Arrangement in connection with mechanical seal
An arrangement in connection with a mechanical seal includes at least two sliding surfaces pressing against each other, which are arranged to seal a gap between a rotating and a non-rotating machining part, and mechanism for providing a sealing fluid flow cooling the sliding surfaces. To provide an optimal consumption of sealing fluid, a valve mechanism is arranged to the mechanism for providing the cooling sealing fluid flow, the valve mechanism being arranged to react to the temperature of the seal and to open and close the flow of sealing fluid according to the cooling need.
The method of controlling sealing fluid flow according to seal cooling need, comprising: providing at least two sliding surfaces pressing against each other, which arearranged to seal a gap between a rotating and a non-rotating machine part, providing means for providing a sealing fluid flow cooling the sliding surfaces, and providing a valve means arranged in connection with the means for providing a cooling sealingfluid flow, the operation of the valve means being based on a memory metal element that is arranged to react to the temperature of the sealing fluid and to open and close the sealing fluid flow according to a cooling need, wherein the valve means isintegrated to the mechanical seal.
Mechanical seals are commonly used in different technical fields to seal gaps between a rotating and a non-rotating machine part. Examples of such rotating and non-rotating machine parts and gaps between them include the body and shaft of apump, for instance process pump, and the gap between them that needs to be sealed so that the pumped process fluid cannot leak out through the gap between the pump shaft and the pump body. The sealing is done between two exactly opposing slidingsurfaces that rotate against each other. In normal use, a mechanical seal naturally also heats up, in which case it is cooled by a fluid flow on the opposing side to the seal. Water, for instance, is used as the coolant. Mechanical seals often alsocontain a second sliding surface pair on the atmospheric side, in other words on the outside, to seal any leakage of sealing fluid to the atmosphere.
Critical operating values in the operation of a mechanical rotary shaft seal include pressure, temperature and a few other factors. Pressure includes the pressure of the sealed product, the pressure inside the seal, or the sealing fluidpressure, the ratio of the above-mentioned pressures with respect to each other, and any changes occurring in the pressures.
As regards temperature, the related issues are the temperature of the sealed product, the temperature of sealing fluid, the temperature of the environment, the temperature of the parts of the seal, especially the sliding surfaces, and any changesin temperature.
Mechanical rotary shaft seals are cooled by means of a sealing fluid that flows continuously through them. The flow is in some cases limited, i.e. the flow is adjusted in such a manner that cooling is sufficient for the conditions prevailingduring the adjustment. In some cases, the water connection from the seal is plugged completely. These solutions use a sealing water adjustment and control unit, for instance, to adjust the flow and pressure of the sealing water of the mechanical seal. The apparatus comprises a flow meter and any necessary adjustment devices for adjusting the flow and pressure of the sealing water.
The flow rate of sealing water is determined using the above-mentioned arrangement. One important task of the sealingwater is to cool the mechanical seal, as stated above. It is, however, difficult to adjust the flow of the sealing water to be optimal according to the temperature of the outflowing sealing water. The above-mentioned solution helps find out the amountof used sealing water, but, for safety, water consumption is often adjusted to be too high.
Further, there is the problem that if the flow of the sealing water is adjusted to be low, the flow orifice is easily blocked by particles in the water, eventhough the orifice were designed to allow water impurities to pass. Flow low-limit alerts caused by orifice blockage are also problematic in practice. Plugging the sealing water outflow connection provides good conditions for a mechanical seal, butthis arrangement does not provide heat removal from the seal. If the temperature rises higher than the temperature designed for a mechanical seal, the seal may suffer damage. The solution is thus not suitable for situations, in which the temperature ofthe seal rises easily. An advantage of the solution is naturally that it does not waste expensive sealing water.
The mechanical seal comprises two sliding surfaces pressing against each other, which are arranged to seal the gap between the rotating and the non-rotating machine part. The seal further comprises an input unit and an output unit for directingcooling sealing fluid to and from the mechanical seal. The seal may also comprise a second sliding surface pair to seal any leakage of sealing fluid to the surroundings.
Ningbo Yinzhou Guowei, mechanical seal Component Factory is a professional engaged in the design, development, manufacture, sale of various cartridge seal and flygt seals business. Production and testing are well-equipped with a high-quality staff.
