Filter, some to cell

3 Pump

T

M

0.6

15 sec

2.3

Effect of condensate

Fill pump and soak Filter

Figure 2.1 570A Principal Dimensions and Controls

2.4

Figure 2.2 Automatic Flow Control Device (AFCD) Section (Shown with restrictors arranged for internal pump)

2.5

NOTES

2.6

Section 3: Operating and Calibration Instructions 3.1

Operational Precautions

The following paragraphs describe in detail the effects of certain operational factors which must be observed in order to achieve the accuracy of which the analyser is capable and to minimise possible damage by accidental operation outside of its design specifications. 3.1.1.

Ambient Temperature

The 570A Oxygen Analyser should be stabilised and calibrated at the ambient temperature at which it is to be used. 3.1.2.

Vibration

The analyser is relatively insensitive to vibration, however, best results will be obtained when it is situated away from heavy vibrations. 3.1.3.

Classification of Areas Of Use

Refer to general Safety Information at the beginning of this manual. Also:WARNINGS 1) DO NOT REMOVE THE BATTERIES IN A HAZARDOUS AREA. 2) DO NOT CLEAN THE PLASTIC CASE IN A HAZARDOUS AREA BY RUBBING IT. THIS MAY GENERATE STATIC ELECTRICITY. WARNING TO PERMIT THE 0-1V OUTPUT CONNECTOR OF INSTRUMENTS MARKED WITH THE BASEEFA NUMBER EX812155X/5 TO BE CONNECTED TO OTHER INTRINSICALLY SAFE APPARATUS. IN THIS CASE THE WARNING "MAXIMUM INPUT 1V" DOES NOT APPLY AND THE PARAMETERS BELOW TAKE PRECEDENCE. THE PARAMETERS FOR THE CONNECTOR ARE : Uo (Umax out) = 10.2V, Io (Imax out) = 12mA, Po (Wmax out) = 30mW, Ci (Ceq) = 0, Li (Leq) = 0, Ui (Umax in) = 10.2V, Co (Cext)  2:F, Lo (Lext)  200mH, Lo/Ro (L/R)  1000:H/Ohm, FOR ALL GROUPS. DO NOT USE THE 0-1V OUTPUT OF INSTRUMENTS MARKED WITH THE BASEEFA NUMBER EX812155X ONLY IN A HAZARDOUS AREA

3.1