【正文】 o for the sake of longterm operating personnel work. The best valve handwheel and chest ( above the operating floor general even meters ), so, the valve is opened and closed more ease. Landing valve handwheel to move on, do not tilt, so as not to operate. Against the wall by the valve device, to allow the operator to stand. To avoid operation, especially acidbase, toxic medium, otherwise it is not safe to. Gate valves do not flip ( . handwheel ), otherwise it will make the medium long term retention valve cap space, easy corrosion valve, but also some technology requirements of the taboo. At the same time to replace the packing is not convenient.Rising stem gate valve, not installed in the ground, or corrosion due to moisture exposed stem.Lift check valve, when the valve installation to ensure its vertical, so that the flexible lifting.Swing check valve, installation to ensure its pin level, so as to swing and flexible.Pressure reducing valve to the upright installed in horizontal pipelines, all directions do not tilt.( two) construction workInstallation and construction must be careful to avoid collision, brittle material valve.Before the installation, should be a check valve, check the specifications, there is no damage identification, especially for the valve stem. Also a few turns, to see whether the skew, because the transport process, the most easily break valve. Will purge valve within the debris. Valve lifting rope, not in the hand wheel or the stem, so as to avoid damage to these ponents, should be in the flange. The valve connecting pipe, must be clean. By pressing the air blowing to iron oxide particles, sand, slag and other debris. These impurities, not only easy to scratch the sealing surface of the valve, wherein large granular debris ( such as welding slag ), also blocked the small valve, so that its failure.Mounting screw valves, should be sealed packing ( hemp lead oil or Teflon tape ), wrapped in a pipe thread, do not get to the valve, so as to avoid the valve memory product, affect the medium circulation.Mounting flange valve, to the attention of symmetrical evenly tightened the bolts. The valve flange and pipe flange must be parallel, gap reasonable, so as to avoid excessive pressure valve, and even cracking. For brittle materials and the intensity is not high valve, paying particular attention to the. To the valve and pipe welding, spot welding should be first, then the closure member to open, and then welding die.( three) protection facilitiesSome valves must have external protection, this is the heat preservation and insulation. The insulation layer is sometimes added to the heat steam pipeline. What kind of valve should be heat or cold, according to the requirements of production and. In principle, where the medium in the valve reduces the temperature too much, will affect the production efficiency or frozen valve, requires insulation, even heating。The 1 flange connected valve body with flanges, and pipe: a flange connected valve.2: thread connection valve body with internal or external threads, and the pipe with threaded connection valve.3: welded valve body with welded joints, and pipe are connected by welding valve.The 4 clamp is connected to the valve : valve with mouth, and pipeline using a clamp connection valves.5 sets of cards: card sleeve and valve connected by pipeline connecting valve. The second chapter the valve installation, maintenance and operationThe correct choice of valve, but also the correct installation, maintenance and operation, so as to give full play to its performance. The first section of the installationValve installation quality, directly affects the use, so the need for careful attention.( a ) the direction and positionMany valves has direction, such as cutoff valve, throttle valve, relief valve, check valve, if installed flip reverse, it will affect the use effect and the life ( such as throttle ), or simply does not work ( such as valve ), and even dangerous ( such as a check valve ). General valve, the valve body has a direction sign。 closure around the valve axis of rotation.The 5 dish: closure disc, around the valve seat within the shaft rotation.The 6 spool valve type: closure in perpendicular to the direction of the channel sliding.In two, according to the purpose, according to the different uses can be divided:1: breaking used to connect or cut off the pipeline medium, such as cutoff valve, gate valve, ball valve, butterfly valve.2 Check: used to prevent backflow medium, such as a check valve.3: adjusting for medium pressure and flow regulation, such as regulating valve, relief valve.The 4 allocation: used to change the medium to flow, distribution medium, such as the three way cock, distribution valve, slide valve etc..Safety valve: 5 in medium pressure exceeds the set value, used to discharge the excess medium, guarantee the pipeline system and safety equipment, such as safety valve, e