Testing of central heating system water

Abstract

A method of testing the concentration of molybdate corrosion inhibitor in water of a central heating system is disclosed. The method comprises testing the iron concentration using an immersion test pad and testing the molybdate concentration using an immersion test pad. In the evaluation of the immersion test pad testing the molybdate concentration, the level of iron evaluated is taken into account. This results in more accurate and reliable results than achieved with known immersion tests.

Description

TECHNICAL FIELD

[0001] The present invention relates to testing of central heating system water, in particular to ensuring that corrosion inhibitors are present in the correct amount. BACKGROUND

[0002] Methods of testing central heating and / or cooling system water for the presence and concentration of various different chemicals are known. For example, colour change "dip tests" are known which can be used to measure the pH of the water, as well as the concentration of iron, copper and corrosion inhibitors. Typically, the corrosion inhibitors comprise molybdate, and the concentration of molybdate is used to determine whether the correct amount of inhibitor is present in the system water.

[0003] "Dip tests" are in the form of a pad impregnated with a reagent, which in turn is mounted on a stick as a carrier. The pad is dipped into a sample of the liquid to be tested, and then the dipped pad changes colour. The colour of the pad can be compared to a reference to determine the concentration of the particular chemical being tested, the pH, etc.

[0004] A method of digitally assessing such dip tests is described in the applicant's co-pending application GB2576942, for example using a mobile phone with a camera to take a photograph of the dip test alongside a colour reference scale, and determining the levels of the various chemicals being tested from a comparison between the colour of the dip test and the colour reference scale, and storing information mapping points on the colour reference scale to the amounts of the chemicals indicated.

[0005] However, due to the variety of chemicals which can be found in central heating system water, and the interaction of different chemicals with the colour change reagents, it has proven particularly difficult to use colour change "dip tests" to obtain a reliable accurate measurement of molybdate in central heating system water. It is an object of the present invention to address this problem. SUMMARY

[0006] According to the present invention, there is provided a method of testing central heating and / or cooling system water for the concentration of molybdate, comprising the steps of:

[0007] testing the concentration of iron in the central heating and / or cooling system water using a first colour change dip test, and comparing the colour of the first colour change dip test to an iron test reference to assess the concentration of iron;

[0008] testing the concentration of molybdate in the central heating and / or cooling system water using a second colour change dip test, and comparing the colour of the second colour change dip test to a molybdate test reference, and assessing the concentration of molybdate based on the comparison of the second dip test to the reference and the assessed concentration of iron.

[0009] It has been found that the colour change dip test can be reliably used to determine the iron concentration in central heating system water. Iron is a common contaminant in central heating system water, but the concentration of iron can vary greatly depending on the size, age, type and condition of the central heating system. The varying iron concentration has an effect on the colour of the molybdate dip test, but by testing and assessing the iron concentration, and then taking into account the level of assessment of the iron concentration when assessing the molybdate concentration, it has been found that accurate results can be obtained.

[0010] In one embodiment, a plurality of colour reference scales are provided for comparison with the second dip test. If the iron concentration is assessed to be in a first range, the second colour change dip test can be compared with a first colour reference scale; and, if the iron concentration is assessed to be in a second range, the second colour change dip test can be compared with a second colour reference scale. In some embodiments, there can be three or more colour reference scales for assessing molybdate, each corresponding to a particular range of values of the assessed iron concentration.

[0011] In an alternative embodiment, a single colour reference scale can form the molybdate test reference, but the mapping of the assessed value of the molybdate concentration on the colour reference scale can change depending on the assessed iron concentration.

[0012] Preferably, the first colour change dip test and the second colour change dip test can be provided as first and second pads on the same carrier. The carrier can be, for example, an elongate stick, which can be made of plastic or another water-resistant material. Preferably, one or more absorbent buffer pads can be provided between the first and second pads. This reduces the likelihood of the colour change reagent from one pad bleeding into the other pad when the pads are removed from the test sample.

[0013] A skilled person can obtain a suitable colour reference scale by preparing a plurality of samples with known iron and molybdate concentrations, performing dip tests using dip test pads impregnated with suitable reagents, and obtaining a colour reference scale for a plurality of ranges of iron concentrations. In one embodiment, a different colour reference scale for assessing the molybdate dip test is provided for each of the following ranges of iron concentrations:

[0014] if the iron concentration is assessed to be > 0 ppm and < 5 ppm, a first molybdate colour reference scale is used;

[0015] if the iron concentration is assessed to be > 5 ppm and < 10 ppm, a second molybdate colour reference scale is used;

[0016] if the iron concentration is assessed to be > 10 ppm and < 20 ppm, a third molybdate colour reference scale is used; and,

[0017] if the iron concentration is assessed to be > 20 ppm, a fourth molybdate colour reference scale is used;

[0018] The plurality of molybdate evaluation colour reference scales, and the iron test colour reference scales, can be provided on a single colour reference card.

[0019] Preferably, the evaluation of iron levels and the evaluation of molybdate levels can be performed by means of a photograph of the dip tests alongside the colour reference scales, by digital evaluation means such as disclosed in GB2576942. BRIEF DESCRIPTION OF DRAWINGS

[0020] For a better understanding of the present application, and to show more clearly how it can be carried into effect, a preferred embodiment will now be described with reference to the accompanying drawings, in which: Figure 1 A dip test carrier comprising a plurality of dip test pads, and a colour reference card comprising a plurality of colour reference scales, are shown. DETAILED DESCRIPTION

[0021] Reference Figure 1 The carrier, in the form of a plastic stick, is indicated by 10. The carrier comprises six dip test pads 12a, 12b, 12c, 12d, 12e, 12f. The carrier and all the dip test pads are dipped into a sample of central heating and / or cooling system water to be tested.

[0022] A carrier with six dip test pads is available from Precision Laboratories, Cottonwood, Arizona, USA, ZIP code 86326. The dip test pads are treated with colour change reagents designed to be sensitive to molybdate, copper and iron, and three of the test pads are designed to be sensitive to pH with different reagents.

[0023] In this embodiment, not all of the dip test pads on this particular six-pad carrier are used directly for evaluating the properties of the water. However, the molybdate test pad and the iron test pad are not adjacent, and in fact the pad between them forms a buffer, preventing the colour change reagent from leaching out of the molybdate test pad. In another embodiment, the "buffer" pad itself does not need to be treated with any reagent, of course.

[0024] The carrier 10 is shown in place on a colour reference card. The colour reference card comprises a plurality of colour reference scales 14a, 14b, 14c, 14d, 14e, 14f. Although each reference scale is shown in the figure as being adjacent to a particular pad, the reference scales are not necessarily used to evaluate the pad adjacent to them. As described in GB2576942, since the evaluation is preferably performed by software running on a mobile device, there is no significant correspondence between the scales used for evaluation and the pads being evaluated.

[0025] It should also be noted that the scale is not marked with numbers or other references, as the scale is designed for software use, which will include more reference information, allowing color comparison with the reference card to assess the amount of chemical present.

[0026] In another embodiment, the assessment can be performed "by eye", in which case it is desirable to have numerical reference information and clear instructions on the color reference card.

[0027] In the present embodiment, the color change dip test pad 12a is treated with a reagent designed to test for the presence of iron in water. It has been found that using a suitable color reference scale 14a, the amount of iron present in most samples of central heating system water can be accurately assessed, regardless of the presence of other contaminants.

[0028] The amount of iron present is itself an important test, as dissolved iron in system water is an indicator of corrosion occurrence. However, it has also been found that the amount of iron present is also important for the correct assessment of the dip test to determine molybdate levels.

[0029] In the present embodiment, four of the color reference scales shown on the card are used to assess molybdate levels, the color reference scale used for assessment being selected according to the iron level being assessed. For example, when the iron level being assessed is > 0 ppm and < 5 ppm, a first molybdate color reference scale 14c is used; when the iron level being assessed is > 5 ppm and < 10 ppm, a second molybdate color reference scale 14d is used; when the iron level being assessed is > 10 ppm and < 20 ppm, a third molybdate color reference scale 14e is used; and when the iron level being assessed is > 20 ppm, a fourth molybdate color reference scale 14f is used. In the present example, based on another dip test pad on the carrier 10, a color reference scale 14b is used to assess the level of copper.

[0030] Central heating system water can contain a variety of different levels of dissolved iron, and the present invention allows for accurate testing to determine molybdate content, which is important to ensure the correct level of corrosion inhibitor in many central heating systems, regardless of iron contamination.

Claims

1. A method of testing a molybdate concentration of central heating and / or cooling system water, the method comprising the steps of: testing the iron concentration in the central heating and / or cooling system water using a first colour change dip test, comparing the colour of the first colour change dip test to an iron test reference to assess the iron concentration; testing the molybdate concentration in the central heating and / or cooling system water using a second colour change dip test, comparing the colour of the second colour change dip test to a molybdate test reference, and assessing the molybdate concentration based on the comparison of the second dip test to the reference and based on the assessed iron concentration; wherein the molybdate test reference comprises a plurality of colour reference scales, and based on the assessed iron concentration, a colour reference scale is selected from the plurality of colour reference scales to be used for the assessment of the molybdate concentration.

2. The method of claim 1, wherein, the first colour change dip test and the second colour change dip test are provided as first and second reagent dip pads on a single carrier.

3. The method of claim 2, wherein, An absorbent buffer pad is provided between the first and second reagent dip pads.

4. The method of claim 1, wherein, the iron test reference and the molybdate test reference are provided on a single reference card.

5. The method of any one of claims 1 to 4, wherein the assessment is performed by image processing software based on a photograph of the colour change dip test next to the reference.

6. The method of claim 5, wherein, the software is adapted to acquire the photograph by a camera built into a device running the software.

7. A non-transitory computer readable medium containing instructions which, when executed on a computer processor, implement the method of any one of claims 1 to 6.

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