TPM

Total productive maintenance (TPM)

TPM

  

Originated  in Japan in 1971 as a method for improved machine availability through better utilization of maintenance and production resources.

Whereas in most production settings the operator is not viewed as a member of the maintenance team, in TPM the machine operator is trained to perform many of the day-to-day tasks of simple maintenance and fault-finding. Teams are created that include a technical expert (often an engineer or maintenance technician) as well as operators. In this setting the operators are enabled to understand the machinery and identify potential problems, righting them before they can impact production and by so doing, decrease downtime and reduce costs of production.

TPM is a critical adjunct to lean manufacturing. If machine uptime is not predictable and if process capability is not sustained, the process must keep extra stocks to buffer against this uncertainty and flow through the process will be interrupted. Unreliable uptime is caused by breakdowns or badly performed maintenance. Correct maintenance will allow uptime to improve and speed production through a given area allowing a machine to run at its designed capacity of production.

One way to think of TPM is "deterioration prevention": deterioration is what happens naturally to anything that is not "taken care of". For this reason many people  refer to TPM as "total productive manufacturing" or "total process management". TPM is a proactive approach that essentially aims to identify issues as soon as possible and plan to prevent any issues before occurrence. One motto is "zero error, zero work-related accident, and zero loss".

TPM is a maintenance process developed for improving productivity by making processes more reliable and less wasteful.TPM is an extension of TQM(Total Quality Management). The objective of TPM is to maintain the plant or equipment in good condition without interfering with the daily process. To achieve this objective, preventive and predictive maintenance is required. By following the philosophy of TPM we can minimize the unexpected failure of the equipment.

To implement TPM the production unit and maintenance unit should work jointly.

Original goal of total productive management:

“Continuously improve all operational conditions, within a production system; by stimulating the daily awareness of all employees” (by Seiichi Nakajima, Japan, JIPM)

TPM focuses primarily on manufacturing (although its benefits are applicable to virtually any "process") and is the first methodology Toyota used to improve its global position (1950s). After TPM, the focus was stretched, and also suppliers and customers were involved (Supply Chain), this next methodology was called lean manufacturing. This sheet gives an overview of TPM in its original form.

An accurate and practical implementation of TPM, will increase productivity within the total organization, where:

(1) .. a clear business culture is designed to continuously improve the efficiency of the total production system
(2) .. a standardized and systematic approach is used, where all losses are prevented and/or known.
(3) .. all departments, influencing productivity, will be involved to move from a reactive- to a predictive mindset.
(4) .. a transparent multidisciplinary organization in reaching zero losses.
(5) .. steps are taken as a journey, not as a quick menu.

Finally TPM will provide practical and transparent ingredients to reach operational excellence.

TPM has basically 3 goals - Zero Product Defects, Zero Equipment Unplanned Failures and Zero Accidents.

The Pillars & their details
a) Efficient Equipment Utilization
b) Efficient Worker Utilization
c) Efficient Material & Energy Utilization

1. Focused improvement (Kobetsu Kaizen) - Continuously even small steps of improvement.
2. Planned Maintenance - It focuses on Increasing Availability of Equipments & reducing Breakdown of Machines.
3. Initial Control - To establish the system to launch the production of new product & new equipment in a minimum run up time.
4. Education & Training - Formation of Autonomous workers who have skill & technique for autonomous maintenance.
5. Autonomous Maintenance (Jishu Hozen) - It means "Maintaining one's equipment by oneself". There are 7 Steps in & Activities of Jishu Hozen.
6. Quality Maintenance (Hinshitsu Hozen) - Quality Maintenance is establishment of machine conditions that will not allow the occurrence of defects & control of such conditions is requored to sustain Zero Defect.
7. Office TPM - To make an efficient working office that eliminate losses.
8. Safety, Hygiene & Environment - The main role of SHE (Safety, Hygiene & Environment) is to create Safe & healthy work place where accidents do not occur, uncover & improve hazardous areas & do activities that preserve environment.

Check List for 5 ‘S’- Own Office/Department

1.	No files on the table except today’s working files. Better avoid keeping IN/OUT trays on the table. This shall make table top clutter free.
2.	Identification mark for  keeping IN/OUT trays.
3.	Identify & mark a place for keeping all the files. Use the concept of visual control while designing and making storage location. Storage space should be such that when items are removed, empty space is visible and different items cannot be put into the same place.
4.	Files should be kept vertically with marking , tagging & Indexing to achieve Zero search retrieval. File numbering system established & all files marked.
5.	Standardization of type of files & should be placed in specified racks
6.	Proper identification & placement for all equipments ie PC, Printer ,Laptop & daily use items ie Lunch box, Water bottle, glass, Pen stand Spectacles, Pen drive, Mobile, Charger & helmet, etc. All items which are frequently  used should be visible.
7.	Ensure no loose wires of PC/Printer/Telephone.
8.	Standard table drawer stationery  templates for keeping all stationery items at fixed place ie Stapler, Stapler pins, Lunch, Highlighter, Marker, Eraser, Pen,U clips, Tape, Calculator, Paper cutter, Visiting card, Pencil & gum etc. Items in desk drawer are positioned as per frequency of use.
9.	Proper placement & identification of all keys.
10.	Record retention as per HR manual   (Chapter XXII PROCEDURE FOR PRESERVATION AND MANAGEMENT OF OFFICE RECORDS AND WEEDING OUT OF OLD RECORDS)
11.	Removal of all unwanted items ie More then required no of Pencils, pens, Used papers, torn files, Old editions of magazines already read, Unused/defective  pens, Old torn literature, More then one calender, unnecessary posters, Old Policy. The essence is to keep current/latest editions of journals, books , literature etc. This requires lots of patience, experience, time and understanding as to what is to be kept. Avoid ‘just in case attitude’ as far as possible.
12.	Proper marking on all electrical switches, Fans, Tubes etc
13.	Proper marking for placement of different Telephones ie Intercom, BSNL or other phones. Telephone no. to be written on the phone.
14.	Signage on the walls/floors ie Exits, Tiger guards lines, Holding area, Toilets, Pantry, PA Office, ED Sect, Red/green lights outside office etc.
15.	Placement of Notice boards to be marked and date of removal stickers for circulars to be used. Old circulars to be removed after the date.
16.	White boards to be maintained & there should place for keeping duster & white board marker.
17.	Deletion of all unwanted files/ mails from the computer.There should be only standard system Icon on the Desktop with one folder for other data.
18.	Office layout at the entrance of each department indicating name, Designation. Photo, location & their roles.
19.	Individual seat should have display of jobs being done at particular place.
20.	Targets for each section / jobs for  customer satisfaction ie performance indicators, Time taken for HBA, payment to suppliers, conveyance loans and various other such type of services.
21.	Updated TPM  activity board display.
22.	“ HALL OF FAME” Concept to be adopted. Every month one employee is identified who have done extraordinary work in his section. Display with his/her photograph and details of the work.
23.	Holding area to be marked. The files/items which can not be decided at the moment for its removal to be kept for further review.
24.	Red Tag Area Concept to be adopted. This is the marked area where all such items which may be useful to others but not being used by any individual, can be kept like Books, Journals, More then required stationary items or any such items.
25.	Common Office equipment ownership plate /maintained by to be written. Specifications, Next service due date, Last service date, Phone no. of service providers may be written. Display standard operating procedures.
26.	Removal of cob-webs and cleaning of ceilings, roof corners, structures. Cleaning of walls, window panes, floor cleaning etc
27.	Paint or draw lines around fixed area ie around flower pots, Office equipments etc.
28.	Overall aesthetics of tables/ equipment to be maintained.
29.	Fire extinguishers – Identify placement/location & ensure refilled/expiry date sticker.
30.	Entrance to department identified and visible.

COMBINED CYCLE POWER PLANT

COMBINED CYCLE POWER PLANT

                   

Preamble

Gas combustion generates high temperature and pressure so that the efficiency of gas turbine is more comparable to that of steam turbine. The Combined Cycle Power Plant or combined cycle gas turbine, a gas turbine generator generates electricity and waste heat is used to make steam to generate additional electricity via a steam turbine. The gas turbine is one of the most efficient one for the conversion of gas fuels to mechanical power or electricity. The use of distillate liquid fuels, usually diesel, is also common as alternate fuels.

More recently, as simple cycle efficiencies have improved and as natural gas prices have fallen, gas turbines have been more widely adopted for base load power generation, especially in combined cycle mode, where waste heat is recovered in waste heat boilers, and the steam used to produce additional electricity.

This system is known as a Combined Cycle. The basic principle of the Combined Cycle is simple: burning gas in a gas turbine (GT) produces not only power – which can be converted to electric power by a coupled generator – but also fairly hot exhaust gases.

Routing these gases through a water-cooled heat exchanger produces steam, which can be turned into electric power with a coupled steam turbine and generator.

This type of power plant is being installed in increasing numbers round the world where there is access to substantial quantities of natural gas.

A Combined Cycle Power Plant produces high power outputs at high efficiencies (up to 55%) and with low emissions. In a Conventional power plant we are getting 33% electricity only and remaining 67% as waste.

By using combined cycle power plant we are getting 68% electricity.

It is also possible to use the steam from the boiler for heating purposes so such power plants can operate to deliver electricity alone or in combined heat and power (CHP) mode.

Fundamental

Combined cycle power plant as in name suggests, it combines existing gas and steam technologies into one unit, yielding significant improvements in thermal efficiency over conventional steam plant. In a CCGT plant the thermal efficiency is extended to approximately 50-60 per cent, by piping the exhaust gas from the gas turbine into a heat recovery steam generator.

However the heat recovered in this process is sufficient to drive a steam turbine with an electrical output of approximately 50 per cent of the gas turbine generator.

The gas turbine and steam turbine are coupled to a single generator. For startup, or ‘open cycle‘ operation of the gas turbine alone, the steam turbine can be disconnected using a hydraulic clutch. In terms of overall investment a single-shaft system is typically about 5 per cent lower in cost, with its operating simplicity typically leading to higher reliability.

                                                                                

Working principle of CCTG plant

First step is the same as the simple combined cycle gas turbine plant. An open circuit gas turbine has a compressor, a combustor and a turbine. For this type of cycle the input temperature to turbine is very high. The output temperature of flue gases is also very high.

This is therefore high enough to provide heat for a second cycle which uses steam as the working medium i.e. thermal power station.

Figure - Working principle of combined cycle gas turbine (CCTG) plant

                         

Air Inlet

This air is drawn though the large air inlet section where it is cleaned cooled and controlled. Heavy-duty gas turbines are able to operate successfully in a wide variety of climates and environments due to inlet air filtration systems that are specifically designed to suit the plant location.

Under normal conditions the inlet system has the capability to process the air by removing contaminants to levels below those that are harmful to the compressor and turbine.

In general the incoming air has various contaminants. They are:

In Gaseous state contaminants are:

• Ammonia
• Chlorine
• Hydrocarbon gases
• Sulfur in the form of H2S, SO2
• Discharge from oil cooler vents

In Liquid state contaminants are:

• Chloride salts dissolved in water (sodium, potassium)
• Nitrates
• Sulfates
• Hydrocarbons

In Solid State contaminants are:

• Sand, alumina and silica
• Rust
• Road dust, alumina and silica
• Calcium sulfate
• Ammonia compounds from fertilizer and animal feed operations
• Vegetation, airborne seeds

Corrosive Agents:
Chlorides, nitrates and sulfates can deposit on compressor blades And may result in stress corrosion attack and/or cause corrosion Pitting. Sodium and potassium are alkali metals that can combine with Sulfur to form a highly corrosive agent and that will attack portions of the hot gas path. The contaminants are removed by passing through various types of filters which are present on the way.

Gas phase contaminants such as ammonia or sulfur cannot be removed by filtration. Special methods are involved for this purpose.

Turbine Cycle

The air which is purified then compressed and mixed with natural gas and ignited, which causes it to expand. The pressure created from the expansion spins the turbine blades, which are attached to a shaft and a generator, creating electricity.

In second step the heat of the gas turbine’s exhaust is used to generate steam by passing it through a heat recovery steam generator (HRSG) with a live steam temperature between 420 and 580 °C.

Heat Recovery Steam Generator

In Heat Recovery Steam Generator highly purified water flows in tubes and the hot gases passes a around that and thus producing steam .The steam then rotates the steam turbine and coupled generator to produce Electricity. The hot gases leave the HRSG at around 140 degrees centigrade and are discharged into the atmosphere.

The steam condensing and water system is the same as in the steam power plant.

Typical Size and Configuration of CCGT Plants

The combined-cycle system includes single-shaft and multi-shaft configurations. The single-shaft system consists of one gas turbine, one steam turbine, one generator and one Heat Recovery Steam Generator (HRSG), with the gas turbine and steam turbine coupled to the single generator on a single shaft.

Multi-shaft systems have one or more gas turbine-generators and HRSGs that supply steam through a common header to a separate single steam turbine-generator. In terms of overall investment a multi-shaft system is about 5% higher in costs.

The primary disadvantage of multiple stage combined cycle power plant is that the number of steam turbines, condensers and condensate systems-and perhaps the cooling towers and circulating water systems increases to match the number of gas turbines.

Efficiency of CCGT Plant

Roughly the steam turbine cycle produces one third of the power and gas turbine cycle produces two thirds of the power output of the CCPP. By combining both gas and steam cycles, high input temperatures and low output temperatures can be achieved. The efficiency of the cycles adds, because they are powered by the same fuel source.

To increase the power system efficiency, it is necessary to optimize the HRSG, which serves as the critical link between the gas turbine cycle and the steam turbine cycle with the objective of increasing the steam turbine output. HRSG performance has a large impact on the overall performance of the combined cycle power plant.

The electric efficiency of a combined cycle power station may be as high as 58 percent when operating new and at continuous output which are ideal conditions. As with single cycle thermal units, combined cycle units may also deliver low temperature heat energy for industrial processes, district heating and other uses. This is called cogeneration and such power plants are often referred to as a Combined Heat and Power (CHP) plant.

The efficiency of CCPT is increased by Supplementary Firing and Blade Cooling. Supplementary firing is arranged at HRSG and in gas turbine a part of the compressed air flow bypasses and is used to cool the turbine blades. It is necessary to use part of the exhaust energy through gas to gas recuperation. Recuperation can further increase the plant efficiency, especially when gas turbine is operated under partial load.

Fuels for CCPT Plants

The turbines used in Combined Cycle Plants are commonly fuelled with natural gas and it is more versatile than coal or oil and can be used in 90% of energy applications. Combined cycle plants are usually powered by natural gas, although fuel oil, synthesis gas or other fuels can be used.

Emissions Control

Selective Catalytic Reduction (SCR):

• To control the emissions in the exhaust gas so that it remains within permitted levels as it enters the atmosphere, the exhaust gas passes though two catalysts located in the HRSG.
• One catalyst controls Carbon Monoxide (CO) emissions and the other catalyst controls Oxides of Nitrogen, (NOx) emissions. Aqueous Ammonia – In addition to the SCR, Aqueous Ammonia (a mixture of 22% ammonia and 78% water) is injected into system to even further reduce levels of NOx.

Merits

Fuel efficiency

In conventional power plants turbines have a fuel conversion efficiency of 33% which means two thirds of the fuel burned to drive the turbine off. The turbines in combined cycle power plant have a fuel conversion efficiency of 50% or more, which means they burn about half amount of fuel as a conventional plant to generate same amount of electricity.

Low capital costs

The capital cost for building a combined cycle unit is two thirds the capital cost of a comparable coal plant.

Commercial availability

Combined cycle units are commercially available from suppliers anywhere in the world. They are easily manufactured, shipped and transported.

Abundant fuel sources

The turbines used in combined cycle plants are fuelled with natural gas, which is more versatile than a coal or oil and can be used in 90% of energy publications. To meet the energy demand now a day’s plants are not only using natural gas but also using other alternatives like bio gas derived from agriculture.

Reduced emission and fuel consumption

Combined cycle plants use less fuel per kWh and produce fewer emissions than conventional thermal power plants, thereby reducing the environmental damage caused by electricity production. Comparable with coal fired power plant burning of natural gas in CCPT is much cleaner.

Potential applications in developing countries

The potential for combined cycle plant is with industries that requires electricity and heat or steam. For example providing electricity and steam to a Sugar refining mill.

Demerits

1. The gas turbine can only use Natural gas or high grade oils like diesel fuel.
2. Because of this the combined cycle can be operated only in locations where these fuels are available and cost effective.

Conclusions

Combined cycle power plants meet the growing energy demand, and hence special attention must be paid to the optimization of the whole system. Developments for gasification of coal and use in the gas turbine are in advanced stages.

Once this is proven, Coal as the main fuel can also combined cycle power plants meet the growing energy demand, be used in the combined cycle power plant.

The advances in cogeneration-the process of simultaneously producing useful heat and electricity from the same fuel source-which increases the efficiency of fuel burning from 30% to 90%, thereby reducing damage to the environment while increasing economic output through more efficient use of resources.