This blog post was made with the purpose of expanding the knowledge base of our readers about The Blake and Knowles Vertical Twin Beam Air-pump and Jet Condenser.
This site below gives a general explanation of the highly rewound Blake and Knowles air pump and jet condenser, which operated in the S.S. Sicamous’s bilge.
If you would like to know what are the functions of air pumps and jet condensers in the 20th century continue reading.
The information that will be given below has been extracted from the following book;
CHAPTER NINETEEN.
AUXILIARY APPARATUS OF A MARINE ENGINE.
What is the Function of the Condensing Plant?
The condensing plant cools the exhaust steam from the last cylinder to a temperature so low that it is reduced to water. The water thus obtained occupies a much smaller space than the steam before condensation, leaving a partial vacuum, which is equal to a reduction of the back pressure in the last cylinder.
The water must be removed by a pump, however, to prevent filling up of the condensing plant. This pump at the same time performs the office of removing any air that might easily be disengaged from the water, under a partial vacuum, and on accumulation, would soon destroy the vacuum.
This pump is called the air pump.
What systems of condensation are in use?
Two systems of condensation are employed, according to the advisability of mixing the cooling water directly with the exhaust steam or not:
(1.) Surface condensation.
(2.) Jet condensation.
What are the characteristics of a surface condensation?
Surface condensation does not mix the cooling water directly with the exhaust steam, but subdivides the condenser into two parts, one for the exhaust steam, the other for the cooling water. The subdivision is thoroughly steam, air and water-tight, and is arranged as a large surface in the form of tubes, so that the cold water may effectively and rapidly reduce the exhaust steam to water.
The air pump of a surface condenser must remove the accumulated air and the amount of condensed water, while a special pump is provided for the circulation of the cooling water over the tube surface.
The surface condenser is employed on ships for salt water navigation, as the condensed water is thus kept fresh, and can be used as feed water for the boilers, to which under modern conditions salt water feed would prove highly injurious and not economical. A surface condenser may prove desirable also in very muddy fresh water, which, if used for feed, would fill the boiler with deposit and scale, to the detriment of the steaming capacity.
What are the characteristics of jet condensation?
Jet condensation mixes the cooling water directly with the exhaust steam.
There is only a single chamber in the condenser, into which the cooling water is passed in form of a spray directly under the entrance of the exhaust steam securing thorough intermingling of the two.
The air-pump in this case removes the air, the condensed water, and also the cooling water.
No special circulating pump is needed, as the excess of the atmospheric pressure over the vacuum forces the water, through the pipe and the spraying nozzle, into the condenser chamber. The jet condenser is employed for fresh water navigation, where the part of the water delivered by the air-pump can be utilized for feeding the boiler, without endangering its safety or efficiency, through formation of scale or incrustation. It is extensively employed on the great lakes and rivers of the eastern coast
What is the arrangement and action of the jet condenser?
The jet condenser is usually a vertical, barrel-shaped vessel that receives the exhaust steam at the top.
The cooling water enters, generally at the side, flowing through an internal tube into the spraying nozzle. In discharging through a large number of small holes a thorough intermingling with the steam take place, producing a quick condensation, while falling to the bottom of the condenser for removal by the air pump. The curved internal tube and nozzle are usually of cast iron, with a large flange bolting on the outside to a face of the condenser, thus allowing removal of the tube and nozzle and access to the interior of the condenser. The injection cock or valve frequently bolts to the same flange.
How is the shell of the condensers constructed?
The shell of all condensers must resist the excess pressure of the atmosphere above the vacuum, and for this purpose, must be tight and rigidly strong. In jet condensers a barrel-shaped form of cast iron easily provides the necessary strength. The jet condenser is small in size and round in section, which facts allow the necessary strength to be conveniently obtained. Nozzles are cast or riveted on for the connection of the exhaust pipe at the top and the air-pump suction at the bottom.
What is the duty of the air-pump?
The duty of the air-pump is remove the air and water from the condenser. In jet condensers it also removes the condensed water and the cooling water, while in surface condensers only the condensed water is pumped. The jet condenser air-pump must, therefore, pump and remove a much larger quantity of water and air than the surface condenser, and is for this purpose larger, unless the latter is arranged to work jet-condensing in an emergency.
What type of air-pump is generally used?
The vertical, single-acting air-pump is generally employed as the most efficient type.
What are the parts of the vertical air-pump?
(1.) The barrel, the suction channel-way and the cover with delivery channel and hot well.
(2.) The bucket, or piston, with its valves, the foot-valves and the head-valves.
How are the stationary parts of the air-pump constructed?
The suction channel-way is arranged at the lowest part of the condenser, so that the water can be readily and completely removed from it. It is often a part of the condenser shell or otherwise bolted to it; and being usually of cast iron, must be strong enough to withstand the full atmospheric pressure. As it usually supports the foot valves, all joints and valve-seat division plates should be fitted in a thoroughly air-tight manner.
The barrel connects generally to a flange or facing of a channel –way and is constructed in composition or cast iron, with composition sleeve tightly rolled in. It is bored truly cylindrical on its working face, with slight recesses at top and bottom, similar to a steam cylinder, for the over-running of the piston or its rings. For quick access to the bucket or foot valves, a hand-hole cover is often fitted above or directly in the bore of the barrel, in order to avoid dismounting the top-cover and head valves (a great saving of time and labour to the engineers).
Unfortunately the Blake and Knowles steam pump and works was taken over by the Worthington Pump and Machinery Corporation alongside with other pump companies. They still make the same kind of pump and jet condenser used in the S.S Sicamous but under a different name, as shown in the pictures below.
The site below takes you to the Worthington Pump and Machinery Corporation if you are interested in what kind of machinery is employed on marine ships. Although now the Worthington Pump and Machinery Corporation is functioning under the name Flowserve
If you are interested in the mechanics of old school pumps that modern day pumps originated from, this site is well recommended.The site given below goes into thorough explanations of different kind of pumps and their hydraulics used to move steam-powered vessels.
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