Page 446 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

412 Applied Process Design for Chemical and Petrochemical Plants

Popping Pressure: the pressure at which the internal
pressure in a vessel rises to a value that causes the inlet
valve seat to begin to open and to continue in the open-
ing direction to begin to relieve the internal overpressure
greater than the set pressure of the device. For compress-
ible fluid service.

Materials of Construction

Safety and Relief Valves; Pressure-Vacuum Relief Valves
For most process applications, the materials of con-
struction can be accommodated to fit both the corrosive-
Figure 7-SE. Rupture disk (top) with Teflon® or other corrosion-resis- erosive and mechanical strength requirements. Manufac-
tant film/sheet seal, using an open retaining ring. For positive pres-
sure only. By permission, Fike Metal Products Div., Fike Corporation, turers have established standard materials which will fit a
Blue Springs, Mo. large percentage of the applications, and often only a few
parts need to be changed to adapt the valve to a corrosive
service. Typical standard parts are: (See Figures 7-3, 7-3A,
and 7-4)

Option 1 (typical only)
Body carbon steel, SA 216, gr. WCB
Nozzle 316 stainless steel
Disc/Seat stainless steel
Blow Down Ring 300 Ser. stainless steel
Stem or Spindle stainless steel
Spring C.S. rust proof or high temp.
Figure 7-SF. Rupture disk (top), similar to Figure 7-SE, except a alloy, rust proof
metal vacuum support is added (see Figure 7-SF(A)). By permission, Bonnet SA-216, Gr. WCB carbon steel
Fike Metal Products Div., Fike Corporation, Blue Springs, Mo. Bellows 316L stainless steel
Option 2 (typical only)
Body 316 stainless steel
Nozzle 17-4 stainless steel or 316 stain
less steel
Disc/Seat Teflon, Kel-F, Vespel or Buna-N
Blow Down Ring 316 stainless steel
Stem or Spindle 17-4 stainless stee I or 316 SS
Spring 316 stainless steel
Figure 7-SF(A). Cross section of disk assembly for Figure 7-SF. By Bonnet 316 stainless steel
permission, Fike Metal Products Div., Fike Corporation, Blue
Springs, Mo. Bellows
For pressure and temperature ratings, the manufactur-
ers' catalogs must be consulted. In high pressure and/or
temperature the materials are adjusted to the service.
Closing Pressure: the pressure established as decreasing For chemical service the necessary parts are available
inlet pressures when the disk of the valve seats and there in 3.5 percent nickel steel; monel; Hastelloy C; Stainless
is no further tendency to open or close. Type 316, 304, etc.: plastic coated bellows; nickel; silver;
nickel plated springs and other workable materials.
Simmer: the audible or visible escape of fluid between The designer must examine the specific valve selected
the seat/ disk of a pressure-relieving valve at an inlet static for a service and evaluate the materials of construction in
pressure below the popping pressure, but at no measur- contact with the process as well as in contact or exposed
able capacity of flow. For compressible fluid service. to the vent or discharge system. Sometimes the corrosive