Monday, 26 July 2010

Meaning of the Hyphen mark(-)




Standard methods of measurements are with several divisions which provides list of descriptive features of work. For an example in CESMM3, has three divisions and SMM have five divisions.
E.g. Class D in CESMM3 (Item 4 &5)
Division 1 – Buildings/Other structures

Division 2 – Brickwork/Concrete

Division 3 – Volume not exceeding 50m3/ 50-100m3


In some divisions it has provided descriptions with hyphen mark(-), e.g. 50-100m3.

Some Qs’s may not clear about the meaning of hyphen mark used in standard method of measurements.

Simply 50-100 means; all numbers from 50 to 100,  excluding 50 but including 100.


Then will see what has stated in few standard methods of measurements.

CESMM3 has stated that “ A hyphen between two dimensions means a range of dimensions which includes all dimensions exceeding that preceding than hyphen but not exceeding that following then hyphen.“

SMM7 has stated that “The use of hyphen between two dimensions in this documents or in bill of quantities shall means a range of dimensions exceeding the first dimension stated but not exceeding the second.”


Transformers


While I’m doing a revised BOQ and cost estimate for a substation, I have noticed transformer type is revised to resin type from oil type. The Standard method of measurement for the project is CESMM3.

In CESMM3, class Z is for Simple building works incidental to civil engineering works. Transformers can be measured under class Z with following divisions.

First division – Cabled building services

Second division – Equipment and fittings

Third division – Equipment

 

What are oil type and resin type transformers?


Oil cooled transformer

For large transformers used in outdoor such as power distribution, the core and coils of the transformer are immersed in oil which cools and insulates.

The oil is cooled by the outside of the tank in small ratings, and in larger ratings an air-cooled radiator is used.

Where a higher rating is required, or where the transformer is used in a building or underground, oil pumps are used to circulate the oil and an oil-to-water heat exchanger may also be used.

Indoor transformers are needed to be fire resistant, then it is not advisable to use oil type within a buildings. But fire-resistant liquids such as silicone can be used as substitute to oil.

 

Cast resin transformers

Cast-resin power transformers encase the windings in epoxy resin. This is one of a dry transformer type. The dry transformers are the transformers without active part immersed in a liquid insulation.

This type is more costly than oil cooled type. This type is generally used in indoor locations.

 

 

From:

1) http://en.wikipedia.org/wiki/Transformer_types#Cast_resin_transformers

2) http://www.google.lk/search?hl=en&source=hp&q=resin+transformers&aq=0&aqi=g1g-m9&aql=&oq=resin+transformer&gs_rfai=&safe=active

 

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