Air / Oxygen Gas Mixer Service Manual Rev 14

1. USER RESPONSIBILITY The Sechrist Industries Air/Oxygen gas mixer is a restricted medical device for sale by or on the order of a physician, and is designed for use by qualified personnel under the direction of a qualified physician. Do not attempt to operate the gas mixer before reading and thoroughly understanding these instructions. The gas mixer will perform in conformance with the specifications and description contained in this service manual and other accompanying labeling when assembled, operated, maintained, and repaired in accordance with the instructions contained herein. The gas mixer must be checked periodically as specified in this manual (see the section “Preventive Maintenance”). A defective or damaged device should not be used. Any necessary repair should be conducted at the Sechrist Industries facility in Anaheim, CA, or by an individual trained and authorized by Sechrist Industries using components provided by Sechrist Industries; contact Sechrist Industries to receive training and authorization to service gas mixers. Sechrist Industries will not be held responsible for unauthorized service work on any gas mixer.

2. WARNINGS AND CAUTIONS WARNINGS mean there is a possibility of personal injury to the operator or patient. CAUTIONS indicate there is a possibility of damage to the gas mixer or other equipment attached to it. NOTES are used to call attention to statements pertaining to more efficient or convenient operation or service of the equipment, or to add clarification information.

WARNINGS •

• •

•

• •

The alarm module will activate if the oxygen or air gas source increases or decreases resulting in a 20 PSI difference between inlet gas pressures. This will affect the gas mixer’s oxygen concentration of the delivered gas. For gas mixer models with alarm reeds, activation of the alarm module will product an alarm sound. This precision gas mixing device is intended for use with Medical-grade Air and Medical-grade Oxygen inlet gas only. Do not modify inlets to accommodate other breathing gases, especially anesthetic gases. Before use on a patient, the oxygen concentration of the delivered gas should be checked at the setting intended for use. A separate, calibrated oxygen analyzer equipped with alarms that can be set for high and low FiO2 readings should be used to monitor downstream from the gas mixer. FiO2 readings should then be adjusted to maintain appropriate blood gas concentrations qualified personnel under the direction of a qualified physician. Oxygen vigorously accelerates combustion. To avoid explosion hazard, do not expose the gas mixer to any instruments or other equipment that may have been contaminated by oil or grease. Gas supplied to the gas mixer must be extremely clean (no more than 25 parts per million (ppm) of gaseous hydrocarbons is allowed). A high concentration of hydrocarbons in the gas supply is a fire hazard. The gas mixer audible alarm may not function when both air and oxygen gas supply pressures are less than the minimum specified inlet gas pressure (30 psig). Excessive supply pressures (> 70 psig) may result in gas mixer damage or malfunction. Use of a suitable supply gas regulation system is necessary.

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•

•

•

• • •

•

The outlets have the capability of providing gas pressures equal to the inlet pressures. Therefore, any attached equipment must provide safety relief protection to prevent excessive pressures from being delivered to patients. Whenever a patient is attached to respiratory care equipment, constant attendance is required by qualified personnel. The use of alarm or monitoring systems does not provide absolute assurance of a warning for every possible system malfunction. In addition, some problems may require immediate attention. The gas mixer does not contain gas-sterilizing filters and will supply the same quality of gas supplied from the gas sources. Use of appropriate gas purity and gas line filters is the responsibility of the user. Liquid water or other contaminants in either supply gas, particularly in the air supply, may cause malfunction of this equipment and any attached equipment. Supply gases should meet gas dryness of .0045 mg water per cubic centimeter of gas. When the gas mixer is used to supplement respiratory equipment, the user must refer to and follow the instructions provided by the manufacturer of the respiratory equipment. Rx only - The gas mixer is a restricted medical device intended for use only by qualified personnel under the direction of a qualified physician. It is responsibility of the procuring organization to assure they have the tooling, equipment and training necessary to perform the tasks outlined within this Service Manual. Hospitals or users who perform certain repairs and/or periodic service without undergoing training by Sechrist Industries assume sole responsibility for any malfunction, which results from improper usage, maintenance, improper or unauthorized repairs, damage or alteration performed. The user of the gas mixer shall have sole responsibility for any malfunction which results from improper usage, faulty maintenance, improper and/or unauthorized repairs, damage or alteration performed by anyone other than Sechrist Industries.

CAUTIONS • • • • • • • • • • •

If resistance is met before stop pin at 1.0 position is reached, do not force the knob. Re-adjust rear seat slightly - just enough to allow free range of movement to stop pin position. Recheck the calibration as described in this manual. Alarm bleed set screw (P/N 3568) is calibrated at factory and should not require calibration. Do not tape, obstruct, or hold finger over alarm outlet port. Permanent damage to reed can be caused by prolonged occlusion of reed outflow. Do not obstruct the bleed flow port on the bottom of the gas mixer. Damage may occur to both front seat and rear seat when rear seat is being installed if needle is not straight up and centered. Do not attempt to dig ball out of hole; damage will occur. Do not immerse the gas mixer. Do not gas or steam sterilize; damage may result. Do not service gas mixers unless trained and authorized by Sechrist Industries using components sourced from Sechrist Industries directly. Refer to Preventive Maintenance section for information about overhaul kit P/N 3658. Preventive maintenance on the gas mixer as provided in this manual must be followed to assure proper continued function and accuracy. Labeling on the gas mixer must remain legible. Do not service gas mixers with a manufacturing date past 20 years.

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3. GAS MIXER OPERATION AND INTRODUCTION TO SERVICE MANUAL GAS MIXER OPERATION 3.1. The Sechrist Industries Air-Oxygen gas mixer is a precision device used to proportion air and oxygen supply gases for delivery to other medical devices. The actual proportioning of the two medical gases is accomplished by using two identical orifices with a double ended tapered needle which is positioned by a threaded positioning shaft and knob in the proportioning module. This method of proportioning is effective only if the supply gas pressures are equal which is not common with hospital medical gas supply systems. The gas mixer uses a “nulling” type regulator method, where a centrally positioned elastomeric diaphragm between two balance regulator module blocks regulates the flow of each gas, essentially dropping the higher-pressure gas to the lower pressure (nulling) and thereby cancelling the pressure difference. The design of the balance regulator module prevents the gas mixers to operate on one gas supply. To safeguard against complete shutoff, the gas mixer also incorporates a bypass/alarm module. This module monitors inlet gas supply pressures and in the event of a greater than 20 psi pressure differential the bypass mechanism will be activated to continue operation of the device using the higher-pressure gas and sound a pneumatic powered reed assembly to alert the medical staff of the supply gas pressure deviation. INTRODUCTION TO SERVICE MANUAL 3.2. The gas mixer has been designed for durability and serviceability. If the criteria for the gas supply are met and the supply is satisfactorily clean and dry, the gas mixer should provide years of use with relatively little care and service. However, should it become necessary, these instructions are provided to serve as a guide for qualified technicians to service and repair the gas mixer low flow models 3500CP-G, 20090, 20099, 20400, 20457, 20549, 3500CP-M1, and high flow models 3600 and 3601. This service manual is designed to take the technician through a step-by-step process to: • Test for proper operations. • Troubleshoot any malfunctions. • Calibrate the gas mixer, if necessary. • Disassemble and reassemble the gas mixer. • Keep the gas mixer operating at its optimum efficiency of design. 3.3. This service manual provides information in a general-to-specific manner, including descriptions of all tools and test equipment required to service Sechrist Industries Air-Oxygen Gas Mixer products. This service manual details the testing procedures necessary to determine optimum working conditions of the gas mixer and if service is necessary based on the outcome of the testing, a Troubleshooting Guide is provided to determine which component module of the gas mixer is involved and what procedures are recommended. 3.4. The procedures necessary for service are given in the Disassembly and Reassembly sections and are broken down into the three unique component modules of the gas mixer. 3.4.1. The Proportioning Module that does the actual gas mixing and proportions the outflow; 3.4.2. The Pressure Balancing Module that takes the incoming gas pressures and nullifies any

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potential differential up to 20 psig, thereby equalizing the incoming gas pressures; and 3.4.3. The Alarm Module that when the alarm is activated, a continuous sound is produced by the reed alarm and the inlet gas with the highest pressure will be delivered by the gas mixer until supply gas pressures are re-established. 3.5. Included photographs and diagrams provide a visual display of the instructions. Exploded diagrams of individual modules will provide a structured way of following the step-by-step instructions for disassembly and reassembly. NOTE: Required service can be significantly reduced by assuring the quality of the supply gases and performing routine filter maintenance. NOTE: In this document, the concentration of delivered gas is described in units of percent (Volume/Volume %) and fraction of inspired oxygen (FiO2). Both unit of measurements are interchangeable; for example, 21% oxygen concentration is .21 FiO2 and 80% oxygen concentration is .80 FiO2.

4. TOOLS REQUIRED The Preventive Maintenance, Service, and Testing procedures covered in this manual are to be performed by individuals trained and authorized by Sechrist Industries. Only procedures covered in this manual are to be performed in the field. Procedures requiring more extensive trouble-shooting and/or component replacement must be performed by Sechrist Industries. Special Sechrist Industries tools and accessories are required to calibrate, disassemble, and reassemble the gas mixer. 4.1. SECHRIST Calibration and Assembly Tool Kit (P/N 3651) (see Figure 1): 4.1.1. Assembly Tool (AT. 1): 1/8" spanner wrench (P/N 3654) 4.1.2. Assembly Tool (AT. 2): 3/8" spanner wrench (P/N 3653) 4.1.3. Assembly Tool (AT. 3): 5/8" spanner wrench (P/N 3652) 4.1.4. Assembly Tool (AT. 4): Mixer Calibration Block (P/N 42210) 4.1.5. Brass Plugs 10-32 (P/N 3635) 4.1.6. Brass 10-32 x 1/16 fitting (P/N IV-310) 4.1.7. Pan Head Screws 6-32x1/4 (P/N IV222) 4.1.8. O-rings -008 (P/N 3534) 4.1.9. O-rings -014 (P/N 3520) 4.1.10. Cap Screws 6/32x1/4 (P/N 3624) 4.1.11. Dowel Pins (P/N IV225)

(1 qty.) (1 qty.) (1 qty.) (1 qty.) (2 qty.) (1 qty.) (2 qty.) (2 qty.) (2 qty.) (2 qty.) (8 qty.)

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Figure 1 Assembly Tool Kit (P/N 3651)

4.2. GENERAL CALIBRATION AND ASSEMBLY TOOLS: 1/16" Allen wrench 3/16" Allen wrench 5/64" Allen wrench 7/64" Allen wrench

7/16" open end wrench 1/2" open end wrench 3/4" open end wrench 1/4" nut driver

9/64" Allen wrench 1/4" Allen wrench 3/32" Allen wrench

Internal tru-arc pliers Needle nose pliers Soft mallet

Medium blade screwdriver Precision Caliper (see Figure 2) Precision Depth Micrometer (see Figure 2) Lubricant for O-rings: Krytox GPL-205 (Dupont)

Figure 2 Caliper and micrometer

4.3. EQUIPMENT REQUIRED FOR TEST SYSTEM: 4.3.1. Oxygen high pressure hose* 4.3.2. Air high pressure hose*

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4.3.3. 4.3.4. 4.3.5. 4.3.6.

Oxygen regulator (2 stage adjustable)* Air regulator (2 stage adjustable)* Flowmeter (0 - 20 LPM)* Pressure gauge (0-100 psig, .25% full scale accuracy, readout accurate to 0.5 psig)*

NOTE*: This service manual details the testing and calibration process of the gas mixer, along with the separate necessary equipment needed. Sechrist Industries also offers gas mixer test stands (P/N 20646) available for purchase that is an all-in-one setup option for the equipment listed above in section 4.3.1 – 4.3.6. Contact Sechrist Industries for more information on P/N 20646. 4.3.7. Oxygen analyzer (calibrated to ±1% accuracy, readout accurate to 0.1% increments) 4.3.8. Sampling reservoir (250 ml bottle, lab flask or tube) 4.4. ROUTINE MAINTENANCE REQUIREMENT: 4.4.1. SECHRIST Parts Kit (P/N 3658) - (See “Parts” section for part numbers).

5. CALIBRATION AND TEST PROCEDURE Before attempting to calibrate or repair a gas mixer, the technician trained and authorized by Sechrist Industries should be familiar with the design and function of the device (see the section “Gas Mixer Operation and Introduction to Service Manual”). The following instructions utilize a numbering system which is to be followed in sequence. All parts are numbered and can be reviewed on the exploded parts diagrams contained herein. TEST PROCEDURE To determine the optimal function of the gas mixer and the potential need for calibration, service or repair, complete the following test procedures and record results in Appendix 1 - Test Procedure Data Sheet. Keep records of routine servicing. 5.1. Initial Test System Set Up (see Figure 3): 5.1.1. 5.1.2. 5.1.3. 5.1.4.

Connect the gas mixer to clean and dry Medical-grade Oxygen and Medical-grade Air gas supplies, which are independently adjustable from 0 to 100 psig. Connect a flowmeter to the outlet of the gas mixer (only necessary for gas mixer models without flowmeter assemblies). Direct the output flow from the flowmeter to a sampling reservoir (i.e. 250 ml bottle, lab flask or tube) while ensuring room air does not enter the reservoir and dilute the gas mixture. Insert oxygen analyzer probe into sampling reservoir.

NOTE: O2 analyzer must be calibrated and accurate to ±1%. 5.1.5.

Adjust the flowrate using the flowmeter to the following: 5.1.5.1. 8 LPM for Low Flow models.

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5.1.5.2.

16 LPM for High Flow models.

NOTE: Low Flow models have an “L” letter and High Flow models have an “H” letter stamped on the bottom of the proportioning block next to the bleed flow port.

Figure 3 Test System for the Gas Mixer

5.2. Proportioning Module: 5.2.1. 5.2.2. 5.2.3.

5.2.4.

Set O2 pressure and air pressure to 50 psig. Compare O2 analyzer readings to gas mixer settings of .21, .30, .40, .60, .80 and 1.0. The gas mixer has a specified accuracy of ±3% full scale. If the oxygen concentration reading varies more than ± 4% between the gas mixer and O2 analyzer reading, calibration or service may be necessary (see Troubleshooting Guide). There is a constant bleed of mixed gas from the bottom of the Proportioning Module. This bleed is between 2.5 to 4.5 LPM for Low Flow models and 8.0 to 10.0 LPM for High Flow models. This is needed to maintain accurate oxygen concentrations at very low flows. These bleed rates are predetermined by the factory and cannot be reset in the field.

5.3. Pressure Balancing Module: 5.3.1. 5.3.2.

With same test system set up as above, select an FiO2 of .60 and observe the oxygen analyzer reading. Vary the inlet pressures to the gas mixer to 40 psig O2 and 60 psig air and then to 60 psig O2 and 40 psig air. If the oxygen concentration varies more than ± 2% from the initial O2 analyzer reading or the alarm bypass module alarm is audible, calibration or service may be necessary (see Troubleshooting Guide).

5.4. Alarm Module: 5.4.1. 5.4.2.

Set air and O2 supplies to 50 psig. The alarm should be silent. Slowly reduce air inlet supply. The alarm should sound between 24 and 28 psig and O2

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5.4.3. 5.4.4.

analyzer should read > 97%. Increase air inlet supply, slowly, to 50 psig; the alarm should reset at or before 40 psig. 5.4.2.1. As the 3500CP-M1 gas mixer model does not have an alarm reed, no alarm sound will be produced. Instead, refer to the O2 analyzer display when slowly reducing air inlet supply and the FiO2 reading should be > 97% between 20 and 28 psig. When increasing air inlet supply, slowly, to 50 psig, the O2 analyzer reading should return to 60 ±3% at or before 40 psig. Repeat step 5.4.2 adjusting the O2 inlet supply; when alarm sounds, O2 analyzer reading should be < 25%. If alarm does not function as per above specifications, calibration or service may be necessary (see Troubleshooting Guide).

5.5. Air Inlet Filtration System (most frequent service required): 5.5.1. 5.5.2. 5.5.3. 5.5.4. 5.5.5.

To test the pressure drop through the water/trap filter or the internal air inlet filter, a test port has been provided on the rear of the gas mixer above the air inlet. With 1/4" nut driver, remove plug from test port and install a Brass 10-32 x 1/16 fitting (P/N IV-310) (see Tool Kit PN 3651). Connect a high-pressure gauge (0 to 70 psig) to the 10-32 fitting. With flow set at 8 LPM for Low Flow (16 LPM for High Flow), set gas mixer knob to .21. Observe pressure indicated at test port. If the difference between the pressure at the test port and the inlet pressure is greater than 5 psig, replace either or both air inlet filters (see “Preventive Maintenance” section).

5.6. Reverse Gas Flow: 5.6.1. Leave the air supply hose connected to the air inlet gas connector of the gas mixer and to the air supply source. 5.6.2. Disconnect the oxygen supply hose from the oxygen supply source but leave the other end of the hose connected to the gas mixer. 5.6.3. Insert the free end of the oxygen supply hose into a vessel, such as a beaker, with at least 1 inch of water. 5.6.4. Turn on the air supply source. 5.6.5. No bubbles should be observed. If there are bubbles, then replace the oxygen fitting duck bill check valve PN 3525 (see Figure 18). 5.6.6. Repeat for the air supply side. If the air supply side fails, then replace the air fitting check valve PN 3525 (see Figure 18). CALIBRATION PROCEDURE 5.7. GENERAL The Sechrist Industries Gas Mixer is calibrated and tested in conditions similar to the environment for which the gas mixer was designed. Medical-grade oxygen and Medical-grade Air gas sources will be required to calibrate the system. A calibrated oxygen analyzer is necessary (be sure O2 analyzer is calibrated to ±1% accuracy, readout accurate to 0.1% increments), and a flowmeter is used to sample the gas mixture being delivered to the oxygen analyzer. To calibrate the gas mixer, the system must be

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broken down into 3 modules: the Proportioning Module, the Pressure Balancing Module and the Alarm Module (see Disassembly and Reassembly Section). NOTE: The order of calibration given must be followed (i.e. the Pressure Balancing Module must be calibrated before the Proportioning Module can be connected and calibrated; and the Pressure Balancing Module and Proportioning Module must be calibrated together before the Alarm Module can be installed and calibrated). NOTE: Be sure the work area is clean and free from any materials or particulates that may contaminate parts during the disassembly and reassembly of the gas mixer. NOTE: Gas mixer models made custom to customer requirements may have different input/output fittings and plug configurations from what is represented in this service manual. PRESSURE BALANCING MODULE (see Figures 4 and 5) 5.7.1. 5.7.2.

To calibrate Pressure Balancing Module, all accessory parts (i.e., pole mount, wall mount, flowmeter) and Proportioning and Alarm Modules must be removed. Using 3/16" Allen wrench, remove 4 screws (P/N 3507) from the air block (P/N 3505) and divide the Pressure Balancing Module into 3 sections: air block (P/N 3505), oxygen block (P/N 3506) and diaphragm assembly (P/N 3510). See Figure 6.

NOTE: Air block and oxygen block are identical for calibration purposes. 5.7.3.

Using a precision caliper (see Tool List), measure the distance between the 2 diaphragm assembly support plates (see Figure 7). The distance should be about 0.800 ± 0.010”. 5.7.4. Locate the measured diaphragm assembly thickness in the Regulator Needle Setting Table (see Table 1) and read across to find the corresponding depth micrometer setting for the appropriate gas mixer model. 5.7.5. Set the depth micrometer (see Tool List) to the setting indicated in the table; rest the micrometer across the block cavity (see Figure 8). 5.7.6. Using either a 1/16" or a 5/64" Allen wrench, loosen set screw (P/N 3518). Using Assembly Tool (AT.) 1, insert into the eccentric adjuster (P/N 3516) and begin turning clockwise (see Figure 8). 5.7.7. The regulator seat (P/N 3512 Low Flow, P/N 3610 High Flow) and the regulator needle (P/N 3514 Low Flow, P/N 3611 High Flow) will move up and down. 5.7.8. As the spanner wrench is being turned (always clockwise), the needle and seat will arrive at top dead center and start back down. As it starts back down, start sliding the depth micrometer back and forth across the needle. Do not bend the needle. 5.7.9. Slowly turning the spanner wrench in very small increments, listen for the tapping noise of the depth micrometer contacting the needle as it slides over it. 5.7.10. At some point in the downstroke of the needle, the depth micrometer will no longer come in contact with the needle. As soon as the tapping noise ceases, the regulator needle is in the proper position. 5.7.11. Using either a 1/16” or a 5/64” Allen wrench, tighten set screw (P/N 3518) to secure calibration. 5.7.12. Calibrate both blocks in this manner and reassemble Pressure Balancing Module by replacing

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diaphragm assembly and securing the 2 block halves with 4 screws (P/N 3507), hand tightening only. NOTE: Position the 2 halves so that they are flush (make sure that the 2 halves of the module face where the Proportioning Module mounts and are flush). 5.7.13. Tighten 4 screws (P/N 3507) in a cross pattern to evenly distribute pressure. 5.7.14. Pressure Balancing Module is now calibrated. NOTE: At the end of all calibration procedures, a test of the Pressure Balancing Module must be performed to confirm the calibration. PROPORTIONING MODULE (see Figures 11 and 12) 5.7.15. Using a 9/64" Allen wrench, attach Proportioning Module to Pressure Balancing Module with 4 screws (P/N 3550). NOTE: Be sure O-rings are in place between the Proportioning Module and the Pressure Balancing Module. 5.7.16. Install faceplate (P/N 3605) with 2 screws (P/N 3559). 5.7.17. Install O-Rings (PN 3520) into grooves underneath Assembly Tool 4 (see Tool List) and install Assembly Tool 4 to occlude high pressure inlet ports to Alarm Module from Pressure Balancing Module. 5.7.18. Install a flowmeter. See Figure 9. NOTE: For Low Flow models with flowmeter assemblies, use the installed Sechrist Industries flowmeter. For Low Flow and High Flow models without flowmeter assemblies, install a flowmeter with a range of at least 0 to 20 LPM to the outlet of Proportioning Module. 5.7.19. Connect Medical-grade Air and Medical-grade O2 gas supplies to the respective inlet adapters. 5.7.20. Connect proportioning output to a calibrated O2 analyzer (see diagram for Test System Set-up Figure 3). NOTE: O2 analyzer must be calibrated and the accuracy of the readout scale must be within ± 1%. All analyzer readings specified throughout the calibration procedures are expressed as true fractional oxygen concentrations. 5.7.21. Low Flow Models: Select a flow of 8 LPM to the O2 analyzer. 5.7.22. High Flow Models: Select a flow of 16 LPM to the O2 analyzer. 5.7.23. Turn adjustment shaft (P/N 3533) by hand until O2 analyzer reads 30%. 5.7.24. Attach the gas mixer knob (P/N 3538AP) to the adjustment shaft (P/N 3533). Align the black indicator on knob with .30 position on faceplate. Using hex wrench, tighten set screw just enough to attach knob: do not fully tighten set screw at this time. 5.7.25. Turn knob to .90 position: check O2 analyzer reading. 5.7.26. Using AT. 3, loosen jam nut (P/N 3543). Using AT. 2, adjust rear seat (P/N 3542 Low Flow, P/N 3615 High Flow) until O2 analyzer agrees with knob reading of 90 ±1% (see Figure 10).

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3565 3564 3566

3506

3515 3514 3521

3518

3516 3517

43456 3522

3512 3521 3525

3523 3524 3516

3505

3635

3517 42557

43456

45226 3508 3511 3510

3524 3525

42556 42557

3521

3523

3522

3518 3512 3521 3514

3507 3515

3566 3564 3565

3507 3507 3507 3502P

Figure 4 - PRESSURE BALANCING MODULE For Low Flow Models

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3565 3564 3566

3506

3612 3611 3521

3518

3516 3517

43456 3522

3610 3521 3525

3523 3524 3516

3505

3635

3517 42557

43456

45226 3508 3511 3510

3524 3525

45226 42557

3521

3523

3522

3518 3610 3521 3611

3507 3612

3566 3564 3565

3507 3507 3507 3603

Figure 5 - PRESSURE BALANCING MODULE For High Flow Models

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Figure 6 - Sections of the Pressure Balancing Module

Figure 7 - Holding caliper tool

Figure 8 - Micrometer across block

Figure 9 - Connecting flowmeter, installing assembly tool (4)

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Table 1 - REGULATOR NEEDLE SETTING MICROMETER READING DIAPHRAGM THICKNESS .810 .809 .808 .807 .806 .805 .804 .803 .802 .801 .800 .799 .798 .797 .796 .795 .794 .793 .792 .791 .790

Low Flow

High Flow

.3975 .3970 .3965 .3960 .3955 .3950 .3945 .3940 .3935 .3930 .3925 .3920 .3915 .3910 .3905 .3900 .3895 .3890 .3885 .3880 .3875

.3850 .3845 .3840 .3835 .3830 .3825 .3820 .3815 .3810 .3805 .3800 .3795 .3790 .3785 .3780 .3775 .3770 .3765 .3760 .3755 .3750

Figure 10 Adjusting the rear seat on the Proportioning Module

5.7.27. Turn knob to the .21 position (making sure knob hits the stop pin), then up to .30 position on

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mixer. O2 analyzer should read 30 ±1%. If necessary, rotate the knob until a reading of 30 ±1% is obtained on the O2 analyzer, and reposition the knob to align the knob indicator with the .30 position on the faceplate. 5.7.28. Turn the knob to the .90 position; adjust the rear seat until the O2 analyzer reads 90 ±1%. 5.7.29. Repeat steps 5.7.27 and 5.7.28 until proper readings are recorded. 5.7.30. Turn knob to 1.0 position; make sure O2 analyzer reads at least 97% (and no higher than 100%) and knob is hitting stop pin. 5.7.31. Using AT. 3, tighten the jam nut (P/N 3543) to secure the calibration of the rear seat. NOTE: When tightening the jam nut, FiO2 may drop due to movement of rear seat. This can be compensated for by setting the gas mixer knob at .90 position and adjusting the rear seat until the O2 analyzer reading is slightly above 90% (around 91%). When jam nut is tightened, O2 analyzer should come down to 90%. 5.7.32. Verify that the full range of positions can be obtained within a ±3% variation. 5.7.33. When calibrations are completed, using an Allen wrench, tighten knob set screw(s) (P/N 46383). 5.7.34. Turn gas supplies "OFF", remove bypass block (AT. 4). 5.7.35. Calibration of Proportioning Module is now complete. ALARM MODULE (see Figures 13 and 14) 5.7.36. Install the Alarm Module to the Pressure Balancing Module with 2 screws (P/N 3624). NOTE: Be sure O-rings are in place between modules. 5.7.37. With the gas mixer still attached to gas supply lines, calibration of Alarm Module can now be performed. 5.7.38. Test procedure for acceptable alarm bleed response: turn O2 valve "ON", regulating to 60 psig, leave air "OFF"; alarm should sound. Turn O2 down to 30 psig; alarm should continue to sound. If alarm sounds, the alarm bleed is fully functioning. 5.7.39. If alarm is not functioning properly, check reed (P/N 55009) before performing alarm bleed calibration. The reed pedal may be damaged or contaminated. 5.7.40. If alarm bleed does need calibration, using tru-arc pliers, remove tru-arc ring (P/N 3570): remove reed cap (P/N 3561), with reed (P/N 55009) and reed retaining ring (P/N 46939): do not disassemble reed cap assembly. 5.7.41. If alarm does not sound at lower range of 30 psig, flow to reed must be increased by adjusting alarm bleed set screw (P/N 3568) clockwise. If alarm does not sound at the upper range of 60 psig, or hesitates when finger is passed over reed cap hole quickly, flow to reed must be decreased by adjusting the alarm bleed set screw counterclockwise. After adjustments, reed cap must be placed in its seat and held by hand to verify alarm function. When full range of alarm has been tested and obtained, install tru-arc ring over reed cap, making sure O-ring (P/N 3569) is in place to seal reed cap assembly. 5.7.42. To calibrate the bypass alarm O2 calibration adjuster (P/N 3622), turn O2 and air to "ON", regulating to 50 psig.

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Figure 11 - PROPORTIONING MODULE (Low Flow)

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Figure 12 - PROPORTIONING MODULE (High Flow)

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NOTE: The O2 calibration adjustment is located under the air inlet: the air calibration adjustment is located under the O2 inlet. 5.7.43. Alarm should be silent. 5.7.44. Using gas supply regulators, set air supply to 50 psig and slowly reduce the O2 supply. The alarm should sound between 24 psig and 28 psig. See note below for 3500CP-M1 gas mixer models. 5.7.45. If no alarm sounds, loosen the jam nut (P/N 3623), turn the O2 adjuster (located under air inlet) (P/N 3622) counter-clockwise slowly until alarm sounds. 5.7.46. If alarm is sounding when gas supply is turned on, turn the O2 adjuster (under air inlet) clockwise until alarm stops: then turn counterclockwise just until alarm sounds. 5.7.47. Reduce O2 pressure to 0 and relieve pressure within hose from gas mixer to regulator. 5.7.48. After venting, no pressure should build in gauge on O2 regulator. NOTE: If pressure starts to build on the O2 gauge, the duck bill valve (P/N 3525) in the O2 inlet is leaking and causing a back flow of air into O2 inlet: clean or replace as needed (see Figure 18). 5.7.49. Open O2 pressure to 50 psig; alarm should stop sounding at or before 40 psig. NOTE: If the alarm continues to sound above 40 psig, rotate the O2 calibration adjuster until the alarm stops sounding. Repeat the calibration procedure from step 5.7.42 until alarm sounds when O2 pressure is between 24 and 28 psig and stops sounding before 40 psig, when O2 pressure is increased. NOTE: As the 3500CP-M1 gas mixer model does not have an alarm reed, no alarm sound will be produced. Follow steps above for alarm calibration above but instead of listening for an alarm sound, refer to the O2 analyzer display and verify the O2 analyzer displays < 25% between 20 and 28 psig when decreasing the oxygen inlet supply and > 95% between 20 and 28 psig when decreasing the air inlet supply. The O2 analyzer reading should return to ±3% points from FiO2 set point at or before 40 psig. 5.7.50. Tighten jam nut over O2 calibration adjuster to secure calibration. 5.7.51. To calibrate the bypass alarm air calibration adjuster, complete steps starting from 5.7.42 to 5.7.50, replacing air for O2 in instructions, remembering that the air adjuster is located under O2 inlet. CAUTION: Do not tape or hold finger over alarm outlet port. Permanent damage to reed can be caused by prolonged occlusion of reed outflow. CAUTION: Alarm bleed set screw (P/N 3568) is calibrated at factory and should not require calibration. Testing for Gas Mixer function. 5.7.52. After all calibration procedures are completed, perform the test procedure (see Test Procedure Section).

20 100000 (Rev. 14) 02/2023

5.7.53. The gas mixer is now calibrated and ready for use. 5.7.54. To reassemble to pole mount or wall mount, see Disassembly and Reassembly Section. 5.8. Below is a table comparing the differences between low flow and high flow components. Table 2 - Low Flow vs. High Flow Components Part Description

Low Flow PN

3514

High Flow PN

Image (Low flow on left, High flow on right)

3611

Regulator Needle (2 qty.)

Regulator Seat (2 qty.)

The low flow needle (left) has a longer extended tip.

3512

3610

The low flow regulator seat (left) has a smaller thru hole opening.

3582

3646

Orifice (1 qty.)

The low flow orifice (left) has a smaller thru hole opening.

3515

3612

Regulator Springs (2 qty.)

The low flow regulator spring (left) has a shorter length.

21 100000 (Rev. 14) 02/2023