Evaluation of antisurge control concepts during esd. Daikin chillers use either a thermal expansion valve for chillers over 600 tons or an. Apr 16, 2012 the main purpose for adding hot gas bypass hgbp to any system is to prevent condensate from freezing on the surface of the evaporator coil when the system is operating at extremely low load conditions. The owner also deserves a system that is the most reliable and the least costly to operate. Suction pressure high low superheat at evaporator outlet. The hot gas bypass valve monitors the outlet pressure of the evaporator and will begin to modulate open as the load on the unit decreases to the point where the evaporator temperature is at the setpoint of the bypass valve.
Air conditioning clinic refrigeration compressors one of the. Centrifugal compressors dynamic considerations for station design. A wide variety of hot gas bypass valve for refrigeration compressor options are available to you, such as material. All hot gas bypass valves operate on a similar principle. Hot gas bypass can stabilize the system balance point by diverting hot, highpressure refrigerant vapor from the discharge line directly to the lowpressure side of the system. Centrifugal compressor hot gas bypass gas compression. The capacity of the cold bypass valve was recommended to be equal or twice the asc valve capacity. The hot bypass was perceived to be the preferred concept to prevent surge due to the proximity to the compressor. Jul 09, 2007 hot gas bypass operation strap a thermocouple to the refrigerant line outlet of the hot gas bypass valve as illustrated in figure 1. May 18, 2017 an internal hot gas bypass device coupled with inlet guide vane for centrifugal compressor includes an inlet guide vane assembly, a driving motor assembly and a gas bypass valve assembly. Hi there, i am looking at the attached centrifugal compression system and i am considering the unmitigated consequences ignoring all tripsinterlocks there are limit switches on the hgb valves and high temperature trips that trip the compressor but these are assumed to not act of the hot gas bypass hgb failing open on either the 1st or 2nd stage compressor. Here, the refrigerant gas is again compressed, and then discharged. Abstract centrifugal compressor systems include many different subsystems that facilitate performance monitoring, operational controls, vibration monitoring, and surge protection, etc. Hot gas bypass operation strap a thermocouple to the refrigerant line outlet of the hot gas bypass valve as illustrated in figure 1.
Basic gas compressor unit pfd, with lumped elements. Hot gas bypass valve refining, hydrocarbons, oil, and. Results from simu lations are presented in order to validate the model and comparison of simulations. The hot gas bypass valve also called discharge bypass valve or dbv monitors the outlet pressure of the evaporator, and will begin to modulate open as the load on the unit decreases to the point where the evaporator temperature is at the set point of the bypass valve. After the mcquay buyout the pf became any dual compressor unit. A new approach to designing centrifugal compressor surge control systems pdf. Psig 1205 control concepts for centrifugal compressor applications 5 in general, changes are slow enou gh that the steady state compressor maps remain valid. Pdf control methods for centrifugal compressors, especially in oil and gas service. Understanding centrifugal compressor surge and control. Troubleshooting compressor problems compressor types and applications compressors are classified as either positive displacement, where intermittent flow is provided, or dynamic, which provides continuous flow of the air or gas being compressed. Surge control and dynamic behavior for centrifugal gas. In specific cases, adding hot gas bypass to the refrigeration system may be necessary in order to achieve all three goals. Surge is defined as the operating point at which centrifugal compressor peak head capability and minimum flow limits are reached.
The purpose of this manual is to provide design engineers with a basic. Turbomachinery controls dedicated to centrifugal and axial compressors use several types of. Us6427464b1 hot gas bypass control for centrifugal chillers. Although the antisurge valve asv is the chief protector, in brownfield projects, often the asv becomes inadequate to deal with a compressor surge due to addition of new. When designing the piping system, designers may be conservative in adding a hot gas bypass. Apr 22, 2014 in addition to an antisurge valve, an axial compressor most often is protected by a hot gas bypass hgbp recycle loop, usually with a hot gas bypass valve. First the essential components of a centrifugal compressor that accomplish the tasks specified above figure 1 are introduced.
These forces can cause severe damage to the close clearance components of a centrifugal compressor such as the thrust and radial bearings, interstage and dry gas seals, and balance piston. Surge control design for centrifugal compressor systems. Standard external hot gas bypass standard external hot gas bypass consists of a valve located in the condensing section. Centrifugal compressor systems include many different. Pf any unit built with a ce046050 frame compressor. If all evaporators are satisfied, all of the thermostats are open, and all liquid line solenoid valves and the hot gas. Hot gas bypass valve refining, hydrocarbons, oil, and gas. Hello, well i have some views about hot gas bypass valve provision in compressor system. Mathison marquette university, united states of america, margaret. Cvhe, cvhg compressor compressed gas from the firststage impeller flows through the fixed, secondstage inlet vanes and into the secondstage impeller. A typical system consists of pressure and temperature transmitters on the compressor suction and discharge lines, a flow differential pressure transmitter across the compressor flowmeter, an algorithm in the control system, and a surge control valve with corresponding accessories.
Compressor surge analysis on two different centrifugal compressors. Daikin chillers use liquid refrigerant cooled hermetic electric motors. The bypass valves are factory adjusted to a setting of 61 psig 35f evaporator temperature. Operation maintenance water cooled centravac with ch530. The prior art system, however, requires manual calibration at two. Methods and systems consistent with this invention control a hot gas bypass valve in a refrigeration system including a centrifugal compressor, a condenser, an evaporator, and a hot gas bypass line between the compressor and the evaporator. Hot gas bypass control for centrifugal chillers york international. The centrifugal compressor is a dynamic device similar to a centrifugal water pump. Leaking hot gas defrost solenoid or hot gas bypass valve. In the westinghouse years pf units could have either 1 or 2 compressors nominal tonnage. Basically this is a system of bypassing the condenser with compressor discharge gas to prevent the compressor suction pressure from failing below a desired setting. Surge control design for centrifugal compressor systems three levels of dynamic surge analysis compressor reliability is directly affected by the interaction between the surge controller, piping system, valves, recycle lines and coolers.
This is mandatory if the antisurge valve isnt installed immediately after the compressor discharge. Compressor the compressors are hermetic scroll type provided with crankcase heater, internal pressure relief valve which provides high pressure protection to the refrigerant system and rubber vibration isolators for quiet and efficient operation. Compressor loss of oil, loss of oil pressure, or cuts off. Royal belgian institute of marine engineers surge detection. Protecting a centrifugal compressor from surge pipeline. Tesi di laurea magistrale process dynamic simulation in. Operation of centrifugal gas compressors can be defined by three operating parameters. Positive displacement compressors include reciprocating piston types of various. Gessler marquette university, united states of america, paul.
Hot gas bypass regulator piped direct to the suction line without a liquid injection valve. The fluid is then slowed down in a volume called the plenum, where the kinetic energy is converted into potential energy in form of a. A typical hgbp valve can infinitely vary the rate o hot gas flow. Troubleshooting compressor problems salemmbrothers. With countless combinations of equipment and layouts possible, how can you best and most responsibly implement hot gas bypass. The equipment and configuration of a typical hot gas bypass test block. Get up to speed on axial compressors chemical processing. Ce centrifugal hermetic pf 150 unit model number unit type. Centrifugal compressor an overview sciencedirect topics. Hot gas bypass valve posted in refining, hydrocarbons, oil, and gas. To prevent overheating, the compressor vendor recommended limiting the capacity of the hot bypass valve to 50% of the asc valve capacity. The knockout drum should be sized to handle process flow and both cold and hot recycle flows if a hot gas bypass valve hgbv is installed. Pdf the dynamic simulation based design of surge protection valves for centrifugal or axial compressors is described. As far as my knowledge, the purpose is to depressurize the system as fast as possible to prevent the compressor from surge than the antisurge control valve during startup and shutdown condition.
In contrast, centrifugal compressors use the principle of dynamic. Tesi di laurea magistrale process dynamic simulation in oil. This tactic keeps the compressor more fully loaded while the. It raises the pressure and temperature of the refrigerant by converting kinetic energy into pressure. This tech tip covers the standard external hot gas bypass. Modeling of a hot gas bypass test block for centrifugal.
Understanding centrifugal compressor capacity controls. The design factors include discharge piping volumes up to the nearest check valve, the valve trim characteristic, the hot bypass valve hbpv. Centrifugal compressor impellers and shafts are subject to fluctuating axial and radial forces when operating in surge. Piping layout, placement of valves, recycle loops, and control valve. Some applications may also have either a cold gas bypass valve or a hot gas bypass valve to provide additional recycle capacity during a compressor shutdown. The hot gas enters the desuperheating chamber at an angle creating a circular hot gas path, wiping the walls of the chamber and giving up.
Pdf control concepts for centrifugal compressor applications. Jul 07, 20 using its hot gas bypass valve, the apr control then bypasses a portion of the hot gas discharge from the compressor through the devices desuperheating chamber and into the suction inlet of the compressor. Connect a set of refrigerant gauges to the suction and discharge service ports of the compressor system. The compressors are equipped with internal motor protector for safe operation. Actually, the working principle of a centrifugal compressor is increasing the kinetic energy of the fluid with a rotating impeller.
A control system and a method are disclosed for automatically controlling a hot gas bypass valve as a function for cooling load and head. The centrifugal compressor components a centrifugal compressor is a machine that reacts to an externally imposed suction and discharge pressure with a certain flow, assuming the driver provides enough power. Modeling of a hot gas bypass test block for centrifugal compressors. Us4248055a hot gas bypass control for centrifugal liquid. A valve controller is provided for controlling the operation of the hot gas bypass valve so as to avoid surging of the compressor in response to temperatures of the chilled liquid entering the evaporator, the chilled liquid leaving the evaporator, and the. The test block uses cooling towers to reject the heat of compression to outdoor air. The compressor assembly is made up of a prime mover and a centrifugal compressor.
Copyright 2017 by turbomachinery laboratory, texas. Pdf surging forwards in compressor protection researchgate. Feb 17, 2004 methods and systems consistent with this invention control a hot gas bypass valve in a refrigeration system including a centrifugal compressor, a condenser, an evaporator, and a hot gas bypass line between the compressor and the evaporator. Cagi and our centrifugal customers all share a common interest and goal to maximize the compressor system efficiency and optimize the system energy usage. Only use hot gas bypass if all other design options fail to meet the demands of the.