Pressure Vessels: What requires regular statutory inspection?

The Mines Safety and Inspection Regulations (MSIR 1995) provide comprehensive guidelines for the inspection and safety of plant, however they are often misinterpreted, which could mean your site has been left non-compliant.

One such commonly misinterpreted and incorrectly applied inspection regulation is that of the time period between statutory inspections of Air and Gas Receivers.

The question: Do Air or Gas Receiver’s less than 150 litres need Statutory Inspections?

The Regulations

The Mines Safety and Inspection Regulations (MSIR 1995) states in Regulation 6.40 (1) that each responsible person at a mine site must ensure that registrable Classified Plant is not to be used if the period of time set out in Schedule 3 has elapsed since it was last found suitable for use by an inspector or person authorised in writing by the State Mining Engineer in a statutory inspection.

More specifically, Schedule 3 states that the statutory inspection period for Pressure Vessels categorized as Hazard Level A, B, C or D is no greater than 3 years, with the exception of:

a) Air or Gas Receivers with a maximum operating pressure of 210 kPa  (30psi) or less;
b) Air or Gas Receivers that have a capacity not exceeding 0.15 cubic metres (150 litres);
c) Pressure Vessels fitted to mobile earthmoving equipment;
d) Pressure Vessels fitted on a train;
e) Gas Cylinders covered by AS2030;
f) Serially Produced Vessels covered by AS2971;
g) Pneumatic Loaders of Explosives.

It is these exceptions, in particular exception b, that are commonly misinterpreted and incorrectly applied. This is predominantly due to a failure of many within the industry to understand exactly what vessels fall under this exception.

Definition of an Air or Gas Receiver

Firstly, it is important that inspectors are aware of the definition of an ‘air or gas receiver’, which is not clearly defined in the Regulations, the Australian Standards or any recognised International Standards.

To clarify this, AME sought the Department of Mines and Petroleum advice on the definition of an ‘air or gas receiver’ to which they replied:

“In the absence of a clear definition in the Regulations or the standards, we should refer to the common dictionary definition. The common dictionary definition for an air receiver is a ‘storage vessel for compressed air usage’.”

150L pressure vesselAME can assume therefore that only pressure vessels less than 150 litres which fall under the definition of a ‘storage vessel for compressed air or gas usage’ should be part of this exception to Statutory Inspections.

The DMP further clarified that hydraulic accumulators and air/oil separators are not classified as an ‘air or gas receiver’ since they are not intended to store pressure  for compressed air or other gas usage. Hydraulic Accumulators and Air Oil Separators that are hazard level D and above are required to have Statutory Inspections regardless of their volume.

The key words here seem to be that the exception applies to vessels intended for ‘storage’ of air or gas for air or gas ‘usage’. We should question if any pressure vessel that is less than 150 litres comes under this definition before stating that it is exempted from Statutory Inspections.

What the Australian Standards say

While it is not specifically stated in the Australian Standards, further clarification that certain types of vessels should be defined and treated separately to an Air or Gas Receiver is given in Table 4.1 of AS3788:2006. This table gives the inspection frequency to the Australian Standards that is required for different types of pressure vessels.

AS3788:2006 - Table 4.1

AS3788:2006 – Table 4.1

This table clearly separates and gives different requirements for ‘Compressed Air Containing Vessels’ to ‘Process Vessels’ or ‘Auxiliary Vessels’, among many others.

Table 4.1 Note 6 defines a Process Vessel as those which form part of a process train and which are subject to changes in temperatures, pressure and/or contents during the process cycle. So all cyclic type vessels should be considered as a Process Vessel, which could include Elution Columns, Desiccant Air Dryer’s and some Chiller type vessels.

Table 4.1 Note 7 defines an Auxiliary Vessel as those which form part of a package or part of a subsystem, for example suction/discharge vessels, filters, knock-out vessels, intercoolers and hydraulic accumulators. So Accumulators as well as Air/Oil Separators which can be classified as a type of filter both fall under this section.

While it is not specifically stated anywhere, Table 4.1 can therefore be used as a guide to see if a pressure vessel should be treated as an ‘Air or Gas Receiver’ or if it falls under a separate type or definition. If the pressure vessel falls under a separate section of Table 4.1, there is a good chance it should not be considered to come under this Statutory Inspection exception.

Pressure VesselThe Final Word

In conclusion, only air or gas receiver’s less than 150 litres should fall under this exception from statutory inspections, and all other types of pressure vessels less than 150 litres should not be exempt from regular inspection.

Also it should be remembered that Regulation 6.26 of MSIR 1995 states that an employer on a mine site must ensure that all pressure equipment is inspected in accordance with the Australian Standards. So all types of pressure vessels regardless of their size still require inspections to the Australian Standards, specifically AS3788:2006.