Document zzM48JawvLY2r9panxLvx4xzR

EVEN THOUGH UNITS LIKE THIS turbine run smoothly up to Inspection time, resist sn urge to postpone dltmenHIiq ADEQUATE INSTRUMENTATION AIDS efficient operation of thlo 2600-kw condensing unit by deteeting sbnormel condition# Establish Adequate Maintenance Program for Industrial Turbines Protect investment, minimize operating coiti by taking steam turbines out of service for inspection at regular intervals. Alf Hansen, turbine specialist. General Electric Co, tells what to look for and how to correct troubles at the start A COOP MANY INDUSTRIAL COMPANIES operate their power plants with little or no standby capacity. And yet a forced shutdown for one day may cost a company the equivalent of the average annual profit on the power plant. Best way to insure continuous powcr cquip. ment operation is to establish a planned schedule of inspection and mainte nance. Some of the gains from a generating insinuation are lost if sn extraction steam turbine U not available end boil ers feed process steam direct to lowpressure lines. Modern turbines, among the most reliable prime movers today, accustom operators to smooth, continu ous operation. So they are occasionally tempted to postpone inspection periods until definite indications of faulty op eration develop. Nevertheless, planned shutdowns for inspection (1) reduce forced outages (2) produce reliable power at minimum cost (3) insure safety of personnel and property. After a sound maintenance schedule has been established, don't gamble by running s turbine o year longer just because it seems to operate smoothly at the time of a planned shutdown. Spore Capacity* Most continuousprocess plants of medium size or larger have standby equipment. Plants with a spare turbine-generator have no dif ficulty adhering to an established main tenance program. When creeled some plants hn standby units, but Increased product!* demands require all units to be on th line continuously. So production and be curtailed during inspection period nnd inevitably equipment does not ts cetve necessary attention. Attempts in made to crowd a 2-week irupeclla period into a long weekend, but a non practicable procedure would be to tab down the powerhouse equipment do ing o 2-week annual-vacation shuido** for the entire factory. INSPECTION FREQUENCY No general rule for frequency of i spcctinns can be applied to all Indus tries or even to all plants within 0* same industry. One large industrid concern operated a turbine for ei|b years without an internal inspection Again, a hospital plant ran two m*Q turbines 12 to 14 years without liftiol the upper half of the turbine costal Undoubtedly these power-plant cratore had good reasons for their dir regard of conventional malntenan* schedules, but this practico cannot ta 89 (J6) POWER January IN* recommended generally. Moreover these operatora will probably be the first l agree that shorter intervals be tween inspections are desirable for boih safety and economy. Another industrial concern, operating three 2000-kw condensing turbines, at one time spent from three to four weeks for annual inspection, cleaning and overhauling of each unit. Their ac curate records show that money for this work was returned in fuel savings within two months after the equipment went back on the line. Some 10 or 15 yean ago manufac turers recommended annual turbine in spections and many users ttiU adhere lo this conservative practico. Today, in the utility plants, turbines are inpected within 12 months after going tato service, and then after every 10,000 operating hour*. U a turbine Is not b> deily service (t may be well to keep the interval between inspections at 10.000 operating hours, but not let total lapsed time exceed three year*. Who Makes Inspections? Some Indus plants have maintenance men they feel are competent to inspect and over haul their turbines, but most concerns find it more satisfactory to employ the manufacturer's field engineers to super vise this work. The latter practice is highly recommended because the serv. ice engineer la factory trained and kept advised of new developments, and Is in constant touch with the equipment de signers. Most industrial insurance companies hove Inspectors in the field, primarily (or their own protection. When con templating an inspection notify the insurance company so their Inspector may make hia own observations. RECORD KEEPINO Turbine inspectors should have a thorough procedure for systematic checking and recording of wear, ero sion, gradual deterioration and func tioning of governor* and safety devices. References at the end of this article eovor various phases of turbine inspec tion and overhaul. Condition of all wearing parts of a turbine should be listed in the inspec tion report Photographs, sketches or templates may supplement this informa tion. Comparison of these data for succeeding inspections will enable pre dicting when parts should be replaced and preventing failure in service. Copies of inspectors' reports should be in the files of both user and manu facturer so that the life history of the unit is readily available lo the parties principally interested. Operating Records. By properly log ging certain readings hourly the oper ator effectively "takes the pulse of the machine." Stage-pressure records indicate where scale accumulates in the turbine steam path. A suddenly incteased stage pres sure usually results from o foreign ob ject passing through the turbine and denting or restricting the nozzles*ahd buckets. A gradually increasing stage pressure is usually caused by scale deposits- When stage pressures plotted against steam flow show sn increase of 109b, it is time to do something about it. If deposits are soluble fn water, the *OWER January (948