The Inspection of Steam Boilers
Let it be clearly understood that if there were no steam generators using steam under pressure there would he no boiler inspection, and no licensing of engineers; it requires no license to be a machinist or a machine tender, no more would a license be essential to run a steam engine, except it were connected with the boiler. The danger to the public arising from their use requires that the care and management of high-pressure steam boilers shall be in hands of careful, experienced and naturally ingenious men, hence it is on the affairs of the Boiler Room that the first tests are made, as to the worthiness of an aspirant for an engineer’s license, hence, too, the success of many firemen in obtaining the preference over engine-builders or school graduates, in the line of promotion as steam engineers.
The inspection laws of the various states and cities are framed after substantially the same leading ideas, and in presenting one the others may be assumed to be nearly the same.
The special province of the Steam Boiler Inspection and Engineers’ Bureau in the police department in New York City is to inspect and test all the steam boilers in the city, at certain stated periods, and to examine every applicant for the position of engineer as to his ability and qualifications for running an engine and boiler with safety.
According to the laws of the State, every owner, agent or lessee, of a steam boiler or boilers, in the city of New York, shall annually report to the board of police, the location of said boiler or boilers, and, thereupon, the officers in command of the sanitary company shall detail a practical engineer, who shall proceed to inspect such steam boiler or boilers, and all apparatus and appliances connected therewith.
When a notice is received from any owner or agent that he has one or more boilers for inspection, a printed blank is returned to him stating that on the day named therein the boilers will be tested, and he is asked to make full preparation for the inspection by complying with the following rules:
Be ready to test at the above-named time.
Have boiler filled with water to safety-valve.
Have 11⁄4-inch connection.
Have steam gauge.
Steam allowed two-thirds amount of hydrostatic pressure.
More particularly stated, the following have been adopted by one or more Inspection Companies:
How to Prepare for Steam-Boiler Inspection
1. Haul fires and all ashes from furnaces and ash pits.
2. If time will permit, allow boiler and settings to cool gradually until there is no steam pressure, then allow water to run out of boilers. It is best that steam pressure should not exceed ten pounds if used to blow water out.
3. Inside of boiler should be washed and dried through manholes and handholes by hose service and wiping.
4. Keep safety-valves and gauge-cocks open.
5. Take off manhole and handhole plates as soon as possible after steam is out of boiler, that boiler may cool inside sufficiently for examination; also keep all doors shut about boilers and settings, except the furnace and ash-pit doors. Keep dampers open in pipes and chimneys.
6. Have all ashes removed from under boilers, and fire surfaces of shell and heads swept clean.
7. Have spare packing ready for use on manhole and handhole plates, if the old packing is made useless in taking off or is burned. The boiler attendant is to take off and replace these plates.
8. Keep all windows and doors to boiler room open, after fires are hauled, so that boilers and settings may cool as quickly as possible.
9. Particular attention is called to Rule 5, respecting doors—which should be open and which closed—also arrangement of damper. The importance of cooling the inside of the boiler by removal of manhole and handhole plates at the same time the outside is cooling, is in equalizing the process of contraction.
Issuing Certificates
These conditions having been complied with, the boiler is thoroughly tested, and if it is deemed capable of doing the work required of it, a number by which it shall hereafter be known and designated is placed upon it in accordance with the city ordinance: Failure to comply with this provision is punishable by a fine of $25. A certificate of inspection is then given to the owner, for which a fee of $2 is paid.
This certificate sets forth that on the day named the boiler therein described was subject to a hydrostatic pressure of a certain number of pounds to the square inch. The certificate tells where the boiler was built, its style or character and “now appears to be in good condition and safe to sustain a working pressure of —— to the square inch. The safety-valve has been set to said pressure.” A duplicate of this certificate is posted in full view in the boiler-room. In case the boiler does not stand the test to which it is subject, it must be immediately repaired and put in good working order before a certificate will be issued.
The Hydraulic Test
The hydraulic test is a very convenient method of testing the tightness of the work in a new boiler, in conjunction with inspection to a greater or lesser degree, in the passing of new work. As a detector of leakages it has no rival, and its application enables faulty caulking to be made good before the boiler has left the works, and before a leak has time to enter on its insidious career of corrosion. The extent to which it enables the soundness and quality of the work to be ascertained is another matter, and depends on several conditions. It will be evident that if the test be applied with this object to a new boiler, the pressure should range to some point in excess of the working load if such a test is to be of any practical value.
What the excess should be so as to remain within safe limits cannot be stated without regard being paid to the factor of safety adopted in the structure.
In addition to the advantage which the hydraulic test affords as a means of proving the tightness of the riveted seams and work generally, it is also of frequent assistance in determining the sufficiency of the staying of flat surfaces, especially when of indeterminate shape, or when the stresses thrown upon them by the peculiar construction of the boiler are of uncertain magnitude. For the hydraulic test, however, to be of any real value in the special cases to which we refer, it is essential that it should be conducted by an expert, and the application of the pressure accompanied by careful gaugings, so as to enable the amount of bulging and permanent set to be ascertained. Without such readings the application of the test in such cases is worthless, and may be delusive. Indeed, the careful gauging of a boiler as a record of its behavior should be a condition of every test, and is a duty requiring for its adequate performance a skilled inspector.
The duty of inspecting a new boiler or witnessing the hydraulic test properly belongs to one of the regular inspecting companies, who have men in their employ specially trained for the performance of such work. The advantage accruing from such a course is well worth the fee charged for the service, and secures a searching inspection of the workmanship, which frequently brings to light defects and oversights that a mere pumping-up of the boiler would never reveal. Such a proceeding in fact, can only prove that the boiler is water-tight, and a boiler may be tight under test although the workmanship is of the poorest character. Besides, it is well to bear in mind that the tightness of a boiler under test is no guarantee of its tightness after it is got to work. In a word, as far as new boilers are concerned, the application of hydraulic pressure unaccompanied by careful inspection and gaugings may be almost worthless, while with these additions it may be extremely valuable, especially in the case of boilers of peculiar shape, and is a precaution that should not be neglected.