Telescoping jack hydrogreenspun.com : LUSENET : Elevator Problem Discussion : One Thread
Has anyone seen earthquake rupture valves installed on a dual jack hydro with telescoping jacks.
We are in an area 2 earthquake zone in Kentucky, and the State elevator inspector requires that all new hydro's have earthquake rupture valves. The code requires the valve to be placed close to the jack head, which will require two valves.
My concern is that these valves operate mechanically, and I believe it will be impossible to get both valves to set simultaneously which will load the car off balance during testing and could bend the car frame.
Any thoughts would be appreciated.
-- Steve (email@example.com), June 28, 2000
Steve: Your concerns are well founded. If I were in your position I would bring the problem to the code authorities and see if one valve at the point where the feedline splits would be acceptable. You might need some backup from a state licensed mechanical engineer. Fred
-- Fred Baltes (Elman101@aol.com), June 29, 2000.
Fred: Thanks for your comments. I did speak with the Chief Elevator Inspector, and he said that he had never encountered this situation before. He also said that he would require us to have two rupture valves since the intention of the valve was to keep from having a free falling car if a fitting or pipe broke.
I'm sure that even if we had one valve on each jack, and only one worked, the car would stop , and this is the main concern, the safety of the occupants.
I am waiting on a reponse from the Architect on the project, as to which type of system he will use. I have asked for a standard type in ground jack with a pvc casing. The deal on this is that its only 19 feet of travel, and they are trying to keep cost down.
-- Steve (firstname.lastname@example.org), June 29, 2000.
Steve, you mentioned that these valves work mechanically - can you give me some more details on that?
Typically, they work on loss of pressure. With such a design, I would think that one "setting" would cause a loss of pressure and activate the second one as well, but I don't really know.
-- John Brannon (akaelevman@AOL.com), June 29, 2000.
The OSV valve is a piloted velocity fuse. It operates on an increase in fluid velocity which increases the pressure drop across the valve. As for single or multiple vlaves on a twin piston, the code committee has addressed this problem in ASME A17.1-2000 188.8.131.52.3. Sorry for the late response. I just found this site. Kirk
-- R. Kirk Muller (email@example.com), August 01, 2001.
This situation is new to me also, because the University has spent very little on modernization or new installation since the state started to require these valves.
We have three units now that have these valves. The first two do not have any name brand or model number on them. The last, which was accepted by the state last month has a Maxton, model #OSVB44 valve.
The size on the valve states "standard" and it is piped in on 3" pipe.
Since it has been a month since the acceptance test was performed, I will try to write the procedure as best I can remember.
The state inspector had the adjuster set the down full speed at 150 fpm (which was the contract speed) with the car fully loaded to meet the rated load.
Then the full speed was set to 155 fpm with the weight in the car.
They then adjusted the rupture valve to set at 155 fpm. After making two or three runs to make sure the valve was consistent, they reset the full load speed back to 150 fpm.
This was the way that the valve was tested as far as I can remember.
I had assumed that the valve set with some type of flow indicator built inside the valve. I don't know.
Hopefully this answered your question. I do not know if this is the way the code requires the valve to be tested, but this is what our State Inspector asked for.
I did find out that Dover is installing a simular setup in a bank across town. They have installed one valve for both jacks. I don't know if they have talked to the state yet. It will be interesting to see if they accept it or not.
Thanks guys for your information, I will be on vacation next week.
-- Steve (firstname.lastname@example.org), June 30, 2000.