MDG41 2018

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New MDG41(Sep 2018) – 15 things you need to know

With much anticipation the newly revised version of MDG41 Fluid Power Systems has been release this week. APT’s Kyle Probert was a part of the committee that reviewed the previous version and worked on updates.

Don’t Panic – here is a quick run down on the changes that may affect your site

1. Definitions – the most significant one is “Matched System” from previous versions and “Matched” (clause 1.5.14 & clause 3.8.7.2) in the current version – discuss this with your hose suppliers.
2. References (Appendix A)- updates have been made to the Standards, Acts, Regulations and Guidelines referenced. The most significant updates have been to
   • AS4024 Safety of machinery & ISO13849 Safety of Machinery
   • AS4343 and AS4458 – Pressure equipment (eg: accumulators and air receivers)
   • AS/NZS1200 Pressure Equipment
   • ISO4079 Rubber hoses and hose assemblies
3. Hazards associated with fluid power systems (clause 2.2)- there is now a comprehensive list of Hazards and explanations of scenarios and consequences. This table would be a great part of your introduction to site process to encourage your staff to think about the system and the hazards that may be present
4. Design of Safety Critical Systems (clause 3.2.3) – there is a lot more guidance on safety critical systems, essentially reference is made to AS4024 Safety of machinery for most of this. In your Risk Assessments for any fluid power system you should be referencing AS4024.
5. Protection from uncontrolled escape of pressurised fluids (clause 3.4.4) – this is a new addition to the design section but condenses a lot of information that was spread over multiple clauses. Here are a couple of points worth noting on this clause
   • The risk of uncontrolled escape of fluids should be managed through risk based methodology. The best way to protect people from this risk is to design the systems so the operator is away from hoses and components, eg: behind covers and guards. Use of pilot circuits operating at low pressure is a good alternative where operators need to be near components
6. Design for maintainability (clause 3.4.7.) – this has been updated and there definitely needs to be an effort to ensure machines are able to be maintained safely and easily. The two most critical items for this would be:
   • the ability to visually inspect hoses and components
   • The ability to easily change filters. Filters are the best method to protect the system from inadvertent operation (eg: stuck valves)
7. Isolation and energy dissipation (clause 3.7) – this is has been updated and is an area that we see often lacking on sites, workshops and from OEMs. A lot of system designs do not adequately address areas of potential trapped pressure. This leaves maintenance personnel with the task of interpreting schematics and identifying trapped pressure for themselves. We believe all systems (from machine attachments to fixed installations) should have a full analysis completed on them to identify any areas of potential trapped pressure and ensure there is adequate equipment installed to detect and diffuse this trapped pressure. For example this could be in cylinders, behind load holding valves, between DCVs and actuators.
   • Clause 3.7.2.e – Two-point verification of a dissipation event – it is vitally important at the design phase that dissipation of trapped pressure is considered and test / dissipation points built into the system.
     • Systems which have been designed correctly (there are a small number of exceptions) should not have to dissipate oil to atmosphere for normal isolation procedures. Even when dissipated through a diffuser this essentially designs in the potential to expose personnel to hot oil. Dissipation should return to the reservoir – if your designers are telling you otherwise seek other advice!
8. Hose assembly energy diffusion devices (clause 3.8.2.8) – additional information has been provided around the use of hose sleeves.  Remember that these hose sleeves are the PPE when it comes to protecting people from high pressure fluids.
9. Hose manufacture and selection (clauses 3.8.6 to 3.8.12) has some new information in it, particularly around Staple Hoses, Matched Assemblies and non-standard fittings. It would be worth discussing with your hose supplier about this.
10. Pressure equipment (clause 3.9) – remember that accumulators may be subject to design and item registration as per WHS Regulations and AS4343.
11. Section 4 on Installations has not changed much, there is a good item on Hose identification colours as a standard.
12. Section 5 – is largely unchanged, it does now cover the “decommissioning” of fluid power systems in line with equipment lifecycle considerations.
13. Operational and Emergency Procedures (clause 6.3) – there are a few more considerations with regards to site standard procedures for fluid power systems – it would be worth reviewing these lists to ensure your site procedures comply.
14. Section 7 – is largely unchanged with the exception of Competence (clause 7.1.1) – there is now reference to two Nationally Recognised Units of competency which meet the expectations of the guideline. This is great for contractors or casual staff who may move from site to site as there is now clear guidance on what is suitable. For sites, this may necessitate the need to review competence of staff and outcomes from existing training programs. The good news is the units listed are entry level or basic units, current apprentices in the industry complete units which are more involved and at a higher level than these. Your current training programs may already cover the requirements of these units of competency. Personnel who have completed MEM18020B Maintain Hydraulic Systems components (previously Hydraulics 1) and/or MEM18021B Maintain Hydraulic System (previously Hydraulics 2) have already exceeded the requirements of this unit.
15. The appendices have a lot of useful information on hose installation, fitting pressure ratings and inspections – this should be delivered to your maintenance staff.