What are Deluge Valves?

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What are Deluge Valves?

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Deluge Valves are used in conditions that call for quick application of large volumes of water and, for that reason, are often integral components in fire protection systems. In this article, PIF explain how deluge valves work, what their advantages and disadvantages are, and where you can lay your hands on one. - http://mepsite.blogspot.in/

Deluge systems deliveriitcenter.blogspot.in large quantities of water, over a large area, in a relatively short period of time. They are commonly used in fixed fire protection systems whose pipe system is empty until the deluge valve distributes pressurized water from open nozzles or sprinklers.

Deluge systems contain more components and equipment than wet pipe and dry systems. So for that matter they are more complex. Detection systems can include heat, smoke, ultraviolet (UV), or infrared (IR).

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Applications for Deluge Valves:

Deluge systems are used in conditions that require quick application of large volumes of water. They create a ‘buffer zone’ in hazardous areas or in areas where fires can spread rapidly. They can also be used to cool surfaces to prevent deformation or structural collapse. Or to protect tanks, transformers, or process lines from explosion.


                                    
Other examples include: tanks containing combustible solutions; equipment pits; storage or process areas containing substances with a low flash point; or product handling systems.

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Advantages and disadvantages of Deluge Valves:

Advantages:

1. Less expensive than other methods,
2. Uses water for extinguishing.

Disadvantages:

1. Can damage sensitive or electronic equipment,
2. Longer clean-up time than powder and gas systems,http://mepsite.blogspot.in/
3. Requires a large water reservoir to operate.

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Air conditioning Systems

Selection criteria for air conditioning systems: 

Selection of a suitable air conditioning system depends on: 

1. Capacity, performance and spatial requirements 

2. Initial and running costs 

3. Required system reliability and flexibility 

4. Maintainability 

5. Architectural constraints Q plant Thermal Distribution System 

The relative importance of the above factors varies from building owner to owner and may vary from project to project. 

The typical space requirement for large air conditioning systems may vary from about 4 percent to about 9 percent of the gross building area, depending upon the type of the system. 

Normally based on the selection criteria, the choice is narrowed down to 2 to 3 systems, out of which one will be selected finally.
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Classification of air conditioning systems: 

Based on the fluid media used in the thermal distribution system, air conditioning systems can be classified as: 

1. All air systems 

2. All water systems 

3. Air- water systems 

4. Unitary refrigerant based systems.

All air systems: 

As the name implies, in an all air system air is used as the media that transports energy from the conditioned space to the A/C plant. In these systems air is processed in the A/C plant and this processed air is then conveyed to the conditioned space through insulated ducts using blowers and fans. This air extracts (or supplies in case of winter) the required amount of sensible and latent heat from the conditioned space. The return air from the conditioned space is conveyed back to the plant, where it again undergoes the required processing thus completing the cycle. No additional processing of air is required in the conditioned space. All air systems can be further classified into: 

1. Single duct systems, or 

2. Dual duct systems 

The single duct systems can provide either cooling or heating using the same duct, but not both heating and cooling simultaneously. These systems can be further classified into: 

1. Constant volume, single zone systems 

2. Constant volume, multiple zone systems 

3. Variable volume systems 

4 The dual duct systems can provide both cooling and heating simultaneously.
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These systems can be further classified into: 

1. Dual duct, constant volume systems 

2. Dual duct variable volume systems 

Advantages of Variable Speed

Advantages of Variable Speed: 

Variable-speed blower motors are designed to provide greater comfort through reduced initial air velocities and noise. When the unit first turns on, the blower operates at low speed, which not only provides less noise than a single-speed blower, but also allows the compressor and coil to ramp up before the unit begins moving large volumes of air through the system.

Most motors are designed to operate at a constant speed and provide a constant output. While in many cases this may be more than adequate, it is not in all. Two-speed induction motors can improve efficiency for refrigerators, air conditioners, and blowers.

Although in theory this can be done with any induction motor application, a greater value is obtained with appliances that run frequently. With a two-speed mode of operation, long time periods that would normally use full power can be replaced by long periods of substantially less power with short periods when full power may be needed.

Currently, residential central air conditioners, blowers (furnaces), and clothes washers take advantage of this technology since small changes in speed can drastically cut down on power usage (power consumption is approximately proportional to the cube root of shaft speed, e.g., a shaft reduction of 10% corresponds to at 27% reduction of power).

2 way and 3 way valves

2-Way and 3-Way Valves

2-way valves are pretty simple and straight-forward. A 2-way valve is any type of valve with two ports: an inlet and an outlet port, typically labeled “A” and “AB” respectively. 2-way valves are used in many applications, from basic on/off to more complex variable flow applications with pumps and VFDs. The type of valve you need for an application depends on the amount of flow, the degree of control, shut-off, and pressure drops over the valve.

 Fig: 2 way valve

Fig: 3 way valve connections


3-way valves have, yes, three ports, labeled “A”, “B”, and “AB”. Port “AB” is common to the “A” or “B” port. 3-way valves are commonly found in constant flow/volume pumping systems and can be either mixing or diverting valves. 3-way valves can be piped in the supply or return. If in the supply, then a diverting valve is used. If piped in the return, a mixing valve is used. Ball valves can be piped to be mixing or diverting, but globe valves require different bodies for mixing or diverting. 

Mixing applications have the 3-way valve configured with two inputs from the supply piping and one output to the return piping, thus mixing together two inputs before sending it out. Mixing valves are most commonly used with modulating control but can be on/off.

Diverting applications have the 3-way valve configured with one input from the supply side and two outputs to the return piping. In general, diverting valves are more expensive than mixing valves.

2 Way Valve:

2 Way (Or 2 Ports) Valve is passing the water in one direction only. so if the valve is fully close it will trap the water before it. this will lead to a pressure increase in this branch

3 Way Valve:

3 Way (Or 3 ports) Valve is passing the water in two directions.
so if the valve is fully open the full amount of water will be moving in one direction, if it closed the water will pass to the other direction, if the valve is partially open then percent of the water will flow through direction 1 and the remaining will pass through the other (for Diverting Valve which installed in the supply line).

In another cases if we install the valve in the return line so if the valve is open water will flow through the unit (Cooling coil as example) then pass through main direction. if the valve is close the water will by pass the unit and then flow through the other direction through the valve (Mixing Valve which installed in the Return line).

This will not cause the pressure rising. Why we use the 2 way valve? when you use the 2 way valves in HVAC system in all the equipment's in your building this means that you will not need all the chilled water to go through your system all the time if you don't need much cooling. so you will be able to reduce the speed of the secondary pumps of your system. this will lead to a huge energy saving in the running cost of your building (depend on the number of Pumps and their sizes). Also you will be able to reduce the size of your pumps. But in this case you have to use Variable Speed Pumps. Also you should have 2 sets of Pumps, One set constant with Speed for Chillers and another set to serve the building. ans also By Pass Valve to guarantee the min flow of the chillers. Otherwise you can use one set with a variable flow chillers. This has to be a decision in the mechanical design stage depend on the cost calculation of the project.

Advantages of 2-Way Valves:

•  „Less expensive to buy and install.
• Result in variable flow which reduces pumping energy.
• Reduced piping heat losses and pump energy.
• Potentially lower costs for pumping and distribution systems.
• System balancing is reduced or eliminated.

Disadvantages of 2-Way Valves:

• Most chillers and some boilers cannot handle widely varying flow rates.
• Differential pressures will increase across control valves, reducing system controllability.

Control Valve Ratings „

• Flow coefficient.
• Close-off rating: Š The maximum pressure drop that a valve can withstand without leakage while in the full closed position.
• Pressure drop: Š The difference in upstream and downstream pressures of the fluid flowing through the valve.
• Maximum pressure and temperature: Š The maximum pressure and temperature limitations of fluid flow that a valve can withstand.

Location of Control Valves:

• „ At the outlet on the top of cooling/heating coils.

1. Avoid coil starvation from water flow (lower pressure)Š
2. Flow of water from the bottom to the top (avoid air bubble).

• Flow measuring & balancing device should be placed after the control valve.
• Provide a means of shut-off to allow a proper means for servicing.

Conclusion:

1. use the 2 way Valve in the system that can withstand the variable water flow
2. use the 3 way valve in the systems that needs a constant water flow.

Selecting & Sizing Valves:

Control valve selection depends on: „ 

• The fluid being controlled.
• Valve style: 2-way or 3-way.
• Control mode: modulating or 2-position.
• Maximum fluid temperature.
• Maximum inlet pressure.
• Desired flow characteristic.
• Maximum fluid flow rate.
• Desired pressure drop when valve is full open.
• Turn-down ratio.
• Close-off pressure.

Flow Characteristic Selection: 

The desired flow characteristic is a function of: „ 

• The heat transfer device being controlled and its flow versus capacity characteristic.
• The control of fluid supply temperature.
• The control of the differential pressure across the valve.

Four Pipe HVAC System

Four Pipe HVAC System:

The system's piping consists of four insulated pipes, two supply and two return lines. One set is dedicated to chilled water, kept between 60 degrees F and 40 degrees F. Another set of pipes is dedicated to hot water, generally kept between 150 degrees F and 200 degrees F. The pipes run to air handlers, which use the chilled or hot water to change the air temperature.

Air Handlers:

• Air handlers in a four-pipe HVAC system can be custom designed to meet a wide variety of heat or cooling demands. They also usually are versatile in that they can be kept in mechanical rooms, on the roof of the building, or with smaller units, in the space above ceilings.

Boilers and Chillers:

• The water in the system runs through two separate systems in order to change the temperature. Cold water is brought down in temperature through chillers, which can be located on the ground or the roof of the building. Chillers come in a wide variety of types to fit different budget and efficiency needs. Water is heated up using a boiler. The boiler is kept either inside or outside. As with the chillers, a number of boiler types are available, for different efficiency and budget needs.
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Advantages Compared to Two-Pipe HVAC:

• The four-pipe HVAC system has a number of advantages over a two-pipe system. Four-pipe systems have separate heating and cooling fan coil units and separate pipes for heating and cooling. This means that hot or chilled water is always available, so the system can immediately change over from heating to cooling mode. Two-pipe systems have to be manually switched over, which is not only inconvenient but time-consuming. Four-pipe systems also can cool some rooms while heating others, offering great flexibility in a building with a variety of heating and cooling needs.

Disadvantages Compared to Two-Pipe HVAC:

• Four-pipe HVAC systems have a number of disadvantages compared to a two-pipe system. They are more expensive to install and maintain and have twice as many valves, coils, controls and pipes to maintain. They also are twice as prone to congestion due to the increased piping.