High Pressure Storage Air Compressor Tank For Air Receiver

High Pressure Storage Used Air Compressor Tank 0.6/0.8 For Air Receiver

Product Overview

A 0.6/0.8MPa air receiver is a stationary compressed air storage vessel installed between the compressor discharge and the plant distribution network. The 0.6MPa version is suitable for low-pressure utility air, light pneumatic workshops, and systems where the compressor setpoint does not exceed 6bar(g). The 0.8MPa version is the more common industrial standard for rotary screw and reciprocating plants operating around 7–8bar(g). In this document, "used" refers to the operating duty of the tank as a buffer and storage receiver; the vessel itself should always be specified, inspected, and certified for its intended pressure class before commissioning.

The air receiver performs four basic functions. First, it stores compressed air so peak demand can be covered without starting additional compressors. Second, it dampens pressure pulsation from reciprocating machines and reduces load/unload cycling of fixed-speed screw compressors. Third, it provides primary cooling and gravity separation of condensate before filters and dryers. Fourth, it gives the system a reserve for emergencies, instrument air, blowdown, and short production interruptions.

For 0.6MPa duty, typical receiver design pressure is selected with margin above working pressure. For 0.8MPa working systems, many plants specify a vessel with 0.8MPa working pressure or a higher design rating depending on code, safety valve setpoint, and compressor cut-out. Correct selection depends on actual free air delivery, demand profile, allowable pressure swing, ambient humidity, downstream drying requirement, and local pressure-vessel regulation.

Working Principle Of An Air Receiver

Compressed air leaves the compressor hot and saturated with water vapor. After the aftercooler and moisture separator, it enters the receiver. Inside the vessel, velocity decreases sharply. Lower velocity, lower temperature, and longer residence time cause three physical effects:

1. Thermal stabilization:​ Air temperature approaches ambient. Cooling condenses part of the water vapor into liquid droplets.

2. Gravity separation:​ Heavy water and entrained oil mist settle toward the bottom of the tank. Automatic or manual drains remove the liquid.

3. Pressure buffering:​ Stored air expands when demand exceeds compressor supply and is recharged when demand falls. The receiver decouples compressor output from instantaneous consumption.

If the dryer is installed after the receiver, the tank acts as a wet buffer: it cools and pre-dries the air, reducing dryer load. If the dryer is installed before the receiver, the tank acts as a clean dry buffer with less condensate but less pre-cooling benefit. For most industrial screw systems, the wet receiver plus after-filter plus dryer plus dry receiver configuration gives the best balance of stability, drying efficiency, and maintenance.

Sizing Method For 0.6MPa And 0.8MPa Receivers

Two methods are used in practice: a quick rule based on compressor flow and a precise method based on pressure swing.

Quick rule: many general industrial references size screw compressor receivers at approximately 10–20 percent of compressor free air delivery, with 15 percent as a common starting point when demand is reasonably stable. For strongly fluctuating demand, references may use 15–25 percent or higher; for very stable demand, 10 percent or slightly below can be evaluated.

Examples at 0.8MPa working pressure:

• 1.0m³/min screw compressor, stable demand: 0.10–0.20m³ receiver; 0.15m³ often used as a baseline.

• 3.0m³/min screw compressor, stable demand: 0.30–0.60m³; 0.45m³ baseline.

• 10.0m³/min screw compressor, moderate fluctuation: 1.0–2.0m³; 1.5m³ baseline.

• 20.0m³/min screw compressor, large fluctuation: 3.0–5.0m³ or more depending on peak events.

Precise buffer formula:

V = (Q × t × Pa) / (P₁ − P₂)

where V is receiver volume in consistent units, Q is the excess peak demand not covered by the compressor during the event, t is event duration, Pa is atmospheric pressure, and P₁−P₂ is the allowable pressure drop. When pressures are in bar absolute, Pa ≈ 1.013bar. When all pressures are entered as gauge values, the differential P₁−P₂ gives the same volume result because atmospheric pressure cancels in the ratio.

Worked example A, 0.8MPa system: compressor delivers 10m³/min. Peak demand during a batch event is 12m³/min. Acceptable pressure swing from 8.0bar cut-out to 6.0bar cut-in. Event duration 30 seconds.

Excess demand Q = 12 − 10 = 2m³/min = 0.0333m³/s.

t = 30s.

Pa = 1.013bar absolute.

P₁ = 8.0 + 1.013 = 9.013bar absolute.

P₂ = 6.0 + 1.013 = 7.013bar absolute.

ΔP = 2.0bar absolute.

V = (0.0333 × 30 × 1.013) / 2.0 = 0.505m³.

A 0.5m³ receiver is theoretically sufficient for this event. In practice, round up to 0.6m³, 0.8m³, or 1.0m³ depending on standard vessel sizes, future expansion, and dryer configuration.

Worked example B, 0.6MPa system: compressor delivers 6m³/min. Peak demand 7m³/min. Allowable swing from 6.0bar cut-out to 4.5bar cut-in. Event 30 seconds.

Excess demand Q = 1m³/min = 0.01667m³/s.

ΔP = 1.5bar absolute after adding atmosphere equally.

V = (0.01667 × 30 × 1.013) / 1.5 = 0.338m³.

Select approximately 0.4–0.5m³ standard vessel, larger if the site expects demand growth.

For fixed-speed load/unload control, receiver volume can also be selected to limit starts. A larger tank extends the time between cut-out and cut-in; a smaller tank causes more frequent cycling. General field guidance for variable-speed compressors is that receiver volume can sometimes be 50–70 percent of the volume used for comparable fixed-speed machines because the drive modulates flow continuously, but final size should still be checked against peak events and pressure stability.

Typical Specifications For 0.6/0.8MPa Air Receivers

The table below lists anonymized ranges. Actual dimensions, weights, and nozzle sizes vary by vessel code, steel grade, insulation, and accessories.

For 0.8MPa screw systems, the receiver working pressure should equal or exceed compressor cut-out. If the pressure switch cuts out at 8bar(g), the vessel working pressure should be at least 8bar(g), and the safety valve must protect the vessel MAWP without exceeding code accumulation limits.

Safety Valves, Gauges, And Drainage

An air receiver is a pressure vessel and must be protected as follows:

1. Safety relief valve:​ At least one spring-loaded relief device sized to prevent receiver pressure from exceeding maximum allowable working pressure by more than 10 percent. Set pressure is normally at or below MAWP; many plants set air-receiver relief at approximately 1.05–1.10 times working pressure when code and vessel stamp allow. No isolating valve may be placed between the receiver and its safety valve.

2. Pressure gauge:​ Visible, calibrated, and ranged so normal operating pressure sits in the useful middle of the scale. A common guideline is gauge range 1.5–3.0 times working pressure; for 0.8MPa service a 0–1.6MPa or 0–2.5MPa gauge is often selected depending on accuracy and reading habit.

3. Bottom drain:​ Every receiver requires a drain at the lowest point. Manual drains are acceptable for small intermittent systems but automatic timed, electronic, or float drains are preferred for continuous plants. Drains remove water and oil condensate, reduce internal corrosion, and prevent liquid carryover to dryers and valves.

4. Overpressure protection hierarchy:​ Compressor pressure switch or transducer sets cut-out; relief valve is the final independent protection. The relief valve must not be used as an operating discharge device.

5. Isolation and maintenance:​ Inlet/outlet isolation valves should allow the receiver to be locked out, depressurized, and inspected without shutting down unrelated systems where the network permits.

Installation Recommendations

• Place the receiver as close as practical to the compressor aftercooler and moisture separator. For wet storage, this improves cooling and condensate dropout. For dry storage, place a second receiver after the dryer.

• Provide a rigid concrete base for horizontal tanks and anchored supports for vertical tanks. Verify seismic, wind, and vibration requirements for the site.

• Maintain clearance for manhole/handhole access, drain service, relief valve discharge, and gauge reading.

• Route relief valve discharge vertically upward or to a safe outdoor location. Avoid discharging relief air into walkways, electrical enclosures, or confined spaces.

• Keep the receiver ventilated and away from direct flame, combustible storage, and excessive ambient heat. Indoor rooms need ventilation compatible with compressor heat rejection.

• Connect grounding/bonding according to electrical and process safety codes.

• For outdoor installation, use weatherproof coating, stainless fittings where appropriate, sun/rain protection, and freeze protection for drains.

• Avoid buried receivers. Codes generally require accessible drains, handholes, and manholes.

Condensate Management

Compressed air condensate may contain lubricating oil, especially from oil-injected screw compressors. The receiver drain should discharge to an oil-water separator before disposal. Frequency depends on humidity, compressor load, and drain type:

• High-humidity summer operation: inspect/automatic drain daily.

• Standard workshop: automatic drain with weekly visual check.

• Low-humidity, intermittent: manual weekly drain may be acceptable if inspected.

Do not allow liquid to accumulate at the tank bottom. Standing condensate accelerates internal corrosion, reduces effective storage volume, and can be re-entrained into downstream filters and dryers.

Receiver Before Or After The Dryer

Wet receiver first: aftercooler → moisture separator → wet receiver → pre-filter → dryer → post-filter → dry receiver. This layout cools air, drops bulk water, stabilizes pressure before the dryer, and extends dryer and filter life.

Dry receiver second: after the dryer, the clean receiver supplies stable low-dew-point air. It reduces pressure fluctuation at sensitive points and provides reserve for instruments, packaging, laboratories, or occasional peak demand.

For 0.8MPa plants with refrigeration or adsorption dryers, a wet receiver of 10–20 percent compressor FAD plus a smaller dry receiver is a common reliable arrangement. For 0.6MPa utility air without strict dew point, a single wet receiver may be sufficient.

Material Selection

Carbon steel is the standard economic choice for general plant air. Internally it should be blast-cleaned and coated or lined when condensate chemistry, humidity, or oil contamination increases corrosion risk. Stainless steel 304 or 316 is selected for food, beverage, pharmaceutical, chemical, marine, and high-purity applications, or where the air is dried to very low dew point and contamination must be minimized. For special gases or aggressive condensate, request material certification, weld procedure qualification, and internal finish specification separately.

Inspection And Maintenance

A receiver requires planned inspection even if it appears simple.

• Daily/automatic: confirm drain operation, check gauge reading, listen for abnormal noise or leakage.

• Monthly: inspect relief valve exterior, gauge accuracy, nozzle and support integrity, coating condition.

• Periodic statutory inspection: according to ASME Section VIII jurisdiction practice, external inspection approximately every two years and internal inspection approximately every five years are common references; local regulations may differ. PED, GB/T 150, and other codes have their own inspection intervals.

• After modification, repair, or overpressure event: perform internal inspection, NDT, hydrostatic test, and recertification before return to service.

• Desiccant/dryer integration: if the receiver feeds an adsorption dryer, keep inlet temperature and oil within desiccant limits; oil fouling in upstream filters increases receiver condensate oil load.

Used Or Second-Hand Receiver Evaluation

If a used 0.6/0.8MPa receiver is being recommissioned, it must be evaluated before use:

1. Verify nameplate: manufacturer, year of construction if available, volume, working/design pressure, MAWP, temperature, material, code stamp, and serial number.

2. Confirm original code compliance: ASME U-stamp, PED CE, GB/T 150 fabrication record, or local equivalent.

3. Obtain fabrication drawings, hydrostatic test report, NDT reports, and previous inspection records.

4. Inspect internally for corrosion, scaling, sludge, desiccant dust if previously connected, and bottom-plate thinning.

5. Inspect externally for dent, weld crack, support movement, coating failure, and nozzle thread/flange damage.

6. Re-test safety valve capacity and setpoint; replace gauge if inaccurate.

7. Perform hydrostatic test at code-specified pressure only after a qualified inspector approves the vessel for test.

8. Do not raise working pressure above the original stamped MAWP. A 0.6MPa tank should not be reused at 0.8MPa unless recertified by the original code authority or a qualified pressure-vessel engineer for the higher pressure.

Application Recommendations

Pressure Drop And System Integration

The receiver itself has low intrinsic pressure loss because内部 velocity is intentionally low. System losses come from inlet diffuser, piping, valves, filters, and dryer. Keep air velocity in connecting pipes reasonable; oversized connections reduce turbulence and re-entrainment of condensate. For 0.8MPa systems, avoid using the receiver as a substitute for correct main-line sizing. If end-use pressure fluctuates more than the process allows, increase receiver volume or improve compressor control before raising system pressure.

Energy Considerations

A receiver does not generate air, but correct storage reduces energy waste.

• Fixed-speed compressors: larger receiver lengthens load/unload cycles, reduces starts, and avoids frequent unloaded running.

• VSD compressors: receiver stabilizes transient peaks; volume can sometimes be smaller, but do not eliminate storage entirely.

• Pressure stability: every unnecessary 0.1bar increase in system setpoint raises compressor power. A receiver that holds tight pressure band avoids artificial overpressurization.

• Cooling benefit: wet receiver reduces dryer inlet temperature and moisture load, lowering refrigeration or regeneration energy.

• Drain management: automatic zero-loss or timed drains reduce air loss compared with continuously open manual drains.

Procurement Specification Checklist

Request written data rather than verbal summaries.

• Operating pressure: 0.6MPa or 0.8MPa working; cut-in and cut-out pressures; maximum allowable working pressure.

• Design pressure, design temperature, and corrosion allowance.

• Volume in liters or cubic meters; vertical or horizontal; footprint and height restrictions.

• Compressor FAD, peak demand profile, allowable pressure swing, and event duration.

• Air quality target: ISO 8573-1 water, particle, and oil classes; dryer type upstream/downstream.

• Inlet air temperature after aftercooler; ambient temperature; humidity; oil-injection or oil-free compressor.

• Material: carbon steel grade, stainless grade, internal coating, external coating, insulation if required.

• Code: ASME Section VIII, PED/EN, GB/T 150, or local pressure-vessel regulation.

• Nozzle size and type: threaded, socket-weld, or flange; inlet/outlet, drain, gauge, safety valve.

• Accessories: safety relief valve capacity and setpoint, pressure gauge range, manual/automatic drain, manhole/handhole, ladder/platform for large tanks.

• Testing: hydrostatic pressure, pneumatic option, NDT method, documentation, nameplate data.

• Installation environment: indoor/outdoor, seismic zone, ventilation, foundation, corrosion class.

• Compliance documents: fabrication record, inspection plan, material certificates, relief valve calculation, drainage and environmental plan.

Frequently Asked Questions

Q1: What is the difference between 0.6MPa and 0.8MPa air receiver selection?

The main difference is working pressure and compressor cut-out. A 0.6MPa receiver is selected for systems that never exceed 6bar(g), while an 0.8MPa receiver is used for standard 7–8bar(g) screw plants. Volume is determined by flow and pressure-swing requirement, not by pressure alone. A higher working-pressure vessel can be used at lower pressure if code, fittings, and safety setpoints are adjusted, but a lower-pressure 0.6MPa vessel must not be operated at 0.8MPa without recertification.

Q2: How large should the receiver be for a screw compressor?

A common quick estimate is 10–20 percent of compressor free air delivery, with 15 percent for stable demand. A 10m³/min screw at 0.8MPa would start around 1.0–2.0m³, often 1.5m³ baseline. If demand fluctuates, use the buffer formula V=(Q×t×Pa)/(P₁−P₂) with excess peak demand, event time, and allowable pressure drop.

Q3: Should the receiver be installed before or after the dryer?

For most industrial systems, install a wet receiver after the aftercooler and pre-separator, then the dryer, then a dry receiver. The wet receiver cools air and drops condensate; the dry receiver stabilizes clean low-dew-point air. If only one receiver is used, place it before the dryer for general screw plants and after the dryer only when the entire upstream air is already filtered and dried.

Q4: What safety devices are mandatory on a 0.6/0.8MPa receiver?

At minimum, a pressure gauge, one or more certified safety relief valves, and a bottom drain. The relief valves must prevent pressure from exceeding MAWP by more than 10 percent, and no valve may isolate the relief device from the tank. Depending on code, additional devices include pressure transmitter, level/condensate alarm, temperature probe, and remote monitoring.

Q5: How often should condensate be drained?

Automatic drains are preferred for continuous operation. In high humidity, check or operate drains daily. In normal workshop duty, automatic drain with weekly inspection is usually sufficient. Manual drains should be opened frequently enough to prevent liquid accumulation. Standing water causes internal corrosion and reduces effective volume.

Q6: Can a used 0.6MPa tank be converted to 0.8MPa service?

Only after engineering review and recertification. Verify nameplate MAWP, material, corrosion allowance, weld condition, and code acceptance. Perform internal inspection, NDT, and hydrostatic test as required by the responsible code authority. If the original stamp is below 0.8MPa, do not raise working pressure until a qualified inspector certifies the vessel for the higher pressure.

Q7: What material is best for food and pharmaceutical air?

Stainless steel 304 or 316 is commonly specified for hygienic utility air, with polished internal welds where required. Carbon steel with food-grade epoxy lining may be acceptable for non-contact general utility, but direct-contact and high-purity systems usually require stainless, validated filtration, and documented inspection. The receiver should always be paired with correct coalescing, carbon, and terminal filtration.

Q8: How is receiver volume affected by allowable pressure swing?

Volume is inversely proportional to allowable pressure drop in the buffer formula. A narrow swing such as 8.0 to 7.5bar requires a much larger tank than an 8.0 to 6.0bar swing for the same peak event. If the process requires very stable pressure, increase receiver volume, improve compressor control, or reduce peak excess demand rather than raising cut-out pressure unnecessarily.

Final Selection Recommendation

Specify a 0.6/0.8MPa air receiver by actual compressor free air delivery, peak demand profile, allowable pressure swing, working temperature, condensate load, and applicable pressure-vessel code rather than by motor horsepower alone. For stable 0.8MPa screw plants, start with a wet receiver of approximately 10–20 percent FAD, verify with V=(Q×t×Pa)/(P₁−P₂), and add a dry receiver after the dryer when ISO 8573-1 purity, instruments, or sensitive production require stable low-dew-point air. For 0.6MPa utility systems, use the same method with lower cut-out/cut-in pressures and smaller safety-set margins. Equip every vessel with code-compliant relief protection, accurate pressure indication, automatic bottom drainage, and scheduled internal/external inspection. Use carbon steel with proper lining for general plant air, stainless for food/pharma/corrosive service, and never operate a used tank above its certified MAWP without recertification. With correct sizing, drainage, and inspection, a 0.6/0.8MPa air receiver improves compressor stability, reduces cycling and energy waste, protects dryers and filters, and provides reliable reserve air for industrial production.