Part five _______

STEAM GAUGE

Some engineers call a steam gauge a “clock.”  I suppose they do this because they think it tells them when it is time to throw in coal, and when it is time to quit, and when it is time for the safety valve to blow off.  If that is what they think a steam gauge is for, I can tell them that it is time for them to learn differently.

It is true that in a certain sense it does tell the engineer when to do certain things, but not as a clock would tell the time of day.  The office of a steam gauge is to enable you to read the pressure on your boiler at all times, the same as a scale will enable you to determine the weight of any object.

As this is the duty of the steam gauge, it is necessary that it be absolutely correct.  By the use of an unreliable gauge you may become thoroughly bewildered, and in reality know nothing of what pressure you are carrying.

This will occur in about this way:  Your steam gauge becomes weak, and if your safety is set at I00 pounds, it will show I00 or even more before the pop allows the steam to escape; or if the gauge becomes clogged, the pop may blow off when the gauge only shows go pounds or less.  This latter is really more dangerous than the former.  As you would most naturally conclude that your safety was getting weak, and about the first thing you would do would be to screw it down so that the gauge would show I00 before the pop would blow off, when in fact you would have I00 or more.

So you can see at once how important it is that your gauge and safety should work exactly together, and there is but one way to make certain of this, and that is to test your steam gauge.  If you know the steam gauge is correct, you can make your safety valve agree with it; but never try to make it do it till you know the gauge is reliable.

HOW TO TEST A STEAM GAUGE

Take it off, and take it to some shop where there is a steam boiler in active use; have the engineer attach your gauge where it will receive the direct pressure, and if it shows the same as his gauge, it is reasonable to suppose that your gauge is correct.  If the engineer to whom you take your gauge should say he thinks his gauge is weak, or a little strong, then go somewhere else.  I have already told you that I did not want you to think anything about your engine-I want you to know it.  However, should you find that your gauge shows when tested with another gauge, that it is weak, or unreliable in any way, you want to repair it at once, and the safest way is to get a new one; and yet I would advise you first to examine it and see if you cannot discover the trouble.  It frequently happens that the pointer becomes loosened on the journal or spindle, which attaches it to the mechanism that operates it.  If this is the trouble, it is easily remedied, but should the trouble prove to be in the spring, or the delicate mechanism, it would be much more satisfactory to get a new one.