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start [2019/02/06 13:43] 79.246.102.94 [Expansion Vessels (Constant Pressure)] |
start [2019/02/07 10:17] (current) superman [==== Chemical Water Treatment and Water Conditioning ====] |
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| Many heating and cooling systems suffer from chronic problems.No matter whether they are small domestic systems or large commercial systems in hospitals or airports. | Many heating and cooling systems suffer from chronic problems.No matter whether they are small domestic systems or large commercial systems in hospitals or airports. | ||
| - | The most common problems are known to all installers and maintenance companies, like sticking thermostatic radiator valves, frequent pump failures, blocked valves, noisy boilers, leaks, increasing energy consumption, system pressure dropping and requiring frequent top-ups, black sludge and reddish-brown water. | + | Many of the symptoms are known to all installers and maintenance companies, like sticking thermostatic radiator valves, frequent pump failures, blocked valves, noisy boilers, leaks, increasing energy consumption, dropping system pressure and requiring frequent top-ups, black sludge and reddish-brown water. |
| Often these problems are seen as normal and unavoidable. Left untreated they will inevitably lead to component and in the end even complete system failure. Power flushing and chemical treatment often fail to cure the problem | Often these problems are seen as normal and unavoidable. Left untreated they will inevitably lead to component and in the end even complete system failure. Power flushing and chemical treatment often fail to cure the problem | ||
| - | and can even make the problem worse. | + | and frequently make the problem worse. |
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| There are also tables available that help to estimate the system volume based on the duty of the boiler or chiller. But care needs to be taken if systems have unusually long pipe runs or have additional buffer tanks. These need to be added separately. | There are also tables available that help to estimate the system volume based on the duty of the boiler or chiller. But care needs to be taken if systems have unusually long pipe runs or have additional buffer tanks. These need to be added separately. | ||
| - | If the volume is estimated it is recommended to err on the high side. This may mean that the expansion vessel is larger than required but this doesn’t matter. In fact the additional capacity can be utilised to increase the water reserve Vwr. | + | If the volume is estimated it is recommended to err on the high side. This may mean that the expansion vessel is larger than required but this doesn’t matter. In fact, the additional capacity can be utilised to increase the water reserve Vwr. |
| ==== Expansion Volume ==== | ==== Expansion Volume ==== | ||
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| ==== Water Reserve ==== | ==== Water Reserve ==== | ||
| - | In addition to the expanded water the vessel also has to accomadate a reserve. The reserve ensures that when small amounts of water are lost from the system then Expansion vessel can still transfer its pressure from the gas cushion to the water side. An empty vessel cannot maintain system pressure. | + | In addition to the expanded water, the vessel also has to accommodate a reserve. The reserve ensures that when small amounts of water are lost from the system then Expansion vessel can still transfer its pressure from the gas cushion to the water side. An empty vessel cannot maintain system pressure. |
| The reserve Vwr=0.005.Vs (min. 3l or more) In accordance with EN12828 | The reserve Vwr=0.005.Vs (min. 3l or more) In accordance with EN12828 | ||
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| ==== Vessel Acceptance or Pressure Factor ==== | ==== Vessel Acceptance or Pressure Factor ==== | ||
| - | Every fixed gas charge vessel has an acceptance. The acceptance is the amount of water relative to the total vessel size it can absorb without exceeding a maximum pressure. In other words the vessel must leave room for the gas side. The more the fixed gas filling is compressed the higher the pressure in the vessel and thus the system. | + | Every fixed gas charge vessel has an acceptance. The acceptance is the amount of water relative to the total vessel size it can absorb without exceeding a maximum pressure. In other words, the vessel must leave room for the gas side. The more the fixed gas filling is compressed the higher the pressure in the vessel and thus the system. |
| - | The acceptance of a vessel is dependant on the working pressure range of the system. That is why the acceptance is determined by the pressure factor Pf.To calculate the pressure factor it is first necessary to determine the gas fill pressure P0 and the maximum or end pressure Pe. | + | The acceptance of a vessel is dependant on the working pressure range of the system. That is why the acceptance is determined by the pressure factor Pf. To calculate the pressure factor it is first necessary to determine the gas fill pressure P0 and the maximum or end pressure Pe. |
| **Pf=(pe+1)/(pe-p0)** | **Pf=(pe+1)/(pe-p0)** | ||
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| ==== Gas Fill Pressure ==== | ==== Gas Fill Pressure ==== | ||
| - | The gas fill pressure is the pressure of the gas pocket inside the expansion vessel. It is very important that this is set correctly. Most expansion vessels are supplied pre-charged to a `standard´pressure usually 1 or 1.5barg. However this pressure must always be checked before installation and adjusted to suit the specific system it is installed in. The position of the expansion vessel in the system also needs to be taken into account. | + | The gas fill pressure is the pressure of the gas pocket inside the expansion vessel. It is very important that this is set correctly. Most expansion vessels are supplied pre-charged to a `standard´pressure usually 1 or 1.5barg. However, this pressure must always be checked before installation and adjusted to suit the specific system it is installed in. The position of the expansion vessel in the system also needs to be taken into account. |
| **P0=Hst+0.3 barg** | **P0=Hst+0.3 barg** | ||
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| - | If the next biggest vessel size is selected it is possible to use the extra capacity as additional water reserve. | + | If the next biggest vessel size is selected it is possible to use the extra capacity as an additional water reserve. |
| The new water reserve can be calculated | The new water reserve can be calculated | ||
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| * Incorrect pump position | * Incorrect pump position | ||
| - | ===== Types of corrosin Monitors ===== | + | ===== Types of corrosion Monitors ===== |
| There are a number of ways that corrosion can be monitored either directly or indirectly. | There are a number of ways that corrosion can be monitored either directly or indirectly. | ||
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| Devices such as micro-bubble separators, pressure step degassers, automatic air vents etc. cannot prevent corrosion. The oxygen in the air bubbles reacts very quickly with the steel it comes into contact with.This happens faster than the separators can expell the air. If the expelled ´air´is analysed it is found to be mainly consisting of nitrogen. | Devices such as micro-bubble separators, pressure step degassers, automatic air vents etc. cannot prevent corrosion. The oxygen in the air bubbles reacts very quickly with the steel it comes into contact with.This happens faster than the separators can expell the air. If the expelled ´air´is analysed it is found to be mainly consisting of nitrogen. | ||
| - | ==== Chemical Water Treatment and Water Conditioning ==== | + | ==== Chemical Water Treatment and Water Conditioning==== |
| The condition of the fill and system water can have a marked effect on the corrosion potential. Water is a cheap and plentiful medium and is, therefore, the preferred liquid. Water isn't just water and water chemistry is very complex. It can be highly corrosive to steel and other metals if certain values such as pH and conductivity are unfavourable. | The condition of the fill and system water can have a marked effect on the corrosion potential. Water is a cheap and plentiful medium and is, therefore, the preferred liquid. Water isn't just water and water chemistry is very complex. It can be highly corrosive to steel and other metals if certain values such as pH and conductivity are unfavourable. | ||
| There are different methods of achieving the right water chemistry. The water can be either conditioned or chemically treated or both. | There are different methods of achieving the right water chemistry. The water can be either conditioned or chemically treated or both. | ||
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