Method for treating domestic water supply installations

Abstract

A method for treating a domestic supply water circuit, that comprises injecting a treatment product comprising silicates into the water flowing in said circuit in order to form a film on the inner surfaces of said circuit, characterised in that the injection of the treatment product comprises at least one step of injecting silicates at a concentration of between 100 and 200,000 milligrams per litre (mg/L) into the water flowing in said circuit for a period of between 10 minutes (min) and 24 hours (h), the flow rate of water flowing in the circuit being controlled within a range of between 0.05 and 100 litres per minute (L/min) and the temperature of water flowing in the circuit being controlled within a range of between 40 and 65 C.

Claims

1. A method for treating a sanitary water circuit of a sanitary water system, comprising injecting a treatment product comprising silicates into the water circulating in said circuit in order to form a film on the inner surfaces of said circuit, wherein the injecting of the treatment product comprises at least one step of injecting silicates, when the sanitary water system is not in operation, at a concentration of between 100 and 200,000 milligrams of silicon per litre of water (mg Si/L water) into the water circulating in said circuit for a period of less than 48 hours (h), at a circulating water flow rate in the circuit in a range of between 0.05 and 100 litres per minute (L/min) and at a circulating water temperature in the circuit in a range of between 40 and 65 C.

2. The method according to claim 1, wherein the silicate concentration in the water circulating in said circuit is adjusted between 500 and 50,000 mg Si/L water.

3. The method according to claim 2, wherein the silicate concentration in the water circulating in said circuit is adjusted between 1,000 and 20,000 mg Si/L water.

4. The method according to claim 1, wherein the injection step lasts between 30 minutes and 12 hours.

5. The method according to claim 4, wherein the injection step lasts between 1 hour and 4 hours.

6. The method according to claim 1, wherein the circulating water flow rate in the circuit is adjusted in a range between 0.05 and 10 L/min.

7. The method according to claim 1, wherein the circulating water temperature in the circuit is adjusted in a range between 50 and 60 C.

8. The method according to claim 1, wherein the method comprises at least two treatment product injection steps.

9. The method according to claim 1, further comprising at least one drying step consisting of emptying the water circuit for a period of between 5 minutes and 2 hours, after at least one of the treatment product injection steps.

10. The method according to claim 9, wherein the at least one drying step is performed after each treatment product injection step.

11. The method according to claim 9, wherein the at least one drying step lasts between 10 minutes and 1 hour.

12. The method according to claim 1, wherein the sanitary water circuit comprises a cold water circuit, and the method further comprises a step of interconnecting the cold water circuit with a hot water supply configured to circulate hot water in the cold water circuit during injection of the treatment product.

13. The method according to claim 12, wherein the hot water supply is a hot water circuit, and the interconnecting of the cold water circuit with the hot water circuit circulates hot water in the cold water circuit during injection of the treatment product.

14. The method according to claim 12, wherein the hot water supply is generated by an external water heater.

15. The method according to claim 1, wherein the silicates are in the form of sodium silicates in solution.

16. The method according to claim 1, further comprising a step of cleaning the sanitary water circulation circuit before injecting the treatment product comprising silicates, the cleaning step comprising injecting acid into the sanitary water circulation circuit.

17. The method according to claim 1, further comprising, after the completion of the step of injecting the treatment product comprising silicates into the water circulating in said circuit in order to form a film on the inner surfaces of said circuit, continuously injecting the treatment product comprising silicates in an amount proportional to the volume of water entering the sanitary water circulation circuit, the maximum amount of product injected not exceeding a >alue set by food standards.

Description

(1) Other advantageous aims and aspects of the invention will become apparent from reading the detailed description of embodiments and the drawings.

(2) FIG. 1 is a diagram illustrating in an overall way a method for diagnosing and treating sanitary water installations according to an embodiment of the invention;

(3) FIG. 2 is a diagram illustrating a method for treating a sanitary water installation according to an embodiment of the invention;

(4) FIG. 3 is a graph illustrating the treatment steps as a function of time of a portion of the method according to an embodiment of the invention;

(5) FIG. 4 is a schematic view of a sanitary water installation configured for a treatment method according to a first embodiment of the invention;

(6) FIG. 5 is a schematic view of a sanitary water installation configured for a treatment method according to a second embodiment of the invention;

(7) FIG. 6 is a schematic view of a sanitary water installation configured for a treatment method according to a third embodiment of the invention;

(8) FIG. 7 is a schematic view of a sanitary water installation configured for a treatment method according to a fourth embodiment of the invention.

(9) Referring to the figures, a method for treating a sanitary water circuit comprises injecting a treatment product comprising silicates into the water circulating in said circuit in order to form a film on the inner surfaces of said circuit. This treatment method may be preceded by a step S0 of diagnosing the condition of the pipes of the sanitary water system and, depending on the results, by a decision on the processes to be carried out as illustrated in FIG. 1.

(10) Referring to FIG. 2, a first step S1 comprises preparing the treatment installation and configuring the sanitary water system for the impregnation process S3, S4. The configuration of the system may notably comprise interconnecting a cold water circuit with an external water heater and/or interconnecting a cold water circuit with a hot water circuit of the sanitary water system of a building or part of a building, so that the temperature of the cold water circuit can be increased to an optimal temperature for the impregnation process. The temperature may be adjusted by controlling the mixture (flow rate) of hot water and of cold water injected into the circuit under treatment during the impregnation process. Various means for automatically adjusting the flow of inlet hot and cold water in order to stabilise the outlet temperature, well known per se, may be used in the treatment installation to adjust the treatment temperature.

(11) The treatment method according to the invention comprises a silicate film impregnation process S3, S4 which is carried out when the water system is not in normal operation. The impregnation process S3, S4 is a one-time event preferably carried out in under 12 h in order to limit the shutdown of the sanitary water system. The treatment method may also comprise, after the impregnation process S2, a process S6 of continuous injection of the treatment product comprising silicates in an amount proportional to the volume of water entering the sanitary water circuit, the maximum amount of product injected not exceeding a value set by food standards. Before impregnation, the treatment method may further comprise a process S2 for cleaning the sanitary water circuit. The cleaning step may notably comprise injecting acid into the sanitary water circuit.

(12) The positioning of the impregnation process S3, S4 is shown in FIGS. 1 and 2. It is performed: In general, after a cleaning process S2, but also at any other time in the life of a sanitary water system, for example, in the case of preventive treatment on a portion of a new circuit. In general, prior to operation with continuous, food standards-compliant treatment S6, but also sometimes prior to operation without treatment, such as, for example, in the case of a pipe in good condition undergoing cleaning due to scale, and where impregnation is applied to avoid problems of coloured water.

(13) Unlike the later steps of over-dosage and of continuous treatment S6, the sanitary water system is not in operation during the impregnation process S3, S4. This makes it possible to apply various silicate injection procedures as well as to use different physical and chemical silicate injection parameter values which greatly facilitate formation of the protective film.

(14) This process is also ideally composed of an alternation of two steps: A step S3 of injecting a silicate solution into the pipes at a concentration exceeding food standards and at temperatures varying between 35 and 65 C., preferably between 40 and 60 C. The purpose of this injection period is to deposit a silicate layer rapidly. A step S4 of drying the protective film, the objective of which is to harden and stabilise the layer by desiccation. This step enhances the resistance of the protective film, but it is not essential, and the impregnation process may also be carried out by an injection step alone.

(15) Ideally, the impregnation procedure comprises a plurality n of cycles, notably at least two cycles, but preferably three cycles, or more. Each cycle comprises an injection step S3 which may be followed by a drying step S4, or simply by a waiting period without emptying the water circuits. The drying step may be performed by emptying the water circuit and allowing air to enter the circuit, followed by a waiting period that may be between 5 minutes and 4 hours, but is preferably between 10 minutes and 1 hour, for example between 20 and 40 minutes. In the example shown in FIG. 3, there are three injection cycles of about 2 hours each, and three drying cycles of about 30 minutes each.

(16) In a variant, one or more of the drying steps may comprise a forced blowing of air, or of a gas that promotes drying of the layer of treatment product, into the circuit under treatment. The forced blowing may be carried out, for example, by means of an air compressor or by means a cylinder of compressed gas.

(17) The adjustable parameters of the injection process S3 are as follows: number of cycles, injection phase duration, silicate concentration (calculated in mg Si/L water), water flow rate and injection temperature. The table below suggests operational values for these various parameters.

(18) TABLE-US-00001 TABLE 1 Values of the various parameters involved in the injection phase Advantageous Preferential Possible example range range Number of cycles () 3 2-10 1-50 Injection duration 2 h 30 min to 10 min to (h, min) 12 h 24 h Si concentration 5,000 mg/L 500 to 100 to (mg Si/L water) 50,000 mg/L 200,000 mg/L Water flow rate 0.3 L/min 0.05 to 0.05 to (L/min) 10 L/min 100 L/min Injection 55 C. 50 to 60 C. 35-65 C. temperature ( C.)

(19) The amount of silicates injected can be defined by the relationship:
M.sub.i=C.sub.i*Q*t(1)
Where Ci is the inlet water silicate concentration (g/L) Q is the water flow rate (L/sec) t is the injection duration (sec)

(20) The deposition yield is very sensitive to many parameters. Indeed, a silicate deposition yield can be defined by:

(21) $\begin{array}{cc}=\frac{M_d}{M_i}& \left(2\right)\end{array}$
Where Md is the mass of silicate deposited (g) Mi is the mass of silicate injected (g)

(22) This yield is particularly sensitive to temperature, but also to silicate concentration, injection duration, flow rate, flow velocity and probably other environmental parameters. In particular, the deposition yield is lower in the case of injection in cold water than in hot water.

(23) The corresponding volume of water to carry out the deposition can be defined by the relationship:
Vw=Md/Ci
Where Vw is the volume of water (m3) Md is the mass of silicate deposited (kg) Ci is the concentration of silicate injected (kg/m3)

(24) This then leads to a relationship establishing the effect of the main parameters (yield, concentration, flow rate and injection time) on the mass of silicates deposited.
M.sub.d=*C.sub.i*Q*t(3)

(25) It should be noted that the deposition yield itself also depends on these main parameters (concentration, flow rate and injection time) and on environmental parameters, such as pH, hardness, alkalinity, etc., as presented in the following equation:
=(C.sub.i,Q,t,par.env.)(4)

(26) The various values proposed in Table 1 are based on the following arguments:

(27) Si Concentrations: Upper limit of 200,000 mg Si/L water: this is the Si concentration found in silicate solutions comprising sodium silicates, particularly Na.sub.2SiO.sub.3. They are in the form of a viscous liquid. This is the saturation limit; at higher concentrations, saturation crystallisation appears. Optimal values between 1,000 and 20,000 mg Si/L water, particularly between 2,000 and 10,000 for injection pump flow rates typically used in sanitary water installations of buildings. For a maximum flow rate of an injection pump of 6 L/h and a water flow rate of 0.3 L/min, this corresponds to a concentration of 5,000 mg Si/L water.

(28) Injection Temperature: Lower limit of about 35 C.: temperature has a strong influence on silicate crystallisation. Below this temperature, the efficiency of silicate deposition on the inside walls of pipes becomes too low for an efficient and economical process. Upper limit of 65 C.: above 65 C., silicates tend to precipitate very quickly, which can cause deposition at the injection site, creating two problems: silicates that precipitated during injection are no longer available for downstream zones and cause an obstruction at the injection site. Optimal value around 55 C.: this is an attractive compromise between inefficiency and excessively rapid precipitation.

(29) Water Flow Rate: Lower limit of 0.01 L/min: at low flow rates, it is necessary to compensate by increasing the injection concentration or duration, as can be seen in equation (3). Upper limit of 100 L/min: the boiler must heat cold water, for example 15 C., to the injection temperature, for example about 55 C. The power consumed by the boiler is proportional to the temperature difference and to the flow rate of water to be heated as shown in relationship (5) below. Therefore, the higher the flow rate, the higher the boiler power must be.
{dot over (Q)}={dot over (m)}*c*T(5)
Where Q is the heat output of the water heater (W) m is the mass flow rate of water (kg/s) c is the heat capacity of water=4185 (J/kgK) T is the temperature difference between (K) the water heater outlet and inlet

(30) Another aspect limiting water flow is maintenance of the silicate concentration. This aspect can be shown by reversing the relationship (3). An optimal value is around 0.3 L/min, taking into account the constraints described above.

(31) Number of Injection Cycles and Injection Duration:

(32) These two parameters depend mainly on the desired quality of the silicate deposition on the wall, given that the time available is limited (generally 24 h max, even 12 h max) since it is often preferable not to shut down a water system for long periods, and preferably not more than one day.

(33) The adjustable parameters of the injection process, including the duration of an injection step, the temperature, the concentration of the treatment product, the composition of the treatment product, the duration of the treatment cycle and the water flow rate, may be essentially the same from one step to another, or may be different from one step to another. For example: the duration of one step may be longer, and/or at a lower temperature, and/or at a lower concentration, than another step, or the duration of one step may be longer, and/or at a lower temperature, and/or at a higher concentration, than another step, etc.

(34) The variation in the parameters may be particularly advantageous between the first injection cycle and the following cycle(s), depending on the condition of the pipes or on the cleaning process carried out before the impregnation process. In order to form a uniform and thin first layer serving as a homogeneous bonding surface to help the uniform growth of a subsequent layer, there may be an advantage to performing the first cycle with a lower concentration of treatment product than the other cycles, but possibly for a longer time and/or at a different temperature. Indeed, as the properties of the inner surface of the pipes before treatment or after cleaning may be highly variable along the sanitary water circuit, particularly the materials and geometric irregularities (bumps, rough edges) on the surface, the rate of film formation on the bare surface of the pipe may be highly variable from one portion of the pipe to another. Slower growth of the first layer may help form a more homogeneous film rather than help rapid growth. Thereafter, for reasons of efficiency and time savings, the growth of the film can be carried out more quickly since the first layer makes the surface properties uniform.

(35) The durations and parameters of the drying cycles may also be essentially identical from one step to another or may be different from one step to another. In particular, it may be advantageous for the duration of the last drying cycle to be longer than the previous ones in order to increase the resistance of the impregnation layer before returning to normal operation, the process being generally more efficient and economical if more drying time is allocated at the end of the impregnation process.

(36) Referring to FIG. 4, the treatment of a simple system comprising a hot water or cold water circuit is illustrated. This situation may arise for various reasons: The building to be treated does not have centralised hot water production but rather individual boilers. The building therefore only has a cold water circuit. For various reasons (different degree of corrosion, different materials, etc.), it is necessary to treat only the hot water or the cold water.

(37) In this case, the assembly is ideally designed as shown in FIG. 4, illustrating a configuration with the following features: main line 1 at the building's entrance valve 2 for stopping the flow in the building hot water supply 3 (in this example forming part of the hot water circuit of the sanitary installation)the water is thus heated from the cold water supply temperature (for example 10 to 20 C.) to the impregnation temperature, for example 55 C. The maximum water flow rate is given by the power of the water heater according to the formula (5). Depending on the building's equipment, this hot water production may be: a. The central boiler of the sanitary hot water circuit may be operated directly to treat the hot water pipes and may be diverted to treat the cold water pipes. b. If the building does not have a central boiler or its volume or heat capacity is insufficient, the element 3 may be an external hot water supply, for example an auxiliary water heater. tank 4 containing the silicate-based pipe cleaning product silicate-based cleaning product 5 suction tube 6 from the cleaning agent to the metering pump metering pump 7 for injecting silicates into the main line silicate supply pipe 8 check valve 9 silicate injection point 10 into the water flow branches 11 for directing the flow into a by-pass valve 12 for stopping the flow in the main line in order to force it through the by-pass by-pass control tube 13 which is removable and allows the quality of the silicate film deposition to be evaluated after application of the impregnation treatment valves 14 for isolating the by-pass from the flow in order to disassemble it for inspection. branches 15 feeding the various standpipes valves 16 for isolating or supplying the standpipe(s) standpipes 17 of a building's sanitary water circuit branches 18 of the various pipes taps 19 at the outlet of each pipe.

(38) In the case of several standpipes 17, it is advantageous to separate or isolate them beforehand by means of a valve. This makes it possible to work independently on different circuits of a building's sanitary water installation and to increase treatment efficiency. Note that in this case, the main flow rate can be adjusted by opening the taps. This can be done alternately or in parallel.

(39) Since the water is loaded with silicate, silicate deposits form when it flows into the sinks. It is thus advantageous to attach a flexible hose to the tap outlet to allow the silicate solution to flow directly into the trap at the bottom of the sink.

(40) It should also be noted that for cold water pipes, it is advantageous to carry out a cooling process before the water is turned back on in order to preserve the protective layer in its entirety.

(41) Referring to FIG. 5, the treatment of a dual system comprising a hot water circuit and a cold water circuit is illustrated. When it is necessary to treat the hot water circuit and the cold water circuit, one may: treat the hot water and the cold water circuit alternately according to the procedure presented in relation to FIG. 4; or proceed more advantageously to reduce working time by connecting the two circuits in series in order to treat them in a single operation as shown in FIG. 6.

(42) This second approach follows the treatment principle shown in FIG. 4, but with a modified configuration having the following additional or modified features: hot water supply 3 comes from the central boiler and not from an external auxiliary water heater flexible hoses 20 for connecting the branches 18 of the hot water circuits to the branches 21 of the cold water circuit cold water standpipe 22 valves 23 for isolating the various cold water standpipes branches 24 of the various standpipes cold water standpipes 25 branch 26 for recovering the injected silicate solution silicate recovery pipe 27 silicate recovery valve 28 isolation valve 29 for the building's cold water supply

(43) The taps 19 are removed in order to connect, using a flexible hose 20, the hot water outlet branches 18 and the cold water outlet branches 21. This makes it possible to carry out the impregnation treatment in the hot water circuit 17, 18 and in the cold water circuit 21, 22 in a single injection operation. The silicate solution is then recovered using a branch 26, a valve 28 and a silicate recovery pipe 27.

(44) Referring to FIG. 7, the treatment of a triple system comprising a hot water circuit and a cold water circuit, the hot water circuit having a loop allowing a return hot water circulation to the water heater 3. When it is necessary to treat a triple cold water and hot water system comprising a circulation loop, one may: proceed according to an approach combining the methods presented in relation to FIGS. 4 and 5 proceed according to an approach for treating the triple system in a single operation as presented below.

(45) The operating diagram is that shown in FIG. 7. It follows the principle of that shown in FIG. 5, but with a modified configuration having the following additional or modified features: hot water circulation pipe 30 (the circulation pump is not shown in this diagram) branch 31 for recovering the injected silicate solution from the circulation pipe silicate recovery pipe 33 silicate recovery valve 32 circulation water inlet isolation valve 34

(46) For this third configuration, in order to carry out the impregnation all at once, the cold water circuit and the circulation circuit may be distributed in parallel, according to a procedure similar to that described in relation to FIG. 5.

(47) When it is necessary to treat only a hot water circuit comprising a circulation circuit, the procedure is similar to that shown in FIG. 7, but without the cold water circuit.

(48) In these diagrams, the direction of flow is always presented from the hot water to the cold water because it is advantageous, the boiler being on the hot water, to avoid having to reconnect the pipes to the boiler. It is nevertheless possible to modify the positions of the inlets and outlets of the treatment solution.