GB2492238A

GB2492238A - Condensate discharge fitting comprising a water repellent internal coating

Info

Publication number: GB2492238A
Application number: GB1211213.2A
Authority: GB
Inventors: Stephen Woolls
Original assignee: Vivendi Solutions Ltd
Current assignee: Vivendi Solutions Ltd
Priority date: 2011-06-24
Filing date: 2012-06-22
Publication date: 2012-12-26
Anticipated expiration: 2032-06-22
Also published as: GB2499719B; GB2492238B; GB201110737D0; GB201211213D0; GB2499719A; GB201302478D0

Abstract

A condensing boiler system 1 has a condensate discharge pipe 3, where at least a part of the inside surface of the condensate discharge pipe is coated with a water repellent (hydrophobic) coating, such as silica nanoparticles. The contact angle of the inside surface of the coated pipe may greater than 120Â°, and is preferably greater than 150Â° so as to provide a â superhydrophobicâ coating. The pipe may be made from a polymer selected from a group including polyethylene, polypropylene and polyvinylchloride (PVC). Preferably, the coated pipe is inclined downwards at an angle of 1Â° to 5Â° for at least part of its length. In a further aspect, a joint configured to connect with a condensate discharge pipe is disclosed, where at least a part of the inside surface of the joint has a water repellent coating.

Description

Superhydrophobic Cèating

FiELD OF THE INVENTION

The present invention relates to condensing boilers and problems arising therewith during extreme cold weather. In particular, the present invention provides a solution to problems caused by frozen condensate, by means of a pipe coated *ith a water repellent material.

BACKGROUND

As part of its commitment to the Kyoto Protocol, in 2005 the UK Government introduced Building Regulations requiring that, unless a more sustainable alternative is available, all hew installations of gas & oil powered domestic heating boilers should be of the condensing type. There are estimated to be some 9 million such boilers currently installed in the UK, with new installations continuing at an approximate rate of 1.5 million per year.

Condensing boilers (e.g. as shown in figure 1) work on the principle of re-using heat that would normally be ejected into the atmosphere from the flue of standard efficiency (non-condensing) boilers. The waste gases are passed through a secondary heat exchanger which extracts additional heat by condensing water vapour to liquid water, thus recovering its latent heat. This process increases the efficiency of the boiler by around 12-15 % and at the same time, reduces the temperature of flue gases from approximately 120-180 °C of conventional boilers, to a temperature between 50 °C and 60°C.

This reduction in temperature causes the water vapour formed during the combustion process to condense. As the droplets of water form, they fall by gravity to collect at'the base of the flue manifold. The remaining gases are expelled to the outside environment through a fanassisted balanced flue. The céndensate jroduced within the appliance is drained into a discharge pipe. Domestic condensing boilers can typically discharge between 1-2 litres of condensate per hour. Often this is piped via the discharge pipe directly from the boiler to external drains.

Building Regulations and manufacturers installation guidelines stipulate that where possible condensate should be discharged into an internal waste pipe.

However, where a boiler is installed on the ground floor the condensate is typically fed into a waste pipe through an external wall of the building and then by an appropriate route to an appropriate drain. Installations on the first or higher floors typically employ a system whereby the condensate is pumped vertically to the discharge pipe into the roof cavity or loft, then through the eaves into a gutter. UK building regulations now stipulate that the pipe cannot be terminated directly into the gutter but must be connected to a vertical downpipe.

In extreme weather, freezing of the condônsate during its discharge causes.

significant problems that can interfere with the functioning of the boiler. Freezing of the pipe or pipes which discharge the condensate leads to blockages and these can have the effect of shutting down the boiler. As a result, users are left unable to work their hot water and/or heating system duringthe coldest periods of the year. This presents a serious problem, particularly for the elderly and/or infirm, and for families with young children. This freezing often takes place where the discharge pipe passes through an external cavity wall and/or in the loft space, making it particularly difficult to thaw and to prevent from re-freezing.

Such freezing can also cause internal damage to the boiler, necessitating repair/replacement more often than would otherwise be required and increasing the maintenance burden and cost of supplying and insuring condensing boilers.

The present approach to solving this problem is to lag exposed discharge pipes with appropriate material, but this is only partially effective. In addition, it is advisable to incline the condensate-discharge pipe(s) at an angle of greater than or equal to 5°. However, this solution also is not always effective and poor workmanship often means pipes are not angled appropriately.

Alternatively, a trace-heating eabl may be applied to the length of the discharge pipe, through which a low current is passed in order to keep its temperature above freezing. This solution has obvious cost implications as it is expensive to install and run, and is wasteful of energy due to the constant heating of the condensate, which is a waste by product of a heating system. Heating waste water to avoid it freezing is not environmentally friendly. Nonetheless, at present this is regarded as the best solution to the problem.

Thus, there is a need for a cheap and effective way to solve the problems caused by freezing of condensate in the discharge pipes of condensing boilers.

The present inventors have now established that when a suitable water repellent coating is applied to the condensate-discharge pipe, this can solve the above problems. Surprisingly, this is so effective that freezing of the condensate can be avoided even when the condensate-discharge pipe is inclined at an angle as low as I ° the horizontal. The solution is also effective over long lengths of discharge pipe such as.wheri 3 metres or more of the discharge pipe is exposed to potentially freezing conditions.

It is envisaged that coated discharge pipes which prevent freezing can be installed not only on new condensing boilers but also retrofitted to current condensing boilers.

SUMMARY OF TUE INVENTION

In a first aspect the invention provides a condensing boiler system having a condensate discharge pipe, wherein at least a part of the inside surface of said condensate discharge pipe is coated with a water repellent coating. It will be * appreciated that the coating is present on the surface exposed to the water, i.e. at least internally.

Viewed from another aspect the invention provides the sise of a pipe, at least a part of the inside surface thereof being coated with a water repellent coating, as a condensate discharge pipe in a condensing boiler system.

In another aspect, the invention provides method for the prevention of the freezing of condensate in a condensate discharge pipe in a condensing boiler system comprising coating at least a part of the inside surface of said condensate discharge pipe with a water repellent coating.

Viewed from another aspect the invention provides a condensate discharge pipe configured to connect to a condensing boiler system at least a part of the inside surface of said pipe having a water repellent coating.

BRIEF DESCRIPTION OF THE FIGURES.

Figure 1 is an illustration of a condensing boiler.

DETAILED DESCRIPTION. . ..

The coated pipe of the invention is a condensate-discharge pipe which forms part of a condensing boiler system. The other parts of the boiler are conventional and a detailed description thereof is not needed here. Preferably, the condensate discharge pipe is suitable for use in or with a standard waste water pipes/gutters/downpipes for domestic and/or commercial use and is compatible therewith in tenns of diameter and/or fittings. It will be appreciated that to ensure the continued effectiveness of the pipe to repel water through the entire discharge pipe system, suitably coated joints may also be required.

* Preferably, the coated pipe is an integral part of the boiler system. For example it may be connected directly to the condensate reservoir or flue manifold.

Suitable pipes may have a transverse cross-section of essentially cylindrical shape, for example round, oval etc. Most preferably the pipe may be essentially cylindrical, i.e. the cross-section may be substantially circular, although it need not be a perfect circle.

Suitable pipes may have a longitudinal cross-section of essentially any shape. For example, the pipe may be essentially straight, twisted or curved, or a combination of these. As noted in detail below, pipes may also taper.

The coated pipe of the invention may be of essentially any length. The length of the pipe may be limited only by the praetiealities of the environment in which the pipe must be installed. The UK building regulations recommend that exposed pipe(s) should be less than 3 metres in length. However, the coated pipe of the current invention is still effective at lengths &eater than 3 metres. For example, the coated pipe may be in the range of 0.1 metres to 20 metres, preferably in the range 0.2 to 10 metres, more preferably in the range 0.3 to 3 metres. Typical lengths of the coated pipe can be at least 0.5 m, such as at least 0.75 m especially at least I m and so on.

The internal diameter of the coated pipe is preferably in the range of 0.1-20 cm. More preferably the internal diameter is 1-10 cm, especially 1.5 to 4 cm. The dimensions of the coated pipes are preferably of standard size.

The pipe to be coated according to the invention may be formed of any material suitable for coating, for example plastic or metal. Preferably the pipe comprises a plastic material. More preferably this polymer is selected from the group comprising polyethylene, polypropylene, polyvinylchloride and polymethacrylates. Most preferably the pipe comprises PVC, such as uPVC and/or poly methyl methacrylate (PMMA). The skilled man is familiar with the types of material used to form pipes for condensing boilers.

The pipe to be coated typically has a wall thickness in the range of 0.1-5 cm.

Preferably the pipe wall thickness is 0.25-3 cm, for example 0.5-2 cm.

The invention primarily relates to the realisation that by coating condensate discharge pipes with a water repellent material, the problem of water freezing within those pipes can be avoided. As the water is repelled by the coated pipe, it simply does not remain in the pipe, and as long as the pipe is angled slightly downwards, the water simply runs away. It will be appreciated that the coating has to be present only inside the pipe. Nevertheless, it may be that for ease of manufacture, both internal and external surfaces of the pipe are coated.

The term water repellent coating means herein a coating which repels water and can be defined by reference to contact angles. The contact angle is used as a * quantitative mçasure of the wetting ability of a particular solid. The contact angle is defined as the angle, 9, made by a droplet of liquid on the surface of a solid substrate. If the liquid spreads completely across the surface and forms a film, then contact angle, 3, is 0°. If there is any degree of beading of the liquid on the surface of the substrate then the substrate is considered to be non-wetting.

The term water repellent is used herein to mean that the contact angle between the coated discharge pipe surface and water is at least 90°, preferably at least 100, such as at least 110 preferably at least 120 0, more especially at least 1300, most especially at least 140°.

Coatings with a contact angle of 1500 or more are referred to as being "superhydrophobic". These materials are the most preferred for use in the invention.

For example, suitable contadt angles would be 160° or more, preferably 165° or more, for example 170° or more. Contact angles are measured using the Static Sessile drop method. The method involves measuring a contact angle goniometre using an optical subsystem to capture the profile of a pure liquid on a solid substrate.

The angle formed between the liquid/solid interface and the liquid/'vapor interface is the contact angle. Older systems used a microscope optical system with a back light. Current-generation systems employ high resolution cameras and software to capture and analyze the contact angle.

It will be appreciated that the water repellent coating on the pipe surface should not be washed away by the fluids within the pipe.

Examples of water repellent coating materials are, for example based on the deposition of polyelectrolyte multilayers. That thight be accomplished by successive dipping in a substrate such as polyallylamine hydrochloride and polyacrylic acid.

Most preferably the coating material is a superhydrophobic material. Typical superhydrophobic materials are described in US 7485343, the disclosures of which are incorporated here by reference. It is preferred therefore if a superhydrophobic coating is achieved using a precursor sol comprising a metal alkoxide, a solvent, basic catalyst, fluoroalkyl compound and water. The sol can be deposited on a surface and exposed to hexamethyldisilazine to form a hydrophobic coating.

Application of UV to that coating allows the contact angle to be tailored.

US7485343 explains the necessary process.

US 2006/0029808 describes a process for providing a hydrophobic coating on a substrate involving a complex sol dipping process but such coatings could be used here. The hydrophobic coating is based on multilayers of polyelectrolyte.

In particular; superhydrophobic coatings of the invention can be those based on nanoparticles of water repellent elements and salts thereof such as silica and alumina. Coatings might also be based on carbon, e.g. using carbon nanotubes.

Essentially, as long as there are no health risks associated with a particular hydrophobic coating material, any such material could be used as a coating herein.

A more recent arid highly preferred coating is based on a silica surface, especially a nanoparticulate silica surface. The formed coating preferably takes the form of a silicon dioxide nanostructure. This can be achieved by, for example, dip coating the discharge pipe in a silica solution and evaporating the liquid. More preferably, coating can involve a sol comprising two materials: amorphous silica and a proprietory polymer (of Lotus Leaf'Coatings). This sol is available from Lotus Leaf Coatings and is sold as a superhydrophobic coating. Superhydrobic coatings of use in the invention are therefore available commercially from suppliers such as Lotus Leaf Coatings. Careful processing of the material system produces a highly advanced nanocomposite coating. in particular dip coating should take place vertically to prevent pooling of the sol and the pipe has to be completely dried after dip coating.

Preferably nanoparticles which form the superhydrophobic coating have a diameter in the range 1-500 nm. More preferably the particle diameter is in the range 1-250 nm, e.g. 1-50 nm, 40-100 nm, or 75-150 nm. A preferred coating comprises silica nanoparticles.

Coatings of the invention may have any thickness as long as they are capable of performing the desired function. Thicknesses in the range 0.01-100 m are envisaged. Preferably the coating thickness can be in the region of 0.1-50 m, more preferably 1-10 1Am, for example 1-3 jim.

* Suitable coatings maybe mono-layer r multi-layer. Multi.4ayer coatings comprise at least two layers, for exampk three layers, four layers or five layers.

Each layer may have a thickness in the range 0.1-50 tm, preferably in the range 1- * 10pm, for example 1-3 Mm.

The coating may be applied by any suitable coating operation such as dip-coating, spin coating or aerosol assisted methods such as rod coating, slot coating and other coating methods which are known in the art.

Preferably the coating is applied by a dip-eoating:process, whereby the target.

length of pipe is fully immersed in a solution, such as a nano-composite solution.

Preferably this solution does not contain substantial amounts of per-fluoro compounds or fluorines. More preferably these compounds are excludçd from the solution, i.e. present in an amount less than trace. The pipe may be removed and allowed to dry in ambient conditions. . . The most effective coating is achieved by dipping vertically and withdrawing the target pipe vertically, achieving an even "once-only" coating.

The coated pipe of the invention is used in combination with a condensing boiler to thus form a condensing boiler system. The term discharge pipe defines the whole or part of the pipe that connects the condensate reservoir to a waste water pipe. It can be the pipe that connects the flue manifold to a waste water pipe, or connects the reservoir to a vertical downpipe attached to the outside of a building and so on, The condensate discharge pipe is most likely to pass through an external wall, such as a cavity wall, to link the condensing boiler to the outside waste pipes.

In general, it is at a point within or just outside an external wall that freezing of the condensate becomes a problem. The skilled man can fully appreciate therefore which parts of the condensate discharge pipe need to be coated. It may be for example that in some installations, a first part of the condensate discharge pipe adjacent the boiler does not need to be coated as that part of the pipe remains within the building and is unlikely to freeze. The coating might only be applied therefore to parts of the pipe which are external or parts which are within a cavity wall or loft space and so on.

It is essential however for at least a part of the condensate discharge pipe to be coated according to.the invention, e.g. at least 20 % of its length such as at least 40% of its length such as at least 50% of its. length, e.g. all of its length.

It will also be appreciated that the discharge pipe mayitself'be formed from a series of smaller pipes and joints, for example to allow bends to be accommodated.

The term condensate discharge pipe is intended to cover the whole or part of the pipe leading from the boiler to the drains and therefore cok'ers pipe units and any joints required to connect pipes together. These joints can be considered to be part of the pipe and will benefit from coating according to the invention.

In a further aspect of the invention, the invention provides a joint configured for use with a condensate discharge pipe comprising a coating as hereinbefore defined. . I. Joints are preferably manufactured so that the inflow pipe will frilly enter the joint without butting against a joint wall. Moreover, the outflow pipe will preferably likewise fully enter the joint without butting against a joint wall. This will ensure that there are no points in the joint that will allow water to collect.

Those skilled in the art will appreciate that the condensate discharge pipe may taper at the end so that it fits snugly to the inside wall of a joint or pipe into which it pushes. Joints and pipes are generally provided with male and female adaptations. Hence the male end may be reduced in size to fit inside a standard 32 mm or 19 mm pipe. It may be that only one end of the pipe needs to be tapered, although if manufacturing is easier for both ends to be tapered, then that would not impact on the efficiency of the pipe.

The condensing boilers of the invention will preferably have a condensate discharge pipe that is at least in part located externally to the building in which the boiler is installed.

The coated pipe of the invention remains effetive for drainage of waste condensate'when.inclined at an angle as low as 19. Preferably the êoated pipe of the invention when combined with a condensing boiler is inclined at an angle of at least I degree or more downwards, preferably 1.50 or more, more preferably 3° or more, more. preferably 5° or more. Angles in the range of I to 5° such as 3 to 5° are envisaged. Ideally this inclination occurs for the entire length of the pipe. In particular, the inclination should be present for parts of the pipe that are external, within a cavity wall or within a loft space.

The invention provides for the use of a coated pipe as hereinbefore described in a condensing boiler system. It is envisaged that this coating technology could be used in general to prevent pipes freezing, especially waste pipes where water is not stored.

The invention also provides for the use of a condensate discharge pipe suitable for use with a condensing boiler system which can be retrofitted to an existing boiler system which does not have.the advantageous pipes of this inyention.

The invention also provides for the use of.a joint suitable for use with a condensate discharge pipe which can be retrofitted to an existing boiler system which does not have the advantageous joints of this invention.

The invention will now be described with reference to the following examples and figure 1.

Example 1

A uPVC pipe was dip coated by full immersion in nano-composite Si solution (containing no per-fluoro compounds or fluorines) available from by Lows Leaf Coatings tinder the trade name "SuperhydrobicCoating".

The pipe was dipped vertically, removed and allowed to dry completely in ambient conditions.

Once fully dry, both the internal and externa' surfaces of the pipe are rendered water-repellent. It is only the internal surface that needs to be water * repellent and the external surface is not important and handling will render the -external surface no longer water repellent. The pipe can be installed in a typical * * condensing boiler system.

* Example 2

* In Figure 1, condensing boiler (1), has fine manifold (2) connected condensate discharge pipe (3). This pipe passes through external wall (4) to connect to outside waste water pipe(5). Condensate.discharge pipe (3) can be provided with a hydrophobic. coating as hereinbefore defined:... * .*

Claims

Claims 1. A condensing boiler system having a condensate discharge pipe wherein at least a part of the inside surface of said condensate discharge pipe is coated with a water repellent coating.
2. A boiler system as claimed in 1, wherein the contact angle of the inside surface of the coated pipe is greater than 120°.
3. A boiler system as claimed in claim 2, wherein the contact angle of the inside surface of the coated pipe is greater than 150°.
4. A boiler system as claimed in any of claims I to 4, wherein said pipe comprises a polymer.
5. A boiler system as claimed in any preceding claim wherein said polymer is selected from thegroup comprising polyethylene, polypropylene and polyvinylehloride.
6.. A boiler system as claimed in any of claims I to 5, wherein the water repellent coating comprises silica nanoparticles.
7. A boiler system as defined:in any of claims 1. to6, wherein said coated pipe is inclined downwards at an angle of Ito 59 for at least part of its length.
8. Use of a pipe, at least a part of the inside surface thereof being coated with a water repellent coating, as a condensate discharge pipe in a condensing boiler system.
9. A method for the prevention of the freezing of condensate in a condensate discharge pipe in a condensing boiler syStem comprising coating at least a part of the inside surface of said condensate discharge pipe with a water repellent coating.io: A condensate discharge pipe configured to connect to a condensing boiler system at least a part of the inside surface of said pipe-having a water repellent coating.11. A joint configured to connect with a condensate discharge pipe at least a part of the inside surface of said joint having a water repellent coating.