OCR Text |
Show -9- to ignite the pilots within a few seconds. This type of flare ignition system has been used for many years. One of the drawbacks of this system is that ignitor lines can accumulate moisture and condensate and ultimately become fouled or plugged. Underground lines should be avoided since these are inevitable havens for the buildup of water and other "plugs." If an underground line must go under a road or other obstruction, it must have a proper slope with a drain accessible for cleanout at the low point. Keep Ignition System Dry Moisture is the single most significant problem to consider when locating and installing a pilot ignition system. The air which is mixed with the gas steam must be dry. If not, it will collect condensate. A condensate trap or small knockout pot must be employed. Wet compressed air will flood ignition lines and short-out spark plugs, preventing ignition of the pilots. Even the use of dry instrument air and/or dryers cannot guarantee the complete prevention of moisture, because the combustion process generates water vapor. A drain valve should be installed at the lowest point of the line between the ignition panel and the pilot as a method of eliminating condensate produced by flamefronts. Before ignition of a flare pilot is attempted, the air valve on the ignition panel should be opened to allow any existing moisture to escape. The spark plug can then be checked by using the pushbutton and sightport. It is important that the proper pipe size be used, as specified by the equipment supplier, along with appropriate air and gas pressures to deliver the flamefront to the pilot with a velocity of approximately 100 ftls (30.5 m/s). Oversized or undersized lines will not produce good results; and they will lead to problems. Oversized lines will cause slow travel of the flamefront, allowing it to cool off and go out. Undersized lines may increase the speed and turbulence of the flamefront and cause it to be unstable. By opening the air valve to approximately 20 psig and the gas valve to about 10 psig, a mixture close to the optimum requirement for a proper flamefront will be achieved. It is imperative that installation instructions must be adhered to. A common problem is the reversal of ignitor and pilot tubes from the pilot gas supply to the pilot venturi. This can be avoided easily if proper care is taken during installa- |