Methods used to ensure boiler is in working order.
Before a new boiler is initially fired, it should be given a complete and thorough inspection on both the fire side and water side. [pic] [pic]
External examination of the boiler should include the visual inspection of the outer surfaces during operation as stated earlier. Other external points that should be inspected and examined include the gauge glasses, water column(s), water level controls, high and low-water alarms and cutoffs, blowoffs, blowdown, feed water valves, check valve, feed line at the entry to the boiler, safety valves, and boiler stop valves or non-return valves. All piping connecting these various controls and accessories should be checked to make certain there are no deposits to stop or impede proper flow through the piping and to the controls.
Examination is necessary of all the pressure parts, drums, tubes, water column(s), blowoff and blowdown valves, safety or safety relief valves, baffles, nozzles, refractory setting, seals, insulation, casing, etc. If any foreign material is found in the boiler, it should be removed.
The period of initial inspection is also a good time for the insurance inspector to check out the boiler. As a general rule, the inspectors like to have an opportunity to inspect the boiler prior to the hydrostatic test.
A hydrostatic test is a way in which pressure vessels such as pipelines, plumbing, gas cylinders, boilers and fuel tanks can be tested for strength and leaks. The test involves filling the vessel or pipe system with a liquid, usually water, which may be dyed to aid in visual leak detection, and pressurization of the vessel to the specified test pressure.
The boiler should be filled slowly at the proper water temperature, venting air through the boiler vent valve. When the boiler is full and all of the air has been vented, the boiler vent valve can be closed. Then the pressure can gradually be raised until the maximum hydrostatic test pressure has been reached.
Safety valves may have to be removed and blind flanges installed over the openings. If safety valves are equipped with threaded inlets, they may be removed and the boiler openings can be plugged. The safety valves may be gagged. However, this method is not a normally recommended practice. The gag should be used only for the hydrostatic test and must be removed as soon as the test is completed. The gag should be installed on the valve and extreme care should be exercised not to tighten the gag screw too tightly. Hand tight torque is generally sufficient. Damage to the spindle and/or seat of the valve may result if the gag is too tight. After safety valves have been gagged for the hydrostatic test and if there is any doubt about their operation, the valves should be removed and sent to an authorized testing facility and tested before the boiler is put into operation. [pic]
An important boiler fitting is the safety valve. Its function is to protect the boiler shell from over pressure and subsequent explosion.
Many different types of safety valves are fitted to steam boiler plant, but generally they must all meet the following criteria:
• The total discharge capacity of the safety valve(s) must be at least equal to the 'from and at 100°C' capacity of the boiler. If the 'from and at' evaporation is used to size the safety valve, the safety valve capacity will always be higher than the actual maximum evaporative boiler capacity. • The full rated discharge capacity of the safety valve(s) must be achieved within 110% of the boiler design pressure. •...