Pressure Testing for Chilled Water Piping

Pressure Testing for Chilled Water Piping

1. Purpose:

The purpose of this method is to make sure that the pressure testing of chilled water piping system is done safely as per client requirement and applicable standars.

2. Scope of Work: 

• This Method Statement covers the hydro static pressure testing of chilled water piping (CHW) pipework at the project and to be followed for all piping works at sites.
• Prior to start of the hydro static pressure testing all other works on the system shall have been snagged by construction team and de-snagged and signed off by the quality department.
• This method statement is for chilled water system black mild steel piping and fittings.

3. Responsibilities:

Construction Manager,

Mechanical Engineer,

Foreman,

Superintendent,

QA/QC Engineer.

4. Pressure Testing Method of Statement:

1. Permit to work for pressure test to be obtained from safety department.
2. All open flanged, valved or screwed ends will be blanked off.
3. The fill point will be installed at the lowest point of the system and a valve vent at the highest point of the system to be tested. The vent will be piped to a drain point.
4. Pressure Gauges with valid Calibration Certificates/Stickers will be fitted adjacent to the pressure pump.
5. Pipe work will be water sufficiently in advance of the test to allow it to come to room temperature so that any sweating can evaporate. When the systems sufficiently filled the vent valve will be opened and allowed to run freely for a period of 5 minutes to ensure all the air is out of the system, at that point the valve will be closed.
6. When the system is full and vented the test rig will be linked to the system and the pressure increased to the required system test pressure, as required by the specification 1.5 the operating pressure. when the test pressure is reached the valve at the fill point will be closed for a period of 15 minutes to stabilize the system, the gauges will be checked to see any pressure has loss due to stabilization, if so the test rig will be applied to bring the system test pressure back up to the specification requirements. Upon re-pressurization the test rig shall then be dismantled for the system.
7. Care will be taken at this point to record the ambient room temperature of the start and finish time of the test. The duration of the test will be 24 hours and temperatures will be recorded frequently.
8. A visual inspection of joints will take place during the test period to check the leaks, if any leakage found the test will be aborted. After the leakage is rectified, the above procedure will be repeated for a re-test to take place.
9. On satisfactory completion of test, witnessed by the client, the pressure will be released through the vent pipe. The system then shall be drained. Pressure testing report shall be prepared and signed by the client or any other concerned party.

5. Health and Safety Requirements:

1. Spot Safety meeting will be done by competent engineer to the working group.
2. Fitting, thread and connections will be checking up for broken or un-threaded parts.
3. To make sure every one in testing area knows that the pressure test will be done and proper tags to be displayed.
4. Ensure that all pipes are fasted properly.
5. Warnings signs will to be displayed  in both English and local language.
6. Valves operations to be understood by operator before pressure test starts.
7. Restrict the access for common people to testing area, use communication system for announcements, etc.
8. Only authorized persons are allowed to check the pipes during the pressure in progress.
9. After the test is complete, the pressure should be released slowly and open all valves once the pressure is zero, to ensure that there is no pressure trapped anywhere in the system.

Air Conditioner Working Principle.

Window air conditioners are very simple appliances. They operate on the exact same principles as a refrigerator, freezer, or dehumidifier.

Please look for information on how window air conditioners work in these areas:

Cooling:

All residential window air conditioners have a cooling system made up of four primary components, a compressor, an evaporator, a metering device, and a condenser. Air conditioner cooling systems are better understood if you think of them as devices that remove warmth from the air rather than cooling the air.

Blower fan:

When the unit is running, the circulating fan and compressor are running simultaneously. The fan motor has two fan blades attached to it on either end. The fan blade on the inside part of the unit continually draws room air over the evaporator coils, which are cold. The fan blade on the outside part of the unit continually draws fresh outside air over the condenser coils, which are warm. Because the evaporator coils are cold, they cause moisture in the room to collect on them, much like a cup of ice water on a warm, humid day. When the amount of moisture increases, it begins to drip down off of the coils into the bottom pan of the air conditioner.

Thermostat control:

The thermostat on a window air conditioner works by sensing the air temperature entering the air conditioner. As the air entering the unit reaches the set temperature it will cause the compressor to turn off. The blower may continue to run depending on the selection chosen on the control panel. Digital thermostats work on a similar principle but display a more precise temperature.

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Selector switches:

The air conditioner selector switches allow the user to choose the fan speed. The compressor always runs at the same speed regardless of the settings. If low cool is chosen, for example, the fan runs at a slower speed but the compressor still offers the same cooling capacity. There are other switches to control louver operation and other features on some units.

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).