I would like to find out how codes on valves and other controls are chosen, for example codes like L14, L16VR and why?

 

Signal names in most control systems are based on some existing standard. Many older, and many current, systems use some perversion of the ASME/ANSI naming convention. A 14 device is a speed-sensing device, or a speed-level sensing device. In GE heavy duty gas turbine control systems, L14HR refers to a logic signal in software that will be a logic "1" when the high-pressure turbine shaft is at rest. L14HS is a logic signal that will be a logic "1" when the high-pressure turbine shaft is at or above synchronous speed (actually, for the purposes of this particular signal, "synchronous speed" is deemed to be something above 95% of rated high-pressure shaft speed for single-shaft generator drive turbines; the presumption is that if the unit accelerates to 95% speed, it will continue to 100% of rated speed).

A 26 device is a temperature-sensing device, usually a switch. L26QA is a logic signal that is a logic "1" when the turbine L.O. header temperature is above the alarm temperature setpoint. (Generally, in GE heavy duty gas turbines, a Q in a signal name usually stands for L.O., but sometimes it's related to fuel flow or water flow or air flow.)

A 63 device is a pressure sensing device (usually a switch). L63QT is a logic signal that is a logic "1" when the turbine L.O. header pressure is below the trip pressure setpoint.

Many systems, including some GE steam turbines and some newer GE heavy duty gas turbines, use a alpha-character designation, such as ZT-nnn or PI-nnn or TI-nnn. I'm not sure which national/international standard this system is, and I don't have much experience with it.

But all of these systems require learing a new "language" to understand them. If you can find the right standard, or the Company's version of that standard, you are well on your way to learning the language and understanding the system.

If you have other questions about GE heavy duty gas turbine signal naming conventions, we'd be happy to answer them. There are a couple of "tricks" and a couple of "hints" that make understanding the signal names very easy. Of course, one still has to memorize what a 5 is or what a 33 is or what a 49 is, but with a little practice that becomes easier and easier. It's the rest of the signal name, that once one learns how to interpret it, makes reading logic a breeze!