Penstock gate deflection 3

[JohnWeal]

I am designing a penstock sliding gate wor a 4.8m wide channel and a 6.3m depth of water.

Are there any standards or recommended guidelines for the amount of allowable deflection?

As the bottom of the door is not within a slot, it is the bottom that is subjected to the greatest pressure / deflection.

Regards
John

 

[MikeHalloran]

How big a rock, boat, house, or Jeep(r) is likely to come down the penstock, and how fast will it be going? That may be a design load case, never mind the water.

What you seem to be talking about is a huge gate valve with a not-so-pretty-good seat. Maybe you can find some hints in the valve industry.

One deflection limit that comes to mind is when the gate bends far enough to become too short for the guides to retain it.

USACE must have design guides for the floodgates they install in/on levees.
They are usually slid into place before the water rises, so they won't be quite appropriate for insertion in a moving stream.

Mike Halloran
Pembroke Pines, FL, USA

 

[JedClampett]

I've fought through this before.

http://www.publications.usace.army....s/EngineerTechnicalLetters/ETL_1110-2-584.pdf

Lots of common sense mixed with a healthy does of conservatism.

 

[JohnWeal]

Thanks guys. Yes i guess the terminology clashes with a turbine feed pipeline...

A sluice gate maybe more clearer.
The max flow is 0.5m/s in the channel.

 

[dhengr]

JohnWeal:
I would look to the hydro-power industry for some stds. I would look to the large consulting engineering firms who design dams and power plants for the electric industry, maybe the U.S. Army Corps of Engineers. These days, we seem to assume that every step of every engineering problem must be codified down to the nth degree, or we can’t figure out what to do and where to start. I would guess that there is a whole lot of good sound engineering judgement and experience involved in designing these kinds of structures. And, that the guiding principle is that the deflection be reasonable and that all of the operating mechanisms must work/function under these deflected conditions. Obviously, the lower portion of the gate must be stronger than the upper portions, because it must resist greater pressures. But, the deflections should be fairly consistent over the height of the gate, because you design it to be stronger and stiffer as you move down the gate. It’s a great big grid work of beams with a face plate on the upstream side, isn’t it? See if you can get your hands on some plans and fabrication drawings for similar gates.

 

[SlideRuleEra]

Great advice from dhengr. Be conservative in sluice gate design, more conservative than any general purpose code would specify. In hydroelectric plant operation it is good practice to keep two independent sets of quick-acting gates between the reservoir and the turbine. This is for redundancy; the sluice gate is one, the other is the turbine's wicket gates used for load control. If both sets were to fail, water flow through the turbine is essential uncontrollable.

In the 1980's we had gate failure on a large unused industrial water supply opening. The visually spectacular unmanageable water discharge received national news coverage (televised CNN, etc.) until slow manual control methods were able to terminate the flow 24 hours later.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[BUGGAR]

Remember, too, that some of these installations fail due to foundation settlement (Boundary Dam, WA State)

 

[JohnWeal]

Many thanks for wonderful replies.

There will be 3 sluice gates as part of an intake structure located on a variable river level from 1.3m to 6.3m depth. Each channel leads to 3 submersible turbine pumps which are 1.05 m3/s capacity. In front of the intake structure there is floating debris boom, followed by a channel rebate for stop logs to provide the double isolation. Next is the inclined trash screen and then the sluice gate.

As the pumps are remove able from within the pump house (floor located above the 1 in 100 flood level) there should be very little reason to have to isolate each channel and man entry into the chamber. And if so, this would be done at low river levels.

The high river levels are not variable throughout the year, just for approx 3 months maximum about this time when there is snow melt from the upstream catchment in the mountains. And of course, this is when the increase in debris arrives.

The response regarding the settlement is noted and I have already put into place trial pits / boreholes request along with our geotechnical team so we get down to bedrock and prevent scour underneath the structure.
Perhaps some of you guys could clarify one thing....
As this project is for Northern Iraq, does this mean that American companies cannot supply equipment for one reason or another?
Once again, many thanks to you all for your excellent responses.
Regards
John
United Kingdom

 

[chicopee]

"As this project is for Northern Iraq" Is this ISIS controlled area and project?

 

[JohnWeal]

No Chicopee. Kurdistan.

 

[JedClampett]

We've (the USA) have been supplying equipment and designs for 15 years now, so I don't see a reason we'd stop now.
Step 1) We design, supply (sometimes pay for) and install.
Step 2) They blow it up or scavenge the parts.
Step 3) Go to Step 1.
I hope that Northern Iraq is a little better.

 

[BUGGAR]

If they're cast iron, we buy all our iron castings from China.

 

[cvg]

Heavy Duty fabricated stainless steel slide gate
D. Design stress shall be the lesser of 1/5 of ultimate tensile and shear or 3/4 of tensile yield strength. Maximum allowable deflection under rated load or head is 1/720th of span.

 

[JohnWeal]

As we are not in saline conditions we going to stainless steel 304L.

I assume that the bottom seal is designed in such a way that as the door deflects under the pressure, (in our case this would be in a 4.8m wide channel[15'-9"]) therefore 6.7mm [0.26"]at the centre of the gate the seal distortion always maintains a seal.

For all the sluice gates I have ordered in the past, I have never gone into such detail as the duty is not as critical as this one.
I don't want to compromise the maximum seal leakage rate standard and am sourcing reputable sluice gate manufacturers who are used to designing and installing sluice gates and actuated drives for this duty.

For a 4.8m wide channel, I have scanned some floodgate images on google and have seen three options:
1) two hoists pulling up from each side of the gate
2) two screw Jack actuators pulling up from each side of the gate
3) one central screw Jack.

cvg, which standard have quote quoted those values from?

Best regards
John

 

[cvg]

spec I wrote for a 48 inch sluice gate for rectangular channel. I think this was mfg by hydrogate.

 

[McDermott1711]

Buy a copy of DIN 19704, Hydraulic steel structures – Part 1: Criteria for design and calculation.

 

[McDermott1711]

Link

 

[JohnWeal]

Thank you McDermott1711.
Will speak to Hydrogate also cvg.