Oxygen blenders

Tri-anim Air/Oxygen Blender: troubleshooting and error codes

The ServiceForge knowledge base holds 16 documented symptoms for the Tri-anim Air/Oxygen Blender, with 27 ranked causes, 55 diagnostic checks with test points and expected values, and 0 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

Blender alarming

Alarm sounds when blender detects a fault condition

Ranked causes

1. Source pressures have greater than 20 PSI differential (common)
2. Alarm system out of calibration (occasional)
3. Dirty gas contaminating alarm system (occasional)
4. Pressure balance chamber not working properly (rare)

First check

Measure air and oxygen supply pressures

Test point: air inlet and oxygen inlet pressure gauges
Expected: Within 20 PSI (30 PSI for overseas units) of each other

2 more checks with pass and fail actions, 4 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Oxygen analyzer reading does not match blender setting patient safety

Analyzer displays concentration different from the blender dial setting

Ranked causes

1. Analyzer out of calibration (common)
2. Blender out of calibration (common)
3. Bleed orifice in auxiliary port restricted (occasional)
4. Air introduced into system after blender (occasional)

First check

Verify analyzer calibration status

Test point: oxygen analyzer
Expected: Analyzer reading should match known reference gas or calibration standard

2 more checks with pass and fail actions, 4 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Blender does not produce correct oxygen concentration patient safety

Output concentration does not match knob setting when measured with oxygen analyzer.

Ranked causes

1. Proportioning valve worn or contaminated (occasional)
2. Balancing chamber diaphragm damaged or misaligned (occasional)
3. Contaminated gas inlet causing inaccurate mixing (common)

First check

Inspect proportioning valve seats for wear or damage

Test point: Valve seat contact areas
Expected: Smooth surface with no visible wear, nicks, or corrosion

2 more checks with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Blender not maintaining pressure or leaking gas caution

Gas pressure drops when blender is connected and pressurized, or audible hissing from outlet or connections.

Ranked causes

1. O-ring seals worn or damaged (common)
2. Check valve balls stuck or contaminated in inlet fittings (common)
3. Internal passages blocked by contamination or moisture (occasional)

First check

Inspect all visible o-ring seals for damage or deterioration

Test point: Proportioning valve, balancing chamber caps and halves
Expected: O-rings intact, not cracked, swollen, or hardened

2 more checks with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Alarm does not sound when gas source pressure drops patient safety

No audible alarm when one gas supply pressure decreases or increases by specified amount relative to the other.

Ranked causes

1. Alarm shuttle stuck or diaphragm failure preventing shuttle movement (occasional)
2. Alarm pressure threshold setting incorrect (rare)

First check

Test alarm response to pressure differential in air supply

Test point: Air inlet pressure regulator or test port
Expected: Alarm sounds when air pressure drops or increases 20 psi below oxygen pressure (30 psi overseas models)

2 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Alarm pressure differential calibration caution

Calibrate low-pressure alarm to activate when supply pressure falls 20 psi below the other supply (30 psi if O2 is 50 psi standard US units, 30 psi differential international).

Ranked causes

1. Alarm activates at incorrect pressure differential (occasional)

First check

Connect 50 PSI Air and Oxygen supplies with pressure gauges

Test point: Supply pressure gauges
Expected: Air 50 psi, Oxygen 50 psi (or pressures standard for area)

2 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Blender inaccurate at unequal source pressures patient safety

Blender output concentration drifts when air and oxygen supply pressures are not equal

Ranked causes

1. Pressure balance chamber not functioning correctly (common)

First check

Set up blender per Figure 18 with equal supply pressures

Test point: blender at 60% setting
Expected: Analyzer reads 57% - 63% oxygen

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration verification

Verify blender output concentrations at all knob positions meet specifications after calibration. Test primary output at specified flow rates and auxiliary output bleed function if equipped.

Ranked causes

1. Blender concentrations out of specification (occasional)

First check

Connect 50 PSI Air and Oxygen supplies with pressure gauges

Test point: Supply pressure gauges
Expected: Air 50 psi, Oxygen 50 psi

8 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Air/Oxygen Blender patient safety

Periodic calibration and verification of gas concentration output to ensure accurate blending ratios and proper alarm function.

Ranked causes

1. Scheduled maintenance requirement per preventive maintenance schedule (common)

First check

Verify oxygen analyzer functionality before use

Test point: Analyzer input
Expected: Analyzer operational and calibrated per manufacturer instructions

2 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Air/Oxygen blender output concentration patient safety

Verify blended gas output matches dialed concentration from 21% to 100% oxygen across flow ranges; standard procedure for preventive maintenance and service

Ranked causes

1. Calibration procedure required per service manual (common)

First check

Verify gas source pressures at input D.I.S.S. fittings

Test point: Air and Oxygen D.I.S.S. fittings on blender bottom
Expected: 50 psi

2 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Proportioning valve Hi/Low flow blender

Establish distance between front and rear seats by positioning front seat relative to fixed rear seat. Knob should reach 100% stop pin simultaneously when rear shaft seats.

Ranked causes

1. Front seat positioned incorrectly relative to rear seat (common)

First check

Rotate shaft counterclockwise to valve seating

Test point: Main valve shaft
Expected: Slight resistance felt, do not force

3 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Proportioning valve Low flow and 0-50 LPM blenders

Establish distance between front and rear seats using live gas supplies and oxygen analyzer to verify concentration at each knob position meets specification.

Ranked causes

1. Front seat positioned incorrectly relative to rear seat (common)

First check

Connect 50 PSI Air and Oxygen supplies with pressure gauges teed in

Test point: Supply pressure gauges
Expected: Air 50 psi, Oxygen 50 psi

7 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Duck bill check valve function patient safety

Verify Air and Oxygen supply fitting check valves prevent back-flow of gas. Reverse flow should not exceed 10 ml/h (0.01667 l/min) on each supply.

Ranked causes

1. Check valve leaking, allows back-flow of gas (rare)

First check

Leave air supply connected and disconnect oxygen supply hose from source

Test point: Oxygen supply inlet fitting
Expected: Oxygen hose disconnected from source but connected to blender

3 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Low flow selector knob positioning and operation patient safety

Set low flow selector knob position on certain blender models to maintain accurate O2 concentration at high and low flows from single primary outlet

Ranked causes

1. Low flow selector knob installed on selective models for accurate multi-flow operation (occasional)

First check

Locate label on blender side for knob position guide

Test point: Label on blender side
Expected: Label present indicating position for flows above and below threshold

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

NEO2 BLEND low flow bleed activation and operation patient safety

Configure and verify NEO2 BLEND internal bleed system for flows below 3 lpm; right flowmeter activates bleed when rotated to vertical position

Ranked causes

1. NEO2 BLEND design requires internal bleed below 3 lpm (common)

First check

Verify right flowmeter is in vertical position for low flow use

Test point: Right side flowmeter orientation
Expected: Vertical position, perpendicular to blender face

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Proportioning valve response at low flow

Verify blender proportioning valve response to knob position at low flow rates to ensure front seat not positioned too far in.

Ranked causes

1. Front seat positioned too far into block (occasional)

First check

Set flow to 30 lpm (50 lpm for 0-50 LPM blenders)

Test point: Flow measurement device
Expected: Flow set to specified value

1 more check with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Community

0 fixes logged by technicians through their AI, with outcomes, for this model.

ServiceForge knowledge base record. Field-unverified unless technicians confirmed it. A teaching summary of the record, not a service manual. Export 2026-10-14.