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252404001 S Valve For Putzmeister Concrete Pump
Whats the diffrence between and S-tube and a Rock Valve?
Having used both valves I feel like there are good & bad to both types. First let me say that as a mechanic there is no question as to the winner. The rock is WAY easier to service. If the s-tube boys would get the hopper out of the way that would help a bunch, but then that would create other problems. I only have two complaints about the rock.
1. The valve is housed in a very tight area (this is why they can seperate the hopper before doing any work on the valve) all of the internal pressure is contained by the very strong lower casting that contains the valve. Since 90% of pumping is alowing the cyl's to load properly anything that makes that more difficult is a serious issue. Bridging of large or excessive ammounts of coarse aggregate that hampers loading may be more evident with the rock due in part to the decreased area available to loading.
2. Much is made of "the concrete wearing on other concrete" inside the valve. My own personal opinion is that it is more efficient to have the concrete flow in total (as with an s-tube) than fight its way thru other pressurized stationary concrete as is the case with the rock.
That being said, and with the understanding that all of this is just my opinion I will say that until you are asked to pump some really raggety-assed crete you probably won't know the difference. In either case the real winner of the 'pump-off' contest will be the machine with the best maintence of its hyd system and wear parts. I love s-tubes, but then I no longer have to maintain them.......... hanging like a bat ;~)
To add a few points for the Rock valve vs S-tube, you can reduce wear on the Rock by hard surfacing it once a year or every few years. Because of its wide feed as stated before, concrete wears on concrete to reduce wear instead of concrete wearing on the bends inside of an S-tube. This makes the Rock very attractive and as Schwing advertises its the only rebuildable valve and you get the most yards in the industry out of a Rock. Also, the pressure spring under the cutting ring allows equal pressure against the cutting point and that the sealing point under concrete pressure is not pressed apart. Therefore because there are no bends in the Rock and it is sealed with a pressure spring, wear is reduced on the wear parts when shifting where in the case of an S-tube, it has bends and to form a proper seal, it must be pressurized with bolts so when shifting, it is always pressurized against the wear parts causing premature wear. Another point for the Rock is because of the way the Rock sits low in the hopper, the concrete isn't compressed by the swivel body inside the hopper by the hopper walls. In my opinion, I think the Rock is wide enough that concrete on concrete while pumping wouldn't cause any problems vs concrete against metal. I have never used an S-tube but I can imagine what they are like to clean out compared to a Rock. Like I say I have never used an S-tube so I don't know too much about them but this is just my opinion and what I know about the Rock Valve along with what Speedy and Bob had to say about it.
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