Why The Injector Don't Work

| January/February 1988

  • # Picture 01

  • # Picture 01

4214 W. Chicago Street Rapid City, SD 57702

Have read the very fine letters on how the injector works. I am sure that any old engine man has had times when the injector would not take water. I will try to cover the causes and cure of those troubles. First under the heading will not pick up water. Here are probable causes. #l-steam pressure too low. Some injectors are designed for higher pressures. #2-air leak in suction line. Many times the pack nut on the inlet hand valve loosens up or packing is worn or dried till it is no longer sealing. All injectors should be equipped with a fine screen at inlet end of the feed pipe or hose, and it may be clogged. If it is hard to get at and you need water now, put a plug in the overflow and turn in some steam; it will blow back through the feed line and screen. Then cool down the feed line with cold water and try again. If that did not do it, take the bottom plug out of the injector, the delivery tube should come right with it. Look for obstructions. Is the feed water line hot? If so, pour cold water over the injector and the feed or suction line and try again. This trouble is usually caused by the boiler check valve not seating right. This problem is rare but I have had it happen. When using a hose to draw water to the injector, a poorly made or old hose can have the lining of the hose separate and when suction is applied it will collapse, shutting off all water flow. This one is hard to find, try a different hose to find out. If feed water is too hot it can't be raised very far by suction.

Now this problem is most common and has the most causes. The injector will pick up water but just overflows. First take the delivery tube out and check all the little holes in the side of it; even a hair in a small injector in one of those holes will give trouble. Hold it up to the light and look through the length of the tube. Anything in there will stop the working of it. I once was using a hose that was shedding flakes of rubber every now and then. A piece of that would lodge in the tapered section of the delivery tube. Another thing, if for some reason you try to take water from a source at a level at or above the injector it won't work unless you pinch down the flow with the inlet hand valve. This takes careful adjustment but can be done. A too long or restricted pipe screwed into the overflow will cause trouble. Use a larger size pipe if you want to deliver the overflow more than three feet. Don't panic if the injector doesn't 'take'; check the possible causes at once then, if it won't work and water is getting low, reduce the fire or kill it with dirt shoveled on it. Don't 'hammer' on the injector. This won't cure anything and will damage the unit if continued. Remember you can't make a hot injector take hot water. Regarding hammering the injector, I have seen one that was hammered in anger and frustration until it was damaged beyond repair.

Once in a while the overflow check will get built up with minerals from hard water. This will make it dribble out the overflow. Take it out and clean it by laying a piece of very fine sandpaper on a flat surface such as a piece of window glass and move it back and forth carefully until the coating is removed.

An injector may work well except every now and then the overflow will make a sound and burp a bit of water then take hold again. This is caused by a tiny leak in the suction line somewhere. To find, plug the overflow and the farthest joint from the injector on the suction line, then turn on a bit of steam and you can see the leak.

Above all, don't fool with the injector till the water gets too low. If you are on a load, shut it down, open the fire door to slow the fire. Watch the gauge pressure, don't let it pop off, as what water is left will leave fast. If it continues to climb, a few shovels of dirt scattered over the fire will subdue it. The dirt can easily be raked down through the fire when you get water in the boiler again. I hope what I have given about troubles will help someone out of a problem sometime.


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