To achieve this state, the multi-stage centrifugal pumps are used where the discharge of the first stage of the pull of the second stage. Such pumps are used with the diffuser rings around each impeller to increase the delivery pressure. This type of pump is therefore often called a 'turbine pump.'
The shaft is in the type of bearings with stainless steel sleeve, which we normally protect a mechanical seal of a high pressure liquid handling. So we offer a separate lubrication arrangement. The oil in the seal chamber is always a bar above the discharge pressure of an accumulator with a pestle, which is operated by air or nitrogen retained.
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Multistage centrifugal pump as a boiler feed pump
Mechanical seals are used in boiler feed water pumps
It is preferable to a vertical pump shaft seal to havethe pump at the upper end only. Mechanical seals are spring loaded to keep the seal faces together. It is important that the cooling and lubrication fluid is fed to the mechanical seal from the lowest point on the pressure side of pump to ensure that some of the liquid reached there, even if primer.
Special head-tanks have been installed for seal lubrication in some applications. You must not run dry, and care must be taken to prevent the ingress of foreign bodies. Many mechanical seals containing a carbon face, and there is a possibility of electrolytic action in the presence of sea water. Usually does not occur in boiler feed water pumps, fresh water, because we treated with chemicals to prevent corrosion using doses as boiler feed water.
In the case of sea water pumps, we do not use mechanical sealing arrangement, but we use a soft packing arrangement. Gland type glands may be packed with soft or metal foil type packaging. The internal pump bearings can be lubricated and cooled by pumping liquid, which is always available when the pump is running. An oiler for the use of fat is also appropriate in some cases.
The picture below shows a seal arrangement. (Click to enlarge and then click the Back button in your browser to return to the same point in this article.) In the picture, D1 and A1 carry and push each other, creating a seal on their surface. A group of parts is connected to the rotating shaft and the other on the engine case. The spring keeps the elements close to each other, maintaining the seal and thus wear.