Overview of Rotating Equipment.pdf
November 18, 2016 | Author: Aiyappa Devraj | Category: N/A
Short Description
Download Overview of Rotating Equipment.pdf...
Description
Overview of Rotating Equipment Speaker’s name Speaker’s role date John Crane Copyright The information contained in, or attached to, this document, contain confidential information that is proprietary to John Crane. This document cannot be copied for any purpose, or be disclosed, in part or whole, to third party without the prior approval of John Crane. © John Crane
An Overview of Rotating Equipment Session Agenda: 1. An Overview of Rotating Equipment 2. Prime Movers – Drivers 3. Rotating Equipment – Driven 4. Connectors – Modifiers & Couplings Further Rotating Equipment: 5. Centrifugal Pumps 6. Positive Displacement Pumps 7. Summary and Conclusions
© John Crane
Introductory Exercise Can you already identify the machines listed below as Drivers or Driven Equipment? Driver
Driven
Compressors Mixers Wind Turbines Hydraulic Motors Fans Steam Turbines Screw Pumps Reciprocating Pumps Diesel Engines Electric Motors © John Crane
1. An Overview of Rotating Equipment In most cases energy is transferred into rotating equipment, from a driving equipment (known as the Prime Mover) to the driven equipment (known as Rotating Equipment or the Functional Machine).
Prime Mover (Driver)
Examples of Prime Movers include: Turbines – Steam, Gas, Water & Wind Internal Combustion Engines Electric Motors
Rotating Equipment (Driven)
Examples of Rotating Equipment include: Centrifugal and Positive Displacement Pumps Compressors Agitators/Mixers/Reactors Electric Generators and Alternators Fans and Blowers
© John Crane
1. An Overview of Rotating Equipment Typical rotating equipment fitted with mechanical seals includes:
• • • • •
centrifugal and positive displacement pumps centrifugal gas compressors and refrigeration compressors turbines (steam, gas, water, wind) agitators / mixers / reactors anywhere a rotating shaft passes through a stationary housing where product has to be contained
© John Crane
2. Prime Movers – Turbomachinery The term turbomachinery describes machines that transfer energy between a rotor and a fluid, including both turbines and compressors. A turbine transfers energy from a fluid to a rotor. A compressor transfers energy from a rotor to a fluid.
Typical Steam Turbine
Typical Centrifugal Gas Compressor © John Crane
2. Prime Movers – Steam Turbines Steam turbines work on the principle of using pressurised steam to rotate turbine blades. This rotation is then used to drive other equipment, in a similar way as an electric motor but utilising the heat and pressure of the steam rather than electricity as the driving energy.
© John Crane
2. Prime Movers – Gas Turbines Gas turbines work on the principle of using pressurised fuels to rotate turbine blades, they can produce a great amount of energy for their footprint size and weight. Their smaller footprint, low weight and multiple fuel applications make them the ideal power plant for offshore use. The rotation is used to drive other equipment, in a similar way as the steam turbine utilising the heat and pressure of the fuel as the driving energy. Hot exhaust gases can be used for steam generation, heat transfer, heating and cooling purposes.
© John Crane
2. Prime Movers – Water Turbines The water turbine converts energy in the form of falling water into rotating shaft power. The amount of power which can be obtained depends upon the amount of water available i.e. the flow rate, and the head or fall through which it depends. The rotating element (`runner') of a reaction turbine is fully immersed in water and is enclosed in a pressure casing. The runner blades are profiled so that pressure differences across them impose a lifting force (the wings on an aircraft), which cause the runner to rotate.
Francis Reaction Turbine Runner Typical Francis Reaction Turbine
Typical Kaplan Reaction Turbine © John Crane
2. Prime Movers – Water Turbines An impulse turbine runner operates in air, driven by a jet (or jets) of water. Here the water remains at atmospheric pressure before and after making contact with the runner blades. In this case a nozzle converts the pressurised low velocity water into a high speed jet. The runner blades deflect the jet so as to maximise the change of momentum of the water and thus maximising the force on the blades.
Typical Pelton Wheel Turbines
Typical Turgo ImpulseTurbine © John Crane
2. Prime Movers – Water Turbines This type of water turbine operates in a similar manner as a wind turbine but exploits underwater currents rather than air, based on the principle that all fluids behave the same way.
© John Crane
2. Prime Movers – Wind Turbines A Wind turbine is a machine that converts kinetic energy from the wind into mechanical energy, and this energy can be used to produce electricity e.g. wind generators / farms, or used to drive other machinery to do useful work e.g. windmills.
© John Crane
2. Prime Movers – Internal Combustion Engines Reciprocating or Hydraulic • Diesel / Gas Engines • Hydraulic Motors A Reciprocating Engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion.
A Hydraulic Motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation).
Diesel Engines © John Crane
2. Prime Movers – Electric Motors An Electric Motor converts electrical energy into Electric Motors mechanical energy. Most electric motors operate • Direct on line (DOL) through interacting magnetic fields and current• Star Delta carrying conductors to generate force. • Variable speed/variable frequency Electric motors are commonly started Direct On Line (DOL) where the full line voltage is applied to the motor terminals. This is the simplest type of motor starter. For Softer starts – Star Delta is preferred where the start is controlled in two phases' Variable Speed/ Variable Frequency allows full control of the start up and operation. Electric Motor
© John Crane
3. Rotating Equipment (Driven) – Centrifugal Pumps Centrifugal • Pumps • Compressors • Mixers • Fans • Propellers
Centrifugal Driven machines are similar to a turbine but operating in reverse. Centrifugal force is defined as moving, or pulling away from a centre or axis. Typically a Centrifugal Pump uses a rotating impeller to increase the pressure of a fluid. Centrifugal pumps are commonly used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into volute chamber (casing), from where it exits into the downstream piping system.
Centrifugal Pump © John Crane
3. Rotating Equipment (Driven) – Positive Displacement Pumps Reciprocating or Hydraulic • • • •
Gear Pumps Screw Pumps Piston Pumps Reciprocating Pumps
Archimedes' screw pump
All Positive Displacement pumps deliver a constant amount of fluid for each revolution or stroke. Gear Pumps use the meshing of gears to pump fluid by displacement. They are one of the most common types of pumps for hydraulic fluid power applications. Gear pumps are also widely used in chemical installations to pump fluid with a certain viscosity. Screw Pumps use one or several screws to move fluids or solids along the screw(s) axis. In its simplest form (the Archimedes' screw pump), a single screw rotates in a cylindrical cavity, thereby moving the material along the screw's spindle. A Piston Pump is where the high-pressure seal reciprocates with the piston. Piston pumps can be used to move liquids or compress gases. A Reciprocating Pump is a plunger pump. It is often used where relatively small quantity of liquid is to be handled and where delivery pressure is quite large. © John Crane
3. Rotating Equipment (Driven) – Compressors A centrifugal gas compressor is a mechanical devise that increases the pressure of a gas by reducing its volume. As with a pump for liquids, a compressor increases the fluid pressure, and can transport the fluid through a pipe. However, as gases are compressible, the compressor also reduces the gas volume whereas the main result of a pump is to increase the pressure of a liquid to allow it to be transported.
© John Crane
3. Rotating Equipment (Driven) – Compressors Centrifugal Gas Compressor Construction Comprises a casing containing rotating shaft, on which is mounted a cylindrical assembly of compressor blades. Each blade on the compressor produces a pressure variation, similar to an aircraft propeller airfoil. Centrifugal compressors also do work on the flow by rotating (thus accelerating) the flow radially.
C
R
=
=
© John Crane
3. Rotating Equipment (Driven) – Compressors Centrifugal Gas Compressor Applications They are used throughout industry because they: 9 have few moving parts 9 are very energy efficient 9 give higher airflow that a similarly sized reciprocating compressor
© John Crane
3. Rotating Equipment (Driven) – Compressors Refrigerant Compressors Designed specifically for air conditioning, heat pumping and refrigeration applications. They are integral components of the refrigeration cycle, in which refrigerant gases are cyclically evaporated and condensed, absorbing heat from the load to be cooled, and delivering it to an open environment where it is dissipated. There are 3 main types of refrigerant compressors: Screw Piston Scroll © John Crane
3. Rotating Equipment (Driven) – Agitators / Mixers / Reactors Agitators / Mixers / Reactors are machines for mixing or agitating a product within a pressure vessel. They are installed in process plants in industries such as chemical processing, pharmaceuticals, pulp and paper processing etc. Applications include: 9 blending 9 dissolving 9 heat transfer 9 solids dispersion 9 solids suspension 9 complete chemical reactions 9 polymerisation 9 crystallisation 9 neutralisation
© John Crane
3. Rotating Equipment (Driven) – Agitators / Mixers / Reactors Most equipment can be classified into three types of configurations: Top Entry – the mixer is mounted through an entry port at the top of the vessel. Bottom Entry – the mixer is mounted through an entry port at the bottom of the vessel. Side Entry – the mixer is normally mounted through a nozzle on the side of the vessel (normally mounted near the bottom of the vessel, to allow mixing at low liquid levels, and during filling and emptying).
© John Crane
3. Rotating Equipment (Driven) – Agitators / Mixers / Reactors Most agitators and mixers operate at low shaft speeds typically around 100 – 500 RPM. The deflection on a long overhung shaft will affect the design of the vessel and the sealing device. They will have to tolerate any run-out or misalignment due to shaft deflection.
© John Crane
3. Rotating Equipment (Driven) – Electric Generators & Alternators Electrical
An Electric Generator is a device that converts mechanical energy to electrical energy. The reverse conversion of electrical energy into mechanical energy is done by a motor; motors and generators have many similarities. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy. An Alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current. Alternators in power stations driven by steam turbines are called Turbo-Alternators. © John Crane
3. Rotating Equipment (Driven) – Fans & Blowers Industrial fans and blowers consist of shaft mounted rotor blades contained within a casing, and are used for creating a flow of gas (air). Fans and blowers have diverse applications in many industries for the following typical processes: Extraction Ventilation Cooling Aeration Drying etc.
Typical Industrial Fan
Power Station Fly Ash Blower
© John Crane
4. Connectors – Modifiers and Couplings Whenever two pieces of rotating machinery such as a pump and a motor need to be connected together, there is the possibility of a direct or indirect connection.
Equipment can be indirectly connected by belts or chains – for example think of a bicycle as the chain transfers pedal power to the wheel:
However indirectly coupled equipment is usually inefficient, due to frictional losses when the belts or chains slip during power transmission. © John Crane
4. Connectors- Modifiers and Couplings The alternative solution is a direct connection between the 2 machines: Prime Mover (Driver)
Motor (Driver)
Connector
Rotating Equipment (Driven)
Pump (Driven)
© John Crane
4. Connectors – Modifiers and Couplings With a Direct Drive between the driver and the driven equipment, some form of connector device is needed: Prime Mover (Driver)
Connector
Rotating Equipment (Driven)
Modifiers Couplings The types of driving and driven equipments being driven will affect the choice of the suitable connector device. There are various types of connector devices commonly in use in process industries.
© John Crane
4. Connectors – Modifiers and Couplings Modifiers are connectors and are so described as they ‘Modify’“ or ‘Change the input to output transmission properties such as: Speed Torque Rotational Direction Examples of Modifiers include:
Fluid coupling Gearbox Belts Chains
© John Crane
4. Connectors – Modifiers and Couplings Modifier A Fluid Coupling is a hydrodynamic device used to transmit rotating mechanical power. It also has widespread application in marine and industrial machine drives, where variable speed operation and/or controlled start-up without shock loading of the power transmission system is essential.
© John Crane
4. Connectors – Modifiers and Couplings
Modifier A Transmission or Gearbox provides speed and torque conversions from a rotating power source to another device using gear ratios.
© John Crane
4. Connectors – Modifiers and Couplings
Modifier A Belt is a loop of flexible material used to link two or more rotating shafts mechanically. Belts may be used as a source of motion, to transmit power efficiently.
© John Crane
4. Connectors – Modifiers and Couplings
Modifier A Chain Drive is a way of transmitting mechanical power. By varying the diameter of the input and output sprockets with respect to each other, the gear ratio can be altered.
© John Crane
4. Connectors – Modifiers and Couplings The other types of connector devices are known as couplings: Disc Gear Grid Chain Diaphragm Elastomeric Rubber Block Universal Joint Rigid Hose Pin & Bush All the above connectors transmit torque and speed without change to the drive characteristics seen with modifiers. Couplings can be used in conjunction with modifiers - they are not in direct competition. © John Crane
4. Connectors – Modifiers and Couplings A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting torque.
© John Crane
Exercise
Can you identify if the Connectors listed below are Modifiers or Couplings? Modifier
Coupling
Universal Joint Gear Box Belt Drive Chain Pin & Bush Chain Drive Elastomeric Fluid Coupling © John Crane
5. Further Rotating Equipment - Pumps Classification of pumps: Pump types are generally classified according to how they transfer energy to the fluid, and the combination of pressure and flow which they are designed to generate: • pumps which pass kinetic energy to the fluid by means of a rapidly rotating impeller are known as kinetic or dynamic or centrifugal pumps • pumps in which the fluid is mechanically displaced are termed positive displacement pumps
© John Crane
5. Further Rotating Equipment - Pumps The Application Data Sheet will usually indicate the ‘Type’ of pump:
© John Crane
5. Further Rotating Equipment - Pumps A pump data sheet or manufacturer’s rating plate should at least contain the following information:
• • • • • • • •
Manufacturer Pump serial No Pump Direction of Rotation Duty Generated Head Duty Flowrate Pump Absorbed Power at Duty Point Pump Running Speed Pump Casing Design Pressure
© John Crane
5. Further Rotating Equipment - Pumps The following data relevant to seal selection should also be included:
• • • • • • •
Shaft Size Pumped Process Fluid (including temperature) Barrier Fluid (including temperature) Suction Pressure Discharge Pressure Chamber pressure API Piping Plan
© John Crane
5. Centrifugal Pumps API 610 / ISO 13709 provides a code to classify the various types:
© John Crane
5. Centrifugal Pumps – OH1 Centrifugal Pump - Horizontal, overhung, flexibly coupled, foot-mounted (OH1)
Semi-open Impeller Seal Chamber
© John Crane
5. Centrifugal Pumps – OH1 Seal Chamber Pressure (OH1) Influenced by: • Size of the impeller for a given shaft • Type of Seal Chamber 1. Traditional cylindrical with throat bushing 2. Cylindrical with open throat 3. Conical or Tapered bore • Diameter of the seal chamber bore adjacent to back of the impeller The radially smaller the back vane ‘sweep’ the lower its effectiveness • The larger the bore diameter the higher the chamber pressure • The smaller the impeller size the higher the chamber pressure Seal Chamber Pressure = Suction + K x (Differential Pressure) where K is a relative % value K = 10% for Chamber type 1 K = 10% to 30% for Chamber type 2 depending on impeller size K =
View more...
Comments
