The textbook explores a variety of typical hydraulic circuits in multiple positions and with color graphics. The presentation of the hydraulic circuits is structured with well-thought-out chapters. Each chapter presents circuits from simple to complex levels. Relevant symbols are portrayed chapter-wise for quick understanding. Most of the symbols used are as per ISO 1219. The types of hydraulic circuits include circuits for conventional hydraulics, electro-hydraulics, closed-circuit HSTs, PLC systems, proportional/servo valve systems, and cartridge valve systems.
The book is meant for hydraulic professionals to refresh their circuit ideas and know more about hybrid hydraulic circuits. This book is specially written for professionals who are confused with many types of complex hydraulic circuits. They can systematically learn the critical areas in simple or complex hydraulic circuits. Teachers and students may also use this book to enhance their hydraulic knowledge. The reader can build up a strong foundation for circuit ideas and may apply these ideas to a hydraulic application considering the operating and environmental conditions, the orientation of the actuators, the type of materials used, and many supplementary factors.
This article is the third part of the following three-part series of articles:
Filtration and Drying Principles in Pneumatic Systems
Filtration Principles in Hydraulic Systems
Filtration Principles of Pneumatic and Hydraulic Systems: A Comparison Study
The filtration principles of pneumatic and hydraulic systems were given in the previous articles. The third part of the three-part series of articles on filtration principles in fluid power systems attempts to make a comparison of the filtration principles, as given in Table 1. A comparative study of the filtration principles would bring out the essential similarities as well as differences in the filtration principles and would provide an overall view of the subject matter.
Table 1 | A comparison of the filtration principles in pneumatic and hydraulic systems
Parameter
Pneumatics
Hydraulics
Medium of energy transfer
Compressed air
Oil
Contaminants
Particles, moisture, oil, +
Particles, chemical contaminants, moisture, air, +
Effect of contaminants
Abrade surfaces Corrode internal parts Reduce functionality and service life of components
Abrade surfaces Corrode internal parts Reduce service life of oil
Cleanliness standards
ISO8573
ISO 11171 & ISO4406 NAS1638 SAE AS4059
Particle removal
Filters
Filters, Magnets
Moisture removal
Dryers, Filters
Vacuum dehydrator
Oil (air) removal
Coalescing filters Adsorption filters
Air bleeds Diffuser (Baffle screen)
Filter types
General purpose filters Coalescing filters Adsorption filters
Pneumatic and Hydraulic Books authored by Joji Parambath
37 books in Paperback and Kindle eBook versions on the subjects of Pneumatics and Hydraulics, authored by Joji Parambath, have been published under Fluid Power Educational Series. Joji Parambath is a trainer in the field of Pneumatics, Hydraulics, and PLC, for over 25 years. All the books are available at Amazon marketplaces.
These books deal with pneumatic system components and circuits. The fundamentals required to understand the core topics are given initially. These books describe the topics on compressed air generation and contamination control, pneumatic actuators, and control valves, in detail. Further, these books present the maintenance, troubleshooting, and safety aspects of pneumatic systems. Many single-actuator pneumatic circuits are given in multiple positions. Many critical positions of pneumatic single-actuator circuits are given to make the reader understand the control circuits easily.
These textbooks deal with the components and circuits of hydraulic systems. The fundamentals required to understand the core topics are given initially. The book describes the topics on hydraulic fluids, filters, power packs (reservoirs, pumps, pressure relief valves) hydraulic actuators, directional control valves, flow control valves, pressure control valves, fluid conductors, and accumulators, in detail. Further, the book presents the maintenance, troubleshooting, and safety aspects of hydraulic systems.
These books explain the basic principles of hydrostatic transmissions. The concepts of open-circuit and closed-circuit HSTs are explained in the book. The topics also include configurations, advantages and disadvantages, and applications of HSTs.
These books enlighten the details of components required for load sensing systems. The operation of load sensing systems in their various operating modes is described in a simplified manner.
The book ‘Electro-hydraulic proportional valves’ explores the technology used in proportional valves. The book also describes the construction of electro-hydraulic proportional valve systems, the details of various types of control elements, characteristics, and applications of proportional valve systems.
The book ‘Electro-hydraulic servo valves’ describes the technology used in state-of-the-art servo valves. The book also describes the construction of electro-hydraulic servo valve systems, the details of various types of control elements, and the applications and characteristics of servo valve systems.
These books explain the functioning of solenoid valves and various electrical control components such as pushbuttons, electro-magnetic relays, limit switches, reed switches, proximity sensors, electronic timers, and counters. The development of many typical single-actuator and multiple-actuator electro-pneumatic and electro-hydraulic circuits are also separately explained in these books. Many circuits are given in multiple positions for a quick understanding of the working of each circuit.
As you are aware, a pneumatic system is an interconnection of various components such a compressor, actuators, control valves, and other elements using fluid conductors. The operation of the pneumatic system is affected by the presence of heat, dust, moisture, leaks, loose bolts, and misalignment in the system. Lack of regular maintenance may result in the premature wear of moving parts, the loss of air and associated pressure drops, and increased downtime of pneumatic components. Therefore, a good preventive maintenance program must be in place for removing the harmful elements from the system from time to time, and usually as per a checklist. In general, maintenance includes the following closely-related activities: (1) Visual inspection, (2) Servicing, (3) Examination, and (4) Overhaul.
Requirements for Preventive Maintenance
The most general requirements of preventive maintenance are as follows: (1) Know the machine, (2) Understand and follow the best maintenance practices, (3) Compile a maintenance checklist, (4) Follow instruction manual, (5) Ensure safety, and (6) Stock spares.
Concern for Safety
The safety of personnel and equipment should always be kept in mind while carrying out routine maintenance activities. Safety can be built into a pneumatic system by incorporating interlocks, power-failure locks, and an emergency shutdown feature. Though the responsibility of building safety into a machine rests with the manufacturer of the machine, every technician should observe and practice relevant safety regulations. Further, every maintenance technician should make a serious attempt to know the hazards involved in his/her occupation.
Activities for Good Maintenance during the Design Phase
The planning for the good maintenance of a pneumatic system begins right from the design stage of the system. That means, the design must facilitate easy maintenance and the efficient removal of contaminants. Further, it is better to plan and design a pneumatic system with correctly-sized and inherently-safe components for its reliability and long service life.
Activities for Good Maintenance during Installation
Additionally, it is required to install a machine in such a way that there is ample space for the operation and maintenance of the machine. It is also essential to provide adequate lighting and a clean environment. The service indicators must be easily visible, and service points must be accessible without any difficulty.
Maintenance, Troubleshooting and Safety in Pneumatic Systems
Joji Parambath
Details of many other books under Fluid Power Educational Series from the same author can be accessed from:
It is essential to maintain various conditioning devices, like coolers, filters, dryers, and lubricators, at regular intervals, for the removal of heat and other harmful contaminants. The routine maintenance activities generally include cleaning, visual inspection, running checks, and servicing of filters, lubricators, and coolers. The reason for any abnormal noises in the system should be investigated immediately.
Plugging Leaks
An essential requirement of any pneumatic system is to stop leakage, as expensive leaks cost big money. Application of soapy water or commercially available leak detecting liquids, like aerosol sprays, on suspected joints, might reveal the presence of leaks. An ultrasonic leak detection instrument can also be used to locate leakages.
Mounting of Components / Machines
The mounting bolts of components must be torqued correctly. Further, every prime mover must be perfectly aligned with the associated load part to reduce undue stress on components, seals, and bearings. A maintenance technician should check for any vibration, loose bolts, or misalignment of components in a system.
