Valve installation

Install fire safe bottom valves Install fire safe valves on major solvent lines Install remote shut off of fuel sources Eliminate points of leakage (flanges, hoses). Replace with fixed/welded pipes Move flammable material storage away from vessel (e.g., pallets, etc.)... 

Internal Re-circulation Operation / Design / Maintenance Internal Re-circulation results from something in the discharge side of the pump strangled valve, clogged filter, over-pressurized header, check-valve installed backwards. 

The key components in the fuel vapor control system include the fuel tank, vapor vent valves, vapor control valve, vapor tubing, the activated carbon canister, and the engine vapor management valve (VMV) [25,26], During normal vehicle operation, fuel tank vapor pressure is relieved through the use of vapor vent valves installed in the vapor dome of the fuel tank. The vent valves are designed to allow for the flow of fuel vapor from the tank, and to assure that liquid fuel does not pass through the valve. 

Consideration should be given to the effects of thermal expansion of liquids and pressure-relief valves installed unless ... 

Ideally, depending on the length of pipe run, locate cylinders outside (for hazardous gases, valves installed within the workplace can be used for remote control of the main supply from the cylinder in the event of an emergency). Site cylinders so that they cannot become part of an electrical circuit. 

Balancing Valve Hand or mechanically operated valve installed in each riser pipe of a multicell tower to control water flow. 

If the control valve size is critical to the overpressure protection of the downstream equipment, and must not be increased, then this is clearly noted in all relevant documentation (specification sheets, flow diagram, operating manual, etc.,) and a warning notice plate is welded to the valve body. In such cases, an actual check of the valve installed or purchased should be made during the startup review. 

In addition, a further mechanism of chattering may be introduced in some liquid PR valve installations if the response characteristics of a control valve in the same system are such that hunting between the two occurs. Generally, this can be eliminated by adjustment of instrument settings or by installation of two valves with staggered set points... 

Figure 7. Pressure conditions for safety relief valve installed on a pressure vessel (vapor phase) supplemental valve used for fire exposure only.

Note that for fired boilers, where the safety valve installation must comply with the ASME Code for Power Boilers rather than the code for Unfired Pressure Vessels, the allowable accumulation is only 6% instead of 10%. Reference also should be made to the Kj and A definitions, above. 

Number of Valves Required - Normally a manufacturer s standard PR valve with Drifdce area equal to or larger than the calculated requirement is specified. In some cases, e.g., large reheving rates or to prevent chattering, two or more valves are necessary. Likewise, if there is an appreciable difference between the calculated orifice size and the available size, multiple PR valves are desirable to more nearly match the available area to the required orifice area. The column for "spares" indicates the requirement, if any, for spare PR valves installed on the equipment. Normally, this applies only in the case of refinery preference or local regulations, but is required in many European countries. 

PR valves installed on heat exchangers and condensers for protection against a split tube should be discharged into a closed system if liquid can be discharged. 

Credit for additional height of the flame center for multiple valve installations may be taken by clustering the safety valve discharge pipes to the atmosphere. The following procedure should be used for determining equivalent diameter and exit velocity to be used in the flame center calculation. Diameter and velocity are based on the total acmal area of the clustered vents. 

Maximum Allowable Accumulated Pressure for Multiple-valve Installation (Other Than Fire Exposure)... 

FOR MULTIPLE-VALVE INSTALLATION (OTHER THAN FIRE EXPOSURE)... 

MAXIMUM ALLOWABLE ACCUMULATED PRESSURE — FOR single-valve installation... 

Used to restrict reversal of flow, check valves should not be considered as positive shut-off valves when flow is reversed, since the seating element is always in the flow stream and subject to erosion (Figures 15-9 to 15-13). A section of a line should not be considered isolated if the only batrier to flow is a check valve. On the other hand, because they do restrict backflow to very low levels, check valves installed in appropriate locations can protect equipment and minimize damage in case of a leak in the upstream line. Some of the advantages and disadvantages of the various check valve configurations are as follows ... 

Figure 7-7A. Pressure level relationship conditions for pressure relief valve installed on a pressure vessel (vapor phase). Single valves (or more) used for process or supplemental valves for external fire (see labeling on chart). Reprinted by permission, Sizing, Selection and Installation of Pressure Relieving Devices in Refineries, Part 1 Sizing and Selection, API RP-520, 5th Ed., July 1990, American Petroleum Institute.

Single pressure relief valve installation. Must be set to operate at a pressure not exceeding the maximum allowable working pressure of the vessel (MAWP), Ref [1] Par. UG-134, but may be set to operate at pressures below the... 

This is Acceptable os there is no Block Valve Isolating any Item. If Block Valve Installed ot A,Safety Volve would be Required to Protect Condenser and Receiver. If Additional Block Valve Installed of B, Safety Valve would be Required for Condenser ond also for Receiver. 

Safety (relief, or safety-relief) valves are used for set pressures from 10 psig to 10,000 psig and even higher. At the low pressures the sensitivity to relieving pressure is not always as good as is required for some processes, and for this reason most valve installations start at 15 to 20 psig. 

Figures 7-10 and 7-18 illustrate a few typical safety valve installations. Care must be shown in designing any manifold discharge headers collecting the vents From several valves. Sharp bends are to be avoided. Often two or more...

Whenever possible the individual installation of valves is preferred, and these should be connected directly to the vessel or pipe line [1, 28]. If a block-type valve is considered necessary for a single valve installation, it must be of the full open type, and locked open with the key in responsible hands, as stated earlier. 

Figure 7-19 illustrates a newer approach at simplifying the dual safety relief valve installation, ASME Sect. VIII, Div. 1, UG-135(b) [1] and API RP-520, Part II Conformance [33]. Note that the SRV valves are mounted on top of each of one dual vertical connections and are bubble tight. Also see cross section view. The flow C, valves for each size device are available from the manufacturer. 

Figure 7-19. Safety selector valve for dual safety relief valve installation with switching. By permission, Anderson, Greenwood and Co. AGGO.

Ideally, the sample should be taken from a valve installed specifically for sampling. When sampling valves are not installed the taking of samples from locations where sediment or water can collect, such as dead ends of piping, tank drains, and low points of large pipes and filter bowls, should be avoided if possible. If samples are taken from pipe drains, sufficient fluid should be drained before the sample is taken to ensure that the sample actually represents the system. Samples are not to be taken from the tops of... 

Maintain a mitrimum of 1 PSi pressure differential across the Slide Valves Install "Radial designed Feed Nozzles Install an automated shutdown System... 

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