keep breaking gate valve stems
keep breaking gate valve stems
(OP)
I work for a water supplier and the operations crews have been assigned the task of operating all the valves in our distribution system. The crews are newly formed and do not have alot of experience. Just recently we have found 4 broken 24-inch gate valves. I suspect the crews are using a hydraulic operator and are setting the force of the operator too high. My question is: On a 24-inch gate valve, probably a Chapman installed in the early 1900s, what is the force that the hydraulic operator should be putting on the stem? I think the stems are bronze alloy??? about 2-inch diameter. Any thoughts? BTW this is my first post and I think this looks like a great forum!!!
Thanks in advance
Jim
Thanks in advance
Jim





RE: keep breaking gate valve stems
How do they break? in open or close position?
I have seen a lot of "inventive tools" used on valves, ranging from the "calibrated" sledgehamer to a pipe handled by 4 guys
RE: keep breaking gate valve stems
RE: keep breaking gate valve stems
Are they using the hydraulic tool on both types of valves, if so what are the limits?
Can it be that they use the 24" setting to open a 4" valve?
Did you see a broken stem? Your answer indicates that the information is reported.
Probably a visit to the "battlefield"
RE: keep breaking gate valve stems
You might have a electrochemical reaction going on within the stem that makes it considerably weaker. This is especially true for a valve that old.
Just for curiosity how pure is your water, both now and historically?
RE: keep breaking gate valve stems
I'll respond to reply in order:
1. Hm.. could it be that the operator is trying to open an already open valve? Are the 4" valves breaking or the 24" valves breaking?
Typically all main line valves are open and bypasses are closed. When the valves were installed a written record included the direction to turn the stem to open the valve and the number of turns. One valve had a broken bypass the rest (four) are beoken main line.
2. Are they using the hydraulic tool on both types of valves, if so what are the limits?
Can it be that they use the 24" setting to open a 4" valve?
I'm not sure. They are not supposed to, but may not know. The limits are why I started this post. I've researched the manufacturers catalogs, but they do not provide that information. I'm looking for the purchse orders in some old records, but do not think I will find them.
3. Did you see a broken stem? Your answer indicates that the information is reported.
Probably a visit to the "battlefield" thumbsup could reveal some more clues.
We will be excavating the valves in a few weeks. I will be able to see whats going on then.
4. You need to get the valve steams to Metallurgical Lab for analysis of the failure.
This is a good idea. Do you know how much it will cost? I will ask to see if its something I can get some $$$ to have done.
5. You might have a electrochemical reaction going on within the stem that makes it considerably weaker. This is especially true for a valve that old.
Just for curiosity how pure is your water, both now and historically?
The water is drinking water. It is the same source since 1930. The only treatment I'm aware of is sand filtration and a minimal amount of chlorine for disenfection. That's about it!!
Thanks again
Jim
RE: keep breaking gate valve stems
Furthermore: Interview the operators who experienced the failures. Look for telltale signs such as 24-inch-plus biceps, thumbs that do not quite oppose, large numbers of banana peels and pinup posters of Jane Woodall in the break room.
RE: keep breaking gate valve stems
The reason for the water purity question is that the purer the water is they more the possibility of "demetalization" of a brass or bronze. This is the dissolution of the material and selectively redepositing the copper. The component where this happens will normally look good but will have no strength. This process is easily discernible.
As far as prices I have no idea at the prices charged for a quick failure analysis of a part such as yours. I would start making a few calls to a local lab if you have one. There are also some online companies that provide this service. I would hope your utility company would have a materials engineer available. Whoever you use just ask for a lab report and not a formal report.