4.8-1

4.8 Design Rules For Quick-Acting Closures (Revision 4)

4.8.0 Table of Contents............................................................................................................ 1 4.8.1 Scope ............................................................................................................................... 1 4.8.2 Definitions........................................................................................................................ 1 4.8.3 General Design Requirements ...................................................................................... 1 4.8.4 Specific Design Requirements ...................................................................................... 1 4.8.5 Alternative Designs for Manually Operated Closures................................................. 2

4.8.1 Scope

4.8.1.1 Design requirements for quick-actuating or quick-opening closures are provided in this paragraph. Specific calculation methods are not provided, however, the rules of Part 4 and Part 5 can be used to qualify the design of a quick-actuating or quick-opening closure.

4.8.2 Definitions

4.8.2.1 Quick-actuating or quick-opening closures are those that permit substantially faster access to the contents space of a pressure vessel than would be expected with a standard bolted flange connection (bolting through one or both flanges). Closures with swing bolts are not considered quick actuating (quick- opening).

4.8.2.2 Holding elements are structural members of the closure used to attach or hold the cover to the vessel.

4.8.2.3 Locking components are structural items that are used to prevent opening of the closure while pressure is applied. Locking components may also be used as holding elements.

4.8.2.4 The locking mechanism or locking device consists of a combination of locking components.

4.8.3 General Design Requirements

4.8.3.1 Quick-actuating closures shall be designed, such that while the vessel is operating, the failure of a single locking component will not:

a) Release the closure;

b) Result in the failure of any other locking component or holding element; and

c) Increase the stress in any other locking component or holding element by more than 50% above the allowable stress of the component.

4.8.3.2 Quick-actuating closures shall be designed and installed such that it may be determined by visual external observation that the holding elements are in good condition.

4.8.3.3 The closures shall also be designed so that all locking components can be verified to be fully engaged by visual observation or other means prior to the application of pressure to the vessel.

4.8.3.4 When installed, all vessels having quick-actuating closures shall be provided with a pressure-indicating device visible from the operating area.

4.8.4 Specific Design Requirements

4.8.4.1 Quick-actuating closures that are held in position by positive locking devices and that are fully released by partial rotation or limited movement of the closure itself or the locking mechanism and any

4.8-2 ASME Section VIII, Division 2 ReWrite Revision 4 _______________________________________________________________________________________________

closure that is other than manually operated shall be so designed that when the vessel is installed the following conditions are met:

a) The closure and its holding elements are fully engaged in their intended operating position before pressure can be built up in the vessel.

b) Pressure tending to force the closure clear of the vessel shall be released before the closure can be fully opened for access.

c) In the event that compliance with paragraphs 4.8.4.1.a and 4.8.4.1.b above is not inherent in the design of the closure and its holding elements, provisions shall be made so that devices to accomplish this can be added when the vessel is installed.

4.8.4.2 It is recognized that it is impractical to write requirements to cover the multiplicity of devices used for quick access, or to prevent negligent operation or the circumventing of safety devices. Any device or devices that will provide the safeguards broadly described in paragraphs 4.8.4.1.a, 4.8.4.1.b and 4.8.4.1.c above will meet the intent of this Division.

4.8.5 Alternative Designs for Manually Operated Closures

4.8.5.1 Quick-actuating closures that are held in position by a locking mechanism designed for manual operation shall be so designed that there would be leakage of the contents of the vessel prior to disengagement of the locking components and release of the closure.

4.8.5.2 Manually operated closures need not satisfy paragraphs 4.8.4.1.a, 4.8.4.1.b and 4.8.4.1.c, but such closures shall be equipped with an audible or visible warning device that will warn the operator if pressure is applied to the vessel before the holding elements and locking components are fully engaged in their intended position or if an attempt is made to disengage the locking mechanism before the pressure within the vessel is released.