Previously, we talked about the air conditioning of Hall in a pioneer hotel in Spain. This time we will focus on the enforcement of cold water and DHW.
Keywords: DHW = Domestic Hot Water | ACS = Agua Calente Sanitaria
Background
The hotel, which is a high-rise building, presents pathologies in the sanitary water installation that affects the development of hotel activity. This is due to the fact that any incidence in the general networks of high plants, both cold and hot, leaves plants 11 to 19 without service.
Object
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The purpose of this report is to analyze the projected and enforced installation in the lower basement, first and tube upstairs to floor 10.
In the analysis, the project documentation and the installation will be verified, the pathologies detected, looking for possible reasons why they have occurred and the reliability offered by the current installation, to take the necessary measures to avoid the incidents that have been occurring.
situation analysis
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In the analysis carried out, a series of pathologies are observed that can pose problems in the short and medium term and that must be verified, studied and repaired. It is therefore recommended that the following sections be analyzed and studied:
Pipelines
The installed pipes are:
- PVC: cold water
- CPCV: Hot water
The PVC and CPVC pipes have the peculiarity that for each diameter the pressures they support are different.
As the diameter increases, the allowable pressure decreases.
in other materials, such as polypropylene, the pressure that it is capable of withstanding is the same for all the diameters of the same series and to achieve this, the manufacturers increase the thicknesses as the diameter increases.
in the CPVC The allowable pressure decreases with temperature.
at 60ºC., 50% of the pressure they withstand cold.
at 71.1ºC., 40% of the pressure they withstand cold.
On the other hand, if the joints are made by mechanizing the tube, a weakening is caused by reducing the thickness in the thread zone.
In PVC and CPVC manufacturers indicate that a groove can reduce the pressure supported by around 50% of what it can withstand under the conditions of the installation.
Another peculiarity of plastic tubes is its high coefficient of expansion with respect to metallics and that require a study implementing bending arms and expansion lyres; With supports that not only have to guarantee the weight of the tube filled with water, but also the stresses that occur in the expansions, establishing fixed points and sliding points, according to the diameter of the tubes and the temperature of the water.
In general, pipes installed in all cases They are higher or slightly higher than the pressures they support, considering a temperature of 60°C in domestic hot water.
During the treatment of Legionella (70ºC.), The nominal pressure permissible by the tubes, set by the manufacturer, has a significant reduction. At some points the pressure in the installation is higher than that supported by the tube at 70ºC.
In case of proceeding to a threaded machining, the pressure would decrease to limits lower than those allowed. Therefore, in no case can it be machined with threads.
Domestic hot water collector
The pressures to which the domestic hot water collector is subjected is higher than the nominal indicated by the manufacturer for the 8-inch tube, therefore, if it has been built with an 8-inch tube, it must be replaced. In addition, it was constructed of black iron which is not supported by the DB-HS4 of the Technical Code as suitable for sanitary water.
Given the location and the pressures it supports, the manifold must be built in AISI 316 stainless steel.
With these diameters the nominal pressures of the hot tubes are reduced, so it would be recommended Build it in AISI 316 stainless steel, once the suitability of this material has been verified with the analyzes of the waters.
soporations
There are no fixed points that are necessary to support the pipe and to guarantee expansion. There are no dilators, which are necessary in the section between ground floor and level 10. The necessary supports must be studied in each case.
Flanges and union accessories
are subjected to an effort for which they have not been designed. The valves have to be freed from any effort, their mission is to open or close and not be subjected to pressure, other than the point where it is located.
materials
In this case the reference is to the use of black iron, which are not approved for sanitary water.
In relation to the plastic pipes, its behavior in cold water is correct, as long as its assembly is adequate and the pressures are higher than those produced in the installation.
Therefore, in the event that the property is proposed to change the pipe in domestic hot water in the areas of greater pressure, it would have to be AISI 316 stainless steel, once an analysis of the compatibility of the water with the pipe has been carried out. In this case, polypropylene will be installed.
possible solutions
- Total support reform.
- Solve the expansion in the hot water and return tubes.
- Replace items that use non-approved materials for sanitary water.
- Replace the 8” domestic hot water manifold if it has been built with a pipe, as the nominal pressure is under operating conditions below the existing ones.Remember that it was built with black iron.
- In the case of the cold water collector, galvanized steel that has a limited life span should not be used.
- In hot water it would not be valid to install galvanized steel tube because it is not suitable for high temperatures.
- If metal tube is used, it must be AISI 316 stainless steel, once its compatibility with the water has been verified.
- All materials used must be suitable for sanitary water.
- Possible deletion of the critical point: The hydraulic circuit between the pressure group and the plant 10. Any minor incident leaves 9 plants out of service; Therefore, the removal of this point is recommended.
Repair
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In this case of enforcement of cold water and DHW in the hotel, the failed coupling is replaced by two VitaLuc (Victaulic) flanges between the area where a failed nipple and the top of the pipe were.
The placement of two PTR brackets with steel flanges that support the pipe in this area more firmly is also carried out.
- It is not correct to install threaded joints.
- It is not correct to install steel flanges.
- The pipe must be rigidly fixed so that it is aligned with the flange.
- The fixing has to support the weight of the pipe filled with water and in the case of hot water, in addition to the efforts caused by the expansions.
- It cannot exert the pressure caused by its weight on the flange.
- It cannot exert pressures caused by a lack of linearity on the bridle, which create efforts that end up causing cracks.
- The degree of tightening given to the flange must be the one set by the manufacturer.
