Spec Check Issue 5: Is Your Motor Clause Causing Confusion?

Welcome to the 5th issue of Spec Check We hope you find it challenging and a reminder for you to review your Master Specification, that is “check your spec!”

When did you last review your electric motor clauses for centrifugal pumps?

Motor descriptions are probably the most ambiguous of all product specifications. We suspect this is due to a misunderstanding of the MEPS requirements in the code. Many consultants will request that motors must be MEPS High Efficiency to AS1359.5, but this is incomplete. It is not enough to simply quote the Australian Standard and compliance to MEPS efficiency.

Further to this are the incoming changes to the European IE standard. Motor manufacturers represented in Australia are pushing the case for Australia to harmonize and align with the IEC world (EU EEA) Single Test Method: IEC 60034-2-1 Motor Efficiency Values: IEC 60034-30 Regulatory Scope: 0.75kW to 375kW, 2P to 6P. Whilst the above changes would reduce confusion and improve international trade, machine manufacturers will likely still need to consider differences in frame and shaft dimensions.

These three questions will serve as a quick health check for your Master spec for electric motors.

1. Does your specification make mention of the relevant standards?
2. Does your specification quote the relevant test method in accordance with the above standard?
3. Does your specification make any mention of metric frames and shaft configurations?

You may well find you say yes to Q1 and a No with Q2 and Q3. If so, you could be inadvertently be specifying a product that is not as efficient as you are expecting and potentially a headache to your client throughout the life of the product.

Where are we heading?

We looked deeper into these questions and offer answers to help align your specifications reflect the current approach in the market.

1. Does your specification make mention of the relevant standards? Always mention current Australian Standards AS/NZS1359.5 & IEC 60034-30]  Note: The efficiency values advised in AS/NZS1359.5:2004, resemble but do not match those of IE2 & IE3 stated in IEC60034-30. This is covered in further detail in the next question. A comparison table of Efficiency Levels AS/NZS1359.5:2004 vs IEC 60034-30 is available from Masterflow on request.

2. Does your specification quote the relevant test method in accordance with the above standard?  AS/NZS1359.2:2004 allows for two test methods:

• Test Method A in accordance with AS 1359.102.3, IEC 61972, IEC 60034-2-1. All motor losses are measured.
• Test Method B in accordance with AS 1359.102.1 and IEC 60034-2 (IEC 34-2) Defined value for of stray losses for each Test Method (A or B),

AS/NZS1359.2:2004 provides 3 tables, each with stated values of efficiency for motors 0.73 to <18.5kW, 2P to 8P. Tables A1 and B1 Minimum Efficiency (MEPS 1) 1 October 2001 to 31 March 2006. Tables A2 and B2 Minimum Efficiency (MEPS 2) From 1 April 2006 Tables A3 and B3 High Efficiency from April 1, 2005.

Most European motors will comply with IE2 but fall short of IE3. For smaller motors, this may be acceptable, but for any motors 30kw and greater, we recommend you also insist on the IE3 motors and ensure you accurately describe this in your specification.

The best way to stipulate high efficiency motors is to quote the Australian Standard AS1359.5, Table A3 test method. This description leaves no room for any doubt and will ensure the client gets a motor of similar efficiency to the European Standard IE3.

3. Does your specification make any mention of metric frames and shaft configurations?

This specifically relates to projects where the close-coupled motor pumps are being supplied, e.g. BakerBloc or BakerLine types. We suggest making some mention of the shaft arrangement of the motor. This will ensure you are not allowing an inferior imported motor that relies on the “extended shaft” design. This means the motor shaft is extended into the pump casing and thus becomes also the pump shaft. Over time the seal will wear and may cause pitting to the shaft necessitating the complete motor/pump replacement (and not just a shaft as would be the case in the Baker or similar brands arrangements). By stipulating the metric frame as outlined above, you will ensure that readily available replacements will always be hassle-free minimising downtime.

In summary, having standard metric frame motors means the client can source a motor from any of the major manufacturers on the local markets rather than be dependent on the particular one from the original equipment manufacturer. Non-standard motors can be costly, and the client will be forced into replacing the whole pump and especially if the manufacturer does not have the motors readily available. Specifying a metric frame means the motor can be replaced instead of the whole pump. The design of pumps that use metric frame motors have an additional layer of protection for the motor, should the seal leak at any point.