The Comparative Merits of Various Systems of Car Lighting.
THE PINTSCH COMPRESSED GAS SYSTEM — THE PLANT ON THE CAR.
The essential features of the plant placed upon each car lit up by the Pintsch gas system are the reservoir for holding the compressed gas, the "regulator" for reducing its pressure to the very low point required for burning and the system of gas piping, burners and lamps.
It will be seen that cocks for attaching the filling hose for replenishing the reservoir are placed on each side of the car, so that on whichever side the line of distributing pipe is located, the car filler can connect the hose without crawling under the car. A pressure pipe is attached to the filling pipe near the reservoir [...] By consulting this gage, the pressure in the gas in the reservoir and the amount available for burning at any time can be ascertained. The reservoirs used on the car are made of various sizes, from 6 ft. to 9 ft. 6 ins. in length and 16 1/2 ins. to 20 1/2 ins. diam., and of special sizes to order when desired. In ordinary passenger service a single reservoir is all that is required; but where very long runs are to be made, two or more reservoirs may be attached to the car. For example, the Pullman cars running from Chicago to New Orleans (burning nearly a dozen lamps) have four large reservoirs, or enough to last an ordinary car with five four-flame lamps, burned four hours per day, for a continuous service of 17 days. [...]
We may note in this connection that the storage tanks used at the gas works and for carrying gas on tank cars are examples or high excellence in metal working. They are 20 ft. long and 4 ft. 2 ins. in diameter, and every seam is welded. In their manufacture the separate rings are first welded, which of course presents no especial difficulty. Each ring is then slightly expanded at one end and enlarged at the other, and the cylindrical portion of the holder is then made by welding together these separate sections. The most delicate operation, however, is welding in the heads, where the only resistance to the welder's hammer is that due to the stiffness of the sheet. These holders are all made at the works of Julius Pintsch in Berlin. The reason for the use of welded instead of riveted seams is, of course, to avoid all leakage.
One of the most important features of the Pintsch system is the regulator, by which the pressure of the gas in the pipes leading to the lamps is maintained at 1/2 oz. no matter whether the reservoir be full of gas at 150 lbs. pressure or nearly exhausted. [...]
The regulator is warranted for five years by the Pintsch Co., and some of them have been in use for 16 years on the railways of Germany without repairs or interference. It is adjusted once for all when made to give the 1/2 oz. pressure used in the distributing pipes, and needs no further adjustments. The fact that differences of pressure in the reservoir can have but an infinitesimal effect on the pressure of the gas in the pipes beyond the regulator, may be appreciated by comparing the areas and leverages of the two fluid pressures. The area of the valve-port for the compressed gas is to the area of the regulator diaphragm as 1 to about 9,000. Their relative leverage is as 1 to 25; hence a difference of pressure of 150 lbs. per sq. in. in the compressed gas will be balanced by a difference of pressure per sq. in. on the diaphragm of 150/25x9,000= 1/1500 lb. or about 1/100 oz.
The pipes leading from the reservoir to the regulator and to the filling valves are jointed by tinning the threads and soldering after screwing the pipes together; or where flange joints are used at the junction with filling valves, regulator, etc., a compound rubber and lead gasket is used, the rubber making a tight joint and the lead serving to protect the rubber to a considerable extent from the action of the gas.
From the regulator onward, the gas being under very low pressure, the same care is not necessary in making the joints and an ordinary 1/2-in. iron gas pipe is used. [...] The gas is led down to the burner from the roof pipe through one of the hollow supporting standards. From here it passes to the center of the lamp and down to the burners. [...] The lamps are made with either two, four or six-flame burners. A check screw with lock nut is attached to each burner: and the height of flame is adjusted by this when the lamps are put up, after which it should not be interfered with. [...]
The lamp globe and shades are packed with asbestos to prevent rattling. and especial care is taken with all joints to prevent them from becoming loose with the constant jar of service. [...]
According to data furnished us by the Safety Car Heating & Lighting Co., the Pintsch lighting system is now in use on over 38,000 passenger cars, divided among the different countries, as follows: