Plant pressure systems

These Regulations have been made under the HSW and deal with broad objectives to be achieved in the operation of complete pressure systems as opposed to dealing with specific requirements for specific pieces of plant. Pressure systems are defined as ... 

The most overlooked hazard and contaminant is water (99). Water reacts with isocyanates at room temperature to yield both ureas and large quantities of carbon dioxide. The presence of water or moisture can produce a sufficient amount of CO2 to overpressurize and mpture containers. As Httle as 30 mL of water can result in 40 L of carbon dioxide which could result in pressures of up to 300 kPa (40 psi). For these reasons, the use of dry nitrogen atmospheres is recommended during handling. If a plant air system must be used, purification equipment, such as oil traps and drying beds, should be installed between the source and the isocyanate vessel. 

Crete piping systems can be lined with special salt-glazed vitrified-clay liner plates, joined with a die-cast aspnalt joint. Concrete pressure pipe is competitive with cement-lined ductile iron for underground plant water systems. 

Process Steam Generation. Steam generated in the process sections of the plant may be at the highest plant pressure level or an intermediate level. Also, the process area may have fired boilers, waste heat boilers, or both. There may be crossties between utility and process generated steam levels. Enough controls must be provided to balance far-ranging steam systems and protect the most critical units in the event of boiler feedwater shortage situations. 

Inert gas-filled motors can also be used in refineries and chemical plants, but their applications are limited. They have tightly fitted covers and oil seals around the shaft to minimize gas leakage, are continually pressurized with an inert gas or instrument air, and are equipped with an internal air-to-water heat exchanger. Inert gas-filled motors are suitable for any hazardous location but require auxiliaries such as cooling water, gas pressurizing system, and control accessories. 

Plant and equipment generally portable tools flexible hoses lifting equipment pressure systems... 

A distinction must be made regarding the length of service of the pressure reducing systems. Fatigue failure of any mechanical system depends on time, i.e., the number of cycles to failure. Therefore, the treatment required for a continuous service may not be justified for a short term service. A System in short term service is defined as one which operates a total of 12 hours or less during the life of the plant. Pressure relief valves typically meet this limit. Systems in short term service exceeding the screening criteria indicated above should be evaluated. 

Other inspection services available include the examination of steel structures (new and existing), electrical wiring installations, containers (to meet Statutory Instm-ment No. 1890), dangerous substances (carriage by road in road tankers or tank containers) to meet Statutory Instmment No. 1059, examination of second-hand plant prior to purchase, plant undergoing repair or modification, the Control of Industrial Major Accident Hazard Regulations (CIMAH) Statutory Instmment No. 1902 and Control of Substances Hazardous to Health (COSHH) and Pressure Systems Regulations. 

High-pressure systems and on dust-collector plants. Will handle some dusty air... 

In reverse-pulse applications, most plants rely on plant-air systems as the source for the high-velocity pulses required for cleaning. In many cases, however, the plant-air system is not sufficient for this purpose. Although the pulses required are short (i.e., 100 milliseconds or less), the number and frequency can deplete the supply. Therefore, care must be taken to ensure that both sufficient volume and pressure are available to achieve proper cleaning. 

Employees and/or the self-employed use the plant at work. For full details of the requirements under these Regulations reference should be made to the following The Pressure Systems and Transportable Gas Containers Regulations 1981... 

Parkinson, J. S. (1979) Inst. Chem. Eng. Sym. Design 79, Kl. Assessment of plant pressure relief systems. PARRY, C. F. (1992) Relief Systems Handbook (Institution of Chemical Engineers, London). 

Low (subatmospheric) pressures are not in general as hazardous as the other extreme operating conditions. But a hazard, which does exist in low pressure plant handling flammables, is the ingress of air with consequent formation of a flammable mixture. Also steam explosions may take place if a volatile material (e.g. water) is fed to a low pressure system which results to a consequent vapourization. 

Siemens-Westinghouse Power Corporation, of Pittsburgh, PA, with a subcontract to Allison Engine Company, evaluated a pressurized solid oxide fuel cell coupled with conventional gas turbine technology without a steam plant. The system was operated at a pressure of 7 atm. The fuel cell generated 16 MW of power and the gas turbine generated 4 MW of power. The process showed 67 % efficiency as developed. An efficiency of 70 % is deemed achievable with improvement in component design. The COE is predicted to be comparable to present day alternatives. NOx levels were less than 1 ppm. 

The source of these compounds is varied. The butanes are found naturally in crude oils and natural gas. They, plus the olefins, are products of various refinery processes and of olefins plants. They are separated by fractionation, except for butadiene and isobutylene, which are sometimes recovered by extractive distillation. They all vaporize at room temperature, so they are handled in closed, pressurized systems.. 

In modern high-pressure systems, blowdown water is normally of better quality than the water supply. This is because plant intake water is treated using clarification, filtration, lime/lime soda softening, ion exchange, evaporation, and in a few cases reverse osmosis to produce makeup for the boiler feedwater. The high-quality blowdown water is often reused within the plant for cooling water makeup or it is recycled through the water treatment and used as boiler feedwater. 

Figure 1 is a schematic representation of the wet oxidation micro-pilot plant. The system consists of three sections, an electrically heated oxidation vessel, a high pressure solvent delivery system, and a water cooled depressurization and collection chamber. A more detailed description of the pilot plant can be found in previous publications (3,4). 

Closed system tests, using an unvented test cell (see Figure A2.5) or Dewar flask, can be used for vapour pressure systems. The runaway is initiated in the way that best simulates the worst case relief scenario at plant-scale. The closed system pressure and temperature are measured as a function of time. Most commercial calorimeters include a data analysis package which will present the data in terms of rate of temperature rise, dT/dt, versus reciprocal temperature (-1 / ), and pressure versus reciprocal temperature (see Figure A2.10). However, it is important to correct the temperature data for the effects of thermal inertia. See 2.7.2. 

Crude oil vapor pressure limitations for pipeline delivery may be comparable to those for tanker loading. However, a pipeline can be specifically designed as a high vapor pressure system to handle gas liquids components mixed with the crude oil, and it is quite possible that North Sea oil pipeline systems will be developed in this manner. It is not expected to be feasible to recover NGL components separate from oil and gas on the offshore platforms and construct separate NGL pipeline systems. It also may not be possible in every field to design a separation system which meets both gas specifications and low crude oil vapor pressure specifications unless an intermediate product is also made. This will be more fully discussed later In this paper. A high vapor pressure crude system will have an NGL separation and fractionation plant at the onshore pipeline terminal. The vapor pressure limitation for onshore crude deliveries will be fixed by TVP limitations at pump station suction conditions. 

Two main principles of temperature measurement use thermocouples and the so-called resistance thermometer. In chemical plants both methods were applied because they are easy to fit and to maintain.The accuracy of the measurement is influenced by, for example, radiation, which must be taken into account. Thermocouples can be inserted into the pressure system using special sealing techniques, or they may be mounted within a protective tube which is introduced into the pressurized volume. Thermocouple-wires are usually protected with an isulating input in closed-end capillaries with outer diameters of at least 0.5 mm. Thermocouples are technically well tested for pressures up to 6 kbar and temperatures to approx. 800°C. Above these ranges the exact measurement is negatively influenced by several parameters, and the deviations must be taken into account. The accuracy of the temperature measurement devices is normally better than 1 °C. 

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