Pressure relief devices valve

Pressure-regulating devices, pressure relief devices, valves, cylinder connections, and hose lines should be inspected at frequent intervals to ensure they are undamaged and in safe working condition. Compressed gas containers with devices and appurtenances that appear to be damaged in any way should not be used, and the supplier should be contacted for instructions on the disposition of the container. 

Nitric oxide is authorized for shipment in cylinders and tank car tanks (ton containers) as a nonliquefied gas. The container must not be equipped with a pressure relief device. Valve outlets must be sealed with a solid threaded cap or plug. See 49 CFR 173.337. [9]... 

AV-9 Handling Acetylene Cylinders in Fire Situations, Provides guidance and practical information on procedures to use when acetylene cylinders are involved in a fire. Includes description of acetylene cylinder construction and potential sources of ignitable leaks from fusible metal pressure relief devices, valve components, etc. (approx. 20 minutes)... 

Pressure-relief-device requirements are defined in Subsec. A. Set point and maximum pressure during relief are defined according to the service, the cause of overpressure, and the number of relief devices. Safety, safety relief, relief valves, rupture disk, breaking pin, and rules on tolerances for the reheving point are given. 

Pressure Relief Devices The most common method of overpressure protection is through the use of safety rehef valves and/or rupture disks which discharge into a containment vessel, a disposal system, or directly to the atmosphere (Fig. 26-13). Table 26-8 summarizes some of the device characteristics and the advantages. 

Emergency Relief Device A device that is designed to open during emergency or abnormal conditions to prevent rise of internal fluid pressure in excess of a specified value. The device also may be designed to prevent excessive internal vacuum. The device may be a pressure relief valve, a nonreclosing pressure relief device, or a vacuum relief valve. 

Selection of Pressure Relief Device - From the range of available pressure rehef valves and other devices, selection is made of the appropriate type for each item of equipment subject to overpressure. Instrumentation, check valves, and similar devices are generally not acceptable as means of overpressure protection. 

This section describes the various pressure relief devices that are commonly used, with their characteristics and criteria for selection. Basic calculation procedures for sizing PR valves are covered in subsequent discussions. 

The pressure relief device used most often in refinery and chemical plant equipment is the spring-loaded, top-guided, high-lift, nozzle-type safety relief valve, which is illustrated in Figure 2. The spring is usually external and enclosed by a bonnet for weather protection, and the bonnet chamber is vented through an internal passage to the valve outlet. 

The capacity of the combination of the rupture disk device and the spring loaded safety or safety relief v alve may be established in accordance with the appropriate paragraphs of UG-132, Certification of Capacity of Safety Relief Valves in Combination with Non-reclosing Pressure Relief Devices. 

Never place a block valve on the discharge side of a pressure relief device of any kind, except see [1] Par. U-135(e). 

Two types of pressure relief devices are available, safety valves and relief valves. Although these terms are often used interchangeably, there is a difference between the two. Safety valves are used with gases. The disk overhangs the seat to offer additional thrust area after the initial opening. This fully opens the valve immediately, giving maximum relief capacity. These are often called pop-off safety valves. 

Receivers are pressure vessels covered by the provisions of BS.4434 1980 and require safety pressure relief devices as outlined in Section 6.10. In cases where there is no shut-off valve between the condenser and receiver, such protection may be fitted to one or the other, providing the total volume is considered. 

Pressure relief valve (PRV) A pressure relief device designed to open and relieve excess pressure and to reclose after normal conditions have been restored. PRV is a generic term applied to relief valve (set up for liquid flow), safety valve (set up for gas or vapor flow), and safety relief valve (set up for either liquid or compressible flow). 

Pressure rated valves, 13 414 Pressure relief devices, fugitive emissions from, 10 71... 

Within this Workbook, the maximum pressure required to fully open the pressure relief device will be referred to as the "relief pressure". (Caution some papers on relief sizing refer to "set pressure" but mean "relief pressure"). For a bursting disc, the relief pressure will be the maximum specified bursting pressure and for a safety valve, it will be the set pressure plus 10% overpressure (or whatever percentage overpressure the valve has been certified at). 

The relief pressure is that at which the pressure relief device is fully open. Safety valves typically require 10% overpressure to achieve this (N.B. this should be checked for each specific application). Thus ... 

Bench or test stand testing Testing of a pressure relief device on a test stand using an external pressure source with or without an auxiliary lift device, to determine some or all of its operating characteristics, without necessarily flowing the rated capacity. This is required on a regular basis when the valve is taken into the maintenance cycle (see Chapter 10) at least to see that there is no shift on the set pressure and that the valve would open correctly during a pressure upset. 

Flow capacity testing The usually special testing of a pressure relief device to determine its operating characteristics, including measured relieving capacity. This tests whether the valve flows the capacity as stated in the literature or as per given flow coefficients, or to simply determine the flow coefficient of the valve as such. This is done on a spot-check basis by independent notified bodies in limited locations worldwide especially approved for that purpose. 

Reclosing pressure relief devices have a variety of names, although there used to be a clear definition based on the US market and API. However, when the Pressure Equipment Directive (PED) came into effect in 1997, this somewhat added to the confusion, as PED uses the overall term safety valve for every pressure-relieving device subject to the PED code. Originally the following were the definitions for the different terms per API and are still in use today. 

A non-redosing pressure rdief device is a pressure relief device designed to remain open after operation. A manual reset may be provided on certain valves. 

Combination capacity factors that have been determined by test and are acceptable to use are compiled by The National Board of Boiler and Pressure Vessel Inspectors in the Pressure Relief Device Certifications publication, NB-18 or the so-called Red Book. This publication lists the combination capacity factors to be used with a specific rupture device and relief valve by manufacturer rupture device/valve models. 

ASME Section VIII Division 1, 1992 Edition Pressure Relief Devices. Ug-136 Minimum Requirements of Pressure Relief Valves specifies the following regarding springs ... 

Alternative energy processes, just like any others, need to be protected from excessively high or low pressures. The methods of protection include pressure regulation, alarm, or safety interlock actuation when preset pressure limits are violated, and providing pressure relief devices, which need to be replaced after each operation (rupture disks) or can automatically reclose (relief valves). The features and characteristics of these devices are discussed in the following subsections. 

The District Engineering Inspectors Report confirmed that the machine was completely isolated and the ammonia system was not protected by a safety valve or any type of pressure-relief device. The cause of the accident was the presence of the steam hose underneath the equipment to melt the ice on the drain valve or to help evacuate the system. The inspectors report could not determine if these preparations were intentional or accidental. [5]... 

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