Practical guidelines vessels

Thomas model is usually appropriate somewhere between these two. These criteria are guidelines only and must be carefully applied. All three models should be tested for borderline cases. In practice, the models are valid only if no mass flows to or from the vessels, negligible reactants are consumed, and heat is generated only by reactions. 

The quantity of flammable liquids or gases or heated combustibles can be indicative of the need for fixed water spray fire protection. Table 8-4, developed from FM Data Sheet 7-14, suggests quantities of flammables where fixed water spray fire protection should be considered based on one insurance provider s guidance. Some company internal guidelines and practices allow up to 5,000 gal (18,927 I) in the largest vessel before water spray protection is recommended. Additional guidance on fixed fire protection is available in API Publication 2030, Application of Water Spray Systems for Fire Protection in the Petroleum Industry, (API, 1998). 

While it is important to take proper precautions (see Appendix 2), properly built equipment offers few hazards if relatively small quantities of liquids are used under pressure. The energy stored in a compressed liquid is of the order of 0.2-0.5 kJ mor kbar" this is much less than in a gas. In the event of the catastrophic failure of a vessel, only around 10 per cent of the liquid would need to escape to reduce the pressure to the atmospheric value, and double-walled vessels are unlikely to suffer a failure of both cylinders. The author has experienced the failure of a piston-cylinder apparatus which led to nothing more than a sudden depressurization. On the other hand, hazards may arise from the low-pressure side, which is likely to be carrying oil at 500 bar or more a pin-hole jet at this pressure can penetrate the human body. The valve threads may become worn and the stems may then be forcibly ejected. So hose connections should be inspected and renewed regularly and, where possible, they should be shielded from personnel, the valves should be mounted with the stems pointing away from the operator, and the guidelines set out in the code of practice (see Appendix 2) should be followed. 

The requirements also indicate that all personnel should be trained and demonstrate competency in ladder access to and egress from a vessel and in the use of appropriate personal protective equipment and sea survival techniques. More important, the guidelines note that risk assessments should account for advances in the industry s knowledge of operations and for new technology and changes in state-of-the-art equipment and that any recommended best practices should evolve as well. 

Information acquired from the above items is not adaptable to any kind of numerical ranking for quantitative safety assessment purposes. However, the information can reveal the owner or user s apparent attention to good practice, careful operation, regular maintenance, and adherence to the recommendations and guidelines developed for susceptible applications. If the assessment indicates cracking and other serious damage problems, it is important that the inspector obtain qualified technical advice and opinion. After all, safety and health are of primary concern regarding pressure vessels. 

This recommended practice provides guidelines for examining the principal causes of overpressure determining individual relieving rates and selecting and designing disposal systems, including such component parts as vessels, flares, and vent stacks... 

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