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Showing posts from July, 2015

Cable Pulling Procedure and Following Conditions in Field

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Cable Pulling Procedure and Following Conditions in Field
Cable pulling procedure and following conditions in the field during cable pulling time is alternately referred as what the cable pulling rightprocedure is?; and what conditions should be followed?, in field level during cable lay due to safe cable pulling. Cable manufacturer have handbooks or cable catalogue that describe the methods of safe cable pulling procedure and conditions.
This article not described details theoretical and mathematical calculation; just tried to make sense basic knowledge for workforce related to cable pulling in field level to pull cable perfectly and safely as well as understand why should follow the cable pulling conditions. Keywords: Discussed keywords in this article are History of Cable InstallationMaximum Allowable Pulling Tension on Conductors, Pulling Tension Calculations, Coefficient of Friction,Sidewall Bearing Pressure,Pulling Multiple Cables in a Duct or Conduit, Weight Correction Factors,P…

How Economizer Works in Centrifugal Chiller

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How Economizer Works in Centrifugal Chiller
Figure shows how economizer works in centrifugal chiller for 2 stage chiller and 3 stage chiller. An economizer can be used in conjunction with multiple expansion devices to improve the efficiency of a multi-stage chiller. In a chiller with a 2-stage compressor, the expansion process can be separated into 2 steps with an economizer chamber between.
Liquid refrigerant from the condenser enters the first expansion device, which reduces the pressure of the refrigerant to that of the second-stage impeller inlet. This pressure drop causes a portion of the liquid refrigerant to evaporate, or flash, and the resulting mixture of liquid and vapour enters the economizer chamber. Here, the vapour is separated from the mixture and is routed directly to the inlet of the second stage impeller. The remaining liquid travels on to the second expansion device and evaporator.
Just before entering the evaporator, the liquid refrigerant flows through a second expan…

Maintenance Procedure of Centrifugal Water Chiller

Maintenance Procedure of Centrifugal Water Chiller What is the maintenance procedure of centrifugal water chiller and how keep your chiller on trouble-less operation. Yes, of course maintenance is important fact for this. Proper maintenance not only give you hassle free smooth operation, it also ensure optimize your property operating lifetime. Most of manufacturer offer some maintenance rules and procedure of their equipments. If user follows these instruction and carry-out the maintenance work correctly, machineries will give maximum usability. 
To keep fit your centrifugal water chiller following general maintenance is required. Although some of the information presented here commonly what is applicable for other types of chiller. 
Maximum time centrifugal chiller after installing put into continuous operation without full-time attendant using BMS (Building Management System) or simple clock system. Actually water chiller is designed for maximum consistency with a minimum amount of ma…

Refrigeration Cycle of Centrifugal Chiller

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Refrigeration Cycle of Centrifugal Chiller
Description of refrigeration cycle is perfectly represented in p-h chart or Pressure-Enthalpy chart. This is the formal way to define the refrigeration cycle which shown in the figure. But understand very first and easily, let’s analyse the components of a 2-stage centrifugal chiller in the framework of the refrigeration cycle as shown in above schematic diagram. Here we considered 2-stage compressor centrifugal chiller to describe refrigeration cycle.
If we follow the refrigeration vapour flow route we find that refrigerant vapour leaves the evaporator and flows to the compressor.  Vapour is compressed to a higher pressure and temperature in compressor. High-pressure refrigerant vapour then travels to the condenser where it rejects heat to water, and then leaves as a saturated liquid. The pressure drop created by the first expansion device causes part of the liquid refrigerant to evaporate and the resulting mixture of liquid and vapour enters …

Why Purge System Is Required For Refrigerant and How Does It Operate in Chiller Compressor

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Why Purge System Is Required For Refrigerant and How Does It Operate in Chiller Compressor
Purge operation system for refrigerant in chiller compressor is carry-out to remove air and moisture; Low-pressure chillers typically include a purge system to remove air and moisture that may leak in, while minimizing the emission of refrigerant.
The purge consists of a small refrigeration system, a pump-out system, controls, and a filter drier. The purge’s refrigeration system includes a small compressor, a finned-tube air-cooled condensing coil, an expansion valve, and an evaporator coil inside of the purge tank. The tank with the evaporator coil separates condensable refrigerant from non-condensable air. Because the purge evaporator operates at a lower temperature and pressure than the chiller condenser, a mixture of refrigerant vapour and air is drawn from the chiller condenser, just above the level of the liquid refrigerant. (This is where air typically concentrates in a low-pressure chiller…

How Chiller Motor works for Long Time keeping Cool

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How Chiller Motor works for Long Time keeping Cool How chiller motor keeps cooling is an important issue because chiller normally works continuously and need to keep cooling; so how chiller motor keeps cooling. A motor is used to rotate the impeller(s). A direct-drive motor is connected directly to the impeller shaft and the impeller rotates at the same speed as the motor. A gear-drive motor transfers its energy to the impeller shaft using a set of gears. This allows the impeller to rotate at a higher speed than the motor. 
The direct-drive motor requires fewer bearings and does not incur gear losses. Additionally, since the compressor rotates at a lower speed, it can be much quieter.
Direct-drive compressors are, however, only practical in centrifugal chillers that use low-pressure refrigerants.
Another important difference in compressor motors is the issue of hermetic versus open. A hermetic motor is totally enclosed within the chiller’s refrigeration system. An open motor is mounted ex…

Expansion Device Orifice Plates of Centrifugal Water Chiller

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Expansion Device Orifice Plates of Centrifugal Water Chiller An expansion device is used to maintain the pressure difference between the high-pressure (condenser) and low-pressure (evaporator) sides of the refrigeration system, as established by the compressor. This pressure difference allows the evaporator temperature to be low enough for the refrigerant to absorb heat from the water being cooled, and the condenser temperature to be high enough for the refrigerant to reject heat to water at normally available temperatures. High-pressure liquid refrigerant flows through the expansion device, causing a pressure drop that reduces the refrigerant pressure to that of the evaporator. This pressure reduction causes a small portion of the liquid to boil off, or “flash,” cooling the remaining refrigerant to the evaporator temperature.
The expansion device is also used as a liquid refrigerant metering system, balancing the refrigerant flow rate with the evaporator load condition. In our example …

Condenser of Centrifugal Water Chiller

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Condenser of Centrifugal Water Chiller The high-pressure refrigerant vapour is discharged from the compressor into a heat exchanger that acts as a condenser. In a water-cooled condenser, water is pumped through the tubes of the shell and-tube heat exchanger while refrigerant vapour fills the shell space surrounding the tube bundle. A baffle inside the condenser helps distribute the refrigerant evenly. As heat transfers from the hot, high-pressure refrigerant Vapour to the water, refrigerant condenses on the tube surfaces. Cooling water flows first through the lower tubes and then through the upper tubes. This produces a nearly constant temperature difference between the downward-moving refrigerant and the tube surfaces, resulting in a uniform heat transfer rate within the tube bundle. Condensed liquid refrigerant collects in the bottom of the shell and flows through the liquid line to the expansion devices and economizer.
Referance-TRANE Chiller

Compressor of Centrifugal Water Chiller

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Compressor of Centrifugal Water Chiller The vapour-compression refrigeration cycle in water chillers vary by the type of compressor used in it. As per size of chillers following type of compressors typically use:
For small size chillers: Reciprocating and scroll type compressors.  For Medium size chillers: Helical-rotary or screw type compressors.  For large size chillers: Centrifugal type compressors.
Centrifugal water chillers can also be divided into two types based on the method used to reject heat to the atmosphere:  Water-cooled or  Air-cooled.
Most centrifugal chillers are water-cooled. Water-cooled centrifugal chillers are generally available from 100 to 3,000 tons [350 to 10,500 kW] as prefabricated machines, and up to 8,500 tons [30,000 kW] as built-up machines.
This particular centrifugal water chiller makes use of a shell-and-tube evaporator where refrigerant absorbs heat from the water flowing through the tubes. The compressor is made up of 1 or more centrifugal impellers. A secon…

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