Hydraulic gates: bolts and nuts 1

[21121956]

Hello everybody:

In the Technical Specifications (for different plants) for gates of a hydroelectric plant, with respect to the seal plates and screws and lock nuts can be read:

Case a. Bolts for J seals: type 304 Stainless Steel, ASTM A 320.
Nuts for J seals: stainless steel A 194 (Armco Nitronic 60).

Case b. Seal plates and bolts: 304 stainless steel.
J seal keeper plate: 410 stainless steel.
Fasteners: Studs, Anchors, screws, nuts and Assembly Bolts: stainless steel.

Case c. Studs and bolts: martensitic stainless steel.
Washers and nuts: austenitic stainless steel.

Case d. Bolts: F593-304 (316).
Nuts: F594-304 (316).

Case e. Bolts: hot dip galvanized carbon steel.
Washers and nuts: stainless steel.

Any comment about the variety of these specs?


El que no puede andar, se sienta.

 

[CoryPad]

Cases a, b and d are essentially the same.

Case c is using a higher strength grade for the bolts, perhaps for higher preload or smaller joint sizes or to avoid galling. Should use standards, like A320 or F593, etc.

Case e looks crazy to me. Are the nuts tapped oversize to accommodate the thick bolt coating. The zinc coating will corrode quickly due to galvanic corrosion from contact with stainless steel. Also should refer to standards.

 

[racookpe1978]

Case e will not "screw" together: A stainless thread (either male or female) will NOT engage into a galvanized thread.

 

[tbuelna]

Some of those combinations seem a bit odd. For example, I don't think the combination of zinc with most stainless alloys results in a suitable galvanic potential. I would also question using higher strength Nitronic 60 nuts with lower strength 304 cres bolts. Normally you would use nuts with slightly lower hardness than the mating bolt/stud, since it usually easier and cheaper to replace a worn nut than it is to replace a worn stud/bolt.

Do you have any idea what criteria was used to select the fastener materials?

 

[21121956]

Hello everybody:

Thanks to all of you for your comments. As I said in my post, these Specifications correspond to some general information for hydropower plants gates, and more specifically for some of them now under normal operation.

Tbuelna,

Case a. Appears in the document "Advanced Materials Selection Guide for Lock, Dam and Hydroelectric Plant Components", by US Army Corps of Engineers, January 2002.

Case b. From the document “Design of Spillway Tainter Gates”. EM 1110-2-2702 of 1 January 2000. US Army Corps of Engineers.

Case c. For a hydropower plant in Venezuela.

Case d. Brochure “Roller Gates”, by Hydro Gate, USA.

Case e. A hydropower plant in Argentina-Paraguay.


El que no puede andar, se sienta.

 

[EdStainless]

I would endorse a, with the two materials exchanged, or c.
None of the others look likely to give the best outcome to me.

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