Air Receiver Inspection & Certification

Air receivers are pressure vessels, subject to strict regulation in major industrial countries worldwide. US follows ASME Boiler and Pressure Vessel Code and OSHA regulations. EU implements Pressure Equipment Directive PED 2014/68/EU. Australia follows AS/NZS 3788 standard. Air receivers without inspection or failing inspection are prohibited from use. Violators face fines, production shutdown, or even criminal prosecution.

Inspection

Pressure Vessel Certification

Inspection Intervals

Different countries and regions have different inspection intervals, but basic framework is similar. All divide into external inspection and internal inspection.

US follows API 510 standard. External inspection interval not exceeding 5 years, internal inspection interval not exceeding 10 years. OSHA requires employers to ensure pressure vessels are in safe condition. Individual states may have stricter rules. California for example requires annual external inspection.

EU member states each set their own inspection intervals. Germany typically requires internal inspection every 5 years, pressure test every 10 years. France's cycle is external inspection every 4 years, internal inspection and pressure test every 10 years. UK after Brexit continues using PSSR 2000 regulations. Inspection interval determined by written examination scheme, usually not exceeding 2 years.

Australia per AS/NZS 3788 classifies pressure vessels into different risk levels. High risk equipment inspected annually. Medium risk equipment 2-3 years. Low risk equipment maximum 5 years. New Zealand requirements are basically same as Australia.

These intervals are for normal operating conditions. If air receiver is in high humidity environment, or compressed air has high oil content and moisture, inspection agency will shorten interval based on corrosion found in previous inspection. Some severely corroded tanks are required to be inspected every 2 years or even annually.

Air receiver manufactured in one country and exported to another must comply with destination country regulations. German tank sold to US needs ASME certification or evaluation by US-recognized inspection agency.

What External Inspection Does

External inspection doesn't require long downtime. Mainly checks equipment's external condition and safety accessories.

Appearance-wise, inspector walks around the tank body looking at several key areas: lower tank body near drain outlet, where water accumulates most and corrosion often starts here; welds, especially where longitudinal and circumferential welds intersect; support to tank connection points where rainwater easily pools. Rust, bulging, dents, cracks all get recorded.

Safety valve check is simple. Look at calibration tag expiration date. ASME code and EU PED both require periodic safety valve calibration. US typically annually. European countries from 1 to 3 years. Tag shows next calibration date. Expired safety valve must be immediately sent for calibration or replaced. Also check if lead seal is intact, hasn't been tampered with.

Pressure gauge also needs periodic calibration. Inspector compares pressure gauge reading against standard gauge. Error exceeding specified accuracy is nonconforming. Some facilities have pressure gauge connection tube clogged with oil, needle doesn't move at all. This situation, inspection directly fails.

Drain valve needs to be operated on site. Open valve to see if it drains normally. Some manual drain valves not used for long, spool rusted stuck won't open. Some automatic drains have float stuck, accumulated water won't drain. These all need to be addressed on the spot.

Inspector will also review operating records. Many small enterprises have no operating records at all, or records are just formality, daily data filled in exactly the same. This situation, inspector will note in report "operating records incomplete," require correction. API 510 and EU regulations both require users to maintain complete operating and maintenance records.

What Internal Inspection Does

Internal inspection requires shutdown. Release compressed air from tank, open manway or remove accessories so inspector can see inner wall.

Preparation before entering tank is needed. Tank may have residual oil and gas, must be thoroughly ventilated. Some facilities use steam to purge inner wall, cleaning oil and rust scale so inspector can see more clearly. Tank entry is confined space work. US OSHA has specific confined space regulations (29 CFR 1910.146). EU countries also have similar safety requirements. Must have work permit, arrange dedicated monitor.

Corrosion

Inner Wall Condition

Measurement

Wall Thickness

Inner wall inspection mainly looks at corrosion. Air receiver interior is long-term in humid environment. Water in air condenses and accumulates at tank bottom, plus oil mist and dust carried in by compressed air, forms highly corrosive mixture. Severely corroded tanks, inner wall has extensive rust pits, touch it and rust flakes come off. Inspector must judge whether corrosion is uniform or pitting. Pitting is more harmful because it forms deep pits locally, weakening tank wall strength.

Wall thickness measured with ultrasonic thickness gauge. Can measure from outside of tank. Measurement points distributed on shell, heads, near welds. Severely corroded areas need denser measurement points. API 510 and EN 13445 both require thickness data compared against original factory thickness or design thickness to calculate corrosion rate. For example a tank with 5/16" design thickness, after 10 years use measured minimum is 0.24", annual average corrosion rate is 0.007". This data determines next inspection interval and tank's remaining life.

Pressure test isn't done every internal inspection. Only when inspector deems necessary. For example tank underwent weld repair, or corrosion is fairly severe, pressure test needed to verify overall strength. Test medium uses water. ASME code requires test pressure at 1.3 times design pressure. EN 13445 requires 1.25 or 1.43 times depending on specific situation. During test, slowly raise pressure. After reaching test pressure, hold for specified duration, observe for leakage or deformation.

Inspection Agencies and Inspection Reports

Air receiver inspection must be done by qualified inspection agency. US inspection agencies need authorization from National Board. EU member states use Notified Bodies designated by each country to perform inspections. These agencies' numbers can be found in EU NANDO database. Australian inspection agencies need JAS-ANZ accreditation.

After passing inspection, inspection agency issues inspection report and inspection compliance label or certificate. US National Board issues inspection sticker. European Notified Bodies update declaration of conformity. Label must be posted in visible location on tank body, convenient for regulatory personnel to check.

Inspection reports must be kept long-term. API 510 requires keeping until equipment is scrapped. EU PED requires keeping at least 10 years. Some enterprises just toss the report. When next inspection comes, can't find it. Inspector has no way to compare historical data, can only re-establish file as new equipment.

User Responsibilities

Users must apply to inspection agency before inspection cycle expires. Many countries now allow online application. Fill in equipment information, select inspection agency, schedule inspection time.

Equipment daily management, daily inspection once is basic requirement. Inspection content is simple: look at pressure gauge reading for normal, listen for abnormal sounds, feel if tank body temperature is abnormal, smell for leaking hissing sound. Find problems, report for repair promptly. Can't operate with defects.

Safety valve and pressure gauge need separate management. These two accessories need periodic calibration. Calibration certificates must be filed and kept. Some enterprises configure two safety valves per tank, one in use, one backup. Swap during calibration. This way doesn't affect production.

Draining is easily overlooked. Water accumulated in tank not drained, over time will corrode inner wall. Drain at least once per shift, drain until no water comes out. Conditions permitting, install automatic drain. But automatic drain also needs periodic check to confirm normal operation.

Compliance

Inspection Sticker

Documentation

Record Retention

Air receiver inspection looks troublesome, actually process is already very mature. Apply on time, cooperate with inspection, implement corrections, equipment can operate safely. Afraid of hassle and skip inspection, accident happening is the real hassle.