Since 1930... Technology of the Heat Exchange

Vacuum Pumps

vacuum pump

SCAM vacuum pumps are mainly used the vacuum production in steam condensing plants.
Many thousands of SCAM pumps have already been manufactured.
SCAM pumps have always been favoured by many Customers in Thermal and Thermo-Nuclear, Petro-Chemical Plants and Steel Mills.
As a reference, it should be mentioned that in Italy they have been installed in all the major Thermo-electric Power Plants.
The range of SCAM pumps range from 2 KW to 75 KW.
A Thermal Power Plant performance depends on the ratio between the hot source and the cold source temperature. Thermo technicians have always tried to increase this ratio that, however, is linked to the difference between the fuel oil combustion temperature (in conventional Power Plants) and the cold source temperature (usually sea, lake, river water or atmospheric air).
Actually, the difference is a theoretic limit that cannot be reached because of the presence of many obstacles, that we try to avoid or reduce since they decrease the Plant efficiency increasing, on the other hand, the actual cold source temperature. An important drawback is represented by the presence of incondensable substances in the steam condenser that working under vacuum, deriving from the re-entry of small quantities of air and from the degassing of process fluids.
The elimination of these incondensable substances can be achieved using water or steam ejectors either of O-ring pumps, but O-ring pumps are not very reliable.
SCAM air pump keeps incondensable substances at a very low level and with the best efficiency in terms of reliability and consumption.
SCAM air pumps intake, at a high vacuum degree, a mixture saturated with air and saturating steam at a much higher temperature than the plant cold water.
Exploiting the mixture compression, the SCAM pumps works by means of liquid pistons created by the rotation of a blade impeller.
The continuous technological development and recent modifications brought on SCAM pumps and on vacuum auxiliaries, which are integrated thereto, make the pumps suitable for all kinds of applications. On the other hand, SCAM air pumps also solve vacuum problems, starting from high pressure.
The quantity of incondensable penetrating in the steam circuit, is linked to the imperfections of manufacture and to the quality of the fluids present in the cycle; since it is generally impossible to make a reliable estimate, data of international rules - such as the H.E.I. Rules - are consulted.
The steam intake quantity depends on the condenser thermal variations and on the climatic and working conditions.
Consequently, the application range of the SCAM pump is extremely wide. Approximately, the reference conditions that can be mentioned correspond to an intake of 50 Kg/h of air and 100 Kg/h of saturated steam at an absolute pressure of 50 mbar absolute pressure. Our pump, because of its operating conditions, is the most suitable equipment to suck gas mixtures rich of steam.


OPERATING PRINCIPLES
SCAM pumps work as a hydraulic turbine with partial injection operated by an electric motor.
The water arriving axially into the water inlet body enters radially the impeller, passing through an element with a rectangular section called distributor.
The drain takes place when the impeller blades run in front of the distributor.
Thus, slightly concave and few millimetres thick water blades are formed.
The incondensable substances and the saturating steam to suck are trapped among the water blades and are led to the drain, where they are expelled by a deaeration system - shown in the general arrangement - consisting of a convergent diffuser where the fluid re-compression takes place.


MANUFACTURING MATERIALS
SCAM pumps are manufactured with suitable materials in order to avoid any corrosive phenomena of their parts in contact with gas or feed water.


PRODUCTION RANGE
SCAM pumps range from the WL 0000 type with a power of 2 kW to the WL 21 type with a power of 75 kW . The choice of the kind of pump for the vacuum production depends on these criteria:
• Dry air weight to suck in Kg/h;
• Absolute pressure to keep;
• Cooling water temperature.
Since this water temperature is generally very near to the cooling water temperature of the condenser in which the vacuum is needed, the dry air capacity is particularly linked, according to a certain load, to the vacuum corresponding to the different circulating water temperatures (see dwg. 6 - Performance Curves).
Another quality of the SCAM vacuum pump is its stoutness: actually, it does not require any gaskets between moving parts, except a stuffing box. Its mechanical design does not require any reduced tolerance or complexly shaped parts.

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