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Thanks for the answers. Sometimes is hard to have proper technique when high force has to be used and if body is in awkward position. Longer torque wrench would definitely help because smaller force would have to be used and therefore create smaller bending torque on the bolt head.

Hi all, If we use long socket extension (comparable to the length of the breaker bar or ratchet) to tightening lug bolts on a car, are we creating greater frictional force underneath the bolt head and in the threads because of the torque that is created that wants to bend the bolt head (torque...

Does someone know formula for calculating earth surface potential for horizontal stripe earth electrode in longitudinal direction. I know how to calculate in transverse direction but I don't know how to calculate in longitudinal direction. Is it safe to connect earthing electrode of the house...

Hi, I am trying to build small earthing electrode in very limited space for a house that doesn't have it. It will be used with RCD (deltaI 300mA or 100mA) in system with 240V. I am choosing between straight horizontal stripe (around 7 m long) and two horizontal stripes (3.5 m long) crossed at...

Does anybody know how pressure drop across the turbine changes when the flow is changing? Does it change like the turbine mechanical efficiency? If we have 60m head with the rated flow flowing through the turbine there will be 60m head drop (or 6 bar pressure drop) across turbine or it will be...

Hello, Local drinking water supply company has problem with high pressure in the pipeline. Reservoir is located 100m above the valley so the pressure inside the pipeline at the bottom is 10 bar and it is supposed to be 4 bar. Average water flow through this main pipe is around 80 l/s. I am...

Actualy potential Owners are suggesting those pipes because of low price. I need arguments against those pipes. The fact that they will leak under pressure is good reason. You sad that You have expirience with hydropower, can you please mention if those pipes need concrete bedding and how...

Thanks for reply! I am not familiar with the prices of CPP so I don't know if this could be better option then GRP. I am interested in culvert concrete pipes only because their low price. You sad that those pipes are not designed for pressure use, but what pressure can they withstand if buried?

Hello, I am analyzing one potential location for micro hydro power plant. Gross head will be between 4,1m and 4,5m. To achieve this head I need 73m long pipeline. It will be placed 1m below ground level in the soil near the river. I analyzed steel and GRP pipes and their prices, but I wonder is...

I am concerned with the situation when I have enough water to produce max power (100kW) and because of low demand in the grid due to higher freq of the grid I have to reduce power production because all generators have to reduce power. So there is possibility that I can deliver all I can produce...

I have one beginner question. If we connect small (micro) power plant (100kW) to the grid in the locality with thousand residents, how can we know if our small power plant will deliver all produced power to the grid? I mean, if in that locality at one moment is very low power demand how can we...

I read that when ac machine is working as a generator internal voltage E always leads terminal voltage V and this is necessary for active power to flow from generator to grid. Can someone explain why is that? I know that rotor magnetic field leads in front of stator magnetic field. But if we...

Does gearbox in small hydro power plants connected to low speed turbines change gears (does this kind of gearboxes exist?) or does it have only one gear ratio. I read that some wind turbines have some kind of CVT gearboxes but I am interested if there is gearbox with three or four gears that...

Here are some information about small hydro: Turbine nominal revolution: 244/min, max. revolution 678/min, Asynchronous generator nominal revolution 1010/min, max revolution 2798/min (15 min), belt drive, no gearbox! Grid freq 50Hz How is that possible that induction generator has that wide rev...

So because rotor magnetic field advances and goes infront of stator magnetic field by some angle, current in the stator is flowing in opposite direction compared to stator current when working as a motor and power is produced. What is the purpose of the gearbox between a turbine and a...

Thank you very much for clarification, but I am confused now about the same thing but with the synchronous generator (one that doesn't use ac-dc-ac converter) that is directly connected to the grid. The grid is controlling the rotation frequency by strong rotating magnetic field and doesn't...

Hi! I would be grateful if someone can explain how is voltage frequency controlled (kept constant) in the squirrel cage induction generator driven through the gearbox by the turbine connected directly to the grid. I read that generated voltage and frequency are controlled by the grid, but I...

http://www.afdc.energy.gov/afdc/pdfs/fueltable.pdf Here are some fuel properties where we can see that in the same mass of fuel diesel and gasoline have very similar amount of hydrogen. As we can see in the same mass gasoline can even contain little less hydrogen than diesel!? Only natural gas...

Compositepro, thanks for great post! Let me see if I understand, if we don't want to see water vapor mist we should have as hot gas as we can (we can't influence gas humidity) when it is leaving tailpipe, so that it has enough time to mix with air (so the relative humidity of mixture gas/air...

When we start the engine on a cold day (below freezing point) there is condensed water vapor (mist) coming from the exhaust. When the engine and the exhaust get hot there is no more water vapor mist coming from the exhaust. Why? When moist hot gases exit the hot exhaust they enter very cold air...