Replacing Shut Off Valves: The Do's, The Don'ts, The Dangers
Replacing shut off valves is a pretty simple matter when you’re doing it in your own home. Whether you’re working with your water or your gas supply, all you need to do to replace shut off valves (assuming that you’ve shut them off properly, of course, by closing the supply valves that lead to them) is drain them, remove them, and connect the new unit with the help of a crescent open end wrench or, if you really can’t do any better, a pair of channel lock pliers.
Of course, if you’re working in a heavy, electromechanical industry, replacing shut off valves can be a dreadfully complicated process, especially when by ‘valve’ you really mean a valve assembly that looks about as simple to the uninitiated as a computer motherboard. NASA frequently has to delay crucial engine tests for weeks when electromechanical valve assemblies show signs of a flow disruption. Just as often as not, the flaw lies in a sensor or transducer improperly measuring the position of the valves. A flaw of this nature, that prevents pilots or operators from getting the information they need to make the right decisions, can be just as dangerous as an actual engine-failure-inducing malfunction.
Thus you can imagine the daunting pressure on someone when they need to perform repairs on a complex electromechanical system like the Hubble telescope. If one of the Hubble’s servo valves were to fail, then incredible observations, like the now famous Hubble Linear observations (immortal footage recording the fragments of the exploded Linear Comet spreading slowly through space) last year, might never be. Without them, we could lose what might be fundamental insights into the nature of the universe. It seems little wonder, then, that spacewalks of the kind required for replacing shut off valves on the Hubble have to be repeated six or seven times before components are ready for operation.
This is equally true underwater. Maintenance of heavy sub sea vehicles, such as floating drill vessels and semi-submersible oil platforms, often requires the use of ROVs, or Remotely Operated Vehicles, robotic machines that frequently require multiple operators to guide their antics on the sea floor. Particularly when working on powerful hydraulics or pneumatics, or with noxious or potentially explosive fluids or gases, the distance from the actions helps to tame operators’ nerves and enables them to work for longer spells at a time, shortening the period replacing shut off valves requires (and so raising productivity).
These sub sea ROVs (astronautical versions of which were actually used on the Hubble space telescope a few months prior to those storied Hubble Linear observations) , and just about every robot in existence, require the use of valves just as much as the machines on which they’re working. It’s something that’s often poorly understood by laypeople with little education on matters of technology, that any motion on the part of a machine requires the transfers of either fluids, gases, or the electromagnetically-induced motion of components such as solenoid valve armatures. The internal combustion engines of cars require the use of valves and solenoids for their operation, all the way from ignition (which requires a starter solenoid to close the contacts that allow current through to the engine) to combustion (which requires valves to deliver controlled amounts of fuel to the cylinder, forcing the piston into motion, which in turn moves the crankshaft) to exhaust gas recirculation (accomplished by means of a solenoid or, sometimes, a valve activated by the vacuum the engine itself creates). It’s because of the constant passage of fluids or gases that valves have to endure, that the cure for an engine failure is so frequently replacing shut off valves.
