Pressure vessels openings

Chlorine is stored and transported as a Hquefied gas in cylinders of 45.4-kg or 68-kg capacity that are under pressure and equipped with fusible-plug rehef devices. Quantities in the range of 15 to 90 t are transported in tank cars having special angle valves on the manhole cover on top of the vessel. Tank barges of the open-hopper type having several cylindrical uninsulated pressure vessels are used for amounts ranging from 600 to 1200 t. Road tankers are used for capacities of 15 to 20 t. 

Optimization of Cycle Times. In batch filters, one of the important decisions is how much time is allocated to the different operations such as filtration, displacement dewatering, cake washing, and cake discharge, which may involve opening of the pressure vessel. Ah. of this has to happen within a cycle time /. which itself is not fixed, though some of the times involved may be defined, such as the cake discharge time. 

HoUow-fiber membranes, therefore, may be divided into two categories (/) open hoUow fibers (Eigs. 2a and 2b) where a gas or Hquid permeates across the fiber waU, while flow of the lumen medium gas or Hquid is not restricted, and (2) loaded fibers (Eig. 2c) where the lumen is flUed with an immobilized soHd, Hquid, or gas. The open hoUow fiber has two basic geometries the first is a loop of fiber or a closed bundle contained ia a pressurized vessel. Gas or Hquid passes through the smaU diameter fiber waU and exits via the open fiber ends. In the second type, fibers are open at both ends. The feed fluid can be circulated on the inside or outside of the relatively large diameter fibers. These so-caUed large capiUary (spaghetti) fibers are used in microfUtration, ultrafUtration (qv), pervaporation, and some low pressure (<1035 kPa = 10 atm) gas appHcations. 

Openings are always required in pressure-vessel shells and heads. Stress intensification is created by the existence of a hole in an other-... 

To determine the Ha, atmospheric head, you only need observe the vessel being drained by the pump. Is it an opened, or vented atmospheric vessel Or is it a dosed and scaled vessel If the vessel is open, then we begin with the atmospheric pressure expressed in feet, which is 33.9 feet at sea level. The altitude is important. The atmospheric pressure adds energ) to the fluid as it enters the pump. For closed un-pressurized vessels the Ha is equal to the Hvp and they cancel themselves. For a dosed pressurized vessel remember that every 10 psia of pressure on a vessel above the vapor head of the fluid will add 23.1 feet of Ha. To the Ha, we add the Hs. 

The ASME code provides the basic requirements for over-pressure protection. Section I, Power Boilers, covers fired and unfired steam boilers. All other vessels including exchanger shells and similar pressure containing equipment fall under Section VIII, Pressure Vessels. API RP 520 and lesser API documents supplement the ASME code. These codes specify allowable accumulation, which is the difference between relieving pressure at which the valve reaches full rated flow and set pressure at which the valve starts to open. Accumulation is expressed as percentage of set pressure in Table 1. The articles by Rearick and Isqacs are used throughout this section. 

Figure 12-12. Skirt openings. (Reprinted with permission from Pressure Vessel Handbook, Publishing, Inc., Tulsa. ...

The most important safety devices in a production facility are the pressure relief valves, which ensure that pipes, valves, fittings, and pressure vessels can never be subjected to pressures higher than their design pressures. Relief valves must be designed to open rapidly and fully, and be adequately sized to handle the total flow of gas and liquids that could potentially cause an overpressure situation. They relieve the pressure by routing this stream to a safe location where it can be vented to atmosphere or burned. 

Other sources for oil spills are listed. For example, if a valve is opened and the operator inadvertently forgets to close it, oil may spill out of the system. If there is not a big enough dike around the system, oil pollution will result. It is also possible for oil to spill out the vent/flare system. All pressure vessels are connected to a relief valve, and the relief valve dis-... 

Another common problem area is having open and closed drain systems tied together. Liquid which drains from pressure vessels flash at atmospheric pressures giving off gas. If this liquid flows in the same piping as open drains, the gas will seek the closest exit to atmosphere it can find, causing a potential fire hazard at any open drain in the. system. 

Vessel drain systems can be very dangerous and deserve careful attention. There is a tendency to connect high-pressure vessels with low-pressure vessels through the drain system. If a drain is inadvertently left open, pressure can communicate through the drain system from the high-pressure vessel to the low-pressure vessel. If this is the case, the low pressure vessel relief valve must be sized for this potential gas blowhy condition. 

Open, gravity drains should not be combined with pressure vessel drain systems. The gas flashing from vessel liquids may exit an open drain system at any point and create a hazard. 

Vessels are sometimes contaminated by material left over from a previous use. For example, tank trucks were filled with a waste sludge containing particles of aluminum. One day the tank truck contained some caustic soda left over from the previous load. The caustic soda reacted with the aluminum, producing hydrogen. The increase in pressure blew open an inspection port and knocked an operator onto the ground. 

Experimental Work. Few experiments measuring the blast from exploding, gas-filled pressure vessels have been reported in the open literature. One was performed by Boyer et al. (1958). They measured the overpressure produced by the burst of a small, glass sphere which was pressurized with gas. 

Benzene (80 ml) is placed in a suitable pressure vessel (soft drink bottle or hydrogenation bottle) and chilled to 5°. The bottle is weighed, and a gas dispersion tube connected to a cylinder of butadiene is immersed in the benzene. Butadiene is introduced into the flask with continued cooling until a total of 32 g has been transferred. Pulverized maleic anhydride (50 g) is added to the bottle, which is then capped or stoppered with a stopper wired in place. The bottle is allowed to stand at room temperature for 12 hours, then is heated (behind a safety shield) to 100° for 5 hours. The bottle is cooled, then opened, and the contents are transferred to an Erlenmeyer flask. The mixture is heated to boiling, and petroleum ether is added until there is a slight turbidity. After cooling, the product is collected, mp 101-103° (yield 90%). 

Code, Section S lII, and are tested at capacity by the National Board of Boiler and Pressure Vessel Inspectors. This type of valve characteristically pops full open and remains open as long as the overpressure exists. 

The implication of this equation is that, because chemical reactions typically take place at constant pressure in vessels open to the atmosphere, the heat that they release or require can be equated to the change in enthalpy of the system. It follows that if we study a reaction in a calorimeter that is open to the atmosphere (such as that depicted in Fig. 6.11), then the measurement of its temperature rise gives us the enthalpy change that accompanies the reaction. For instance, if a reaction releases 1.25 kj of heat in this kind of calorimeter, then we can write AH = q — —1.25 kj. 

A relief valve is installed on the bottom of a pressure vessel. The entrance to the valve is 4.5 in. diameter, and the exit (which discharges in the horizontal direction, 90° from the entrance) is 5 in. in diameter. The loss coefficient for the valve is 4.5 based on the inlet velocity. The fluid in the tank is a liquid with a density of 0.8 g/cm3. If the valve opens when the pressure at the valve reaches 150 psig, determine ... 

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