Description and Overview
An air receiver is probably the most common type of unfired pressure vessel. However, due to minimum size inspection thresholds employed by the vast majority of jurisdictions, many of the smaller air receivers will not qualify for a mandatory inservice inspection. The typical inspection threshold sizes referenced in jurisdictional regulations are 5 cubic feet or 15 cubic feet in volume as long as the maximum allowable working pressure (MAWP) does not exceed 250 psi, or 1-½ cubic feet in volume as long as the MAWP does not exceed 600 psi. The inspector must review the jurisdiction's inspection requirements to ensure compliance with the appropriate size and pressure limitations.
Air receivers are typically constructed in accordance with ASME Section VIII, Div. 1, and stamped with either the ASME "U" or "UM" symbol. Manufacturers who specialize in air receivers will construct a large number of these vessels in an assembly line process. The Manufacturer's Data Report, for "U" stamped vessels, and the Manufacturer's Certificate of Compliance, for "UM" stamped vessels, may include multiple vessels. This practice is described in ASME Section VIII, Div. 1, paragraph UG-120(a).
While most air receivers are of simple design consisting of a shell and two dished heads, some are designed to incorporate a filter or separator element within the vessel. These vessels may be "T" shaped with one bolted flat head which provides access to the filter or separator element. These uniquely shaped vessels are commonly found in use with large industrial air compressors.
Air receivers will be installed in any facility requiring a reservoir of compressed air. Compressed air uses include:
Pneumatic Cylinders or Pistons
Sand- or Shot-Blasting
The design of a compressed air system is dictated in part by the pressure, volume, and air quality (including cleanliness and dryness) needed in any given industry or process. The size of the air receiver in the system is normally based on the volume of air produced by the compressor and the user's desire for a stated capacity in cubic feet per minute (cfm) at a specified pressure. The air receiver helps in maintaining a constant pressure in the system by minimizing the fluctuations of a compressor cycling on and off.
Appurtenances, Settings, and Piping
An air receiver must be protected from over-pressure. This is usually accomplished by means of a spring-loaded pressure relief device. The set pressure of the pressure relief device must not exceed the MAWP marked on the air receiver. The minimum relieving capacity of the pressure relief device must meet the requirements of ASME Section VIII, Div. 1, paragraph UG-125. Under most circumstances this would require a pressure relief device with enough relieving capacity to prevent the pressure in the air receiver from rising more than 10% or 3 psi, whichever is greater, above the MAWP marked on the air receiver. For an inspector familiar with boiler nameplates which indicate either the maximum generating capacity of the boiler or the minimum required relief valve capacity, verifying the capacity of a pressure relief device on an air receiver will be more of a challenge. The inspector needs to obtain the output of the compressor(s) supplying the air receiver. This information may be on a label or nameplate on the compressor or it may have to be obtained from the compressor manufacturer's published specifications.
Since air receivers are typically constructed out of carbon steel, they are subject to internal corrosion from water which has condensed from the compressed air. ASME Section VIII, Div. 1, paragraph UG-25(f), requires a suitable drain opening in such vessels.
Air receivers with integrally mounted compressors and motors should be installed as recommended by the manufacturer. Since there is usually some vibration produced by a reciprocating-type compressor/motor unit, many manufacturers provide spring-loaded or elastic compound dampers to mount between the floor and the air receiver base.
Clearance measurements, if any, must comply with all jurisdictional and manufacturer requirements.
Most jurisdictions do not require inspection of any piping associated with an air receiver.
Part 1 of the National Board Inspection Code addresses installation requirements and must be followed when mandated by the applicable jurisdiction.
Common Observations and Problems
Internal corrosion, vibration, and external impact damage are the most common problem areas for air receivers.
Unless the air compressor is operating in the driest desert, water vapor in the compressed air will condense to liquid water as the temperature of the compressed air falls. In the simplest system, this happens in the air receiver. In more elaborate systems, the air is conditioned to extract part or almost all of the moisture before entering the air receiver. One compressor manufacturer's informational literature claims the water vapor content at 100°F of saturated compressed air equals about two gallons per hour for each 100 cfm of compressor capacity. Some air receivers are fitted with automatic condensate drains while others rely on a manually operated drain valve. If condensate is allowed to collect in the air receiver, its volume is decreased which can lead to increased cycling by the compressor. The condensate can also carryover through the air distribution lines and cause problems with air powered tools. The most detrimental effect of the condensate is internal corrosion of the air receiver. Since it is internal, it is never seen by the vessel owner and its effects are often discounted or ignored. In severe cases of corrosion, the vessel thickness may have decreased below the minimum wall thickness necessary for the MAWP stamped on the vessel. Under those circumstances, the MAWP can be decreased to a point that is supported by the remaining wall thickness, but in most cases the vessel is removed from service until it is repaired or replaced.
Vibration caused by an integrally mounted compressor/motor unit can cause cracking in the welds attaching the compressor/motor mount to the air receiver or in the welds attaching the base to the bottom of the air receiver. If they occur, the cracks will often "run" or propagate into the vessel material. Vibration damage can also occur where rigid piping is connected to the air receiver.
External impact damage can be caused by vehicles, machinery, or objects hitting the air receiver. One inspector observed a large dent in an external air receiver mounted on a portable air compressor used in a quarry. He was told it was caused by a limestone boulder which fell on the compressor from an upper rock ledge. Hazards can exist almost anywhere.
Most air receivers will show a minimum design metal temperature (MDMT) of -20°F on the nameplate. This should be acceptable under most conditions. However, if the air receiver is installed outside or in an unheated structure in very cold climates, it could be susceptible to brittle fracture.
Upon entering the area where the air receiver is operating, the inspector should perform a general assessment of the air receiver, piping, and associated systems. The inspector should then:
review the current operating certificate (if one was issued in the past) and compare the information to the associated air receiver and its nameplate;
compare the pressure relief device data (set pressure and relieving capacity) with the air receiver nameplate and compressor output data to ensure the pressure relief device is adequate for this installation;
inspect the pressure relief device operation as described in the National Board Inspector Guide for Pressure Relief Devices;
check all support and mounting bracket attachment welds and the affected vessel walls for evidence of cracking;
check for external damage such as dents or gouges;
ask the owner or owner's representative to verify the operation of the automatic condensate drain if applicable, or open the manual drain valve;
check connected piping to ensure it is properly supported and not imparting excessive loadings on the air receiver.
The inspector should perform an internal inspection of the air receiver as required by the jurisdiction. Some air receivers have dedicated inspection openings while others (especially smaller ones) use the inspection openings for the attachment of piping, instruments or similar attachments as allowed by ASME Section VIII, Div. 1, paragraph UG-46(f)(7). If an internal inspection is impractical, the jurisdiction may accept thickness readings obtained with an ultrasonic tester compared with original thickness values. The original thickness values can be found on the Manufacturer's Data Report or Manufacturer's Certificate of Compliance. Although the practice is not required by ASME Code, some air receiver manufacturers include the shell and head thicknesses on the nameplate.
Additional information to aid inspectors of air receivers can be found in the following publications and sources:
National Board Inspection Code
ASME Section VIII, Div. 1
Manufacturer's Installation, Operation, and Maintenance Documentation
Jurisdictional Laws, Rules, and Directives
CPS Hire carries a range of horizontal and vertical air receivers in stock. All air receivers are MADE IN AUSTRALIA, to Australian Standard AS1210.
All receivers are supplied finished in "battleship grey" industrial grade enamel, and supplied with pressure gauge, manual condensate drain and safety relief valve as standard.
CPS Hire can also supply air receivers to your specifications. If you require an air receiver not on our list, just ask! Special size, colour, high pressure, project specific?
Whether 90 or 10,000 litres, 10, 13, 20, 45 or 50 bar, all CPS Australian compressed air receivers are designed and manufactured to the highest quality standards to ensure exceptional safety and durability. You only get genuine quality with genuine AS1210 Aussie made air receivers. Moreover, they are exceptionally corrosion resistant and guarantee perfect sealing. This is due to a combination of the precision thread finishing process that takes place following galvanisation, and the extensive protection measures that are taken during transportation.
Air Receiver Tanks
Free Standing, Vertical Air Receiver Tanks.
Design & Certified to AS1210.
Manufacturer's Data Report provided in accordance with AS4458.
OH&S Registered Designs approved for workplace use in all Australian States & Territories.
Industry preferred socket sizes & placement.
External surfaces are abrasive blast cleaned, primed & finish coated in two-pack polyurethane paint.
'Process Blue' external colour indicates compressed air in accordance with AS1345.
Ready for Transport, individually packed in a horizontal position inside a full timber crate with plastic bag cover.
Available for delivery Australia wide.
Inspection intervals up to five years
Meticulous design in accordance with Australian regulations enables 5-year inspection cycles. This not only reduces inspection costs, but also increases compressed air efficiency and availability.
Optimal corrosion resistance
All CPS air receivers are hot-dip galvanised both internally and externally in accordance with DIN EN ISO 1461, which means they last approximately 3 times longer than conventional models.
Excellent maintenance access
Cleaning, maintenance and receiver inspection tasks are made simple thanks to generously sized access openings. Efficiency is further enhanced as a result
The threads on all CPS air receivers are precision finished directly after the galvanisation process to enable quick, reliable installation.
An air receiver is essential to every compressed air system to act as a buffer and a storage medium between the compressor and the consumption system. There are in principal two different air receivers in a compressed air system:
PRIMARY receiver - located near the compressor, after the after-cooler but before filtration and drying equipment
SECONDARY receivers - located close to points of larger intermittent air consumptions
The maximum capacity of the compressor in a well designed systems always exceed the maximum mean air consumption of the system (maximum mean air consumption is the mean air consumption over some reasonable time).
Since the maximum capacity of an air compressor also always exceed the minimum air consumption in the system - the compressor must modulate its capacity during normal work, often by using primitive strategies as on/off modulating or more advanced strategies as frequency drives and inverters. Primitive modulating strategies cause more pressure variations in compressed air systems than more advanced strategies.
In addition, the air consumption vary due to the process supported. In shorter periods the demand for compressed air may even exceed the maximum capacity of the compressor. In fact, it is common in well designed systems not to design the compressor for the maximum peek loads.
Air receivers in compressed air systems serves the important purposes of equalizing the pressure variation from the start/stop and modulating sequence of the compressor storage of air volume equalizing the variation in consumption and demand from the system In addition the receiver serve the purpose of collecting condensate and water in the air after the compressor
Sizing the Air Receiver
The air receiver must in general be sized according the variation in the consumption demand the compressor size and the modulation strategy.
In general it is possible to calculate the maximum consumption in the system by summarizing the demand of each consumer. The summarized consumption must be multiplied with a usage factor ranging 0.1 - 1 depending on the system. In practice it is common that the manufacturer use standardized receivers for specific compressor models based on their know-how.
For calculating the receiver, note that it is necessary with a pressure band for the receiver to be effective. If the consumption process requires 100 psig and the compressor is set to 100 psig, there is no storage and no buffer. Any increased demand will make a pressure drop below 100 psig until the compressor responds by increasing the air volume compressed.
If the compressors operates at 110 psig the difference between 110 psig and 100 psig accounts for the air stored in the receiver. If the demand increases, the pressure can drop 10 psig before the minimum requirement is met. Pressure and flow controllers can be used after the receiver for stabilizing downstream pressure to 100 psig and flattening demand peaks. Note that in a compressed air system the pipe work also makes the purpose of a buffered volume.
A commonly used formula to find a receiver size is:
t = V (p1 - p2) / C pa (1)
V = volume of the receiver tank (cu ft)
t = time for the receiver to go from upper to lower pressure limits (min)
C = free air needed (scfm)
pa= atmosphere pressure (14.7 psia)
p1 = maximum tank pressure (psia)
p2 = minimum tank pressure (psia)
Example - Sizing an Air Receiver
For an air compressor system with mean air consumption 1000 cfm, maximum tank pressure 110 psi, minimum tank pressure 100 psi and 5 sec time for the receiver to go from upper to lower pressure - the volume of the receiver tank can be calculated by modifying (1) to
V = t C pa / (p1 - p2)
= (5 sec) (1/60 min/sec) (1000 cfm) (14.7 psi) / ((110 psi) - (100 psi))
= 122 ft3
Air Receivers: Why Air Receivers are Required
Air receivers are tanks used for compressed air storage and are recommended to be in all compressed air systems. Using air receivers of unsound or questionable construction can be very dangerous. Therefore, the American Society of Mechanical Engineers (ASME) has developed a code regarding the construction of unfired pressure vessels, which has been incorporated into many federal, state, and local laws. This particular code is ASME Code Section VIII Division 1. Air receivers should always meet or exceed this code in addition to any other state, municipal, or insurance codes that may apply. In Australia we use local standard AS1210. It is possible to certify overseas air receivers to local standard but this involves a lot of paper work and cost. Better buying Australian Made AS1210 and comply from the start with guaranteed quality.
For information purposes only:
The ASME also approves the receiver accessories. They are equipped with a safety valve, which is set at a pressure lower than the working pressure for which the air receiver was stamped and at a higher pressure than the operating pressure, to safeguard against excessive pressure. In addition, receivers have a drain valve to eliminate accumulated moisture. They also have pressure gauges, handholes or manholes, and a base for vertical air receivers. Standard receivers are designed for horizontal or vertical mounting.
Air receivers serve several important purposes:
• Decrease wear and tear on the compression module, capacity control system and motor by reducing excessive compressor cycling.
• Eliminate pulsations from the discharge line.
• Separate some of the moisture, oil and solid particles that might be present from the air as it comes from
the compressor or that may be carried over from the aftercooler.
• Help reduce dew point and temperature spikes that follow regeneration.
• Offer additional storage capacity made to compensate for surges in compressed air usage.
• Contribute to reduced energy costs by minimizing electric demand charges associated with excessive
starting of the compressor motor.
The benefit of extra storage capacity alone outweighs the additional cost of this component.
Wet vs. Dry Receiver:
There are wet air receivers (supply) and dry air receivers (demand).
Wet Receivers: Wet receivers provide additional storage capacity and reduce moisture. The large surface area of the air receiver acts as a free cooler, which is what removes the moisture. Because the moisture is being reduced at this point in the system, the load on filters and dryers will be reduced. The term "wet receiver" refers to the storage vessel or tank placed immediately after the
compressor. This device helps with contaminant removal, pressure stabilization and
Dry Receivers: When sudden large air demands occur, dry air receivers should have adequate capacity to minimize a drop in system air pressure. If these pressure drops were not minimized here, the performance of air dryers and filters would be reduced because they would no longer be operating within their original design parameters.The term "dry receiver" refers to the receiver placed after the air dryer and other air
Air receiver sizing:
The size of the air receiver is dependent upon air usage and the compressor style. The general rule to size a air receiver is:
• Receiver Size = Compressor ACFM * 1 Gallon/ACFM
• For a 200 ACFMCompressor = 200 Gallons
• With a Conversion Factor of 7.48 Gallons/Cubic Ft. = 27 Cubic Ft.
Wet receivers should be installed downstream of the moisture separator and before other purification equipment. Dry receivers are installed after purification equipment. All air receivers should be on blocks or some other small foundation to keep them dry and rust-free. There also should be enough space left around the receiver to allow for easy draining.
Exercise care when installing air receivers outdoors because any condensed moisture may freeze and interfere with the operation of drain valves, pressure gauges and safety valves. Never install a valve between the air receiver and the safety valve. The exhaust from the safety valves should be directed away from personnel and in a way that the thrust will tighten threaded pipe fittings if it lifts and blows, as opposed to unthreading them.
Pressure gauges should be of good quality and large enough to read while standing on the floor. Install an isolation valve between the gauge and the tank so that the gauge can be removed and replaced or recalibrated every six months without depressurizing the tank. It is essential that air receivers have an automatic trap/drainage system. Also, the receiver needs to be bolted or clamped to the floor or base on which it is mounted in case of a line fracture.
Moisture should be drained from the receiver regularly, especially in cold weather to avoid problematic accumulation. If you need to add any braces, struts, base supports or nozzles to an air receiver, use an ASME Coded weld shop for any welding or repairs. Many companies have a policy to annually hydrotest the air receiver's integrity. Besides hydrotesting, older air receivers should be checked periodically with an ultrasonic thickness gauge or meter. Corrosion effects can be determined by comparing readings of head and shell to the nameplate.
Home News Pressure Vessel Registration Requirements - Australia
Pressure Vessel Registration Requirements - Australia
FAQ: Australian Pressure Vessel Registration
Over the years there have been many changes in the way the various State Work Health and Safety Authorities around Australia have determined when and how a pressure vessel must be registered. As a result, there is often confusion. Over the past 12 months a great deal has been accomplished in harmonising the various States. The following frequently asked questions may assist in helping that understanding. The following Frequently Asked Questions are given on good faith and based on the understanding FEC has acquired:
1. Do all States in Australia have the same Rules for Registration of pressure equipment?
All States, with the exception of Western Australia and Victoria, have the same registration requirements. Fortunately the registration requirements for Victoria differ little and indeed for the purposes of registration can be deemed the same as the other States. As such only Western Australia (WA) differs sufficiently to prompt additional considerations. WA will only accept designs that comply with the Pressure equipment design Codes AS1210, ASME BPV Code Section VIII or the British Code BS5500. All other States will accept design codes published by recognised standards organisations.
2. When does a pressure vessel need to be registered?
The governing Australian Standard that dictates this issue is AS4343. Here an attempt is made to quantify the risk associated with the pressure vessel. If AS4343 is applied correctly and results in a hazard rating of A, B, C or D, the pressure vessel must be registered as a design. In addition, if it results in a hazard rating of A, B or C, the vessel must be plant registered before it can be used. All States agree on this principle.
3. What is the difference between registering a design and registering an item of plant?
This is often a point of confusion. Before an item of plant can be registered, the design should be first registered. It is possible to have one design registered and many vessels fabricated using that one design. Once fabricated and before being placed into operation, the item of plant must be plant registered. Design registration requires a designer and a Verifier to sign off on the design as being safe. Plant registration requires a competent person (e.g. an appropriately qualified pressure vessel inspector) to have inspected the vessel and make a declaration that the plant is safe to operate. The competent person must have inspected the plant to certify that the plant has been maintained in accordance with the instructions of the designer, manufacturer and relevant Australian Standards, codes of practice and legislation.
4. What is the difference between a Designer and a Verifier?
A purpose of having both a Designer and a Verifier is to ensure that there has been a deliberate effort to make sure nothing has been overlooked in the design process. In that regard, there is little difference between a Designer and a Verifier; both are experienced pressure vessel designers. The Verifier is the final check over the design and as such there is an expectation that the Verifier is appropriately experienced (see Note 8). Again to ensure that the process is as comprehensive as possible, the Verifier must have had no input into the initial design activity. This ensures the review by the Verifier is carried out without prior assumptions or prejudices. It is possible for the Designer and Verifier to be in the same employ, but the company must have a JAS/ANZ accredited Quality Assurance system that specifically deals with procedures to ensure independence of the Designer and Verifier.
5. Do all pressure vessels need to be designed in accord with AS1210?
While this was once the case, it is no longer required. Aside from Western Australia, strictly speaking the pressure vessel can be designed in accord with good engineering principles. In the case of WA, the design must be carried out either in accord with AS1210, ASME BPV Code Section VIII, Divisions 1 or 2 or the British Standard, BS5500. For all other States, appreciating that both the Designer and Verifier need to agree, the expectation is that a recognised appropriate International Design Code will be used. It is also an expectation that the International Design Code be available in the English language mainly to permit the State Authorities the opportunity to carry out a design audit if they so wish.
6. Is it permissible to mix Design Codes and their Associated Fabrication Code?
While this is untested, the State Acts and Regulations do not mandate how a vessel is designed and hence fabricated. However, if it is declared that a vessel is designed to a particular Code such as AS1210, it must also be fabricated to the associated fabrication Codes which in the case of AS1210 will be AS4458, AS3992 and AS4037.
7. Does a Pressure Vessel that has been designed to ASME BPVC Section VIII require a U-Stamp for use in Australia?
The use of a U-stamp is only an issue at the time of plant registration. It is not an issue at the design registration stage as the U-stamp is a physical stamp that is applied to a vessel at the completion of fabrication. Only the State of Victoria will permit the plant to operate without having a U-stamp. All other States require the full compliance to the design and fabrication Code. The ASME BPVC Section VIII specifically requires the application of the U-stamp (in most cases) and as such in States other than Victoria a U-stamp is required. If ASME does not require a U-stamp, then in those (few) cases, it is permissible not to have one. The intent of registration is to ensure complete compliance with the Code applied and in this case, it is ASME BPVC.
8. Does the designer or the Verifier need to be Australian or based in Australia?
No. Neither the Designer nor the Verifier need to be Australians or based in Australia. On the other hand, one needs to appreciate the legal implications of neither the Designer and/or Verifier having a presence in Australia in the event of litigation action. The legislation does impose a duty on the Design Verifier and hence it is preferable that the Verifier be based in Australia. Queensland Workplace Health and Safety has recently (3rd October 2014) imposed the requirement for a Design Verifier to be an RPEQ.
9. Can the applicant be the Designer or the Verifier?
While it is permissible for the Designer to be the applicant for Design Registration, it is not permissible for the Verifier to become the applicant.
10. Does the Applicant need to be Australian or based in Australia?
The Applicant’s office must be in the State to which the design or plant registration is being registered. This is a sensible ruling as it ensures the registration of design and plant are distributed throughout all States.
11. If a design is registered in one State, will it be recognised by all other States?
Yes. Any pressure vessel design registered in any State will be recognised by all other States. There is no exception to this amongst States. However, there is a difficulty due to Western Australia (WA). Although it will recognise the design registration, it will not recognise the plant registration if the design and fabrication is to any other Code than AS1210, ASME BPVC Section VIII or BS5500. There is no simple "work around" to this dilemma and the applicant must simply be aware.
Plant Registration QLD: http://www.deir.qld.gov.au/workplace/training/registrations/plant/index.htm
Plant Design Registration QLD: http://www.deir.qld.gov.au/workplace/licensingregistrations/plantdesign/index.htm
The answers to these frequently asked questions are provided on good faith and to the best knowledge of FE Consultants Pty Ltd at the time of publication. These answers further cover technical issues in a general way and are intended for information purposes only and should not be regarded as technical advice. In all cases, registration requirements are the responsibility of the relevant States or Territory Government body. If in doubt, particular queries should be referred to the relevant governing body. Further advice should be obtained before taking action on any issue dealt with in this publication.