Instrument Air Quality Test SOP

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• Document control header (SOP INST 018)
• Purpose, scope and references
• Safety, tools and prerequisites
• Numbered step by step procedure
• Acceptance criteria and records
• Approval block for sign off

1. Purpose

To protect positioners, I/P converters and actuators from water, oil and dirt in the air supply.

2. Scope

Instrument air systems from dryer outlet to the farthest users.

3. References

• ANSI/ISA 7.0.01 quality standard for instrument air
• ISO 8573-1 air purity classes
• Dryer and filter manuals

4. Responsibilities

• Instrument technician: carries out the work and records results.
• Instrument engineer or supervisor: reviews and approves the records.
• Operations: grants the permit, isolates the process and returns the equipment to service.

5. Safety Precautions

• Work only under a valid permit to work and follow the site isolation (lockout tagout) procedure.
• Wear the PPE required for the area: safety helmet, glasses, gloves and safety shoes as a minimum.
• In hazardous areas use certified or intrinsically safe test equipment, or obtain a gas free certificate and hot work permit.
• Inform the control room before starting, and before returning the instrument to service.
• Bleed air slowly; compressed air jets can injure.

6. Tools and Equipment

• Portable dew point meter
• Oil and particle test kit or filter membrane holder
• Pressure gauge

7. Prerequisites

• Test points identified: dryer outlet and end of headers.

8. Procedure

8.1 Dew point

1. Connect the dew point meter at line pressure and wait for a stable reading.
2. Compare with the requirement: at least 10 °C below the minimum ambient temperature (ISA 7.0.01).

8.2 Oil and particles

1. Pass a measured volume of air through the test membrane or detector tube.
2. Compare with the site limit or ISO 8573-1 class.

8.3 Pressure

1. Record header pressure at the end user during normal demand.

8.4 Record and act

1. Record results; raise work orders for dryer, filter or drain problems.

9. Acceptance Criteria

• Pressure dew point at least 10 °C below minimum ambient.
• Oil and particles within site limits.
• Supply pressure within the design range at end users.

10. Records

Related tools

This is a generic procedure. Adapt it to your site permit system, the manufacturer instructions and your quality system before use.

Frequently Asked Questions