Piping restrictions

Piping Restrictions - No restrictions such as check valves, flame arresters, orifice plates, etc., are permitted in the outlet piping. 

The detonation flame arrester mnst be able to arrest ten deflagrations with and withont a pipe restriction downstream of the flame arrester and five nnrestricted stable and overdriven detonations. The UL standard states, after tests determine the maximnm nnsta-ble (overdriven) detonation, the arrester is to be snbjected to fonr additional nnstable detonations with the length of pipe that resnlted in the maximnm nnstable (overdriven) detonation. The arrester is also to be snbjected to five stable detonations. ... 

Forced flow, as in water flowing in a tube or a pipe. The impermeable walls of the pipe restrict the flow to the course of the pipe (one-dimensional degree of hydraulic freedom), with only one inflow point and one outflow point (Fig. 2.11c). 

The heater (Figure 5.1c) is applied to a copper pipe, restricted by copper rings and closed off by an outer jacket of stainless steel. The copper pipe enables heat to be transferred uniformly from heater to nozzle and improves heating of the nozzle at the dead ends of the heater, while the jacket counters outward heat radiation. This design provides a uniform temperature distribution in the nozzle, especially at high operating temperatures, and good durability. The admissible thermal density for such heaters is up to 15 W/cm. ... 

When the air-water mixture enters the larger, vertical stand-pipe in Fig. 1.2, the velocity of the air-water mixture goes down. Some of this reduced kinetic energy is converted back into pressure. This I know because the pressure in the stand-pipe is atmospheric pressure. This has to be because the top of the stand-pipe is the 3-inch vent pipe sitting on the roof of my house. The air sucked down the toilet bowl escapes through this 3-inch vent. If a bird s nest or snow clogs the vent, then the trapped air builds pressure in the stand-pipe. The backpressure from the stand-pipe restricts the flow of water from the bowl, and the toilet can no longer flush properly. 

Axial movement may be a cause for pipe restriction. When this is the case, it is common to apply split collars around the outside diameter of the pipe with solvent-welded joints to protect the pipe from contact with concrete. It is recommended that the solvent-welded joints between the collars and the pipe exterior be allowed to dry for at least 48 hours prior to pouring concrete in the area. 

Release the slings Hit by pipes Restricted view Crushing injury 2 2 M See above... 

As a vessel is loaded, it moves downward because of deflection of the load cells and support stmcture. Pipes rigidly attached to a vessel restrict its free movement and assume some portion of the load that cannot be measured by the load cells. This is very detrimental to scale accuracy. Deflection of the load cell is unavoidable deflection of the vessel support stmcture should be minimized. Anything which increases vessel deflection, eg, mbber pads used for shock protection, must be avoided. The total number of pipes should be minimized and be of the smallest diameter, thinnest wall possible. Pipe mns to weigh vessels must be horizontal and the first pipe support should be as far as possible from the vessel. Alternatively, a section of mbber hose or flexible bellows should be used to make the final connection to the vessel. The scale should be caUbrated using weights, not by means of an electrical simulation method, which cannot account for the effects of the piping or test the correct functioning of the scale. 

Cahbration can also be accompHshed usiag material weighed on another scale. The accuracy of this method depends on the accuracy of the other scale, and care must be taken not to lose any of the weighed material. Scales can also be caUbrated electrically usiag a load cell simulator if the load cells rated outputs are known accurately. This method does aot test the mechanical fiinctioning of the scale and is not very accurate, particularly if it has attached piping that restricts its vertical movement. 

In many appHcations, especially in the chemical and semiconductor fields, the closest possible approach to isothermal operation may be desired. Under these conditions, the effects of vapor velocity must be considered if the velocity of the vapor exceeds about Mach 0.1, when a noticeable temperature differential shows itself in the heat pipe. If near isothermal operation is desired, designers restrict the vapor velocity to lower levels. 

The simplest method of reduciag stresses and reactions is to provide additional pipe ia the system ia the form of loops or offset-bonds. When physical limitations restrict the use of additional bends, a multiple arrangement of several small-size pipe mns may sometimes be used. Owiag to stress intensification, the maximum stress generally occurs at elbows, bends, and Ts. Thus, heavier-walled fittings may reduce the stress without significantly impairing flexibiUty. FiaaHy, effectively located restraints can reduce thermal effects on the equipment. 

Orifice Meter The most widely used flowmeter involves placing a fixed-area flow restriction (an orifice) in the pipe carrying the fliiid. This flow restriction causes a pressure drop that can be related to flow rate. The sharp-edge orifice is popular because of its simplicity, low cost, and the large amount of research data on its behavior. For the orifice meter, the flow rate for a liquid is given by... 

Materials of Construction for Bulk Transport Because of the more severe service, construction materials for transportation usually are more restricted than for storage. Most large pipe lines are constructed of steel conforming to API Specification 5L or 5LX. Most tanks (cars, etc.) are built or pressure-vessel steels or AAR specification steels, with a few of aluminum or stainless steel. Carbon steel tanks may be hned with rubber, plastic, nickel, glass, or other materials. In many cases this is practic and cheaper than using a stainless-steel tank. Other materials for tank construction may be proposed and used if approved by the appropriate authorities (AAR and DOT). 

For top-feed applications, the most convenient assembly is that shown in Fig. 18-95. The depth of the dam must, of course, be sufficient to contain the total quantity of feed shiny required for the test. Since the test leaf is mounted on top of the vacuum receiver, it is nec-essaiy to provide a valve between the test leaf and the receiver so that the desired operating vacuum may be obtained in the receiver before the start of a test run. It is imperative, however, that there be no restriction in this valve. The preferred choice is a ball valve with the full bore of the drainage piping. 

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

This would be induced or caused by operation, if the plant operators strangle valves to control production tlow. Any other discharge flow restriction (clogged filter, pipe obstruction, or tin-calibrated automatic valve) would produce the same evidence. Talk with the plant engineer about this situation and show him the evidence on the pump. 

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