CNR 6167

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Nalco Continuous Blow-down equipment (manufactured by the National Aluminate Corp. of Chicago) was used to control the quality of the water inside the boiler in order to prevent foaming and priming and to protect the boiler from the effects of the impurities in the water. The CBD consists of a valve located on top of the boiler or on the side of the firebox (as illustrated below) which is operated by a sensing line that draws steam from the valve chest on the fireman's side which in turn exhausts the water into a separator located near the cab. The separator uses centrifugal force to separate the water and sludge from the steam. The steam then exhausts through the top, while the sludge and water falls to the ground.

"As feed water is added to a locomotive boiler and changed to steam, the concentration of dissolved solids in the boiler steadily increases. Eventually the boiler water would foam, unless preventative measures are taken. Water and dirt would be carried along by this sludgy foam, clogging superheater, valves, and causing excessive wear on cylinders and other surfaces. This concentration of dissolved solids must be kept below the foaming point for efficient operation and the common remedy has been to change water or wash boilers frequently ... which delays locomotives and adds to expense. Another remedy has been to blow-down boilers on the road, where haphazard hand control is relied upon to open a large valve intermittently. Usually in this case, the blow-down is discharged straight out from the side of the engine, creating a hazard to life and property along the right-of-way. It may also be blown back on the train, damaging the appearance and finish of the equipment.

The Nalco Automatic Continuous Blow-down has been adopted by a large number of leading railroads as the correct method of controlling blowdown. The Nalco Blow-down eliminates the expense of frequent washouts and the waste and uncertainty of hand control. As steam is used, the Type ACS Nalco Blow-down automatically keeps the concentration of dissolved solids below the foaming point ... no manual control is required. The discharge is in proportion to the steam used and occurs only when steam is used. There is no danger to equipment, or to persons and property along the wayside ... The Nalco Separator discharges clean dry steam above the cab roof, while the sludge and water drain by gravity to the roadbed. Operation is independent of grades or changing water levels inside the boiler. Thus excessive blowdown does not take place when the engine is laboring on an ascending grade. Also, there are no complicated parts ... the automatic control valve is the only moving part. Most important of all .. , the Nalco Blow-down does not require any attention from the enginemen. They are free to attend to their operating duties .. , an important consideration in view of high speeds and heavy traffic. The Type ACS Blow-down is one of the developments of the Nalco System and has proved its safety and reliability through years of service throughout the country. Used in connection with Nalco Water Treatment, it has made possible the placing of locomotives on an extended washout basis."

For additional information, look up patents #1966776 and #1968651 at the United States Patent and Trademark Office.

Installation of Nalco Continuous Blow-down System

An early arrangement, was wherein the CBD valve was installed on the side of the firebox, usually on the Fireman's Side, and is what is shown on the diagram above. The Separator was installed on a bracket ahead of the turret (on the Fireman's side) with the Piping running to and from the Separator running down the side of the firebox (still on the fireman's side). Two engines that have been observed with this arrangement are CNR 6243 and 6254. This method appears to have been short lived, as it appears that most engines were refit the the next arrangment.

By far the most common arrangment on larger motive power is as seen on CNR 6167. In this arrangement, the valve is installed on top of the boiler, ahead of the safety valves, while the separator is installed behind the cab. All piping along the boiler is hidden beneath the jacketing, and the only piping that is visible, are the pipes on the back of the cab.

Continuous Blow-down Valve

Blow-down Separator

Piping to and from Blow-down Separator

Drain from Blow-down Separator

On the topic of the sensing line, I've seen pictures of the line in photographs of engines with the jacketing removed, and in every case, I've noticed that the pipe takes what I'll call the "scenic route" to the blow-down valve!