WO2014170705A1

WO2014170705A1 - Method and device for cleaning the inner surface of pipelines, primarily drinking water pipelines

Info

Publication number: WO2014170705A1
Application number: PCT/HU2014/000031
Authority: WO
Inventors: Gyula CSÓKA; Zoltán BÍRÓ
Original assignee: Duna-Kut Kft.; Fövárosi Vízművek Zrt.
Priority date: 2013-04-16
Filing date: 2014-04-14
Publication date: 2014-10-23
Also published as: HUP1300228A2; HU229851B1

Abstract

Method and device for cleaning the inner surface of pipelines, primarily drinking water pipelines A method for cleaning the inner surface of pipelines, primarily drinking water pipelines, comprising the step of removing the slimy and/or solid contamination from the surface to be cleaned applying a cleaning water jet. The invention is essentially characterised by that dry ice pellets are fed to the cleaning water jet applying air pressurised to 7-12 bar. A device for cleaning the inner surface of pipelines, primarily drinking water pipelines, comprising a tank (12) holding cleaning water (7), a cleaning water hose (1) adapted to convey the cleaning water (7) from the tank (12) to the pipeline (18) to be cleaned, and a cleaning head (3) wherein the cleaning head (3) is mounted to the end of the cleaning water hose (1) introduced into the pipeline (18) to be cleaned. The device is essentially characterised by that a coupling hose (2) of a dry ice-pellet feeder (14) is introduced into the cleaning water hose (1).

Description

Method and device for cleaning the inner surface of pipelines,

primarily drinking water pipelines

The invention relates to a method for cleaning the inner surface of pipelines, primarily drinking water pipelines, wherein the slimy and/or solid contamination is removed from the surface to be cleaned applying a water jet. The method according to the invention is carried out utilising a device comprising a tank holding cleaning water, a cleaning water hose adapted for conveying cleaning water from the tank into the pipeline to be cleaned, and a cleaning head disposed at one end of the cleaning water hose, said end being introduced into the pipeline to be cleaned.

Distribution pipelines of drinking water systems are usually made from cast iron or carbon steel. These pipelines are particularly sensitive to contaminants deposited on the inside pipe wall. During years of prolonged operation, a soft, loosely deposited, slimy biofilm layer builds up on the inside surface of the pipes that are in contact with water. The biofilm forms due to the changes of water temperature, dissolved oxygen content, and chemical equilibrium characteristics from iron, manganese, and calcium ions and other ions prone to precipitate. This slimy layer may cause microbiological and biological water quality deterioration. In a longer period of time, a shell-like solid layer is formed by the above compounds on the surface, which, in addition to deteriorating water quality, also reduces the cross sectional area and thereby the flow capacity of the pipeline. These factors make it imperative that the inside surface of pipes is cleaned in a regularly recurring manner.

There are several widely applied methods for cleaning the inside surface of pipelines. According to a known solution, the pipeline is opened up at two locations, followed by introducing a wire rope into the pipe and passing it along the length of the section to be cleaned. A cleaning device is attached to one end of the wire rope, while a rope drum is attached to the other end. The device is pulled along the pipeline by winding the wire rope on the rope drum.

An apparatus for cleaning a pipeline containing a pressurized liquid is disclosed in patent HU 160,613, wherein the pipe wall is cleaned by the chiselling action caused by the pressure change of the liquid flowing under pressure in the pipeline. The patent HU 173,356 relates to a pneumatically operated device capable of cleaning pipelines. The essential feature of the invention is that a cleaning head portion, fitted with cleaner spikes, is connected by means of a threading to a rod ending in a piston, the rod being attached by a flange to a pipe cleaning body such that the cleaning head portion may be displaced along a predetermined path.

Hungarian patent HU 219,655 discloses a method and apparatus for cleaning drinking water distribution pipelines. The essential feature of the method . is that pressurized air pulses are introduced into the pipeline section to be cleaned, the water flow being maintained in the pipe. The apparatus comprises a compressor, an aggregate in operative connection with the compressor, and a control unit which operates a shutoff device disposed in the air feed line.

Prior art methods and devices do not allow for the quick, simple and hygienic cleaning of the inside surface of drinking water pipelines. Methods involving exclusively mechanical cleaning are slow to operate and do not clean the surface to a sufficient extent. Cleaning methods applying pneumatic means or hydraulic shock waves are not capable of disrupting to a sufficient extent the solid contaminant layer deposited on the inside surface of the pipeline. Furthermore, the above cited cleaning methods are not capable of biological cleaning.

The document KR 20090018333A relates to a dry ice spraying apparatus for cleaning water pipelines without excavation. The apparatus is adapted for removing a contaminant layer deposited on the inside surface of the pipeline utilising a dry ice spraying head applied to means introduced into the pipeline.

Dry ice spraying technology is capable of biological and microbiological purification of water, while the sudden temperature drop occurring when the dry ice particles hit the wall results in rupturing to a certain extent the solid contaminant layer formed on the surface. However, this rupturing action is not sufficient for completely removing the contamination, especially in case of larger-diameter pipes.

Our invention is based on the recognition that, in case dry ice is conveyed to the surface to be cleaned applying high-pressure water instead of utilising air in a previously known manner, the rupturing effect of the dry ice caused by sudden temperature change and the particle separating effect of high-pressure water will apply to the contaminant layer simultaneously. Under the effect of micron-sized bubbles formed in the water-gas system developed under the prevalent high pressure from the carbon dioxide gas forming during the sublimation of dry ice the solid layer deposited on the wall of the pipeline is disintegrated, and the contaminant particles are carried away by the high-speed water flow together with the constituents of the biofilm.

The pursued objective is achieved by the invention by providing the features included in claims 1 and 5. Features of the preferred ways of carrying out the invention and of the preferred embodiments are defined in the dependent claims.

The method and device will now be described in detail by way of the below included specification and the preferred embodiments, with reference to the accompanying drawings, where

Fig. 1 is a drawing illustrating the principle of the method according to the invention, Fig. 2 is a schematic drawing showing the device according to the invention,

Fig. 3 illustrates an exemplary embodiment of the device according to the invention, and

Fig. 4 shows a larger-scale view of the cleaning head and the coupling hose of the device according to the invention.

Fig. 1 is a schematic drawing illustrating the pipeline cleaning method according to the invention. A cleaning head 3 is mounted on the end of a cleaning water hose 1 , the cleaning head 3 being inserted into the pipeline 18 to be cleaned. Pressurized cleaning water 7 is fed through the cleaning water hose 1 into the cleaning head 3 and is conveyed to the surface to be cleaned through the openings 11 of the cleaning head. The cleaning water has a pressure of 80- 20 bar, preferably 100 bar. A coupling hose 2 adapted for conveying the dry ice pellets to the cleaning water hose 1 is attached at an angle a to the hose. The angle a is an acute angle, preferably in the range of 10-15°. The high pressure cleaning water 7 jet carries with it the dry ice pellets 4 fed therein through the coupling hose 2 applying pressurized air. The pressure of the transport air is 7-12 bar, preferably 7 bar. The particle size of the dry ice pellets is 4-6 mm. The dry ice particles are "sucked in" from the Y-shaped hose coupling by the high-pressure cleaning water 7 jet. Entering the high-pressure cleaning water 7 jet, the air and dry ice pellets 8 form an aqueous mixture of cleaning water and dry ice 9 while sudden gas formation also occurs. Dry ice pellets shrink to micron-size in the aqueous mixture of cleaning water and dry ice 9, while the microparticulate aqueous mixture of cleaning water and dry ice 10 cools down to an extremely low temperature. The aqueous mixture, saturated with carbon dioxide, is blasted against the wall of the pipeline 18 to be cleaned through the openings 1 1 of the cleaning head 3 at a pressure of 100 bar. The hardened contaminant layer located on the inside wall of the pipeline 18 gets ruptured in a spiderweb-like fashion by the sudden fall of temperature, deteriorating the adherence of the layer to the wall. The mushy mixture leaving the cleaning head 3 at a pressure of 100 bar removes both the loose and firm contaminant deposits from the wall of the pipeline, while the cleaning water. 7 also disinfects the pipe. Contaminants are carried away by the cleaning water 7 saturated with carbon dioxide, and leave the pipeline as a biologically inactive material. This substance has no environmentally harmful effects and does not require extra measures from the aspect of environmental protection.

Fig. 2 shows the schematic view of the device according to the invention. A tank 12 holding the cleaning water 7 is connected to a pressure booster unit 13 by a cleaning water hose 1. From the pressure booster unit 13 the cleaning water hose 1 , together with the cleaning head 3 mounted to its end, is introduced to the pipeline 18 to be cleaned such that the cleaning water 7 can reach the inside surface of the pipeline 18. An essential component of the device is the dry ice-pellet feeder 14 that is connected to the cleaning water hose 1 by means of a coupling hose 2. Dry ice pellets are fed from the dry ice-pellet feeder 14 to the coupling hose 2 applying pressurized air having a pressure of 7 bar.

An exemplary embodiment of the invention is described in detail with reference to Fig. 3. For carrying out regular cleaning of drinking water distribution pipelines, the components of the device should be mounted on transport means. The tank 12, the pressure booster unit 13, the hose holder unit for the cleaning water hose 1 , as well as the dry ice-pellet feeder 14 are all mounted on the transport vehicle. In order to carry out the method, working pits 15, 16 should be dug at two suitable locations along the pipeline 18, and the pipeline should be opened to make it accessible for carrying out the method. After parking the transport vehicle beside one of the working pits 15 the cleaning head 3 may be introduced into the pipeline 18. As it is illustrated in detail in Fig. 4, in a manner known per se the cleaning head 3 is arranged such that the cleaning head is guided along the inside of the water pipeline by the runners attached to it. The openings 1 of the cleaning head 3 are inclined rearwards relative to the principal axis of the cleaning head 3 at such an angle that the reaction force of the jet leaving the cleaning head propels forward the cleaning head.

Returning now to Fig. 3, after introducing the cleaning water hose 1 into the pipeline 18, the cleaning process begins by first opening the shutoff appliances of the high-pressure cleaning water 7, and then opening the shutoff valve 5 of the coupling hose 2. The "mushy" mixture that contains microparticles and travels through the cleaning head 3 at a pressure of 100 bar removes both the loose and firm contaminants from the wall of the pipeline. At the same time, the pipeline is also disinfected by the chemical action of the water saturated with carbon dioxide. Under the effect of the transport medium, that is, water saturated with carbon dioxide, the sludge produced during the process returns to the starting working pit 15 as a biologically inactive substance. It can then be removed from the pit by pumping and can be transported to a disposal site where it may be processed in an environmentally friendly manner.

As dry ice sublimates during the process according to the invention, the formed carbon dioxide gas can be vented from the opened-up pipeline by natural draft, or, if necessary, may be disposed of utilising a fan to blow large amounts of air into the pipeline. The amount of the applied dry ice has to be optimised such that it can have both a mechanical and a disinfecting effect and such that at the same time gas formation can be kept under control.

Utilising a single working location a 300-metre section of the pipeline can be cleaned. The method and device according to the invention may be applied for cleaning pipelines with a diameter of 50-1600 mm. It is expedient to dig the starting working pit 15 at a location where a fire hydrant or other appliance is installed.

The improvements over prior art methods for cleaning water distribution pipelines, achievable applying the method according to the invention, are summarised as follows:

- the method is environmentally friendly, since the sludge is pumped to a container simultaneously with the cleaning operation, and thus it may be transported to a processing facility, rather than being discharged to the environment at the working location or being pumped into the sewer system where it may cause obstructions or further contamination.

- in addition to providing a disinfecting effect, it also removes loose and solid contaminants from the distribution pipeline,

- it is able to restore the water carrying capacity of the pipeline,

- a 300 m-long pipe section may be cleaned from a single working location, and thereby the number of working pits (and hence the amount of earthwork required) is reduced,

- the duration of the cleaning process carried out from a single working location is 40-60 minutes. List of reference numerals

1 cleaning water hose

2 coupling hose

3 cleaning head

4 dry ice pellets

5 shutoff valve

6 check valve

7 cleaning water

8 air+dry ice pellets

9 aqueous mixture of cleaning water and dry ice pellets

10 microparticulate aqueous mixture of cleaning water and dry ice pellets

11 opening

12 tank

13 pressure booster unit

14 dry ice-pellet feeder

15 working pit

16 working pit

17 venting location

18 pipeline

Claims

1. Method for cleaning the inner surface of pipelines, primarily drinking water pipelines, comprising the step of removing the slimy and/or solid contamination from the surface to be cleaned applying a cleaning water jet,

characterised by that

dry ice pellets are fed to the cleaning water jet applying air pressurised to 7-12 bar.

2. The method according to Claim 1 , characterised by that the cleaning water jet has a pressure of 80-120 bar, preferably 100 bar.

3. The method according to any one of the previous claims, characterised by that the particle size of the dry ice pellets is 4-6 mm.

4. The method according to any one of the previous claims, characterised by that the pressure of the air is 7 bar.

5. Device for cleaning the inner surface of pipelines, primarily drinking water pipelines, comprising

- a tank (12) holding the cleaning water (7),

- a cleaning water hose (1 ) adapted for conveying the cleaning water (7) from the tank (12) to the pipeline (18) to be cleaned,

- a cleaning head (3) mounted to the end of the cleaning water hose (1 ) that is introduced into the pipeline (18) to be cleaned,

characterised by that

- a coupling hose (2) of a dry ice-pellet feeder (14) is introduced into the cleaning water hose (1 ).

6. The device according to Claim 5, characterised by that a check valve (6) and a shutoff valve (5) are built into the coupling hose (2).

7. The device according to Claim 5, characterised by that the coupling hose (2) is introduced to the cleaning water hose (1 ) at an acute angle (a) of 10-15°.