Swing check valves

Nominal valve size Gate Globe, lift check, swing check A and B Angle and lift check B... 

Swing Check Valves These valves (Fig. 10-156) are used to prevent reversal of flow Normal design is for use only in horizontal lines, where the force of gravity on the disk is at a maximum at the start of closing and at a minimum at the end of closing. Unhke most other valves, check valves are more likely to leak at low pressure than at high pressure, since fluid pressure alone forces the disk to conform to the seat. For this reason elastomers are often mounted on the disk. Swing checkvalves are available with low-cost insert bodies. 

Qieck Valve - A check valve is acceptable in a process pressure reheving path, provided that (1) the valve opens in the pressure reheving direction, (2) the valve is of the swing-check or wafer type with no external actuation or dampen mechanism, and (3) the pressure drop is included in the system analysis. 

Check No No To restrict reversal of flow Isolation Swing check Valves only some cases Low /."-tp"... 

Assumed the following valve types are NOT used as Isolation valves Air Operated Dlaphram, Solenoid Operated, Pressure Relief Safety, Swing Check, or Tilting Disk Check. 

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

Terminate discharge pipe below liquid level or add a couple of elbows or a swing check valve to provide enough back pressure for elector to "seal". 

Conventional swing check valve Fully open 135... 

I I I I I I oood StOO OOOa 4 wto IO--1 1 1 1 1 1 UlOOl OOUl OIO- OOtOUl O JW Swing check valve ... 

Swing Check Valves These valves (Fig. 10-159) are normally designed for use in horizontal lines or in vertical lines with normally upward flow. Since their seating force is primarily due to pipeline pressure, they may not seal as tightly at low pressures as at higher pressures. When suitable, nonmetallic seats may be used to minimize this problem. 

Tilting-Disk Check Valves These valves (Fig. 10-163) may be installed in a horizontal line or in lines in which the flow is vertically upward. The pivot point is located so that the distribution of pressure in the fluid handled speeds the closing but arrests slamming. Compared with swing check valves of the same size, pressure drop is less at low velocities but greater at high velocities. 

Pipe size, in. Standard ell Medium radius ell Long- radius ell 45-deg ell 0 Tee ST Gate valve, open Globe volve, open O Swing check, open... 

The equivalent length of one 8-in-long-radius elbow is 14 ft of pipe, from Table 6.22. Since the pipe contains four elbows, the total equivalent length is 4(14) = 56 ft of straight pipe. The open gate valve has an equivalent resistance of 4.5 ft, and the open swing check valve has an equivalent resistance of 53 ft. 

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