The plan was for the 720 MW Mangdechu project to generate around 3 bn units a year at the rate of Nu 4.12 a unit to generate Nu 12.3 bn in revenue of which around Nu 4 bn would be deducted for loan repayment.
This may still be possible if BHEL can fix the many issues in the four turbine units of the project by January 31st 2020, otherwise, Bhutan stands to loose revenue from May onwards when higher water flows will demand the operation of three turbines and the monsoon from June onwards will need all all four turbines functioning at optimum capacity.
After a host of problems crept up with the four generating units of 180 MW each, BHEL, in November 2019, was given time till 15th December 2019 to fix all the issues.
Lyonpo Loknath Sharma of the MoEA said, “There were some teething issues with the units and BHEL was told that it should be fixed by December but somehow there are a couple of issues which requires some additional parts and a technical team. They have promised that it will be fixed by the end of January 2020 by any means.”
The issues had started cropping from June 2019 itself when the four units were being commissioned with a gap of 15 to 10 days from each other.
Around July 2019 Unit 4’s ‘Upper Guide Bearing’ or the top outer section of the unit started heating up as the turbine was in motion.
A similar problem occurred with the third unit around the end of November 2019.
On September 28th 2019 the 3rd Unit developed a serious problem when the brake applied by itself as it was in full motion generating 180 MW leading to the finishing of brake pad and black carbon inside the unit.
Then if that was not enough oil was leaking out of the bearing system of the four units to the effect of around 100 liters in a month.
MHPA was also not happy with the way the water nozzle injectors that sent water to the peltons worked and wanted a reprogramming. There was also a problem in one of the six nozzles of unit two.
However, the main challenge was the ‘Governor System’ or the centralized computerized system not getting accurate reading from some of the thousands of sensors.
It now appears that the main issue that BHEL has to resolve is around this Governor System and its many sensors which need to give accurate readings for the system to function effectively.
A lot of work has been done one unit 1 and 2 and currently work is going on on unit 3 and 4.
The Joint Managing Director (JMD) of MHPA Chencho Tshering said that from the 100 liters of oil per month that came out of the four units earlier it has now been reduced to around 15 liters and the aim to to stop all leakage.
On the break applying by itself he said that BHEL had suggested that perhaps someone had pressed the break by mistake or a hard vibration on the control board must have activated the break. Chencho said he works with professionals and so no staff would have done that for sure.
He said that the break will need some additional work which will be done before 31st January.
On the upper guide bearing heating up in the two units Chencho said that each unit is around 385 metric tonnes and spins at around 6 to 7 revolutions per second at great speed. He said that time is required to stabilize the units and even the smallest errors could lead to heating.
Chencho said that if one looks at the region and beyond the Commissioning dates of the Mangdechu units were the fastest with a gap of only 10 to 15 days between each unit. He said that the aim was to meet the date of commercial production so that Bhutan could capitalize on the Nu 4.12 per unit tariff.
On the governing system and the sensors, Chencho said that it is a matter of calibrating the sensors and meters like those for oil and water level, temperature, water pressure etc.
Chencho said that the target of the project is to achieve 75 percent of machine availability and usage of 90 percent of the water throughout the year which would be very efficient for a hydro plant.
The project due to low water flow is currently generating 110 MW from its two turbines.
The Nu 8 bn BHEL equipment have a one-year liability period but since the equipment were faulty from the start the defect liability period has not been started by the project which will only do so once the full repairs or replacements are done.
If the issue is not fixed by May once the river level starts rising, then there could be huge revenue losses for the project.
The Mangdechu episode has again raised long standing quality concerns with BHEL equipment and re-opened the debate to have competitive bidding for electro-mechanical equipment instead of giving it on nomination basis to BHEL.