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Types of check valves

Posted by glili0216 
Types of check valves
February 19, 2011 08:45AM
Types of check valves
A ball check valve is a check valve in which the <a href=http://www.cnweilan.com/185-cast_steel_swing_check_valve.html>swing check valve</a> closing member, the movable part to block the flow, is a spherical ball. In some (but not all) ball check valves, the ball is spring-loaded to help keep it shut. For those <a href=http://www.pigment.cn/caiying.asp>pigment orange 16</a> designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the main seats of ball check valves are <a href=http://www.pigment.cn/caiying.asp>pigment yellow 3</a> more or less conically-tapered to guide the ball into the seat and form a positive seal when stopping <a href=http://www.chinajesbon.com/product/rotational-mould-plastic-mould.html>plastic mould</a> reverse flow.
Ball check valves are often very small, simple, and <a href=http://www.zzvalves.com/product/globe-valves.html>globe valves</a> cheap. They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc., manual air pumps and some other pumps, and refillable dispensing syringes. Although the balls are most often made of metal, they can be made of other materials, or in some specialized cases out of artificial ruby. High pressure HPLC pumps and similar applications commonly <a href=http://www.open-electric.com/product/distribution-box.html>distribution box</a> use small inlet and outlet ball check valves with both balls and seats made of <a href=http://www.rides-china.com/major-rides.html>amusement equipment</a> artificial ruby, for both hardness and chemical resistance. After prolonged use, such check valves can eventually wear out or the seat can develop a crack, requiring replacement. Therefore, such valves are made to be replaceable, sometimes placed in a small plastic body <a href=http://www.ndvalve.com/product/pressure-reducing-valve.html>pressure reducing valve</a> tightly-fitted inside a metal fitting which can withstand high pressure and which is screwed into the <a href=http://www.chinaplayground.com/>play equipment</a> pump head.
There are similar check valves where the disc is <a href=http://www.furniturer.cn/dining-table-sm-z05table.html>dining table</a> not a ball, but some other shape, such as a poppet energized by a spring. Ball check valves should not be confused with <a href=http://www.petsupplies-china.com/>dog chew</a> ball valves, which is a different type of valve in <a href=http://www.cn-dajiang.com/double-chambers-vacuum-sealer.html >vacuum sealer</a> which a ball acts as a <a href=http://www.tanq-play.com/rotational-mould.html>rotational molding</a> controllable rotor to stop or direct flow.
A diaphragm check <a href=http://www.wzglasses.com/>optical glasses</a> valve uses a flexing rubber diaphragm <a href=http://www.vovalve.com/>forged valves</a> positioned to create a normally-closed valve. Pressure on the upstream side must be greater than the pressure on the downstream side by a <a href=http://www.skf-bearing-supplier.com/>skf bearing</a> certain amount, known as the pressure differential, for the check valve to open allowing flow. Once positive pressure <a href=http://www.kingosteel.com/>stainless steel pipe</a> stops, the diaphragm automatically flexes back to its <a href=http://www.flowmeter-china.com/vortex-flow-meter45.html>vortex flowmeter</a> original closed <a href=http://www.ehuachina.com/>air brake valve</a> position.[1>
A swing check valve or tilting <a href=http://www.changhongmachine.com/>printing machine</a> disc check valve is check valve in <a href=http://www.baofalighter.com/>torch lighter</a> which the disc, the movable part to block the flow, swings on <a href=http://www.qj-chem.com/template/yellow-pigment.htm>pigment yellow 13</a> a hinge or trunnion, either <a href=http://www.discountmonclercoats.com/>moncler jackets</a> onto the seat to block reverse flow or off the <a href=http://www.hy-bandsaw.com/>band saw</a> seat to allow forward flow. The seat <a href=http://www.nflornhl.com/>authentic jerseys</a> opening cross-section may be perpendicular to the centerline between the two ports or at an <a href=http://www.printedinchinaonline.com>commercial printing</a> angle. Although swing check valves <a href=http://www.lifejackets.com.cn/en/products-detail.asp?id=278&pid=2&classid=180&nclassid=580&m=3>inflatable life raft</a> can come in various sizes, large check valves are often swing check valves. The flapper valve in a flush-toilet mechanism is an example of this type of valve. Tank pressure holding it closed is overcome by manual lift of the flapper. It then remains <a href=http://www.qj-chem.com/template/red-pigment.htm>pigment red 48</a> open until the tank drains and the flapper falls due to gravity. Another variation of this mechanism is the clapper valve, used in <a href=http://www.defvalves.com/product/plug-valve.html>plug valve</a> applications such firefighting and fire life <a href=http://www.greegoo.com/product/solid-state-relays-ssr.html>solid state relay</a> safety systems. A hinged gate only remains open <a href=http://www.greegoo.com/product/miniature-circuit-breakers-mcb.html>miniature circuit breaker</a> in the inflowing <a href=http://www.baitevalve.com/>globe valve</a> direction. The clapper valve often also has a spring that <a href=http://www.kokokid.com/product/indoor-playground-equipment.html>playground equipment</a> keeps the gate shut when there is no forward pressure.
A stop-check <a href=http://www.oxmvp.com/>swiss made watch</a> valve is a check valve with override <a href=http://www.baitevalve.com/product/plug-valve.html>plug valve</a> control to stop <a href=http://www.bh-machinery.com/>slitting machine</a> flow regardless of flow direction or pressure. In addition to <a href=http://www.goodvalve.cn/>globe valves</a> closing in response to <a href=http://www.qj-chem.com/>paint pigments</a> backflow or insufficient forward pressure (normal check-valve behavior), it can also <a href=http://www.hzqs.com/english/src.html>slip ring</a> be deliberately shut by an external <a href=http://www.cheapmbtuksale.com/>mbt sale</a> mechanism, thereby preventing any flow regardless of forward <a href=http://www.helmetonsale.com/>helmets</a> pressure.
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