The Coop Program: Resolving Engineering Problems

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Table of Contents

Coop Programme Overview
Gas Turbine
Thrust Bearings
The Exhaust
Heat Exchanger (Radiator) Cleaning
Results

Coop Programme Overview

The College of Applied Engineering offers an opportunity for its students to undergo practical training under the cooperation programme. A coop programme provides an opportunity for students to apply theoretical knowledge gained in class in a real industrial setting. This programme allows students to have a chance of practical application and work experience in the engineering field of study. Students learn critical areas in which practical and theoretical concepts relate. The coop programme ensures that students think critically during the attachments in order to enhance their skills, language use, and problem solving abilities. The programme also benefits students as they learn to work with a team in a busy industrial environment. To this end, students on coop programmes learn critical elements of the engineering profession in a real industrial situation.

Fuel Tanks

PP10 gets its crude oil from Saudi ARAMCO by pipelines. It also receives diesel supply through trucks. The company has eight trucks in which two trucks are allocated for unrated crude oil while the other six are for rated crude oil. In addition, there are also additional two storage tanks for diesel.

Departments of power plant

PP10 power plant has three distinct divisions (see figure 1.2) as follow:

Maintenance department (MND)
Operating department (OPD)
Technical service department (TSD)

MMG (Mechanical Maintenance for GE)

GE machines require maintenance based on the average hours of operations. As a result, GE machines have three forms of maintenance, which include:

Combustion Inspection (CI) required after every 8000 hours
Hot Gas Path Inspection (HGPI) required after every 16000 hours
Major Inspection required after every 32000 hours

MIC (Maintenance Instrument Control)

MIC division ensures that the gas turbine is safe by monitoring pressure switches, temperature switches, and other components of the turbine. It also replaces some of the electronic components of the system. In addition, the division makes decisions on the type of maintenance required for gas turbines.

MEL (Maintenance Electric)

MEL division monitors and maintains all motor units alongside generators, lamps, and electric devices within the station. The division also makes critical decisions on fixing, replacing, or calling for professional helps for their generators.

Gas Turbine

A gas turbine is also known as the combustion turbine or the turbine element. It is a rotating system, which extracts energy from the flowing combustion gas. A gas turbine consists of an upstream compressor, which is connected to a downstream turbine, as well as a combustion chamber at the middle. In the combustor, energy gets into the gas stream in which air is mixed with the fuel and lighted. The temperature, velocity, and the volume of the gas flow increase due to the combustion process. This passes through the nozzle over the blade of the turbine and spins the turbine in order to power the compressor.

The description of the gas turbine is based on the Brayton cycle. In this case, the compression of air occurs isentropically while combustion takes place at a steady pressure and expansion over the turbine takes place isentropically as it assumes the starting pressure.

Components of Gas Turbine

The major parts of a gas turbine are:

Air inlet
Router
Starting motor
Compressor
Combustion system
Turbine
Exhaust

In addition to the mentioned parts, there are also other parts, such as pipes, valves, and hydraulic oil among others. However, these are the main components of the gas turbine system.

Air Inlet

A gas path is the course through which gases flow through into the gas turbine from the air inlet. The air passes through the compressor, combustion chamber, and the turbine to the exhaust as shown in figure 2.2. The gas turbine also consists of a duct for supplying clean air into the turbine.

The Router

The router is an elongated duct that has compressor blades and turbine blades. It weighs approximately eight tonnes. It also has three different Journal Bearings, which are located separately.

Starting Motor

A starting motor rotates the duct or the router when the unit starts. It is an approximately 500-horse power with capability of reaching 52000 rpm. It also rotates the router at 6 rpm during stoppage as it cools down. The starting motor also joins the gearbox to supply the power to the duct or shaft (figure 19).

Compressor Section

The role of the compressor is to receive the inlet air and raise the pressure from the atmospheric pressure of one bar to eight bars. Air then moves to the composition section.

There are 17 rows with rotating blades within the compressor, which are connected by bolts to the rotor. The compressor also consists of stator (stationary) blades. Rotator blades are responsible for providing the required force to compress the air, whereas stator blades direct the flow direction of the air to the discharge part of the compressor.

The compressor also consists of two casings. Both the upper case and lower case have stator blades. During troubleshooting, only the upper case may be removed while the lower case cannot because it lies on the ground (see the figure). If the compressor can operate adiabatically, then it can change the second principle of thermodynamics.

The Combustion Chamber

The combustion system is a reverse-flow model in which the combustion chamber is located near the edge of the compressor discharge casing as illustrated in figure 2.8. Usually, the numbering of combustion chambers assumes a counterclockwise direction when observed from a downstream direction from the top of the gadget. The combustion chamber also has fuel nozzles, an ignition system with a plug, a flame detector, and crossfire tubes. The turbine runs from the hot air that comes from the blazing fuel.

Spark Plugs

The two retractable-electrode spark plugs are responsible for the combustion as they discharge. The spark plugs are joined to the flanges on the combustion system, which are located in the liner and flow sleeve in the next combustion chamber. The figure 2.11 shows a normal arrangement of spark plugs. The ignition transformer supplies the energy to spring-injected and pressure-retracted plugs. The spark from one or both of these plugs starts the fuel when fired at the unit. Other chambers’ ignitions result from the crossfire from tubes that join reaction areas of the rest of the chambers. When the rotor speed rises, the chamber pressure makes the spark plugs to draw in and remove electrodes from the combustion area.

Turbine Section

A turbine consists of four rows as shown in figure 16. After the process is complete at the composition chambers, the flow with high temperature of 1100⁰C and pressure goes to the turbine. The turbine that supplies high-speed movement to the tube requires 3600 rpm in order to achieve the right velocity for the generator. The gas turbine consists of turbine rotor, shrouds, the casing with nozzles, exhaust diffuser, and exhaust frame.

Turbine Casing (Shell)

The turbine shell is responsible for regulating axial and radial positions of nozzles and shrouds. It shows the clearance at the turbine and a given position of the nozzles to the position of turbine baskets. The position is important for the gas turbine performance. Hot gases within the shell supply heat flow into the shell. It is imperative to lessen the heat flow into the shell and restrict temperatures in order to control the shell diameter.

Journal Bearings

Bearing 1

The first bearing assembly can be found at the middle of the inlet casing with an active or loaded thrust bearing, unloaded thrust bearing, and the journal bearing. In addition, it also has two ‘running type’ ring seals, two labyrinth seals, and a casing unit where all the parts are fixed. All components are joined to the housing unit in order to eliminate chances of rotating. The base of the housing unit also acts as a part of the inlet casing. The upper part of the housing is different casing unit, which is an extension bolted to the lower part of the system. The extracted air that comes from the compressor in the 5^th stage pressurises the labyrinth seals at all ends of the housing. There is oil in the ‘running type’ ring seals at both ends of the thrust-containing cavity, which restricts the inflow of the air into the cavity.

Bearing 2

The second bearing subassembly is within the centre line where it is supported by the inner cylinder of the compressor-discharging casing. The support originates from the ledges within the horizontal and axial point at the base centre line. This allows for a relative changes that result from variations in the temperature when the bearing stays at the centre within the discharge casing.

The bearing assembly consists of a liner, labyrinth seals, and a bearing housing. It can be found at the inner barrel in a pressurised space flanked by the turbine and the compressor. The second bearing liner cannot rotate because of the shaft and an anti-rotating pin within the lower part of the bearing liner.

Bearing 3

The third bearing subassembly is at the end of the turbine shaft within the centre of the exhaust frame assembly. The bearing has a tilting pad, three labyrinth seals, two floating ring seals, and a bearing casing unit. Every pad has a design and assembly that allows it to generate high-pressure oil film between the bearing surface and the pads. This results into a symmetrical loading or ‘clamping’ outcome on the bearing surface, and it helps in enhancing the stability of the shaft. The pads can move in two dimensions, which allow them to tolerate a certain level of shaft misalignment.

Thrust Bearings

The thrust bearings are in the first bearing housing where they support the thrust loads of the gas turbine rotor components. A thrust bearing system consists of the shaft member (thrust collar) and a stator member or bearing. Under normal operation circumstances of the gas turbine, the thrust load of the rotor unit assumes unidirectional position. However, the system will reverse its direct when it starts or stops. Therefore, two thrust bearings are placed in the first bearing unit to support the thrust loads that come from either direction. The loaded (active) thrust bearing is the bearing that drives the thrust load during the regular operations while the unloaded (inactive) thrust bearing takes the load in start-up or shutdown operations of the system. The system requires flooding oil to run.

The Exhaust

The exhaust system removes hot gases after the turbine has gained the energy. The exhaust system must be long enough to limit its impacts on the neighbouring residential areas and support the flow at 1093 kg/hr x 10-3 of toxic gas (figure 17).

Heat Exchanger (Radiator) Cleaning

Problem

Observations from several units indicated that there was energy loss in the net power by about 15 MW. The power plant consists of 40 GE units. This would result into a loss of over 600 MW of power.

Observations

The following data were collected from the unit observation.

Output power loss of 20 MW
High temperature of 60 ⁰F from the inlet water because of the lube oil header
A low temperature difference of 5 ⁰F between inlet and outlet temperatures
A small difference temperature of 10 ⁰F between the lube oil header (170 ⁰F) and alarmed temperature (180 ⁰F)

General

The heat exchanger system supplies the heat between fluid streams of different inlet temperatures. System cools fluids in the evaporator or condensers based on their temperature variations. Heat exchangers have important applications in different industries, such as air conditioning, power generation, desalination, manufacturing, and refrigeration among others. The commercially available heat exchangers may be categorised based on their geometric configuration of heat transfer surface, capabilities, and flow arrangement among other critical capabilities. A common example of heat exchanger is the shell-and-tube type. Its classification is based on the type of the shell and the number of tubes alongside other geometric features. Generally, shell-and-tube heat exchanger has the following components:

Shell and shell-side nozzle
Tubes
Baffles
Tube sheets
Tube-side channels and nozzles
Channel covers
Pass divider

Procedures

From these observations, it was imperative to seek services of a specialised firm to conduct internal cleaning. However, internal cleaning processes did not yield the expected outcomes, and the company conducted external cleaning, which provided the desired results.

Results

Some of these results were outcomes from the previous work.

A difference of temperature existed between inlet water and outlet (15 – 20 degree)
The lube oil header temperature declined to 135 ⁰F while the alarmed temperature declined to 150 ⁰F
The power output assumed its normal units of outputs

The report captures activities of the coop plan for a period of 28 weeks at Power Plant 10. It highlights Gas Turbine (GT) and its parts, case studies about the efficiency of a gas turbine and heat exchanger (radiator) Cleaning. From this conclusion, one can conclude that resolving engineering problems requires structured thinking without hurried processes because of the nature of a specific issue. Field problems appear simpler than classroom-based tasks, but all class contents are applicable in the field. Hence, the coop programme reinforces the learned contents during real-life applications.

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