Discharge piping

Similarly, the nominal size of the discharge pipe should be as large as or larger than the nominal size of the valve outlet. Sometimes it may be necessary to increase the pipe size not only to limit the pressure drop, but also to avoid high vapor velocities. 

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The equations for nozzle flow, Eqs. (6-114) through (6-118), remain valid for the nozzle section even in the presence of the discharge pipe. Equations (6-116) and (6-120), for the temperature variation, may also be used for the pipe, with Mo, po replacing Mi, pi since they are valid for adiabatic flow, with or without friction. 

For additional information, see Simpson (Chem. Eng., 75(6), 192-214 [1968]). A critical Fronde number of 0.31 to ensure vented flow is widely cited. Recent results (Thorpe, 3d Jnt. Conf. Multi-phase Flow, The Hague, Netherlands, 18-20 May 1987, paper K2, and 4th Int. Conf. Multi-phase Flow, Nice, France, 19-21 June 1989, paper K4) show hysteresis, with different critical Fronde numbers for flooding and untlooding of drain pipes, and the influence of end effects. Wallis, Crowley, and Hagi (Trans. ASME J. Fluids Eng., 405 13 [June 1977]) examine the conditions for horizontal discharge pipes to run full. 

For quick pump selec tion, manufacturers often give the most essential performance details for a whole range of pump sizes. Figure 10-30 shows typical performance data for a range of process pumps based on suction and discharge pipes and impeller diameters. The performance data consists of pump flow rate and head. Once a pump... 

A common form of turbine pump is the vertical pump, which has the pump element mounted at the bottom of a column that serves as the discharge pipe (see Fig. 10-46). Such units are immersed in the liquid to be pumped and are commonly used for wells, condenser circulating water, large-volume drainage, etc. Another form of the pump has a shell surrounding the pumping element which is connected to the intake pipe. In this form, the pump is used on condensate service in power plants and for process work in oil refineries. 

An acid egg, or blowcase, consists of an egg-shaped container which can be filled with a charge of liquid that is to be pumped. This container is fitted with an inlet pipe for the charge, an outlet pipe for the discharge, and a pipe for the admission of compressed air or gas, as illustrated in Fig. 10-58. Pressure of air or gas on the surface of the liquid forces it out of the discharge pipe. Such pumps can be hand-operated or arranged for semiautomatic or automatic operation. 

Discharge piping leaking under liquid level in sump-type design. 

Though not specified in the code, supports for discharge piping from relief valves must be adequate to withstand the jet reaction produced by their discharge. 

The length should be sufficient to extend beyond the locations of the reactors discharging into the vessel so as to simphfy discharge pipe runs (for a horizontal vessel). 

Each vent device discharge pipe is extended into the vessel and its end is fitted with a deflector device. This disperses the jet stream of solids (catalyst) and liquids discharged and dissipates this force, which should otheiwise be exerted on the vessel wall immediately opposite. 

Overflows cause by pump failure or restrictions in discharge piping... 

This system, although simple, with only one pump, is more or less representative of all systems. This sy stem is eomposed of 180 ft of pipe 40 ft of 6 inch suction pipe, and 140 ft of 4 inch discharge pipe. 

Hf system piping = Hf suction piping+ Hf discharge piping. 

There are 5 valves in all. There are two 6 ineh gate valves in the siietion pipe. There is a 4 ineh gate valve, a 4 inch globe valve, and a 4 ineh cheek valve in the discharge pipe. The formula is ... 

This could also be induced by design, if the pumps are oversized, or by high velocity and friction head in discharge piping of inferior diameter. 

A pipe size incrcascr can be used in the discharge piping. This will reduce the fluid velocity and friction losses. An isolation valve with a low loss characteristic such as a gate valve should he placed after the increaser and check valve. 

Leak in discharge piping. Lube oil temperature or gummy deposits in bearings. 

Zj, 2= Elevation at discharge and suction, respectively gpm = Flow rate of liquid being pumped, gal/min dj = Diameter of discharge pipe, in. d, = Diameter of suction pipe, in. 

Open Disposal System - This is discharge piping of a PR valve which releases directly to the atmosphere. 

Closed Disposal System - This is the discharge piping for a PR valve which releases to a collection system, such as a blowdown drum and flare header. However, a closed system can also be a process vessel or other equipment at a lower pressure. 

Pump and Downstream Equipment - A PR valve is required for a pump when the shutoff pressure of the pump is greater than the design pressure of the discharge piping, downstream equipment, or pump casing. Positive displacement pumps normally require such protection, while in most cases centrifugal pumps do not. 

The following design features should be applied to the discharge piping and header for approximately 90 m downstream from the PR valve in question. 

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. 

The length of discharge piping must not be greater than 5 pipe diameters. 

Screw compressors are rotary positive displacement machines. Two helical rotors are rotated by a senes of timing gears as shown in Figure 10-8 so that gas trapped in the space between them is transported from the suction to the discharge piping. In low-pressure air service, non-lubri-cated screw compressors can deliver a clean, oil-free air. In hydrocarbon service most screw compressors require that liquid be injected to help provide a seal. After-coolers and separators are required to separate the seal oil and recirculate it to suction. 

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