Types of Valves :-
1. Balancing valves
2. Butterfly Valves
3. NRV (Non Return Valves)
4. Ball valves
5. Modulating control valves
6. Pressure regulating valves
7. Float valves
8. Y-strainer
9. Pot strainer
10. Expansion Tank
1. Balancing Valves - Balancing valves are used in chiller's evaporator's outlet or in chilled water supply lines. These valves have a scale marked on it to adjust the flow of water through the pipe by opening or closing the valve. At the time of commissioning the required flow (USGPM) according to design calculations is adjusted and fixed for the operation.
These valves control the flow of fluid through the system and perform the functions in many unique ways. A very effective control over mechanical and electromechanical properties is used to regulate the liquid flow rate as per parameter of design. The advance level of functionality of these valves makes them to be used in modern plumbing, HVAC, refrigeration etc. These valves may be defined as regulatory devices as well, because these are used to regulate the pressure between inlet and outlet. The main purpose of these valves to use in HVAC or plumbing application is to maintain the constant flow and pressure of liquid and to create hydraulic balance in the circuit.
These valves are very helpful tool for the designing engineers to make effective design with proper control of the liquid flow. These valves are used only for the purpose to control the water flow and to regulate the pressure. The balancing is done more effectively and proper control over flow reduces the issues of pressure and temperature.
HOW BALANCING VALVES WORK?
Different kind of balancing valves have different functions and ways to perform. These valves mostly use a perfect regulation that helps to create a constant output from variable inputs. Even if the losses in pressure change the flow rate or loss due to turbulence, after passing these valves all losses are recovered and flow rate consistency is achieved easily and more effectively.
TYPES OF BALANCING VALVES
There are two types of balancing valves.
1. Static Balancing valves
2. Dynamic Balancing valves
STATIC BALANCING VALVES
Static balancing valves are also called as manual valves. The two ports on the left as shown in figure are used to determine the pressure of the liquid before and after passing through the valve. This valve has a pool or spindle mounted on it with different ratings to manually adjust the flow rates by rotating it clockwise or anticlockwise as per requirements.
DYNAMIC BALANCING VALVES
These valves are called as constant flow valves or automatic balancing valves. These valves are used where possibility of fluctuations or turbulence is higher due to long water pipe runs. The function of these valves are performed either by drag coefficient of flow or by using differential pressure to change the valve opening. The opening or closing of the valve is performed by using a combination of electric and mechanical components or in easy words an electrical motor is used to rotate the spindle of the valve. To create a constant flow rate alternative routes or ways are used as an option to maintain the pressure.
SELECTION OF VALVES
Every valve is selected as per pressure requirements or as per application requirement. Normally PN (Nominal Pressure) rating is used to select the valves as per design and pressure requirements in the system. This rating describes the pressure wearing capacity of the valve. There will be no leakage or damage will occur if the valve is selected as per pressure limits. In HVAC mostly PN 14 and PN 16 rating valves are used.
2. Butterfly Valves :- As the name suggests the butterfly valve looks like a butterfly. These valves are used in chilled water pipes at the end and starting points of each units or pumps and all fittings are fixed in between these valves. These vavles are used for the maintenance purpose or for breakdowns to stop the flow of water. These valves too can be used for balancing but only for very low gpm flow.
3. NRV or check valves :- NRV stands for Non Return Valve. These valves are used at discharge outlets of pumps as the water in pipes once passed through these valves can't flow back. These valves has a door of either single or two high quality plates. These valves are very usefull and are used definitely in chilled water piping system to protect the pumps from sudden impact of water on its pump assembly or blades. If NRV is not used in the system the pumps motors will demage. On the body of these valves an arrow is always marked from the manufacturer to show the direction of flow of water.
4. Ball valves :- These valves are used in chilled water line of small sizes. These valves are used at the inlet and outlet of each indoor units like FCU, AHU and in cooling towers.
5. Modulating control valves :- As the name suggests the modulating control valves are used to control the flow of chilled water through the indoor units. If the temperature in the conditioned space is achieved then it will stop the supply of chilled water and by pass the chilled water to the return water pipe. These valves are operated by a electric motor on the top of this valves and motor is directly connected to the valve shutter.
6. Pressure regulating valves :- These valves are used to regulate the pressure of water in chilled water pipes at the time of commissioning.
8. Y-strainer :- Y-strainer is a very important fitting which is used in the chilled water line. Y strainer is used to remove tiny particles in water and works like a filter. Y strainer is used always in supply lines of indoor units and in suction line of pumps. This valve consists a filter in its body which works on the gravity to filter the water. These valves should be fixed in such a way that the part of the vavle which contains the perfurated sheet as a filter and can be opened comes downwards as show in the figure.
9. Pot strainer :- Pot strainer works similar to the Y-strainer but the construction of these strainers is very different. These strainers are fixed in the main return pipe bringing all return water from the building to the pumps and connected to the suction line of pumps header.
The water starts to expand and if we don't use expansion tank in chilled water return line the pressure will build up in the pipes and it can cause leaks at various fittings and valves joints and threads even this pressure can burst the pipe too. So to control the expansion of water in the chilled water piping system expansion tanks are used. An automatic pressure releif valve remains in function and release the extra pressure.
