of the steam atomizing burner, they have had constantly under investigation every new development which offered reasonable promise of improvement. The mechanical atomizing type of oil burner had been in use for some time in marine work. This burner, however, while offering promising possibilities, had not commercially shown as high efficiency as the steam atomizing burner, and the capacities obtainable were considerably lower per burner.

"At the time the conversion of the Savannah and Pawtucket plants to fuel oil was under consideration, the Babcock & Wilcox Company had just completed development of a large capacity, mechanically atomizing, force draft oil burner. A thorough study of the manufacturer's experimental installation convinced the Stone & Webster engineers of the superiority of this burner and of its ability to meet the exacting requirements of the Savannah and Pawtucket plants, and it was accordingly selected for these installations. The Savannah Installation

"The Savannah Company has two power stations. The Indian Street Station, the older, has been equipped with conventional front shot steam atomizing burners. The bulk of the power is generated at the Riverside Station, which was built by Stone & Webster in 1912. It is the latter station which has been equipped with the new type of Babcock & Wilcox burner, this being the first commercial installation of the kind.

"The Riverside Station, which normally supplies the power requirements of the entire electric railway system of the city of Savannah and suburbs, and the greater part of the electric power and lighting for the community, is equipped with horizontal type turbogenerators, exhausting to surface condensers, with the usual complement of auxiliaries. The boilers which supply steam for the generators are Babcock & Wilcox in 665 hp. units, with 20 ft. tubes arranged 14 high and 21 wide, and equipped with Foster superheaters. All boilers were originally equipped with stokers for bituminous coal.

"Fig. 732 shows a view of the transformed boiler room. The stokers have all been removed and four oil burners installed under each boiler. As shown in the figure, the lower part of the furnace front is covered by a steel plate blast box, in which are set the registers and burners and through which the forced draft is supplied. The arrangement of furnaces is shown in Fig. 717.

"Fuel oil is received at the overground steel tank storage at Riverside by pipe line direct from the supply station of the oil company. From the Riverside storage, oil may be fed by gravity to a two-compartment underground service tank for use at the Riverside Station, or pumped by a motor driven Kinney pump to a similar service tank for the Indian Street Station, which is several hundred feet away and at a higher level. In the service tanks the oil is heated to about 100 degrees F.; it is then pumped to the burners through high pressure heaters. At the Riverside Station the oil reaches the burners at about 230 degrees F. and at pressures varying up to about 210 lb., dependent upon the capacity desired. The high pressure oil pumps and heaters are housed in a separate fireproof room constructed within the station building. Forced draft is supplied by turbine and motor driven Green fans.

Remarkable Operating Results.

"The Savannah oil burning installation has now been in operation seven months, and the results throughout have been extremely gratifying. The furnace design has met all requirements, and tests, the results of which are given in the accompanying tabulation, also partly presented in the curves of Fig. 737, show that the high efficiency obtained at the boiler rating is held in a remarkable degree at extreme overloads. "Since the adoption of fuel oil the Savannah River

side boilers have been operated normally at about 250 per cent of their rated capacity, and there has been no instance of tube trouble through the seven months of operation, although the boiler feed water is by no means entirely free from solid impurities. All indications are that general maintenance will be low. Operation has been found extremely simple. Only two conditions require adjustment at the furnace, oil pressure and draft, and it has been possible to schedule these conditions and their adjustments so accurately that the every-day operating performance closely apDroximates the best test results.

In

"A single size of burner tip has been selected which fulfills all requirements of normal operation. Also, there is no adjustment of air registers for burners in operation, as these are set wide open. There are, thus constant orifices for the admission of both air and oil. The proper relations between the oil and air pressures throughout the capacity range has been determined by analysis of the combustion gases, and an additional scale etched upon the dial of the air pressure gage gives the corresponding oil pressure required. operation the oil valves are adjusted to give the oil pressure indicated on the oil scale of the air gage for whatever air pressure is being carried at the moment, and the resulting conditions are right for proper combustion. The simplicity of the fireman's work is very evident. No difficulty is experienced in maintaning smokeless conditions with varying loads at all ratings. "An interesting outcome of the increased furnace efficiency has been the effect upon the superheater performance. When burning coal the steam was superheated on the average about 140 degrees F., and it was necessary to keep constant watch of the condition of boiler heating surfaces to avoid exceeding this figure. With combustion entirely completed in the furnace, as occurs with the oil burning installation, and the resulting increased heat absorption by the first pass of the boiler proper, the superheat imparted by the same area of superheater surface is reduced approximately one-half..

Tests of the New Installation.

"During May, 1920, the Stone & Webster Station Betterment Division, with the co-operation of a rep resentative of The Babcock & Wilcox Company and the local plant operators conducted a series of tests on one of the Riverside boilers for the purpose of formulating a proper operating schedule and incidentally to determine the actual efficiency of the installation. The boilers of the plant are set in batteries of two, but to ensure constancy of radiation conditions the boiler in battery with the test boiler was not under fire during the tests. Fig. 717 is typical of the entire plant and shows the details of boiler and setting to which the test results apply.

"For the special purposes of the test a separate oil pump and heater were set up in the Riverside boiler room and all oil actually weighed as fed to the test boiler. Feed water was measured by two 3 inch x 1 inch Venturi meters especially calibrated through their range by Prof. Allen of Worcester Polytechnic Institute. These meters, which have a capacity of 45,000 lb. per hour each, were installed in the front and rear feed connections respectively and, as only one feed was used at low ratings, so permitted good scale indications on the the manometers for all desired rates of boiler output. Centrifugal feed pumps were used and the flow was very steady. The tests were of four and five hours' duration, with three to four hours' preliminary operation under test conditions, insuring almost absolute constancy of results throughout the actual test period.

Test Results.

"The data of the Riverside oil burning tests are presented in considerable detail in Table XCV, and the more important of the results are also shown in the

curves of Fig. 737. There are certain features which, perhaps, require some explanation: Test No. 8 at 168 per cent of boiler rating shows an efficiency slightly below the corresponding value of the curve of Fig. 737. For this test the percentage of excess air was deliberately increased, because, although no evidence of incomplete combustion had been detected in previous tests, it was feared that the air ratio might possibly have been held too low, permitting the escape of some slight trace of CO. From the test results, however, this had evidently not been the case. In the test following, the air excess was reduced to the same low figure previously allowed. It will also be noted that for Test No. 9 at 114 per cent of boiler rating, a negative value is shown for the draft loss through the boiler. At this low rating, the chimney effect of the furnace and first pass evidently created a greater pressure reduction at the point of furnace draft measurement than was required to carry the gases through the two remaining passes of the boiler.

"The efficiency curve speaks for itself. The values given are, to be sure, gross efficiencies, but any deduction for heat supplied to oil pumps, heaters, and forced draft fans is negligible, as the exhaust steam is fully utilized for heating boiler feed water. So far as known there is no other boiler installation giving efficiencies approximating 80 per cent at 300 per cent of boiler rating."

Since the above article was written by Mr. Pope and Mr. Philo the Blackstone Valley Gas & Electric Co.'s plant has started operating with Lodi burners with very satisfactory results. Preparations are being made to run tests there in the near future.

A plant that has been of particular interest in a number of ways in connection with the installation of these new mechanical oil burners is that of the Narragansett Electric Lighting Co. at Providence, Rhode Island. At the time they secured their oil contract and were considering the installation of oil burners in place of their underfeed stokers, the Lodi burner was still in an experimental stage and no commercial plants were in operation. As this plant is equipped with thirty-two 600 hp. Babcock & Wilcox boilers, operated normally at about 200 per cent of rating with coal, it was a matter of considerable importance to determine with absolute certainty the best type of burner to meet their requirements. In order that as little change as possible be made in the plant, and also to make it readily possible to return. to coal burning should necessity require, it had been decided to leave the stokers in place under the front end of the boilers, the stokers being suitably protected from the oil flames. The bridge walls were to be removed and the oil burners installed under the mud drum.

Because the Lodi burners had shown very promising results under test conditions at Bayonne, although not yet commercially on the market, coupled with the fact that steam atomizers were at that time used practically universally in stationary power plants, led the Narragansett Company to make preparations for running a series of comparative tests in their own plant to determine the relative merits of the two types for their installation. Accordingly, after suitably investigating the field, three boilers in the plant were fitted with a trial installation of a well known type of flat flame steam atomizer, three. atomizers fitted per boiler. Some time after the

completion of this installation, and as soon as it could be secured, one boiler near by was fitted with Lodi burners, using four atomizers per boiler. The steam atomizers were fitted to operate natural draft, the stacks being 200 feet above the boiler room floor. The mechanical burners were fitted with double fronts and supplied with forced draft from the stoker ducts. Fig. 734 shows the boiler, furnace and burner equipment used in the trial installation of the mechanical burners. The steam atomizers were placed in a similar position shooting forward, a suitable checkerwork of firebrick being installed in front of the burners, the air supply being drawn from the boiler room. The furnace volumes of the two installations were practically the same, approximately 1270 cu. ft.

The steam atomizers had been in service some four months before the mechanical installation was complete, and during that time some difficulties were experienced with tube losses, although it should be said by way of explanation in this connection that due to the necessary use of jet condensers in this plant, raw water is used for about 88 per cent of feed, and although the water is unusually good boiler feed water, it does naturally contain a certain amount of impurities, total solids being ordinarily less than 3 grains per gallon.

The rating conditions at this plant are so much higher than those usually encountered in oil burner installations that, as the Lodi Burners readily met