Ball check valve

Use is made of screw tip valves, popularly called non-return valve, ball check valve, or sliding ring valve. They are used in reciprocating injection and injection blow molding machines (IMM and IBMM) to control the melt flow in one direction (Chapter 4). There is also the smearhead for IMM, IBMM, and extruder. Back flow will not occur... 

Angle valve,open Ball check valve, open -Swing check valve, open, 45°-Y Globe valve, open l80 close screwed return. ... 

In line, ball check valves, fully open. 150... 

A valve is a mechanical device that controls the flow of liquids, gases, or loose material through piping systems. There are many types of valves, including butterfly valves, gate valves, plug valves, ball valves, and check valves. 

Ceramic materials, including sapphire, have been used extensively in HPLC pumps for more than 20 years as pistons and check valve components. These materials have also been used to construct heads because of their good chemical stability. The use of ceramics is limited, however, because of high cost and brittleness. Although many systems have one material as the primary construction material, the wetted surfaces of a pumping system can contain several other materials. Therefore, for material-sensitive applications, all the materials in the HPLC eluent flow path should be considered. Materials that may be encountered are polymeric materials for pump seals such as fluoropolymers, polypropylene, and Teflon sapphire pump pistons and check valve seats ruby check valve balls Kalrez, KelF, or ceramic washers and spacers polymer-based transducer components and in older systems connections and joints made with silver solder. 

Check valves prevent back flow. The ball check valve, shown in Figure 8.3, is particularly simple in that it has no moving parts requiring close clearances bet-... 

Figure 29 The scheme for an Asahi contactor (1) operating section (2) resin hopper (3) ball-check vahre (4) filter (5-7) valves (8) solution distributor (9) exhausted resin outlet (10) drain.

In the Asahi contactor there are no valves to direct transfer of ion exchanger. A successful solution to this problem has been affected through the development of a ball-check valve system for the loading of ion exchanger. 

PVC spring-loaded ball-check valve 3/s" barb x 3/s" barb, Buna-N seal McMaster- Carr 7933K33 1... 

PVC spring-loaded ball-check valve /g" barb x 3/8" barb. 

Connect a 6 /2" piece of /8 tubing to the outlet port on the second bubbler and connect that to the ball check valve. Connect a 4" piece of 3/8 tubing to the other side of the check valve. This will be connected to a 3/8 HB X V4 barb that has been inserted into the water filter. When... 

The flow can be smoothed by using two pistons which work parallel but in opposite directions. Another design is the use of tandem pistons arranged in series, whereby the first one conveys slightly more than the second. This allows to compensate for mobile phase compressibility and helps to suppress cavitation, i.e. the formation of vapour bubbles during the filling stroke. Some pumps use double-ball check valves with a second seat and ball on top of the first one. The electronics of the pumps are also designed to compensate for the compressibility of the eluent (which fortunately is low, e.g. 1% per 100 bar). 

Check valves (o) lift check (i>) ball check (c) swing check. 

Lift-check and swing-check are the two major value types of valves used in process work. The lift-check, or ball-check, is most often used in two-inch and smaller sizes. It has a ball or guided plug which is lifted by fluid pressure and does not have a tendency to slam — as the swing-check type does. For this reason, the lift-check valve is preferable for services having irregular or frequent reversals of flow. 

Figure 2.1-6 (a) Small-volume reciprocating pump head. Single ball check valves are used for controlling the air/fluid flow (Superpressure Inc.), (b) Laboratory scale positive displacement pump (syringe pump High Pressure Equipment Co.). 

The precision of both piston and diaphragm reciprocating pumps depends greatly on the efficient functioning of the reservoir and column ball check valves, which must be perfectly designed. They are made of stainless steel or, for miniTHal wear, sapphire. Sometimes the seats of the check valves are in sapphire and the balls in ruby. The pistons can be made of stainless steel, glass or sapphire. 

The solvent must be perfectly clear, as any solid impurity will prevent good seating of the check valve balls, so a filter should be included in the reservoir tubing line. Sometimes a filter is included in the inlet manifold of the pump. 

A sudden rush of liquids from equipment into the drainage system would cause compression of entrapped gases in the sewer ahead of the stream and a vacuum behind the stream. Such pulsation drains all the traps and permits permeation of odors and sewer gases. The breather system, by proper installation of vents, is always installed according to code. In order to prevent the back rush of liquids, a ball check is installed ahead of a condenser. Both check valve and subsequent trap should be accessible for cleanout. The bell of the trap extends down from the perforated or gridded floor screen and covers a portion of the drain pipe extending above the bottom of the drain pit. More commonly the floor drains, drain screen, bell, and outside case of the pit are cast iron. 

Figure 5.5 Recommended practice of installing ball check valves to isolate a level glass. (What Went Wrong Second Edition, by Trevor A. Kletz. Copyright 1988 by Gulf Publishing Company, Houston, TX. Used with permission. All rights reserved.)...

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