PROPER USE OF SILK SCREEN
(This article is reprinted intact from The Right of Way, published by the Pennsylvania Threshermen's & Farmers' Protective Association, issue of March 26, 1919, courtesy of Howard Gibble, Mount Joy, RD 1, PA.)
A little article on York county's trouble with the fire insurance companies regarding the use of a spark screen when near a barn might be interesting to the threshermen. After our committee, composed of Edward Jacobs, W. D. Slonaker, George Jacobs and T. G. Cooke, visited several of the largest insurance companies doing business in York county and explained to them the principle of the cone-shaped screen usually used we found we had no fight with them as they accepted our explanation and were well satisfied.
Inasmuch as the currents of steam, smoke and cinders are in the center of the smoke stack the current is divided by the point of the screen and heavy sparks and cinders are deflected and thrown against the sides of the smoke stack. Unless the draft is very great the spark will drop into the smoke box which accounts for the smoke box filling with ashes and a cleaning is frequently needed. If the spark does not fall into the smoke box it will strike the cast ring to which the screen is attached to and be thrown sideways and down to the ground where it will do no harm.
Even though the ring holding the screen be raised several inches above the top of the smoke stacks it is still considered and efficient spark arrester and gives sufficient protection and entirely fills the requirements of the underwriters' policy. But they ask us to use extra precaution when putting a machine in the barn by closing or dropping the screen tight on the top of the smoke stack, making it spark-proof if not too large a screen be used.
They asked and recommended that nothing larger than one-half inch mesh be used on a cone-shaped screen where the current of smoke and sparks strike the screen at an angle and a three-eighth mesh on a flat screen, but asked us to use a still smaller one if possible. A one-eighth mesh can be used if the ring on the screen be raised two inches above the top of the smoke stack. This gives very good protection when lowered for a few minutes when very close to a building.
It is next to impossible to keep in all sparks when wood is used or the farmer has carelessly placed his pile of coal on a lot of chips or bark. But, brother threshermen, have your screen and keep it in use as above explained and the farmer is sufficiently protected and within the requirements of the underwriters of the state.