Hello, I am a civil engineering student in India. Recently my class went on a study tour to a construction site where we saw one concrete pump using a rock valve and another using the S valve. I was just wondering which is the superior technology since opinion was divided among the engineers there. One operator I spoke to said that the S valve clogs more frequently than the rock though. Could you please help me out in this since I am planning to do a project on concreting this semester. Thanks for replies in advance.

It is a difference of opinion. Some will say S valve is Better some would say Rock valve is better, some will say C valve is better, heck some may even say Gate valve is better... There is no better or worse.

Contrary to most belief, all valves have the design ability to pump all pumpable mixes to the same effect. However, where problems arise is when the mix is not as 'pumpable'. The key to any valve design is the cutting/pressure ring. In an ideal world if all cutting/pressure rings are equal any valve can match it with any competitors valve.

The problem is at higher pressures the mix will tend to bleed the water. It is very hard to establish a leak proof valve system 100% of the time. i.e before some operating wear has taken place.

In saying that, if a valve is blocking up, it isn't necessarily the valve design, but the tolerances between the seal of the valve and the body of the transition section.

From a real life standpoint, the debate always lies in which valve is better, but in reality they are judged on which is more economical, robust, easier to maintain, easier to operate and cost effective.

In a nutshell: 

If it comes down to operating cost = Rock valve

If it comes down to robust = S valve

If it comes down to simplicity of operation and maintenance = C tube

*Each is geared to a different market

Hello Avinash, The thing is the ideal valve depends on the type of concrete present. In India concrete mixes are very rough and do not have rounded aggregates like in the developed countries so the valves used here have to be pretty rugged. Both valves mentioned by you are good but the RL Rock valve(not the ordinary rock you mentioned) is better in the sense that it can pump the rougher varieties of concrete and lasts longer than the S valve. In-fact even the gate vale has a wide application in India due to it's sheer robustness and it is the only valve in India that can pump very large aggregates.

I have ran gates,spades,rocks,c-valves,rs2000 rock valve,swing tube,ball valve, univalves, and in my opinion the most durable least maintenance is the s-tube, the c-valve and gates and older valves would pump harsher mixes due to the decreased cylinder sizes and less reduction but cant hold a candle to the modern s-tubes dependability, the rock valve is a good valve but in my experiences has more problems with harsher mixes than does the s-tubes.both are great systems and will pump well if all wear parts are in good condition.

You missed one Pumbo: If it comes down to pumping rocks and beer cans, a gate is the way to go.

A gate machine handles big rocks well,but the beer cans have to be a little bit damp.

Nice one Red_Hand...+1 Rep!

Avinash, Both the valves use basically the same technology. They use Hydraulic cylinders to actuate the valve, which switches between two concrete cylinders. Since Schwing is the largest selling concrete pump in India, people will swear by the rock valve. But, S-Valve is fast catching up, with Putzmeister, Sany and others using S-valve.