S–valve Technology: Putzmeister
For the tough daily operation at the construction site, a concrete pump has to be powerful, unflagging, robust, undemanding, and reliable. This especially applies to smaller construction sites where they have to render versatile service as inexpensive concrete pumps. In the case of large projects with high-rise and long distance conveying, these machines have to offer real power. It has to be done with minimal mass forces, very quiet operation and with quick switch-over.
Latest concrete pump is based on the S-valve technology. In India, it is found that the majority of the market still uses gate valve pumps, which have been outdated and phased out in Europe in the 70's because of high wear & tear. The Gate valve technology which still represents the majority of the pump population in India has too high level of wear and tear. That is the reason why customers who have tested S-valve technology are very pleased with the long service life of the main wear parts and by the low diesel and hydraulic oil consumption.
The S-valve technology allows pumping with higher concrete pressure to reach higher output at great heights. At the same time, the wear & tear of an S-valve pump is lower and so the operation costs are considerably lower.
Besides the lower operation cost, the pump operation is also more comfortable. Due to the close circuit of an S-valve pump, the pump and pipeline can be cleaned by simply pumping water instead of concrete. With S-valve concrete pumps, reverse pumping is also possible which solves the choking problem in many cases without disassembling and cleaning of the pipeline.
Concrete pumps with 'S-transfer tube' have been setting new world records in vertical and horizontal delivery. Wherever extremely stiff and abrasive mixes of concrete are encountered, this S-valve system is really useful. It is not surprising that due to this advanced technology in truck-mounted concrete pumps, they are affectionately known as the "S-tube Elephants."
Putzmeister concrete pump achieved the world record in long distance concrete conveying at the French Le Refrain with 2015m, and a record pump height of 606 m at the Burj Khalifa Tower in the UAE 2008. In both these cases, the pumps and accessories are still not operating at their limits. Even with difficult concrete, they can be counted on to perform reliably on continuous duty.
The S-valve is the first choice for jobsites with concrete pressures above 85 bars. This is especially useful for long pumping distances over stationary pipelines. The Putzmeister S-valve is especially designed for long life and high concrete pressure. This results in long service intervals and increased availability of the machine. To extend the life of the S-valve, the inside wall can be rebuilt by hard face welding.
The Spectacle wear plate is fitted in the hopper, to the openings that lead to the delivery cylinders. The wear ring is fixed to the inlet opening on the S-transfer tube & the thrust ring lies between the wear ring and S-transfer tube entry. Because of the very abrasive mixes, this 3 piece System is subjected to many different types of Wear and load stress while the pump is in operation:
- Sliding abrasion on both contact surface of the wear parts.
- Blast jet wear on the outer edges of the wear ring and inner edges of openings on the spectacle plate.
- Impact stress at the parting plane, between spectacle plate and wear ring.
- Flow abrasion on openings of the spectacle plate and wear ring.
The optimised hopper shape reduces concrete settlement and residual concrete. The hopper is easy to clean: residual concrete is simply emptied via a cleaning valve. The line is cleaned by conveying a sponge ball in a reverse pumping mode.
As and when there is wear and tear of the s-tube due to friction against the spectacle plate, the automatic ring optimally seals the system. This prevents the bleeding out of concrete lines through the fine gaps caused due to abrasive nature of the concrete and thus reduces the danger of blockages. This automatic ring compensates for the wear & seals automatically. This results in an even wearing of parts and therefore prolongs service life. The large stroke volumes reduces the number of strokes and hence the wear and tear. The wear extensive areas are especially protected by chroming, face welding or hardened inserts.
The S-valve has very few wear parts and all parts of the S-tube are easy to change. The hopper remains mounted when the few wear parts require replacement.
Hydraulic and switch-over cylinders are outside the concreting area and remain clean. The delivery pistons are centrally lubricated for a safer and longer service life. The hard-chrome layer of the delivery cylinders assures a still longer service life of the pistons and the cylinders and protects against corrosion. The non-contacting end-position impulse switch of the pump cylinder is wear proof.
The truck-mixers have optimum access due to the minimum projection of the reduction elbow. The concrete hopper extension can be folded open for easy servicing. All these advantages make the S-valve technology really beneficial for the entire concrete pumping operation.
NBM&CW October 2011
