Pump PW.4.13 with complete installation of working water in a closed system. Shell and tube heat exchanger. Execution for explosion hazard zone. Application in the woodworking industry.

Features:

• high quality,
• guaranteed long-term, reliable operation and easily available spare parts,
• product adjustment to individual customer's requirements,
• constant technical supervision as well as guarantee and post-guarantee service,
• low costs of purchase and maintenance,
• relatively long life-time in hard working conditions.

Principle of Operation. Construction

The principle of operation of a compressor with a rotating liquid ring is as follows: Encased in cylinder "O", part of which is filled with a liquid, there is a blade impeller "W" with a hub of a large diameter. As soon as the pump is started, the rotation of the impeller causes the liquid to circulate and be pushed against the walls of the casing to form a liquid ring. If the impeller is positioned eccentrically relative to the casing, then a liquid-free gap in the form of a crescent is left around the hub; the crescent is divided by the impeller blades into several compartments. The size of the compartments will grow at first, only to decrease after the bottom position is passed. The side walls (screens) provide axial closure to the compartments; now, if two openings are cut in the side walls, one of them (suction window "S") at the beginning of the crescent and the other one (discharge window "T") at the end of it, then the expanding compartment will cause the gas to be sucked into the compartment; then, as the capacity of the compartment is reduced, the gas will be compressed and discharged. Since a portion of the liquid that forms the liquid ring is always forced outside through the discharge window together with the discharged gas, the volume of the liquid has to be made up.

The design of compressors with a rotating liquid ring is determined by the above principle of operation. The devices are rotating, valveless, positive-displacement pumps. Part of the working liquid that forms the ring is discharged together with the gas and is made up continuously. The pump consists of fixed parts such as the casing (also referred to as distance body), control disks (also called suction elements and discharge elements), side bodies closing the pump, together with bearing bodies, seals and packings, and moving parts, such as impellers, the shafts, ring seals and bearings mounted on the shaft. Both sides of the shaft are sealed with a cord packing or end-face mechanical seal.

From the point of view of their design, the blowers are not much different from single-stage vacuum pumps - they are reversible devices. The only difference between them lies in their power consumption and has been taken into account in the choice of pumps with propulsion motors. Vacuum pumps and blowers with a rotating liquid ring were first manufactured in 1950 and have been constantly improved since then. They are used in a number of factories all over Poland and abroad.

They are characterized by:

• such features as compact design,
• reliable operation,
• simple maintenance (the working elements need no lubrication),
• low operating costs.

In terms of their technical parameters, the blowers are comparable with products of reputable European manufacturers. Their assumed technical and operating parameters were validated in long-term tests.

Installation

A complete vacuum unit, or compressor unit, consists of the following elements:

• vacuum unit,
• working liquid separator,
• piping,
• valves and fittings.

All suction and discharge piping must be precisely made and accurately arranged to avoid the effect of moments and forces, exerted on the compressor flanges. To this end, the pipes should be sufficiently extended to compensate for thermal elongation of the piping; another option is to use compensation bellows.

The pipes must be thoroughly cleaned to remove any corroded material and welding spits. No solid is allowed into the compressor, otherwise the rotating mechanism of the pump will be damaged. The direction of gas flow in the compressor is indicated by the arrows on the suction and discharge bodies. The openings of the piping on the suction and discharge sides and that of the working liquid inlet must be at least the size of connections. The pipe openings must not be covered up by any seals.

The discharge pipe may be directed vertically not higher than 1 m off the connector pipe of the compressor. Unit hydraulic losses in the pipes should be minimized. The device is installed in either one of the three ways, depending on the type of operation:

Operation type - Open system, with direct supply of fresh water to the pump as the working fluid.
This type of operation is applied when water consumption is of little importance. If the pressure of water from the network is unstable and fluctuates by more than 25%, then the vacuum pump ought on its own to suck in water from the tank to which the supply of fresh water from the network is controlled by a float-type valve or by a notch in the tank. The level of water in the tank ought to be at the same height as the pump shaft. When the vacuum pump is in operation and there is no need to separate the removed water and gas on the discharge side, then the tank that separates working water may be omitted. In that case, the discharge pipe is directed to the drain.

Operation type - The working liquid is introduced in a closed circulation system.
This type of operation is recommended in particular for handling caustic and noxious gases. If resistance of flow in the heat exchanger is too high, then an auxiliary pump should be provided. In the case of intermittent operation, when the pump operation for several minutes is followed by a period of time long enough to effect reduction of the temperature of the circulating liquid to a set value, the heat exchanger may be omitted.

Operation type - The working liquid is introduced in a combined system.
This type operation is recommended for normal operating conditions. There is less fresh liquid than in operation type 1. To keep a compact design of the unit, the vacuum pump may be provided with a separator, mounted on the pump discharge pipe (this applies to operation types 1 and 3).

Operating Requirements

• Irrespective of the type of operation, the compressor (vacuum pump or blower) needs to take up a sufficient quantity of working liquid.
• To reach the parameters given in this catalogue, the temperature of the working liquid discharged from the vacuum pump, as measured at the pump outlet, must be kept at or below 15oC (for water). If, for some reasons, this can not be achieved and the water is at a higher temperature a reduction of capacity will result. The capacity data given in this catalogue ought to be corrected using the k = f (t, ps) coefficient according to the chart given in the catalogue. The working point of the vacuum pump should be above the limiting curve.
• The piping and the walls of the working liquid tank are exposed to the presence of rust and dirt, and they need cleaning as the impurities build up. If the working liquid is water with high concentrations of calcium compounds, it needs to be softened. Otherwise, the compressor has to be dismantled after at least 6 months of operation, cleaned thoroughly to remove any deposit or rinsed with appropriate chemicals, for instance 5% solution of hydrochloric acid in water, taking the usual precautions.
• In the operation of two-stage vacuum pumps, if cavitation (noises) occurs, then the working point is below the limiting curve in the chart k = f (t, ps); in such case, the aeration valve should be in the open position during the pump operation or the temperature of the working liquid should be lowered. If these measures do not help, further operation is prohibited, otherwise the pump will be damaged as a result.

The influence of working water temperature on the suction pressure and vacuum pump capacity

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