Emerson Daniel 762, User Manual

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1 Introduction
Topics covered in this chapter:
• Purpose of this manual
• Description of the Models 762, 763, 765, 766 and 767 Control Valves
• Agency certifications for the Models 762, 763, 765, 766 and 767 Control Valves
1.1 Purpose of this manual
This manual provides guidance to owners and personnel in the installation, operation and
maintenance of the
Daniel
TM
Models 762, 763, 765, 766 and 767 Control Valves manual,
3-9008-562 . It is imperative that product owners and operation personnel read and follow
the information contained in this manual to ensure that the control valve is installed
correctly and is operating according to the design certifications and safety considerations.
1.2 Description of the Models 762, 763, 765, 766
and 767 Control Valves
1.2.1 General features of the control valve
In many applications, such as pipelines, storage terminals and marine loading and
unloading, it is necessary to include surge relief systems for the purpose of equipment and
personnel protection. Surge pressures result from a sudden change in fluid velocity and,
without surge relief, these surge pressures can damage pipes, other piping components,
equipment and personnel.
These pressure surges can be generated by anything that causes the liquid velocity in a line
to change quickly (e.g., valve closure, pump trip, Emergency Shut Down (ESD) closure) and
subsequently packing pressure. Total surge pressure may be significantly above the
maximum allowable pressure of the system, leading to serious damage to your valuable
assets.
The fundamental requirements of surge relief systems include the need for fast acting,
high capacity valves which can open very quickly to remove surge pressures from the line
and then return to the normal (closed) state quickly but without causing additional
pressure surge during closure. These valves are often required to open fully in very short
periods of time, so that they may pass the entire flowing stream if conditions dictate.
Long pipelines can produce dangerous pressures when static product is shut-in between
valves and thermal expansion occurs. In this situation, pressure relief will be required.
Although the time of operation and valve capacities are not as crucial in such applications,
they remain as key elements of safety in the system and proper regard to selection and
operation is imperative.
Introduction
User manual 3