Structural Pins

[minorchord2000]

I need to specify smooth shear pins for heavy duty steel lid used in a very high temp environment (800 deg F). The steel bracket plates are ASTM A515 Grade 70. The pins will be located between two parallel lugs. A plate will be in between the lugs and the pin will connect the plate to the lugs. The sizes are approximately 2" diameter and 2.75" diameer. The steel lid rotates about the pins during the opening and closing operations. I need the pins to be compatible with A515 Grade 70 steel. Any help will be appreciated.

 

[dhengr]

Well that’s about as clear a mud. You’re looking at it, but we can’t see it from here. Now imagine the multiple number of sketches that could be drawn all fitting your description. We should waste our time guessing at what help you need, because you didn’t have the time provide sufficient info. for a meaningful exchange.

You could clear some of that up with a sketch showing some dimensions, weights and loads, side view, plan, etc. showing the lid motion. Why the two different diameters, how many cycles per day, is pin wear or plate wear or lug wear preferable? Are these shear pins or hinge pins? What types of material compatibility issues are you worried about? Isn’t differential thermal movement more likely the biggest problem?

 

[hokie66]

In what way do you need compatibility? Aren't the pins a separate item? If you are intending to weld the pins, I wouldn't do that.

 

[minorchord2000]

I have attached a drawing of the lid assembly. The lid can rotate from the closed to the fully open position using hydraulic actuators. I also labeled where the location of the two hinge pins along with the maximum shear load on each pin. I have the proposed sizes of the pins. I am looking for a suitable ASTM call out for hinge pins suitable in a high temp environment.

 

[dhengr]

Minorchord:

Well, one of my sketches does approx. your sketch, a hinged lid. It appears that you only have one lug on the tank wall, and that’s where the 2.75" dia pin is located, and it’s in double shear. Can the tank wall take that 30k + load? Then you have two plates off the lid which are hinge pinned to the lug. But, then you have a double tunged clevis outside the two lid plates at the end of the cylinder rod, and that doesn’t look quite right. Why isn’t that just a pinned end, single plate, on the cylinder rod, and btwn. the two lid plates. It looks like you have a shielding plate btwn. the two lid plates, near the hot part of the lid. It might be tempting to terminate this a little higher, and add a similar shielding plate off the tank and lug, and curved up to match the lid plates when closed, and meeting their shielding pl. This would better protect that hinge pin when the lid’s open. I would press a bushing into the lug and fix the pin to the lid pls.


I’ve done these kinds of details on coke quench cars and the like in the past, but it’s been so long ago that I don’t remember what pin materials we used. I would work with your local supplier of polished and hardened round bar stock to pick this mat’l. and the bushing mat’l. There isn’t anything particularly exotic about the mat’ls. you are talking about, at least as I remember, so I’m not sure what compatibility issues you are concerned about. Your pin shear stresses look low enough, but the pin bearing stresses should be checked on the side pls. and the bushing. That’s a Hertz bearing stress problem. Your 800°F is about the temp. where steel start to exhibit some strength loss as temps. go higher, but good shielding should help that. That’s an interesting design problem, I’m surprised the hydraulics and high temps. aren’t more of an issue.

 

[minorchord2000]

dhengr

Thanks for your quick response. There are two pins, i.e. near and far and it is symmetrical. There are two lugs at each of the 30 kip pins. The triangular plate above this pin is comprised of two plates which straddle the two parallel lugs. The pin goes through all 4 thicknesses of steel.

The upper pin at 21 k connects a clevis at the end of the push/pull rod.

 

[dhengr]

Minorchord:

Is there a top view of the lid, showing the lid in plan? Your words aren’t sayin what your picture is showin, at least I wasn’t gettin it. Although I do see now how your sketch could conform with what I think your saying. Are your lugs the small triangular pieces affixed to the tank, and are there four of them? Each set of two lugs (near and fare, some dist. apart) has a 2.75" dia. hinge pin which takes a 30k load, for a total load of 60k? Then you say... “The triangular plate above this pin is comprised of two plates which straddle the two parallel lugs. The pin goes through all 4 thicknesses of steel.” I called your ‘triangular plate’... two lid plates or plates off the lid, and now you say there are four of these also. Then, are there two hydraulic cylinders also? And, we no longer have a round lid?

I would go with two lugs, on the tank, at each 2.75" hinge pin location (near and fare) and only one lid hinge plate at each location (near and fare), nested btwn. the two lugs. My reasoning is that the more plates you have stacked up at each hinge pin, some dist. apart, you get to the point where you have to line bore those holes, in place on the tank, to get things to line up and function. So, get rid of one of the lid hinge pls. at each hinge pin location, and make things a little easier on yourself. Now, on the lid hinge pls. add thickening doughnuts, weld all around at the hinge holes, and line bore them once they are attached to the lid. This gives added bearing width and reinforcement at each lid hinge pl. and this hole is the one that should be bushed now. The lugs might be welded to a shaped base pl. (doubler pl., approx. 6.75' rad., same as O.D. of the tank), they can be line bored and finally welded to the tank. But, I still can’t tell you what pin material to pick.