faulty insulation in the backside
Pipelines in frost-prone
During the Permafrost periods with night temperatures below -15 ° C and maximum daytime values of -5 ° C, drinking water and heating pipes, but also solar pipes, keep freezing.
The VDI guideline 2069 - Freeze protection of water-carrying pipes - is to be used for the planning, construction, operation and maintenance of water-carrying systems in frost-prone areas.
Freezing is a slow processleading to the formation of a Ice plug leads. Only when the flow movement is no longer possible does the pipe freeze over its entire length. The freezing of pipes from two sides or in blocked pipe sections is particularly critical. This creates high pressures in the still liquid medium, which are far above the permissible nominal pressures of the system components and which can lead to the pipes and, in particular, connection points bursting. Every freeze presupposes a prolonged stagnation of the water.
If water-carrying pipes through outside ventilated sides are laid behind the knee sticks, these lines are particularly at risk. Faulty pipe insulation leads to this Freezing from 2 sides. But pipes that freeze evenly are in many cases still undamaged after the frost period.
When water too ice freezes, then stretches it is out and enlarged be volume. Simultaneously takes his Dense. This is why ice is lighter than water with the same volume. ice is next to the liquid and gaseous the 3. State of aggregation of water and forms at normal pressure, the presence of crystallization nuclei and a temperature lower than 0 ° C (Melting or freezing point).
Pure water only freezes at -46 ° C. By a vibration and or pollution the supercooled water freezes abruptly a. This phenomenon is also known under the term "Black ice"if z. B. supercooled rainwater hits the street and gets a Ice sheet forms.
It can happen that Lines freeze over, if bad or non-insulated pipe parts already in the Minus range (<0 ° C) have cooled down, but due to the Flow rate the water flowing past has not yet frozen. By the Switch off or that failure the pump the water comes to a standstill. Through the sudden ice formation arise very high pressures in the pipeline. Here the pipe may act like one Freezing collar.
Liquid water at minus 46 degrees - Anna Heise - German Physical Society e.V.
Chilled water and black ice - Dr. Holger Hofmann - experimentis
Pressure increase in a shut-off water-filled pipe when water is “converted” into ice. The yellow line describes the pressure curve without taking into account the elastic properties of the pipe material. If the elastic behavior is taken into account, the pressure increase is slightly lower than calculated using the example for two different copper pipe dimensions. The ones also drawn in Bursting pressures are calculated from the material parameters for copper.
Increase in pressure in the water pipe due to ice formation
Source: Dr.-Ing. Thorsten Pfullmann
|Frost protection measures in buildings that are not used constantly or infrequently|
The question arises again and again which measures have to be taken to get a Freezing of water-filled components (Water pipes, odor traps [siphons], toilet bowls, but also above-ground rain cisterns, rain barrels, garden hoses, high-pressure cleaners and pond pumps) in not all the time or rarely used buildings (vacant houses, holiday homes) prevent. When the building is not in use and a Heating not in operation should be set, then the safest option the water from all water-bearing or. water-filled components (Heating, all water pipes, devices (DHW storage), cisterns, toilet bowls and odor traps [siphons]) empty.
There are a few things to consider here.
- Water heating systems you will never be able to empty it completely and you will not be able to blow it out with compressed air. It can therefore make sense to fill the systems with a mixture of water and antifreeze, which must be checked regularly.
- If the Drinking water pipes are laid with a slope, the water can be drained at the deepest point. The lines must be ventilated at the top. It is safer to blow out the lines with compressed air. Corrosive and hygienic problems exist here in metal drinking water pipes. Such systems must be flushed and sampled when they are put back into operation.
- At electric drinking water heatern The power supply must be interrupted before emptying so that the heating element does not burn out.
- Floor drains, toilet bowls and Urinals can be dried out with a rag. It is better to add antifreeze or salt to the water. Adding salt is very unsafe.
- Odor traps The water seal on the component can be emptied at wash basins, shower trays and bathtubs But here, too, the measures that are used for the toilet bowls are preferable. Of course, these filled odor traps must not be rinsed.
- Empty odor traps let the gases from the sewage system into the building, which can lead to significant odor problems. This method should not be used, especially in furnished buildings, as the smells can settle in the facility. The entry of vermin is also reported. For these purposes meanwhile Dry siphons which are mostly only suitable for condensing boilers, geothermal heat exchangers or on cooling registers of air conditioning systems.
Becomes a building again and again used regularly (e.g. weekend house), then the heating should be on "Frost protection". When selecting the temperature, care must be taken that the rooms over Room thermostats be regulated, as z. B. in a south-facing room with a room thermostat (Reference room) is used to regulate the whole house, can still be plus degrees, while rooms facing north can already be minus degrees. Here the system temperature should be set as low as possible and the circulation pump must not be switched off automatically. You should also consider whether it would not make more sense to have the system with a Water-antifreeze mixture to fill if the house is not regularly monitored, as it goes unnoticed Heating failure which problems can occur as in an unheated building. A specialist company that adjusts this system should get a so-called "Frost letter"get signed.
Heating tapes, heating cables
Function of self-regulating heating tapes
Heating tape - heating cable
Self-regulating heating cables consist of two parallel supply conductors, embedded in a networked plastic heating element (matrix) doped with carbon particles.
If the temperature rises during operation, the plastic expands through molecular expansion. The bond between the carbon particles is reduced. The resistance increases and the performance decreases. This process is reversed when it cools down. The resistance decreases and the performance increases. In this way, the heating output adapts individually to the heat demand at each point.
This physical property of not exceeding the specified temperatures makes it possible to lay self-regulating heating cables crosswise and to dispense with a temperature limiter.
|Advantages of the self-regulating heating cable:|
- Different temperature ranges
- Demand-oriented gradation
- Chemical resistance
- Can be cut from the roll
These heating tapes are mainly used for frost protection and temperature maintenance.
Deliberate freezing of pipes
To change a valve, replace defective components or expand work, the water does not always have to be drained. Here is the use of Freezers makes sense.
|operation manual- Rems company|
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