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Thread starter
sigamana
Start date
Oct 14,Tags
In summary, the conversation was about designing a servo motor for a spillway gate for a dam. There were doubts about determining the pushing force for a piston carrying a heavy load of 275 tons at a speed of 0. m/min. Suggestions for books or articles to read and contacts in the community were requested. The conversation then delved into discussing the geometry of the gate and actuators, the operating pressure of cylinders, and the weight and friction forces of the gate. The question of whether a vertical gate and radial gate of the same size and frictional forces have the same pulling and pushing force was also raised. The expert summarizer suggests that the gate will close under its own weight and discusses the differences in hydrostatic forces
sigamana
am currently designing a servo motors for a spillway gate for a dam , I have some doubts on how to determine the pushing force( the force needed to drop the spillway gate at a safe rate) for a piston carrying a heavy load of 275tons at a speed of 0. m/min(this speed was pre-determined by me because I wanted a for the spillway gate to close in 40 min having a total stroke of 8m) can anyone chat suggest books or articles that I should read or who to speak to in this community that could get me closer to the solution
Best regards
Sigamana
Science Advisor
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To help with this question we need to know the geometry of the spillway gate and actuators.
Is the gate a radial gate that is hinged on pins?
Is gate moved by a hydraulic cylinder using hydraulic oil from a pump?
How many and what size cylinders are you considering. Stroke, rod and cylinder diameter?
What is the maximum operating pressure of your cylinders?
sigamana
Baluncore said:
Thank you Mr BaluncoreThe Gate is radial with a skin plate bent to a radius of 13.5m height 7.8 length 6m the gate is hinged on pins (specifically trunnions) , its moved by 1 double acting hydraulic cylinder using oil from 1 pump .Gate is attached to a suspension bar that consequently is atteched to the hydraulic cylnderthe total stroke is mmCylnder diameter - 590mmRod diameter - 133mmWEIGHT of gate - 275 tones taking into account the suspension bar that weighs 58 tonsSum of friction forces - 291.245KNTime estimated for opening gate - 20 min v=0.44 m/mintime estimated for closing gate 40min v=0.220 m/minI will attach a file with a picture of gate please tell me if i missed any details that could help understanding this problem .
sigamana
For more information, please visit hydraulic gate.
sigamana said:
Sorry forgotMaximum operating pressure = 75 bars
Hyo X
I'm not a hydraulic engineer or mechanical engineer, but don't you just need to balance forces? You are not trying to accelerate the gate, you are just trying to overcome frictional forces. So maybe the pushing force is = sum of friction forces?I am assuming that frictional forces includes the effect of water pressure on your 7.8x6 m^2 area gate. http://en.wikipedia.org/wiki/Floodgate#Physics Is 75 bar the pressure in the hydraulic system or on the spillway gate?
Science Advisor
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In the OP you are concerned by &#;some doubts on how to determine the pushing force (the force needed to drop the spillway gate at a safe rate)&#;.
Firstly the gate will close under it's own weight. You will need to regulate the flow of hydraulic oil to limit the closing rate of the gate. Potential energy will be released as the gate closes so it will tend to over-run a servo motor and cause the motor to operate as a generator.
In that situation a DC motor would always operate with current flowing in the same direction. That current would generate the torque needed to oppose the suspended load through the hydraulic system. By increasing the current slightly the gate would rise, by reducing the current slightly the gate would fall. The mechanical system will have low friction, so the difference in motor current either side of that needed to support the suspended mass will be small.
If the flow of oil is controlled without the use of the servo motor, then the oil flow rate regulator will reduce the oil pressure generated by the suspended mass and geometry. The product of pressure drop and flow rate would heat the oil in the pressure reducing flow regulator, that heat is usually radiated from an oil cooler or the bulk oil reservoir tank.
sigamana
Thank you ...
May i also ask does a vertical gate same size under the same frictional forces and a radial gate same size same fricional forces have the same PULLING and PUSHING FORCE? ...i ask this because i was comparing the results for pulling and pushing forces of my system and the one that they already built and they didnt take to account the fact that the gate is radial
Science Advisor
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A gate of height 7.8m and length 6m will have an area of 46.8 m2. When closed, with a 7.8m difference in water levels between the faces, there will be a hydrostatic force of about 6 * 7.8 * 1.5 = 70.2 tonnes force against the gate. The hydrostatic pressure against the gate will be zero along the upper edge but maximum along the lower edge.
A radial gate transfers all those hydrostatic forces to the trunnions. There will be very little friction from the small area of the lip seals at the sides of the gate when it is moving. A radial gate should therefore close under it's own weight.
A vertical sliding gate has friction on the surfaces that bear the differential hydrostatic force. Because of the friction, if there is a difference in water levels across the gate a vertical gate will require an additional force to it's weight alone when raising or when lowering the gate.
I notice in the provided diagram, that the hydraulic cylinder is being used to retract against the weight of the gate. That places the rod in tension which is good. It requires greater pressure and less flow though because of the piston face area and cylinder volume differences. There will never need to be oil pressure in the top of the cylinder against the piston. The speed of gate movement will therefore be proportional to hydraulic oil flow rate, independent of whether the gate is rising or falling. It is normal to expect a cylinder to have a factor of two difference in velocity between extending and retracting, but that is not the case with this design since only the rod side of the piston is working under pressure.
A 275 ton spillway gate is designed to control the flow of water in a dam or reservoir. It is typically used to release excess water during times of heavy rainfall or to regulate the water level in the reservoir to prevent flooding.
Hydraulic design is essential in determining the size and strength of a spillway gate. It involves calculations and analysis of water flow, pressure, and force to ensure the gate can withstand the expected conditions and effectively control the water flow.
The hydraulic design of a 275 ton spillway gate takes into account the expected water flow, the type of materials used in construction, the size and shape of the gate, and the surrounding topography. Other factors such as potential for debris or ice buildup are also considered.
The size of the spillway gate is determined by a combination of factors, including the expected water flow, the size and capacity of the reservoir, and the topography of the surrounding area. In addition, safety regulations and standards must also be followed in the design process.
The main challenges in designing a 275 ton spillway gate include accurately predicting the water flow and pressure, ensuring the gate can withstand extreme conditions, and considering potential environmental impacts. Additionally, construction and maintenance costs must also be taken into account for the overall design process.
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