WO1996034706A1

WO1996034706A1 - A method for cleaning pipelines in ventilating systems

Info

Publication number: WO1996034706A1
Application number: PCT/SE1995/000496
Authority: WO
Inventors: Jan Olofsson; Mikael Gustafsson
Original assignee: Jan Olofsson; Mikael Gustafsson
Priority date: 1995-05-05
Filing date: 1995-05-05
Publication date: 1996-11-07
Also published as: AU2755995A

Abstract

A method of cleaning pipelines, particularly ventilation pipelines and ventilation ducts in a ventilation system (1) with the aid of a generally spherical cleaning nozzle (13) connected to a source of pressure medium, e.g. to an air compressor, through the medium of a delivery line (14), the cleaning nozzle (13) being of the kind that includes a slot or one or more nozzle orifices (16) which face rearwardly of the direction in which the nozzle is inserted, wherein medium exiting from the slot or orifices is intended to clean the inner walls of the pipeline and to generate reaction forces which cause the nozzle to move along the pipeline (12), the method comprising the steps of a) connecting a dust extractor (7) to an opening (9) in one of the pipelines (12) of the ventilation system (1) so as to create a subpressure in the pipeline in conjunction with activating the cleaning nozzle (13); b) inserting the nozzle (13) into the pipeline; and c) causing the nozzle (13) to move in the pipeline (12) with the aid of the delivery line (14), wherein prior to step a) the openings (6) of the ventilation system (1) are throttled against the surrounding atmosphere to control the amount of air that can be drawn by suction into the ventilation system (1), so as to place the ventilation system under high subpressure and to restrict the amount of air that can enter the system, wherein the medium withdrawn by suction from the system with the aid of the extractor (7) is comprised of the pressure medium blown from the cleaning nozzle (13) while the nozzle is at work.

Description

A METHOD FOR CLEANING PIPELINES IN VENTILATING SYSTEMS

The present invention relates to a method for cleaning pipelines in ventilation systems in accordance with the preamble of Claim 1.

It is known to remove deposits and fine particles from the inner wall of a ventilation duct with the aid of pressure- operated cleaning nozzles. A subpressure is generated in the pipeline in conjunction with activating the cleaning nozzle, by connecting a "dust" extractor to the ventilation system. The air sucked into the ventilation system through the openings together with the pressure medium exiting from the cleaning nozzle entrain dust (fines) and deposits which are carried to the pipeline to which the dust extractor is connected.

An example of known pipeline cleaning methods and apparatus is described in Swedish Patent Specification 500 862. In order to avoid problems with dust and particles that are blown into the rooms in which the pipeline openings open out, it is also known to provide these openings with an air permeable filter; c.f. for instance the International Patent Application WO 90/12662.

It is known from aerodynamics and hydrodynamics that when a medium, e.g. air, flows along a wall, there is formed a boundary layer between the wall and the medium. The thickness of this boundary layer will depend on the nature of the wall surface and the flow rate of the medium, among other things. In the case of smooth surfaces and low medium speeds, the medium particles will flow parallel with the surface to form a laminar boundary layer between wall ^' and medium, within which frictional resistance is low. On the other hand, the flow will be turbulent when the wall surface is uneven and the medium has a high rate of flow. When the flow is turbu¬ lent, obstacles, e.g. bodies, located in the path of the flowing medium will give rise to very high flow resistances. These flow resistances derive mainly from the high subpress- ures that are generated in the eddy-current-generated vortex regions at the rear of the obstacles.

Since those quantities of air drawn through the openings of the ventilation system by the dust extractor, together^" with those quantities of air delivered through the cleaning nozzle, are much larger than those quantities of air for which the system is designed, very high flow rates will be generated, particularly in the pipeline or pipelines to which the air volumes sucked into the system are combined. Because of the high flow rate, the irregular nature of the pipeline as a result of cross-lines or branch lines connected thereto, varying cross-sectional areas and the valves and other devices connected to the pipeline, eddy currents and turbu¬ lent flow will occur upstream in these pipelines of the ventilation system. As a result, some of the dust, deposits and other contaminants removed from the inner wall surface of the pipeline will not accompany the air flow to the dust extractor, but will collect at locations where a particularly high flow resistance prevails, for instance at pipe bends, behind butterfly valves and transitions between different cross-sectional areas of the pipeline.

The problem is caused, however, because a large air flow is required through the ventilation system in order to clean away dust and deposits effectively, and the earlier mentioned problem cannot therefore be alleviated simply by reducing the flow of cleansing air through the system. Insufficient air flow would unavoidably result in particles falling onto the bottom of the pipes and thus remaining in the system.

The object of the present invention is to provide a novel and improved method of the kind defined in the introduction which will assist in eliminating the drawbacks encumbered by the known technique. This object is achieved in accordance with the invention with a method of the aforedefined kind having the characteristic features set forth in Claim 1.

The invention is based on the concept of generating a large subpressure in the ventilation system, by throttling the amount of air that can be sucked in through the openings of the ventilation system, wherein the medium extracted by the dust extractor is comprised of the pressure medium blown from the cleansing nozzle while the nozzle is at work.

In the case of the majority of ventilation ducts, it has been found beneficial to construct the ventilation system as a generally closed system, by sealing all openings of the ventilation system against atmosphere, wherein the only medium withdrawn by suction from the ventilation duct via the dust extractor is comprised of the pressure medium blown from the cleansing nozzle while the nozzle is at work. Alterna¬ tively, the openings of the pipeline in which the extractor works can be provided with a respective air-permeable filter while remaining openings in the ventilation system are effectively sealed against the surrounding atmosphere, so as to allow a given quantity of air to enter the system.

The invention will now be described in more detail with reference to a non-limiting exemplifying embodiment thereof and also with reference to the accompanying drawings, in which

Fig. 1 is a perspective view of one embodiment of a ventila¬ tion system installed in a building structure, with which the inventive method is applied;

Fig. 2 is a fragmentary view, partly in section, of a dust extractor connected to one end of the ventilation system shown in Fig. 1 and in which a cleaning nozzle works; and Fig. 3 is a side view of one example of a cleaning nozzle intended for use with the inventive method.

Referring to the drawings, there is shown in Fig. l an example of a ventilation system 1 installed in a building structure 2 and functioning to effect a change of air in the rooms or spaces 3 in said device of structure. The ventila¬ tion system 1 includes a main pipeline 4 having connected thereto branch pipes 5 provided with openings 6 in the form of valves or like devices, these openings opening out in each room or space of the building structure.

Fig. 2 illustrates a dust extractor arrangement 7 which is connected to an inspection opening 9 , suction valve or like device included in the main pipeline 4 of the ventilation system, by means of a connecting device 8. The connecting device 8 includes a flange 10 which seals against the wall

11 through which one end 12 of the main pipeline 4 extends. The dust extractor arrangement 7 can be activated to create a subpressure in the ventilation system 1, such that air will be sucked continuously from the ventilation system at the same time as air is sucked in through the opening 6 of said system.

Fig. 3 illustrates an example of a typical cleaning nozzle 13 that can be used when practicing the inventive method. The nozzle 13 has a generally spherical configuration and is connected to a pressure medium source, for instance to an air compressor, through the medium of a delivery conduit 14 in the form of a flexible hose. The cleaning nozzle is mounted at one end of the hose and can be inserted into the pipeline

12 through an insertion opening 15 provided in the connector 8. The cleaning nozzle 13 includes a slot or one or more nozzle orifices 16 which face rearwardly of the direction in which the nozzle is inserted into the pipeline. The air exiting from the slot or nozzle orifices -is effective in cleaning the inner wall surfaces of the pipeline and also generates reaction forces which drive the nozzle along the pipeline 4.

When the system is to be cleaned, the cleaning nozzle 13 is inserted into a ventilation duct to be cleaned and supplied with compressed air, to which a cleansing agent and/or a disinfectant may optionally be added. Compressed air will then flow at a high velocity rearwardly from the nozzle orifices 16 provided around the periphery of the nozzle 13, causing the nozzle to be driven along the duct by the reaction forces generated by the air exiting from the nozzle, while entraining the hose. The nozzle 13 lies against the inner wall of the pipeline and is anoeuvered laterally by twisting the hose to one side or the other. At the same time, the duct is placed under a subpressure through the medium of the dust extractor arrangement 7, wherewith dust and solids dislodged or falling from the inner wall surfaces of the duct are extracted therefrom by the extractor.

However, in order to avoid large air movements in the duct, and therewith the occurrence of upstream turbulence in the duct, the quantity of air that can be sucked into the ventilation system 1 when the dust extractor 7 is at work is restricted by throttling the openings 6 of the ventilation system in relation to the surrounding atmosphere. The openings are preferably throttled before commencing to clean the system, by providing one or more openings with a cover 17 which includes a valve or like device by means of which the outlet area of the opening can be controlled and there- with also the amount of air that enters the system and the subpressure generated therein.

Since the majority of ventilation systems are, in themselves, not completely airtight, it has been found suitable to completely seal the opening 6 against the surrounding atmosphere, which can be easily effected by taping-over the openings. The subpressure and the air which flows into the ventilation system through pipe joins, valve shafts, etc., together with the pressure medium that is ejected from the cleaning nozzle 13 when the nozzle is at work has been found suitable to avoid large air movements, eddy formations, vortices and turbulent flows upstream in these pipelines of the ventilation system 1.

The present invention is not restricted to the aforedescribed and illustrated embodiment thereof, since modifications and changes can be made within the scope of the inventive concept as defined in the following Claims.

Claims

1. A method of cleaning pipelines, particularly ventilation pipelines and ventilation ducts in a ventilation system (1) with the aid of a generally spherical cleaning nozzle (13) connected to a source of pressure medium, e.g. to an air compressor, through the medium of a delivery line (14), said cleaning nozzle (13) being of the kind that includes a slot or one or more nozzle orifices (16) which face rearwardly of the direction in which the nozzle is inserted, wherein medium exiting from said slot or orifices is intended to clean the inner walls of the pipeline and to generate reaction forces which cause the nozzle to move along the pipeline (12), said method comprising the steps of a) connecting a dust extractor (7) to an opening (9) in one of the pipelines (12) of the ventilation system (1) so as to create a subpressure in the pipeline in conjunction with activating the cleaning nozzle (13); b) inserting the nozzle (13) into the pipeline; and c) causing the nozzle (13) to move in the pipeline (12) with the aid of the delivery line (14), characterized by throttling in relation to the surrounding atmosphere the amount of air that can be drawn by suction into the ventilation system (1) through the openings (6) prior to carrying out step a) above, so as to place the ventilation system under a high subpressure and to restrict the amount of air that can enter said system, wherein the medium withdrawn by suction from the system with the aid of said extractor (7) is comprised of the pressure medium blown from the cleaning nozzle (13) while the nozzle is at work.

2. A method according to Claim 1, characterized in that said throttling effect is achieved by providing one or more of the openings (6) of the ventilation system (1) with a cover means (17) which includes a variable valve or like device.

3. A method according to Claim 1, characterized in that the throttling effect is achieved by sealing-off all of the openings (6) of the ventilation system against the surround¬ ing atmosphere.

4. A method according to Claim 3, characterized by taping over the openings (6) of the system pipelines (5; 12) such as to achieve said sealing effect.