Small and medium condensate pumps are horizontal multistage pumps of the sectional Ks or spiral type KsD.
Let’s consider condensate pumps of the KsD type.
Condensate pumps of the KsD type are designed for pumping condensate in steam-water networks of thermal and power units of thermal power plants, as well as clean water with a temperature of up to 125 ° C in heat and water supply systems, metallurgy.
A distinctive feature of this type of pumps is:
- cast spiral housing with horizontal connector;
- first stage impeller – double-sided inlet (type D) in order to increase suction capacity;
- symmetrical arrangement of impellers to balance the axial force acting on the rotor;
- assembly and disassembly can be done without disconnecting the pipelines.
Materials of the main parts of condensate pumps type KsD:
- pump housing – gray cast iron;
- bearing housings – gray cast iron;
- impellers – gray cast iron;
- sealing rings and diaphragms – gray cast iron;
- shaft – alloy carbon steel;
- protective bushings – chromium steel.
As an example of the design of KsD type pumps, consider the KsD 125-140 condensate pump.
Condensate pump KsD 125-140 (Figure 1) – centrifugal, horizontal, spiral type, three-stage, with the first stage impeller of a double-sided inlet, the second and third – a single-sided inlet.
Figure 1
The basic part of the pump is a housing with a horizontal split in a plane passing through the axis of the pump. The pump body is a cast iron casting of complex shape, consisting of two parts (pump cover and pump body), in which semi-spiral inlet and spiral outlet channels, transfer channels of the flow part, as well as chambers (thermal barriers) for cooling the end seals are cast. In the lower part of the housing, inlet and discharge pipes, support legs and trough-shaped brackets for collecting leaks, as well as fastening bearing housings are cast. The inlet pipe is directed vertically downward, and the pressure pipe is directed horizontally to the side. The location of the pipes in the lower part of the housing makes it possible to disassemble the pump without dismantling the pipelines. In the upper part of the housing (lid) there are threaded holes for air release, which are plugged with plugs. To remove steam accumulated in the supply channels of the first stage, there is a pipeline in the upper part of the suction cavities that connects to the steam space of the condenser. At the bottom of the housing there are threaded holes for draining water, which are plugged with plugs. The trough-shaped brackets of the housing have holes for drainage of leaks. In the pump body, in the places where the impellers are sealed, sealing rings and diaphragms for interstage seals are installed.
The pump rotor is an independent unit and consists of a shaft, a set of impellers, input sleeves, protective bushings, bushings, oil deflectors, bearings and fasteners. To balance the axial force, the impellers of the second and third stages are installed on the shaft with inlet funnels in opposite directions. The operating wheel of the first stage of the double-sided inlet provides increased suction capacity of the pump. Inlet sleeves and protective bushings are installed on common keys with the impellers and fixed in the axial direction with round nuts and lock washers. A gap is provided between the third stage wheel and the inlet sleeve, which serves as a compensator for thermal expansion when the impellers are heated by the pumped condensate.
The assembled pump rotor is dynamically balanced.
To seal the points where the shaft exits the pump casing, gland type end seals with a water seal are used. Condensate is supplied to the water seal ring under pressure to prevent air from being sucked into the pump. To cool the seal, the pump housing contains chambers in which cold process water supplied from an external source circulates.
It is possible to install mechanical seals.
The pump rotor is supported by rolling bearings, which are installed in bearing housings with a horizontal split. The support bearing (single row ball bearing) on the drive side absorbs radial loads. The thrust bearing (double-row angular contact ball bearing) at the free end of the shaft absorbs residual axial forces and radial loads. Bearings are lubricated with liquid, ring (crankcase) lubrication using a splash ring. Oil level indicators are provided to monitor the oil level. The bearing housings are equipped with chambers for water cooling of oil in oil baths.
Alignment of the rotor with the stator is carried out by moving the bearing housings with adjusting screws. After final alignment, the bearing housings are fixed relative to the pump housing with tapered pins.
An asynchronous motor with a squirrel-cage rotor is used as a drive.
Pump and motor are mounted on a common foundation frame and are connected to each other using an elastic sleeve-pin coupling. The coupling is closed by a guard.
The symbol of the pump means: KsD – condensate with a first-stage impeller of type D; 125 – flow rate in m3/h; 140 – head in m.
