The Safety Relief Valve Handbook

Design and Use of Process Safety Valves to ASME and International Codes and Standards

Marc Hellemans

• Publisher: Butterworth-Heinemann
• Year: 2009
• ISBN:
  9780080961187
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

The Safety Valve Handbook is a professional reference for design, process, instrumentation, plant and maintenance engineers who work with fluid flow and transportation systems in the process industries, which covers the chemical, oil and gas, water, paper and pulp, food and bio products and energy sectors.

It meets the need of engineers who have responsibilities for specifying, installing, inspecting or maintaining safety valves and flow control systems.

It will also be an important reference for process safety and loss prevention engineers, environmental engineers, and plant and process designers who need to understand the operation of safety valves in a wider equipment or plant design context.

• No other publication is dedicated to safety valves or to the extensive codes and standards that govern their installation and use. A single source means users save time in searching for specific information about safety valves
• The Safety Valve Handbook contains all of the vital technical and standards information relating to safety valves used in the process industry for positive pressure applications.
• Explains technical issues of safety valve operation in detail, including identification of benefits and pitfalls of current valve technologies
• Enables informed and creative decision making in the selection and use of safety valves
• The Handbook is unique in addressing both US and European codes: - covers all devices subject to the ASME VIII and European PED (pressure equipment directive) codes;- covers the safety valve recommendations of the API (American Petroleum Institute);- covers the safety valve recommendations of the European Normalisation Committees;- covers the latest NACE and ATEX codes;- enables readers to interpret and understand codes in practice
• Extensive and detailed illustrations and graphics provide clear guidance and explanation of technical material, in order to help users of a wide range of experience and background (as those in this field tend to have) to understand these devices and their applications
• Covers calculating valves for two-phase flow according to the new Omega 9 method and highlights the safety difference between this and the traditional method
• Covers selection and new testing method for cryogenic applications (LNG) for which there are currently no codes available and which is a booming industry worldwide
• Provides full explanation of the principles of different valve types available on the market, providing a selection guide for safety of the process and economic cost
• Extensive glossary and terminology to aid readers' ability to understand documentation, literature, maintenance and operating manuals
• Accompanying website provides an online valve selection and codes guide.

Chapter 1. History

It is believed that the French scientist Denis Papin was the inventor of the Safety Valve, which he first applied to his newly developed steam digester at the end of the seventeenth century. Safety Valves were indeed designed and used for many years mainly for steam applications or distillation installations throughout Europe (Figure 1.1).

Figure 1.1 Denis Papin

The Safety Valve was kept closed by means of a lever and a movable weight; sliding the weight along the lever enabled Papin to keep the valve in place and regulate the steam pressure.

The device worked satisfactorily for many years and was even commercialised until the beginning of the twentieth century (Figure 1.2).

Figure 1.2 Early 20th century-type weight-loaded Safety Relief Valve

Some believe, however, that Papin was only the inventor of some improvements and that Safety Valves were already being used some 50 years earlier on a steam digester designed by Rudolf Glauber, a German-Dutch alchemist. In his Practice on Philosophical Furnaces, translated into English in 1651, Glauber describes the modes by which he prevents retorts and stills from bursting from an excessive pressure. A sort of conical valve was fitted, being ground airtight to its seat, and loaded with a ‘cap of lead’, so that when the vapour became too ‘high’, it slightly raised the valve and a portion escaped; the valve then closed again on itself, ‘being pressed down by the loaded cap’.

The idea was followed by others, and we find in The Art Of Distillation, by John French, published in London; the following concerning the action of Safety Valves:

Upon the top of a stubble (valve) there may be fastened some lead, that if the spirit pressure be too strong, it will only heave up the stubble and let it fall down.

It should be realized that the word steam, for which application safety valves were later further developed, was still unknown at the time, being of later coinage.

Around 1830 Timothy Hackworth developed an open-ended Safety Valve for the steam trains and boilers that were first being built around that time, which was the start of the Safety Valve design as we know it today. However, the steam installations didn’t really become much safer with the safety devices then in use (Figure 1.3).

Figure 1.3 First open-ended spring-operated Safety Relief Valve

Because of the number of boiler explosions and related fatalities in Europe, a select committee of the British House of Commons, looking into the explosions on steam ships reported in June 1817:

Boilers – should have two safety valves, they shall be inspected and penalties be inflicted on unauthorised persons interfering with the Safety Valves.

Many explosions were caused by inadequate boiler design or by people rendering the Safety Valves inoperative in order to increase the boiler pressure. Due to further explosions, 1882 saw the passing of the Boiler Explosion Act, in which a boiler was defined as

Any closed vessel used for generating steam or for heating water, or for heating other liquids or into which steam is admitted for heating, steaming, boiling or other similar purposes.

In Great Britain, voluntary bodies such as the Steam Users Association supplied reports to the government beginning in 1854. In the period from 1881 to 1907, there were still a total of 1871 boiler explosions investigated by the Board of Trade. These explosions accounted for 732 fatalities and 1563 non-fatal injuries.

In the United States, the safety records were just as bad. In the period from 1906 to 1911, there were 1700 boiler explosions in the New England area alone, accounting for 1300 fatalities.

In 1901 Parliament passed the Factories and Workshop Act further regulating steam boilers. Among the improvements were

A steam gauge and water gauge are to be fitted to the boiler and the boiler and associate safety devices are to be inspected every 14 months.

The American Society of Mechanical Engineers (ASME), was asked by the government to formulate a design code, and developed the famous Boiler and Pressure Vessel Code between 1911 and 1914 as a set of safety rules to address the serious problem of boiler explosions in the United States. Average steam pressure in those days had reached only about 300PSI (20bar). Europe and other parts of the world used the code as a basis for their own safety rules.

The ASME Boiler and Pressure Vessel Code, Section I, became a mandatory requirement in all states that ‘recognized the need for legislation’.

This code included rules for the overpressure protection of boilers, based on the best industry practice of the time. The principles of today’s code rules for overpressure protection is little changed from the first code.

With the expansion of the process industries, the need for a code that would be applicable to ‘unfired’ vessels (roughly, every pressure-containing vessel that is not a boiler) was identified, which gave rise to the Section VIII of the ASME code. Today, the ASME Boiler and Pressure Vessel Code is composed of 12 sections:

Section I = Power Boilers

Section II = Materials

Section III = Rules for the Construction of Nuclear Power Plant Components

Section IV = Heating Boilers

Section V = Nondestructive Examination

Section VI = Recommended Rules for the Care and Operations of Heating Boilers

Section VII = Recommended Guidelines for the Care of Power Boilers

Section VIII = Pressure Vessels – Division I

Section IX = Welding and Brazing Qualifications

Section X = Fiber-Reinforced Plastic Pressure Vessels

Section XI = Rules for Inservice Inspection of Nuclear Power Plant Components

Section XII = Rules for the Construction & Continued Service of Transport Tanks

With the growth of the petroleum and petrochemical industries, the American Petroleum Institute (API) sought uniformity of the dimensional and physical characteristics of pressure-relieving devices. To date, the API has published the following internationally acknowledged documents:

RP* 520 = Sizing, Selection and In...