Valve outlet

For saturated steam keep control valve outlet velocity below 0.25 mach. 

Starting at the flare tip calculate logical segments using Figure 1 until all relief valve outlet pressures are found. 

Mak s article show s how the isothermal assumption is slightly conservative (higher relief valve outlet pressures) when compared to adiabatic. 

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. 

In addition to the above back pressure limitations based on valve capacity, balanced bellows PR valves are also subject to back pressure limitations based on the mechanical strength of the bellows or bellows bonnet, or the valve outlet flange rating. The back pressure specified for the valve is governed by the lowest back pressure permitted by these various criteria. 

The discharge line diameter must be at least equal to the diameter of the PR valve outlet flange. 

Tsnlatinn Valves - Isolation valves in the individual PR valve outlet lines should be provided to permit safe removal of one PR valve for maintenance during plant operation. 

PR Valve Outlet Piping - The outlet piping from a PR valve must be at least equal in size to the valve outlet flange. 

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For gases with specific heat ratios of approximately 1.4, the critical pressure ratio is approximately 0.5. For hydrocarbon service, this means that if the back-pressure on the relief valve is greater than 50% of the set pressure, then the capacity of the valve will be reduced. In other words, if the pressure in the relief piping at the valve outlet is greater than half (he set pressure, then a larger relief valve will be required to handle the same amount of fluid. 

Relief valves vented to the atmosphere should have tail pipes equal to or larger in diameter than the relief valve outlet that extend vertically a minimum of one foot above building eaves, or eight feet above adjacent platforms on operating areas. The tail pipes should be provided with a drain located such that the exhaust through the drain hole does not impinge on vessels, piping, other equipment or personnel. 

Due to the extremely small pilot flow, the pilot on gas/vapor valves normally discharge to atmosphere through a weather and bug-proof fitting. Pilots for liquid service valves have their discharge piped to the main valve outlet. 

In parallel with the refillable cylinder market, the non-refillable cylinder has emerged to supply the needs of the leisure market and the DIY enthusiast, to name but two. These are broadly divided into those with a valve outlet and the pierceable cartridge. Both are designed to be disposed of when finally exhausted. 

Figure 40.20 shows a typical relief valve. System pressure simply acts under the valve disk at the inlet of the valve. When the system pressure exceeds the pre-load force exerted by the valve spring, the valve disk will lift off of its seat. This will allow some of the system fluid to escape through the valve outlet. Flow will continue until the system pressure is reduced to a level below the spring force. 

To prevent interchange of fittings between cylinders of combustible and non-combustible gases, the valve outlets are screwed left-hand thread and right-hand, respectively (Table... 

To prevent interchange of fittings between cylinders of combustible and non-combustible gases, the valve outlets are screwed left-hand and right-hand thread, respectively (Table 9.2). Primary identification is by means of labelling with the name and chemical formula on the shoulder of the cylinder. Secondary identification is by use of ground colours on the cylinder body. Unless specified in Table 9.2, gas and gas mixtures shall be identified by a colour classification indicating gas properties in accordance with the risk diamond on the cylinder label e.g. 

SR greater than 1 refers to fuel lean conditions, while SR less than 1 refers to fuel rich conditions. To convert from fuel rich to fuel lean experimentally, a portion of the helium in the reactant gases was replaced with an equal volume of 02 using a 4-way switching valve. The pressures of the switching valve outlets were balanced such that only the reactant concentration is changed while keeping the flow rates and the pressure constant. 

There are a number of vendors that sell solenoid actuated Teflon valves, which are easily interfaced to a computer. Care must be taken to chose a design where the internal volume at the valve outlet can be flushed easily between steps, however [110], Rotary selection valves have been used as well, but given the number of rotations needed for a 200 cycle deposit, various failure modes revealed themselves. 

Normal Operational Releases Process storage or sewer vents, relief valve outlets, tank seals, which are considered normal and acceptable practices that release to the atmosphere. 

Recovery is a measure of the degree of pressure recovery at the valve outlet from the low pressure at the vena contracts. When flashing occurs at the vena contracts and the pressure recovery is high, the bubbles collapse with resulting cavitation and noise. The more streamlined the valve, the more complete the pressure recovery thus, from this point of view streamlining seems to be an undesirable quality. A table of recovery factors of a number of valve types is given by Chaffin (1980) such data usually are provided by manufacturers. 

Valve outlet connection standardized by the Compressed Gas Association (CGA) (see ref. S). Corrosion of the manual control valve is indicated by sticking on opening and closing, in which case the valve is taken apart and cleaned. 

Constant superimposed backpressure Usually backpressures that occur when a safety valve outlet is connected to a static pressure source and doesn t change appreciably under any conditions of operation. In this case, conventional valves may be used if the valve spring setting is reduced by the amount of the constant backpressure (Figure 3.8). 

As an additional feature, an auxiliary filter can be fitted with a drain valve to regularly clean the filter and prevent clogging. This drain can also, on demand, be piped to the main valve outlet or it can be piped on site to a purge collector. The purge valve can be programmed to open at pre-set intervals. The mini-valve for the drain, shown in Figure 5.43, can also be an automated ball valve I would recommend not lower than a 55 j, filter element with a minimum area of 80 cm2 and an approximate volume of 50 to 75 cc. 

Whatever the configuration, it is essential to ensure that fluid cannot collect on the downstream side of the SRV as this impairs the performance of the valve. In addition it can cause corrosion and/or damage of the spring and internal parts. Many SRVs, but by far not all, are provided with a built-in body drain connection if this is not used or not provided, then a small bore drain should be fitted in the outlet piping close to the valve outlet. 

While here the tail pipe has the right construction and orientation, it is unfortunately not equipped with a drain. Therefore dirt can accumulate and create excessive backpressure, and can enter the valve and damage the seat surface, causing valve leakage after operation. The size of the tail pipe at the connection is smaller than the valve outlet. This will provide excessive built-up backpressure. Again, these considerations must be taken into account when sizing the valve, as the valve may otherwise be undersized. ... 

On a positive note, here the oudet tail pipe is the same size as the valve outlet size and is equipped with a drain system. ... 

In any case, the noise intensity should only be referenced in areas where operating personnel normally work, which is very unlikely to be near an open valve outlet as this would mean incorrect installation practices had been applied. 

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