One of the main problems in the operation of autonomous heating systems and water supply is the pressure drop. Water hammer in the water supply system and water heating, resulting from this sharp drop, can cause serious damage. He needs to be warned, agree?
We will tell how to prevent the phenomenon and neutralize its negative consequences, ensuring the continuity of the contours. You will learn from us what methods are used to eliminate water hammer in systems transporting water to water-filling valves and heating devices.
The nature of the water hammer is disassembled in the article presented for review. Lists preventive measures that preclude the occurrence of a dangerous situation. Schemes, photo-illustrations and video are attached for visual perception of a difficult topic.
The content of the article:
- What is a water hammer?
- Causes of water hammer
How to avoid problems?
- Option 1. Smooth system overlap
- Option # 2. Application of automatic devices
Ways of complex system upgrade
- Method # 1. The use of compensators and shock absorbers
- Method # 2. Installation of a diaphragm type safety valve
- Method # 3. Equipping a thermostatic control valve with a shunt
- Method # 4. Using a thermostat with super protection
- Preventive maintenance
- Conclusions and useful video on the topic
What is a water hammer?
The hydraulic shock is a short-term but significant pressure surge in a fluid-filled system. This phenomenon occurs at the time of the collision of the fluid flow with an obstacle in its path. The characteristic examples of the occurrence of such barriers include a sharp overlap of valves, a sudden stop of the pump, an airlock, etc.
Faced with an obstacle, the flow of water by inertia continues to flow with the speed with which it moved until the appearance of a barrier. The first layers that are in contact with an obstacle are compacted at the same speed due to the arrival of the next layers.
Due to the constant injection of new layers of flow, the pressure is rapidly increasing, and the fluid is “looking” for a way to dump its part in order to discharge it.
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The consequences of water hammer in the water supply and heating system cannot always be immediately determined. Sometimes the circuit looks and works quite normally.
However, the impact of water hammer will necessarily affect the performance of the network. For example, will cause depressurization of the pipe along the weld
A common consequence of a water hammer in the water supply is a broken metal pipe through the threaded connection.
Metal-plastic and plastic pipelines are extremely sensitive to hydraulic impacts. Such situations should not be allowed, especially if the pipes are laid in a hidden way.
Water hammer almost always makes sanitary plumbing seals unprofitable - gasket fittings and reeling at the joints of pipes
There are frequent cases when the bodies of water faucets and filters are splitting due to a water hammer. A small fistula that appeared at first is sure to increase and it will flow
After exposure to pressure, many times exceeding the operating parameters, the factory settings of the pressure gauges are lost or they generally become unusable.
Usually after the occurrence and impact of water hammer, water flow meters have to be removed and calibrated again.
Danger of late water hammer
Rupture of welded metal pipes
Broken water pipe thread
Plastic pipe rupture
Damage to the coils and gaskets
Shut-off valves in plumbing
Failure of the pressure gauges
Problems with water meters
A similar situation almost always occurs when the flow breaks ball valve or latch. At first glance, the phenomenon may seem harmless. And because many owners do not give him special attention.
But in fact, when detecting the prerequisites for a maturing defect in pipes and fittings, it is worthwhile to eliminate it as soon as possible. Indeed, due to hydraulic shock, splits and cracks appear in the heating system, as well as equipment damage.
This serious problem can be preceded by clicks and knocks, as well as extraneous noise in the water supply pipes, accompanied by a characteristic “growl”.
Flashing occurs predominantly in those places where larger pipes are connected to pipes of smaller cross section. Water running along their inner walls faces an imperfect, but still an obstacle.
The regular occurrence of water hammer adversely affects the operation of the system, significantly reducing its service life.
In the event of emergency situations from the effect of hydraulic shock may suffer:
- equipment (tightness of pipelines is broken and heating devices are destroyed);
- property (water flowing from the damaged network will flood the housing and damage furniture);
- household (if a violation occurred in the heating system, there is a danger of severe thermal burns).
According to statistical data, the “lion's share” of pipeline accidents, which is about 60%, is due to hydraulic shock. More often, the negative effects of such an effect can be observed in worn-out pipes, covered with corrosion.
The consequences of regular hydrodynamic impacts can be unpredictable, and the most common among them is a breakthrough.
Most of the trouble he delivers long pipelines, for example, during the arrangement "Warm floor"through the circuits of which the liquid heated to a certain temperature circulates.
The degree of damage depends largely on the place of occurrence of the obstacle: if it is at the beginning long pipeline, the value of the increased pressure will be insignificant, but if at the end - much higher.
Most often, the effect is manifested when the pipes of different diameters were involved in laying the heating system. If the "mixed" pipes with the help of adapters are not brought to a common "denominator", an increase in pressure in the heating system is inevitable. In this situation, to protect the system, the circuit is equipped with a special valve - a thermostat.
Causes of water hammer
The physical nature of this phenomenon lies in the complete loss or significant reduction in the capacity of the water pipes, as a result of which the fluid pressure in the system rises.
In houses where engineering communications were illiterately designed and equipped, it is often possible to hear characteristic tapping and clicking in the pipeline.
They are an external manifestation of water hammer and occur when a fluid circulation suddenly stops in a closed system, and then its movement also suddenly resumes.
In the role of natural obstacles in the pipeline often air plugs, adapters from a larger diameter to a smaller one, or installed stop valves
If an obstacle arises in the path of a water stream moving at a certain speed, its movement speed slows down and the volume continues to increase. Finding no way out, it forms a backward wave, which, colliding with the main water mass, increases the pressure in the system. Sometimes it can reach a threshold of 20 atm.
Due to the tightness of the line, the accumulated volume has nowhere to go, but powerful energy still seeks to find a way out to the external environment. The impact force resulting from such a collision creates the danger of a pipe bursting, which does not have an adequate margin of safety.
For this reason, for the arrangement of the system it is necessary to use seamless water-gas pipes, corresponding to GOST 3262-75, or pressure metal-plastic analogues produced according to GOST 18599.
From the permanent impact of water energy, both the pipeline itself and the rigid elements of the system will gradually or quickly collapse.
The main factors provoking the occurrence of water hammer in pipes are:
- interruptions in operation or failure of the circulation pump;
- the presence of air in a closed loop system;
- power outages;
- with a sudden overlap of valves.
Short-term increase in pressure in a closed circuit due to the discharge of fluid over the set standards may occur if the impeller starts its movement at high speeds when the pump is turned on.
Recently, with the arrangement autonomous heating system instead of old valves and valves, ball valves are increasingly being used, the device of which does not provide for smooth operation.
Their ability to have a high-speed effect has a reverse side, being one of the most common causes of a water hammer.
If at start-up the system does not release air from it, when the ball valve opens, there is a collision of air with a practically incompressible fluid.
In terms of safety, screw taps are more preferable, since due to the gradual unwinding of the axle box, they ensure smooth opening / closing of the valves.
A similar situation occurs when air is not released from the circuit before the system is started. At the time of opening the tap water is faced with an airlock, which in a closed system is a kind of pneumatic shock absorber.
How to avoid problems?
To reduce the intensity and neutralize the effect of overpressure will help competent protection of the water supply system.
Protective mechanisms for autonomous systems against hydraulic shock in most cases are aimed at smoothing the flow of water mass
To prevent the creation of excess pressure of a single and permanent nature both in a separate section of the circuit and in the whole system, a number of basic measures are used.
Option 1. Smooth system overlap
This is one of the basic requirements for starting and shutting down piping systems, which is clearly spelled out in regulatory documents.
The fact is that the energy of water hammering due to the elasticity of the pipe walls acts simultaneously not with all of its strength. Due to the compensation of elastic deformations, it is divided into several time intervals.
And therefore, with the same total impact force, the impact power at a certain moment will decrease significantly. Through a smooth start, it is possible to prolong the process of pressure build-up, minimizing significant damage to the system.
When choosing valves, preference should be given to products that have a relatively large water span.
Cranes, the design of which provides a large gap until the moment of water shut-off, are installed at the equipment installation stage.
Option # 2. Application of automatic devices
Automation should be configured for smooth correction of static pressure in the system. To achieve the desired effect, the installation of pumps with automatic change in the speed or the units with electronic control, which are equipped with built-in frequency converters, helps.
The use of automatic systems will allow to control the flow of fluid, as well as read the testimony of its pressure in the pipeline
Pumps equipped with automatic adjustment of the engine speed can smoothly increase / decrease the pressure in the system. At the same time, the software simultaneously performs two tasks: it tracks the pressure change in the water supply system and automatically adjusts the pressure.
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Automatic control systems for pumping equipment in autonomous water supply networks work only in tandem with hydraulic accumulators.
The hydraulic tank included in the circuit with an elastic membrane inside allows you to create a supply of water and form a compensating air chamber that will smooth out the effects of excess pressure
In closed heating systems, a membrane tank, an expansion tank, can be prevented by a hydraulic shock. It is red, structurally similar to the hydraulic tank, but it performs exclusively pressure compensation work during the expansion of the coolant.
If in the water supply system include additional pumping stations designed for pumping water from the reservoir to the consumer, the responsibility for reducing the action of water hammer is partially assigned to of them
Accumulator against water hammer
Membrane tank action
Diaphragm tank for closed heating
Additional pumping station
Ways of complex system upgrade
Comprehensive modernization of the system involves the installation of equipment aimed at neutralizing the effects of overpressure.
Method # 1. The use of compensators and shock absorbers
Dampers and hydroaccumulators simultaneously perform three functions: collect the liquid, while eliminating its extra volume from the system, and also help to prevent undesirable phenomena.
The compensating device, the role of which performs the accumulator, set in the direction water movement in those intervals of the heating circuit, where the probability of pressure fluctuations in the system.
The accumulator or extinguisher is a steel flask with a volume of up to 30 liters, including two separated by a rubber or rubber membrane section.
When an overpressure occurs in the system, the water column of the first section begins to press on the separation membrane, due to which it bends in the direction of the air chamber
As the pressure rises, water hammering “drops” into the tank. Due to the bending of the rubber membrane in the direction of the air chamber at the moment of raising the water column, the effect of artificially increasing the volume of the contour is achieved.
Pipes made of heat-resistant reinforced rubber or elastic plastic are used as damping devices.
The elastic material of the damping devices spontaneously quenches the energy of a water hammer at the point where the pressure has reached a critical value.
To achieve the desired effect, it is enough to use a product with a length of 20-30 cm. If the pipeline has a greater length, the area of the shock absorber is increased by another 10 cm.
Method # 2. Installation of a diaphragm type safety valve
Diaphragm-type safety valve is placed on the pipeline outlet near the pump in order to release a predetermined amount of water with excess pressure.
The safety valve, equipped with a rigid seal, which serves as a quick pressure relief, is a reliable autonomous system fuse.
Depending on the manufacturer and type of model, the safety valve is driven by an electric command of the controller, or by using a quick-action pilot device.
The device triggers when the pressure exceeds the safe level, protecting pump station with a sudden stop of the equipment. At the time of a dangerous surge of pressure, it opens fully, and when it drops to a normal level, the regulator closes slowly.
Method # 3. Equipping a thermostatic control valve with a shunt
The shunt is a narrow tube with a lumen of 0.2-0.4 mm, which is set in the direction of circulation of the coolant. The main task of the element - with the appearance of overloads gradually reduce pressure.
A narrow tube, the cross section of which does not exceed 0.2-0.4 mm, is placed on the side from which the liquid enters the thermostat
The method of shunting is used when arrangement of autonomous systems, which pipeline is made only from new pipes. This is due to the fact that the presence of rust and sediment in old pipes can reduce the efficiency of shunting to “no”. For this reason, when using a shunt at the entrance to the heating circuit, it is recommended to install effective water filters.
Method # 4. Using a thermostat with super protection
This kind of fuse that monitors the pressure in the system and does not allow it to work after the indicator reaches a critical point. The device is equipped with a spring mechanism placed between the thermal head and the valve. The spring mechanism is activated at an overpressure, preventing the valve from completely closing.
Such thermostats are installed strictly according to the direction indicated on the case.
In addition to strictly observing the rules for operating pipelines, timely preventive measures help prevent accidents. After all, all processes in the water supply system or heating circuit are interconnected. And the water hammer is only the final destructive “drop” that can lead to negative consequences against the background of the unsatisfactory technical condition of the water supply system.
Pipeline vibrations and changes in pressure values contribute to the formation of microcracks in the metal structure. The defects formed over time upon the onset of a water hammer immediately manifest themselves in areas of increased internal stress: mechanical joints, bends and welding seams.
Prevention consists in balancing the heating system, which is carried out after the completion of installation or the repair of heating in a private house
The main complex of work performed in the prevention:
- security group health check: safety valve, air vent and pressure gauge;
- periodic pressure check behind the diaphragm of the expansion tank, and if unsatisfactory results are found, and its adjustment;
- system leak testing and checking the degree of pipe wear;
- valve position trackingnd shut-off and control valves for leakage;
- regular check of filters, delaying scale, sand and particles of rust, if necessary - cleaning and washing elements;
Prevention, aimed at maintaining the good condition of water supply and heating system, includes simple types of work. But you should not ignore them. After all, this can lead to significant spending of money and time to carry out full repair work.
These protection measures are most effective if they are applied in a complex. But thanks to an integrated approach to solving a problem, you will be able to neutralize the negative consequences and thereby prolong the service life of the system.
Conclusions and useful video on the topic
Video # 1. Water hammer as it happens:
Video # 2. Test of the effectiveness of the damper:
Water hammer in the water supply system is a frequent occurrence that can cause serious harm. And your task is to fix the problem as soon as possible.After all, if you repeat the situation, the elements of the system will soon fail. And repair after that will cost much more.
Ask questions and write, please, comments in the block below. We are waiting for your stories about how you recorded a water hammer in the system or noticed its consequences. Interested in your opinion on the information provided.