COMPRESSOR HANDBOOK phần 10 pps

21.18 CHAPTER TWENTY-ONE Engine turbocharger lubricating oil pressure Engine turbocharger lubricating oil temperature Engine/compressor main bearing temperature Fire detection system shutdown Fuel level (low) Lube oil pressure (low) Lubrication flow (low) Lubrication oil consumption Lubricator flow (low) Metal (in oil) particle detection Motor bearing temperature Motor bearing vibration Motor overload Motor power failure Motor purge fan failure Motor vibration Motor winding failure Motor winding temperature Oil cooler temperature in and out (high) Oil filter Differential (high) Oil level–compressor (low) Oil level—driver (low) Oil level—lubricator (low) Scrubber level (high) Scrubber level (low) Suction, discharge, interstage pressure (high) Suction, discharge, interstage pressure (low) Suction, discharge, interstage temperature Vibration—compressor (high) Vibration—cooler (high) Vibration—driver (high) Water cooler temperature in and out (high) Water pump differential pressure (low) 21.15 SPECIAL COMPRESSOR CONTROLS The compressor industry has created a demand for special control systems and sensors for problems unique to compressors. Among these are: COMPRESSOR CONTROL SYSTEMS 21.19 FIGURE 21.10 Pneu- matic compressor packing case purge control panel to control packing leakage. (Courtesy of Autocator Products Division, T. F. Hudgins, Incorporated). Packing case purge control Rod drop measurement and alarms Vibration monitoring Vibration sensors Mounting vibration sensors Metal particle detection in lubrication oil Lubrication flow sensors Sensors for pulsating compression pressures Eutectic temperature sensors Energy management Cylinder pressure measurement 21.15.1 Packing Case Purge Controls Control systems used to maintain purge gas on packing cases designed to prevent leakage of process gas along the rod to atmosphere have proven effective. Mea- surement of vent gases is used as a diagnostic tool to determine the rod packing wear and replacement schedule. 21.15.2 Surge Control Centrifugal and axial compressor surge control is a specialty area of compressor capacity control and safety. These systems are necessary to provide stable operation on high speed centrifugal compressors. 21.20 CHAPTER TWENTY-ONE FIGURE 21.11 Flow meter connection for measuring purge and packing leakage flow. 21.15.3 Compressor Rod Drop Measuring rod drop is an effective tool in determining when rider rings should be replaced and can minimize cylinder wear. Rod drop occurs in a horizontal compressor cylinder as piston or rider rings wear, allowing the piston to descend. The intent of a compressor rod drop measuring system is to alarm this event prior to the piston contacting the cylinder. Three measurement systems are in use today. These are: 1. Pneumatic eutectic sensor is a bracket mounted sensor located beneath the rod. As the rod rubs on the sensor, the friction causes the eutectic solder to melt, allowing the pneumatic control system to vent and alarm or shut down the machine. 2. Proximity rod drop measurement without the crank angle monitoring system is an electronic equivalent of the pneumatic system alarming when the rod reaches a set point. The operator can also observe a read-out and trends from the system display. 3. Proximity rod drop sensor in conjunction with a crank angle detection system which measures rod position at exactly the same point within the rod stroke. The proximity probe is an eddy current sensor. The output varies in response to rod position. Measuring a specific crank angle allows the operator to be assured of the piston position at the time of measurement. COMPRESSOR CONTROL SYSTEMS 21.21 FIGURE 21.12 Metal particle detector. 21.15.4 Vibration Monitoring Vibration monitoring systems are necessary for determining the health of a machine. An experienced analyst can determine the exact cause of a noise or condition by analyzing the vibration patterns. The system complexity can vary with speed and critical nature of the machine. If a machine is equipped with vibration alarms, these signals can alert the operator to call for an extensive vibration analysis by a specialist using portable diagnostic equipment to determine the exact cause of the vibration. The other option is to provide the extensive analysis diagnostic system as part of the installation and machine controls. 21.15.5 Vibration Sensors 1. Inertia sensors are available as pneumatic valves and electric switches. These are intended to respond to vibration on low speed equipment and in ranges from 0 to 3000 cpm to 0 to 12000 cpm, at vibration sensing ranges 0 to 5g’s and 0 to 10 g’s. These devices are sensitive to vibration parallel to the axis of the sensor mechanism. 2. Eddy current sensors measure machinery motion and are frequently used to monitor moving shafts because direct contact is not necessary. Position, dynamic motion, and wear are now measurable using these sensors. 3. Accelerometer based sensors sense impact events and are available with and without conditioning. Conditioning, either in the sensor or in the control system, converts the accelerometer signal to velocity or displacement signals proportional to vibration. The conditioned accelerometers convert the low powered signal from the sensor intoa4to20mA or 1 to 5 volt DC signal, and can be connected to electronic monitors that are not especially designed for monitoring vibration. Unconditioned sensors have low output signal and are intended to be connected to an electronic monitor that includes the conditioning and vibration monitoring system. 4. There is a wide selection of read-out devices and systems that provide indica- tions and alarms, computerized systems data storage, and trending of the following data. This is a very specialized technology and there are manufacturers 21.22 FIGURE 21.13 Metal particle detection diagram. COMPRESSOR CONTROL SYSTEMS 21.23 providing this service worldwide. Typical displays, either in velocity or displacement, would be: Running speed vibration Crank case deflection Compressor crosshead vibration Compressor cylinder head vibration 5. Compressor valve covers can be monitored temporarily by accelerometers as part of a portable compressor analysis diagnostic system to determine valve condition and operation. Selection of vibration sensors requires careful analysis of machine speed, sensor location, and vibration amplitude based on experience or manufacturer’s data. Vi- bration on low speed machines (120 to 1,500 rpm) is commonly measured in mils or mm displacement. High speed machine (360 to 90,000 rpm) vibration is measured in inches per second or mm/s velocity. 21.15.6 Mounting Vibration Sensor ‘‘Bearings take the load during vibration’’ and are the desired vibration monitoring points. The restraint provided by the base can limit vertical movement, therefore, the sensor must be mounted where the most movement is predicted. 21.15.7 Metal Particle Detectors Metal particles in oil are an indication of: A. Contamination B. Machinery wear Metal particles from bearings, pump wear, cylinder wear, and other failures have been detected by these sensors prior to the build up of temperature or vibration. These systems provide a constant monitoring for metal particles in the lubricating fluid. The application requires a small oil side stream from the dirty side of the filter to flow through a perforated printed circuit card within a suitable housing. As the particles complete the circuit, the alarm circuit is energized. These detectors respond to all conductive particles. Sensors for ferrous only particles are also available. 21.15.8 Lubrication Low Flow Sensors Compressor lubrication system failure can be detected by monitoring switches or valves which remain in a ‘‘healthy’’ condition with flow. As lubrication system flow diminishes, or stops, the sensor trips. 21.24 CHAPTER TWENTY-ONE More sophisticated electronic systems actually measure the flow and transmit the data to computers. The alarm set point can be in the flow monitor or in the computer. 21.15.9 Pressure Sensors The need to measure engine firing pressures and compression pressures has caused several very rugged sensor types to be developed to withstand the pulsation and high temperatures. The rugged construction is necessary because these sensors are mounted on the cylinder for measuring internal pulsating cylinder pressures. The sensors have piezo-electric and strain gage elements and are proving valu- able for controlling operating conditions by computer and evaluating the machine performance. These are available with and without the requirement for water cooling. 21.15.10 Cautions Sensors must be installed in accordance with the ISA recommendations and ASME codes and Regulations Agency codes. Sensors must be protected from corrosive fluids and excessively high pressures and temperatures. Temperature sensors can be protected by suitable thermowells. Static pressure sensors can be protected by suitable gage isolators where necessary. These are sealed diaphragm devices especially designed for this purpose. 21.16 TEMPERATURE CONTROL (OIL AND WATER) Controlling oil and water temperatures is essential in order to maintain proper running clearances. In addition, proper temperatures minimize wear, maintain clearances and proper lubricant viscosity, and prevent condensation in the crankcase. Temperatures are controlled by either self-contained thermostatic valves or temperature control valves with controllers. 21.16.1 Self Contained Thermostatic Valves Special self contained three way valves using internal copper impregnated expand- ing wax elements were developed for the compressor and engine industries. These valves are located in the oil and water piping. During a cold start-up, the fluid is recirculated back to the heat source (bypass position). As the machine warms up, and approaches the element set point, within COMPRESSOR CONTROL SYSTEMS 21.25 5ЊFto7ЊF, the element begins to close the bypass port and send fluid to the cooler. The valve will modulate flow to bypass and cooler in order to maintain the set temperature maintaining a constant flow volume through the machine. Sizes are selected for a pressure drop of 2 to 7 psi in order to be certain of proper velocities and to maintain heat transfer to the element for proper response. These valves are available with a variety of body materials, trim, and seals. Material compatibility and codes must be considered. As an example, API rec- ommends that piping systems containing hydrocarbons be of steel construction. Certain lubricants are not compatible with standard o-rings and the thermostatic valves must be specified accordingly. Commercially available sizes range from 1/2 inch to 8 inch flanges. Available materials are cast iron, steel, ductile iron, bronze, and stainless steel. 21.16.2 Cooling Water and Lube Oil FIGURE 21.14 Cooling water and lube oil systems. 21.26 CHAPTER TWENTY-ONE 21.17 ELECTRIC MOTOR AND PNEUMATICALLY OPERATED TEMPERATURE CONTROL VALVES Three way temperature control valves have been designed for use with pneumatic cylinder and electric motor operators. The need to provide very low pressure differential, yet maintain control, were considerations. External actuators allow the use of remote sensing elements and controller to suit the application. Pneumatic and electronic industrial controllers can be used with these valves and operators to regulate temperatures. Another option is to use the central plant process control system. The pneumatic controller allows the valve to be placed in a hazardous area such as a gas pipeline compressor station. Proportional controls which vary the output according to the input, proportional, integral, derivative (PID) controls provide a more precise control regulation by eliminating the offset between the desired and actual temperatures. The derivative action attempts to anticipate temperature changes based on the cyclic rates of change experienced by the system. I to P converters are used to interface an electronic controller to a pneumatic operator. Commercially available in sizes range from 2 inch to 16 inch flanges. Industrial control valves can be used in this service, but do operate at higher differential pressures. 21.18 ENERGY MANAGEMENT SYSTEMS Energy management systems provide dramatic cost savings where multiple machines are used in industries such as foundries, automotive or process plants, as well as pipeline and process industries. Careful analysis and control of machine run time, along with capacity control, will optimize power consumption. An added benefit is reduced machine wear and maintenance. 21.19 SPECIFICATIONS, CODES, AND STANDARDS Refer to the following publication for suggested specifications, codes, and standards. Instrument Society of America—ISA S5.1 Instrumentation Symbols and Identification S5.4 Instrument Loop Diagrams S5.5 Graphic Symbols for Process Displays RP12.6 Installation of Intrinsically Safe Systems for Hazardous (Classified) Lo- cations COMPRESSOR CONTROL SYSTEMS 21.27 Standards and Practices for Instrumentation National Electrical Manufacturers Association—NEMA ICS 3–1978 Industrial Systems ICS 6–1978 Enclosures for Industrial Controls and Systems American Petroleum Institute—API API 670–Vibration, Axial-Position, and Bearing-Temperature Monitoring Sys- tems API 618–Recommended Practice for Compressor Emissions Monitoring API RP–550 Manual on Installation of Refinery Instruments and Controls API RP–520 Design and Installation of Refinery Instruments and Controls API RP–521 Guide for Pressure Relief and Depressuring Systems API RP–14F Recommended Practice for Design and Installation of Electrical Systems for Offshore Production Platforms Underwriter’s Laboratories, Inc.—UL Standards for Safety Factory Mutual System—FM Approved Standards and Data Sheets National Fire Protection Association—NFPA National Fire Codes Volumes 1 through 16 [...]... compression, or propane/butane refrigeration compression Two basic types of positive displacement compressor packages will be discussed in this section: reciprocating gas compressors, and rotary screw gas compressors Reciprocating gas compressors can handle from 60 horsepower to 7,200 horsepower (using a 6-throw compressor frame and an electric motor driver) Although reciprocating units are the most common... by the compressor packager 23.9 CONTROL PANEL & INSTRUMENTATION The control panel is the brain of the compressor package It operates in conjunction with numerous safety switches to monitor the compressor package and protect it FIGURE 23.6 Typical compressor lubrication system 23.12 FIGURE 23.7 Typical electric panel display (Reprinted with permission from Altronic Controls, Inc.) PACKAGING COMPRESSORS... (ЊF) (23.5) PACKAGING COMPRESSORS 23.8 23.11 COMPRESSOR LUBRICATION To keep size and weight down, packages are usually built around high speed compressors This makes lubrication of the cylinders and piston and rod packing critical The lubrication system is determined by the size of the cylinder and rod A separate force-feed lubricator driven off the crankshaft supplies oil to the compressor cylinders... ideal for large volume/low suction pressure applications and have fewer maintenance and vibration problems 23.1 COMPRESSOR SIZING Most packagers have a compressor sizing program available to choose a compressor frame and driver to compress the gas under the desired conditions To properly size a compressor, the following must be provided: suction pressure, discharge pressure, gas analysis or gas specific... Wiley Series in Geotechnical Engineering 2 Rowan, Robert L & Associates, Inc., Re-Grouting Reciprocating Gas Compressors, 5 Year Repairs vs 20 Year Reliability Criteria, 1:12 Grouting Technology Newsletter CHAPTER 23 PACKAGING COMPRESSORS Judith E Vera Project Engineer Energy Industries, Inc Compressor packages can be used for a variety of applications including gas boosting, gas gathering, gas lifting,... frequency As these values are less than comparable frequen22.1 22.2 CHAPTER TWENTY-TWO FIGURE 22.1 Assoc., Inc.) Skid mounted / packaged compressor (Illustration courtesy of Robt L Rowan & FIGURE 22.2 Block mounted compressor (Illustration courtesy of Robt L Rowan & Assoc., Inc.) COMPRESSOR FOUNDATIONS FIGURE 22.3 22.3 Pile cap foundation (Illustration courtesy of Robt L Rowan & Assoc., Inc.) 22.4 CHAPTER TWENTY-TWO... document Major engineering firms, operating companies, and equipment manufactur- COMPRESSOR FOUNDATIONS 22.5 ers that have their own in-house guidelines are represented on the committee Additionally, under the sponsorship of the Pipeline Compressor Research Counsel, Southwest Research Institute, along with interested industry users of compressors, much needed data on both dynamic and thermal stresses in foundations... electric motor depending on the end user’s specific requirements Although the primary components of the packaged gas compressor unit are the compressor frame and its driver, numerous other parts are essential to the efficient operation of the unit 23.1 23.2 CHAPTER TWENTY-THREE 23.2 BASE DESIGN Gas compressor package bases are designed of sufficient mass to support the weight of the entire package Bases can... skid for scrubber placement The engine and compressor set on a pedestal which is preferably filled with concrete It is important that this pedestal is one solid piece on reciprocating compressor packages The natural vibrating forces in a reciprocating package on a pedestal that is two separate pieces can cause skid failure or misalignment of the engine and compressor during normal operation A typical... as shown in Fig 23.2 23.3 SCRUBBER DESIGN Scrubbers are designed to remove solids and liquids from the gas before they reach the compressor cylinder This is necessary because the tolerances in a compressor are such that any foreign matter can damage the internal parts of the compressor Scrubbers should be placed before each stage of compression On a multi-stage unit, the interstage scrubbers are required . control systems and sensors for problems unique to compressors. Among these are: COMPRESSOR CONTROL SYSTEMS 21.19 FIGURE 21 .10 Pneu- matic compressor packing case purge control panel to control. temperature Vibration compressor (high) Vibration—cooler (high) Vibration—driver (high) Water cooler temperature in and out (high) Water pump differential pressure (low) 21.15 SPECIAL COMPRESSOR CONTROLS The compressor. and axial compressor surge control is a specialty area of compressor capacity control and safety. These systems are necessary to provide stable operation on high speed centrifugal compressors. 21.20