Page 469 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Process Safety and Pressure-Relieving Devices 435

Table 7-3 Table 7-4A
Typical Metal Disk (Single) Bursting Pressures at 72°F Typical Recommended Maximum Temperatures
Using Different Metals for Metals Used in Disks

Disk Minimum Burst Pressure Max. Temperature, F
Size PSIG@ 72°F (Without Liners)
Aluminum 250-260
Alum Silver Nickel Mon el In cone I 316SS Silver 250-260
X" 160 450 600 700 1120 1550 Nickel 750-800
� II 65 220 300 350 560 760 Mone I 800
I" 29 120 150 180 250 420 Inconel 900-1000
1-w· 22 80 iOO 116 160 275 316 Stainless steel 900
2" 13 48 60 70 110 150
3" 10 35 45 50 80 117 Source: Various manufacturers' technical catalogs.
4" 7 26 35 40 70 90
6" 5 20 25 30 47 62 Table 7-48
8" 4 15 20 23 34 51 Typical Recommended Maximum Temperatures
10" 4 16 17 30 43 for Linings and Coatings with Metals Used with Disks
12" 3 13 15 25 36
14" 3 ]] 13 21 31 Teflon® FEP Plastic 400
16" 3 10 12 19 28 Polyvinylchloride 150-180
18" 3 9 11 17 24 Lead 250
20" 3 8 9 16 22
24" 3 Source: Various manufacturers' technical catalogs.
30"
36"
Safety-Relief Valve: normally selected for vapors and
(-) = Consult factory gases as may be found in all types of industrial processes.
�special designs of some manufacturers may exceed] 50,000 psi for small Characteristically this valve will open only enough to allow
sizes. The pressures listed are generally typical but certainly not the only
ones available for the size shown. the pressure to drop below the set pressure, and then it
will reseat until additional overpressure develops. If the
Note: pressure persists or increases, then the valve will remain
1. Maximum burst pressure depends upon disk size and applica- open or increase its opening up to the maximum design,
tion temperature. Pressures to 80,000* psig are available. but as the pressure falls the valve follows by closing down
2. Other materials and sizes are available upon request. until it is folly reseated. Of course, as in any installation of
3. Other liner materials are available upon request. Minimum any "safety" type valve, the valve may not reseat complete-
burst pressures will change with change in liner material. ly gas tight. In such cases it may be necessary to switch to
4. For larger sizes or sizes not shown, consult your representative,
or the factory. Courtesy, Continental Disc Corp., Bui. 1184, p. a stand-by valve and remove the leaking valve for repair.
4-5. [See Figures 7-7A and 7-7B.J

Special Valves: because of the difficult and special seal-
ing requirements of some fluids such as chlorine and
Dowtherrn, special valves have been developed to handle
the requirements.

Code, Section VIII, and are tested at capacity by the Vacuum Relief and Combined Pressure-Vacuum Relief for
National Board of Boiler and Pressure Vessel Inspectors. Low Pressure Conditions: normally used for low pressures
This type of valve characteristically "pops" full open and such as 1 ounce water to 1.5 psig above atmospheric by
remains open as long as the overpressure exists. special spring or dead weight loading; and for vacuum
protection such as 0.5 psi below atmospheric. Usually
these conditions are encountered in large process, crude
Relief Valve: normally selected for liquid relief service oil, ammonia, etc., storage tanks. See later section cover-
such as hydraulic systems, fire and liquid pumps, marine ing this topic.
services, liquefied gases, and other total liquid applica-
tions. The valve characteristically opens on overpressure Rupture Disks: used for low as well as high pressure pro-
to relieve its rated capacity, and then reseats. tection of vessels and pipelines where sudden and total