Sunday, March 24, 2013

Manpower Planning for Concreting

Suppose on a project, one had to complete 1000 cum of concrete in a month, how should one plan the manpower for that.

Ofcourse productivity depends on the type of structure, but I am speaking of a general approach and not specific to a certain type of structure.

For a general concrete structure we can assume 0.1 ton of rebar per cum of concrete on the average.

So 1000 cum of concrete works out to 100 ton of rebar.

Based on site observations a barbender with 2 helpers does approx 0.4 ton of barbending,cutting and fitup in a day.
So 1 gang of barbenders ( 1 main barbender and 2 helpers) would do approx 10 tons of reinforcement work in a month ( assuming 25 working days)

Hence to do 100 tons of rebar in a month 10 gangs would be required.

For shuttering, we can assume that 4sqm of shuttering would be required per cum of concrete.
Hence for 1000 cum of concrete, 4000 sqm of shuttering would be required.

One carpenter with 2 helpers do approx fit up of 4.5 sqm of shuttering in a day.
So 1 gang of carpenters would do appox 112.5 sqm of shuttering in a month
Say 100 sqm in a month

So in order to compete 4000 sqm of shuttering in a month, 40 gangs of carpentars are required.

Wednesday, March 13, 2013

Key Construction Risks from Systems Outside the Boundary Wall of the Plant

Generally all systems outside the boundary wall of a thermal power plant carries a huge construction risk.

These systems include:
1. Cross Country Pipeline for delivering the water to the thermal power plant
2. Transmission Line  for delivering the electricity produced at the plant to the nearest point in the grid
3. Railway Siding for delivering coal to the power plant

Generally the amount of risk is directly proportional to the length of system. For instance, a cross country pipeline of 60kms carries a much bigger risk than a cross country pipeline of 20 kms.
Generally for Cross Country Pipeline and Transmission Line, we only need to get Right of Way (ROW) which is sort of lease model and need not actually acquire the land. However for Railway Siding, we have to actually purchase the land. Land acquisition is a long and cumbersome process as there maybe more than 2000 individual land owners for a railway track of 20 km length.

For Cross Country Pipeline, its a better strategy is run your cross country pipelines  parallel to the road or a national highway and offset it from the highway by 10 to 30 metres. Generally the land around the highways is owned by Highway Authority or other Government bodies and getting the ROW is much simpler. However, as there maybe plans to make the highway from 2 lanes to a 4 lane highway in a few years and you maybe asked to relocate your pipeline. The plant owner must protect himself against this by leaving sufficient distance from the edge of the road or highway.

Additionally our pipeline may also be crossing local roads, national highways, rivers, canals, railway lines, other pipelines, petroleum pipelines etc. While finalizing the route of the cross country pipeline we must have a very clear strategy for overcoming all these challenges.

Monday, March 11, 2013

How many energy units are produced by Power Plant in a single day

The electrical meter installed at our home measures energy units in KW-hr.
On the average, we consume about 300 units per month in non summer months (no AC), so really we are consuming about 300 KW-hr of electricity per month.

Say an average of 10 units per day.

So how many KW-hr does a power plant of of 300 MW size produce ?

Per day the power plant would produce = 1000 X 24 X 300 units =  72,00,000 units

However, the power plant would consume some of the power produced by it to run its own auxiliaries such as the coal handling plant, boiler feed pump, fans , pumps etc.

Hence on the average, auxiliary consumption is approximately 7% of the generated power for a unit of 300 MW sizing.

So the gross exportable power of the plant is 0.93 X 72,00,000 = 66,96,000 units

Further, we also need to consider the Plant Load Factor as the power plant would not be running contionously throughout the year.  It may have to take shutdowns for maintenance,  non-availability of coal, grid failures etc.

An average Plant Load Factor to consider for a new plant is 0.85 

So the net exportable power produced by a unit of 300 MW per day is 0.85 X 66,96,000 = 56, 91, 600 units per day.

If this plant was supplying power to only residential houses, then theoretically this power plant could power 5,69,160 houses considering an average of 10 units consumed by single house per day.

However in reality the Transmission, Distribution and Theft Losses in India are very high to the tune of 40 percent and this is where real change in policy is required.