Types of pumps: 1. Reciprocating pump. 2. Gearwheel pump. 3. Centrifugal pump. Delivery lines and discharge lines to ...........
From the pump are often fitted witch non - return valves to prevent the liquid from flowing hack. The double acting displacement pump has a simultaneous suction action and discharge action. The volumes of the pump chambers are increased and decreased by the reciprocating motion of the piston, discharge valve 1 is closed by suction, suction valves 2 is open. Discharge valve 2 is opened by the pressure of the liquid, suction valve 2 is closed. Discharge valve 2 and suction valve 2 are moved by suction. Discharge valve 1 and suction valve 1 are moved by suction. The liquid enters the pump - housing on the suction side is carried around between the teeth of the gearwheels. The liquid is discharged through the discharge line. The liquid enters the pump house through the suction inlet and is discharged through the suction line by the centrifugal force that is cruised by the...
Pumps: 1. Displacement pumps: a) reciprocating type, - single-acting ram pump, - double-acting ram pump, b) rotary type, - gear-wheel pump, 2. Centrifugal pumps. Pumps are used on board ship. These pumps can be divided into two main groups. Two main groups are displacement pumps and centrifugal pumps. Centrifugal pumps consist of an impeller inside a casing. This impeller rotates at high speed. The liquid is thrown by centrifugal force against the surrounding casing. The liquid enters through a suction pipe at the center. The liquid is then discharged through the delivery outlet. In displacement pumps the volume of the pump chamber is increased by raising the piston. This causes a vacuum. Into this vacuum the liquid is drawn from the suction pipe. The piston is then lowered. This decreases the volume of the pump chamber. It forces the liquid out into the delivery pipe. A simple kind of reciprocating displacement pump is the single - acting ram pump. This consists of a ram moving up and down inside a chamber. The chamber is fitted with a non- return suction valve and a non -return delivery valve. When the piston moves up, a vacuum is formed in the chamber. Liquid is drawn into the chamber through the suction valve. Then the piston moves down. This creates a force on the liquid. The liquid is forced out through the delivery valve. Another type of reciprocating displacement pump is the double- acting piston pump. This works on the same principle as the single -acting pump. The chamber is fitted with suction and return valves at the top and bottom. The liquid can be drawn in and discharged on each stroke. The gear -wheel pump is an example of a rotary displacement pump. It is used for pumping lubricating and fuel oils. It consists of interlocking gear wheels. The gear wheels rotate. Each tooth on both wheels leaves a vacuum for liquid to flow into. The next tooth to enter forces the liquid out. The liquid enters a space, is carried round and then forced out into the delivery tube.
Measuring tools. Dividers -are intended for drawing circles, and taking off or setting out dimensions. Dividers are available in the following range of size: 100, 150, 200, 250, 300, 400 and 500mm. Calipers -are tools used for measuring the outside dimensions of machine parts, transferring dimensions etc. Calipers are similar to dividers in design, the only difference is in the shape of their legs. Inside calipers - are intended for measuring the internal dimensions of machine parts, the ends of their legs are bent outwards for this purpose. Vernier height gauges - are used for scribing horizontal lines parallel to the surface of the surface plate, for transferring dimensions from the scale onto the work piece which is laid out. Steel scales or rules - there are intended for linear measurements of blanks and various other articles. The rule is provided with divisions spaced at intervals of 1mm. Vernier calipers - are tools used for measuring external and internal linear dimensions, the depth of slots, and for laying out work pieces. The vernier depth gauge -is intended for accurate measurement of the depths of holes in machine parts, key grooves, blind holes, etc. Micrometer calipers - are used for measuring outside dimensions to an accuracy of 0,01mm. The inside micrometer is a tool with a micrometric screw used for internal measurements. A thickness gauge - serves to test and measure clearances between mating surfaces. A screw pitch gauge -is a set of thin steel strips which are notched on one edge according to various thread pitches. To find the pitch of a given thread, select the appropriate strip, apply it to the thread and see whether any light passes between the thread and the gauge profile. Bevel protractor - this tool can be adapted for all types of work where angles are measured or laid out. A set square - is used for testing surface at right angles to each other and for scribing lines at 900. The spirit level - is intended for testing surfaces to see that they are straight and also for checking the work in vertical and horizontal directions. Plumbs -are used for checking whether the vertical is true enough. The stethoscope - is used for listening to turbine. It consists of a fibre ear - piece to which is attached a steel rod.
Fitting tool. Hand shears are used for severing metal sheets and wire .the shears are made of steel ;the sides of the jaws are hardened and ground. Drills are used for drilling cylindrical holes in solid metal . Mechanics use either of two kinds of drill; twist drills and flat drills. Countersinks are used for machining drilled holes before they are reamed and also for drilling cylindrical or conical holes. Reamers are tools for reaming holes to obtain the specified fit or for accurately aligning the holes in parts to be joined together .A tap is a tool for cutting threads internally in various metals .Taps are made in the form of steel rods with threads cut on them and longitudinal flutes. Vices are intended for holding objects in position while work is carried out on them .Vices can be classified according to their design into bench parallel and hand types .Bench vices are sturdy and simple in design, so they can be used for a wide range of operations .They are made of soft steel with jaws of tool steel welded on. Parallel vices are of two types :swivel or plain .The base of the vice is bolted to the bench. Such vices are normally made of grey cast iron. A hydraulic press is intended for carrying out hydraulic tests on parts of marine machinery and mechanism such as cylinder heads ,valve bodies and filters .A hydraulic jack is extensively used in ships repairs. It is intended for removing screw propellers from the tailshafts. Bulley blocks are devices widely used in repairing ships for raising and lowering heavy parts of engines .