valve type

Although many different types of valves are used to control the flow of fluids, the basic types can be divided into two general groups, they are stop and check valves.
Stop Valves
It can be divided into four general categories: gate, globe, ball , and butterfly valves.

GATE VALVES.- they are used when a straight-line flow of fluid and minimum restric­tion is desired. it is so named because the part that either stops or allows flow through it acts somewhat like the opening or closing of a gate and is called, appropriately, the gate. The gate is usually wedge shaped. When it is wide open, the gate is fully drawn up into the valve, leaving an opening for flow through it the same size as the pipe in which it is installed. they are not suitable for throttling purposes since the control of flow would be difficult due to it design and since the flow of fluid slapping against a partially open gate can cause extensive damage to it. Except as specifically authorized, it should not be used for throttling.
They are classified as either RISING­STEM or NONRISING-STEM valves. On the nonrising-stem it shown in figure 9-19 the stem is threaded on the lower end into the gate. As the handwheel on the stem is rotated, they up or down the stem on the threads, while the stem remains vertically stationary. This type of it almost always has a pointer-type indicator
GLOBE VALVES.- it is probably the most common in existence. it derives its name from the globular shape of it body. However, positive identification of a globe valve must be made internally because other types may have globular appearing bodies. it inlet and outlet openings are arranged in several ways to suit varying
BALL VALVES.- as the name implies, are stop valves that use a ball to stop or start the flow of fluid. The ball performs the same function as the disk in it. When it handle is operated to open the valve, the ball rotates to a point where the hole through the ball is in line with it body inlet and outlet. When it is shut, which requires only a 90-degree rotation of the handwheel for most valves, the ball is rotated so.
BUTTERFLY VALVES.- it is one type of which is shown in figure 9-21 may be used in a variety of systems aboard ship. they can be used effectively in freshwater, saltwater, JP-5, F-76 (naval distillate), lube oil, and chill water systems aboard ship. The butterfly valve is light in weight, relatively small, relatively
it has a body, a resilient seat, a butterfly disk, a stem, packing, a notched positioning plate, and a handle. The resilient seat is under compression when it is mounted in the body, thus making a seal around the periphery of the disk and both upper and lower points where the stem passes through the seat. Packing is provided to form a positive seal around the stem for added protection in case the seal formed by the seat should become damaged.
Butterfly valves are relatively easy to maintain. The resilient seat is held in place by mechanical means, and neither bonding nor cementing is necessary, Because the seat is replaceable, the valve seat does not require lapping, grinding, or machine work.

Introduction of flameout protector

• The purpose of flameout protector:
  When we use the cook top, the fire may be extinct because of the wind or overflowing water. In this case, the protector may cut off gas to prevent some accidents happening because of its leakage, such as poisoning, explosion or fire. In this way, it realizes its safety protection function.
• Working sketch-map of flameout protector
  The first step: Piezoelectricity
  Piezoelectricity
  Magnet breathes the valve Thermocouple
  Flameout protector (MPU)
  The initial working period (ignition)
• The second step: Valve-open condition
  The top of the thermocouple is heated by fire, and it causes thermo electromotive force. Then it will be in series between the closed circuit and it. Outside force and the magnetic field breathe the valve and keep it open, and the gas channel is open.
• The third step: Cut off gas in sudden flameout condition
  When the fire is extinct because of wind or overflowing water, the thermo electromotive potential will minish quickly, and the ferrite core will come back to its original place to cut off the gas because of the loss of the spring effect.
• Attention:
  1. Thermocouple
  1) There mustn’t be any damage or peeling off for the cover of insulation wire or insulation sleeve, otherwise it will cause short circuit, which will influence the normal operation of it.
  2) The fix-up of the thermocouple must dissipate heat to reduce the heat accumulation of fixing board and thermocouple copper. This can shorten the valve-closing time when there is sudden flameout.
  3) The heated part of a thermocouple must be on the top of 2-3mm. Not to put the top into the fire, otherwise it may reduce the potential and shorten its life.
  2. Solenoid valve
  1) Prevent it from being strongly striken in the process of installation and shipment, otherwise it may influence its normal performance.
  2) Before installation, the user must check it flatly on the test clamps with some prepressing. It is not allowed to be freely-flip. This assures that magnetic material won’t be damaged by colliding, otherwise it will influence the magnetic force.
  3) Clean the impurity such as aluminum or oil left on the inner wall of the stove and the surface of it.
  4) Keep the good connection of the solenoid valve and thermocouple. Prevent the safety protection device from operating abnormally because of too big contact resistance.
  5) The warehouse of it must be dry and ventilated and strictly prohibit extrusion.