Machinery pressure systems

Motion of fluids in which local velocities and pressures fluctuate irregularly, in a random manner. Predictive maintenance technique that uses principles similar to those of vibration analysis to monitor the noise generated by plant machinery or systems to determine their actual operating condition. Ultrasonics is used to monitor the higher frequencies (i.e., ultrasound) that range between 20,000 Hertz and 100 kiloHertz. 

For systems comprising equipment, sub-systems and incorporated apparatus several safety directives may apply, therefore, each relevant part of the system must comply with the essential requirements of the directive(s) applicable to that part. Note that the essential requirements of individual directives are quite diverse and broad ranging. Where one system forms part of another, for example a pressure containment system forming part of a machine, the pressure system must comply with the essential requirements of the Pressure Equipment Directive (EC 1997) and as an integrated system with the requirements of the Machinery Directive (EC 2006a). 

Many techniques have been developed to reduce these risks to a minimum and this chapter looks at some of those techniques that are available to the designer and user of modem equipment. What is not dealt with is the other vital element in the interface - the operator - and the training necessary to ensure his/her safety and how it matches the equipment, the culture and the working methods of the particular organisation. Essentially the term work equipment encompasses any equipment used in the course of work. However, in this chapter work equipment will be considered in four major frmctional areas machinery, power tmcks, cranes and lifts, and pressure systems. 

Figure 13.13 High-pressure piston pump heads (a) vertical monoblock pump head (according to Hammelmann) (b) piston pump head with Y-piece source Institute of Process Machinery and Systems Engineering, University of Erlangen-Nuremberg, Germany).

Hydrate formation is possible only at temperatures less than 35°C when the pressure is less than 100 bar. Hydrates are a nuisance they are capable of plugging (partially or totally) equipment in transport systems such as pipelines, filters, and valves they can accumulate in heat exchangers and reduce heat transfer as well as increase pressure drop. Finally, if deposited in rotating machinery, they can lead to rotor imbalance generating vibration and causing failure of the machine. 

Certain types of equipment are specifically excluded from the scope of the directive. It is self-evident that equipment which is already regulated at Union level with respect to the pressure risk by other directives had to be excluded. That is the case with simple pressure vessels, transportable pressure equipment, aerosols and motor vehicles. Other equipment, such as carbonated drink containers or radiators and piping for hot water systems are excluded from the scope because of the limited risk involved. Also excluded are products which are subject to a minor pressure risk which are covered by the directives on machinery, lifts, low voltage, medical devices, gas appliances and on explosive atmospheres. A further and last group of exclusions refers to equipment which presents a significant pressure risk, but for which neither the free circulation aspect nor the safety aspect necessitated their inclusion. 

Monitoring should include the usual parameters worthy of surveillance in high-speed turbo machinery the temperature of journal bearings, vibration and axial position of the pinions, inlet and discharge temperatures combined with discharge pressure from the individual compressor stages, and various lube oil system devices. Competent manufacturers make sure all measurement locations are completely prewired on the machine and made available at predefined interfaces or in terminal boxes for connection at the plant site. 

Pipe used for low-pressure applications such as transporting air, steam, gas, water, oil, etc. Employed in machinery, buildings, sprinkler and irrigation systems, and water wells but not in utility distribution systems can transport fluids at elevated temperatures and pressures not subjected to external heat applications. Fabricated in standard diameters and wall thicknesses to ASTM specifications, its diameters range from Vs to 42 in. o.d. 

FCE, of Danbury, CT, teamed with Allison Engine Company to evaluate a carbonate fuel cell combined with a gas turbine and a steam turbine generator. The system was operated at ambient pressure. The net power of the hybrid system was 20.6 MW and the NOx levels were less than 1 ppm. The process showed a 65 % efficiency with off-the-shelf turbomachinery and 72 % efficiency with cycle specific machinery. The COE is predicted to be comparable to present day alternatives. 

The original GC control system took the form of a central room which monitors the flowllne6, oil, water, and utility sections, plus a smaller satellite control room monitoring the gas compression and gas conditioning section of the plant. Closed loop process control, such as separator liquid level, pressure, flow and temperature control were handled by local pneumatic analog controllers. The key process variables are displayed in the control room via electronic instrumentation. All the key process and equipment trouble alarms are annunciated m the control rooms, plus the on/off status of key machinery and open/close status of key valves are displayed. 

In the PCU and primary system, however, there is only one compressor to manage mass flow rate while there are several different circuits. To achieve the desired control of helium mass flow rate compressor control provides little flexibility. Rather inventory control is used to obtain a flow rate proportional to heat exchanger power. Because density is proportional to pressure for fixed temperature, by varying pressure and maintaining constant speed turbo-machinery, gas velocity remains constant and mass flow rate (proportional to the product of density and velocity) is linear with pressure. Thus, pressure is manipulated through coolant mass inventory so that it is proportional to heat exchanger power so that in turn mass flow rate is proportional to heat exchanger power. Results obtained for this control scheme are described below. 

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