TPi October 2008

f i t t ings feature on . . .

Fi t t ings

Photo – Norres Schlauchtechnik GmbH & Co KG (page 34)

Schroeder Valves GmbH manufactures the SMV multifunction valve, a further development of the company’s proven SSV technology. The SMV valve provides protection of centrifugal pumps from adverse effects of warm-up in the partial-load area like cavitations, flow interruption and dry operation. This protection is guaranteed by the automatic release of the minimum flow. It also provides a reliable non-return valve function in the main delivery stream, and automatic degasification and therefore continuous filling of the pump in order to avoid dry operation pump damage and destruction. Observations from practical applications gave the impulse for the new development. Operation breakdowns, damages and other problems caused by dry pump operation have often been observed in fluid gas plants as well as Multifunction valve

in pump stations of fuel depots. These problems mostly occurred during times of start-up and restarts of pumps, often even during the presence of operation personnel. Inmost cases, such pumps in processing plants are operated by remote control started by a central plant control. Therefore a supervision of sufficient pump degasification pump filling is not possible. Insufficient fluid filling of the pumps, however, can result in extensive damages as well as operation breakdowns. In case of fluid gases in the boiling point the transformation of fluid into gas already happens by a minor temperature increase in the stopped pump. This gas volume then presses the fluid out of the pump towards the suction pipe with the result of the pump filling up partly or totally with gas.

This can be caused by the temperature influence from outside as well as from the after-heat of the pump immediately after disconnection. Depending on the pump type it will become completely dry or filled up with gas in a way that the impellers cannot build up delivery pressure when the pump is re-started. Thus the pump operates dry and seconds later considerable damages occur, possibly leading to destruction of the pump and environment. The automatic degasification integrated in the Schroeder multifunction valve provides a continuous degasification of the stopped pump and secures a constant filling with the delivery fluid. The centrifugal pumps must be completely filled with fluid for a safe start or re-start of the pump plant, with immediate increase of the differential pressure and correct delivery of the medium.

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Tube Products International October 2008

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