#Isolation Valve First Step towards #Safety

Isolation First Step towards Safety

Safety of Operator is one of the most important aspects for any system design. System must be designed considering safety aspects in mind.

Isolation of system from any human Hazard is first step towards safety. Sampling systems are often handling samples at very High Hydraulic Pressure and Temperatures. In some cases these samples can be hazardous and toxic gases. System must be isolated and Lockout (Tag out) before system is inspected, maintained, cleaned or repaired. Isolation procedures must be included as a part of operation and maintenance manual for any sample handling system.

 The aim of an isolation procedure is to:

•  Isolate all forms of potentially hazardous energy (High Pressure and Temperature samples) to ensure that an accidental release of hazardous energy does not occur
• Ensure that entry to a restricted area is tightly controlled.

Importance Isolation Valve for High pressure and Temperature steam samples:

Steam and Water Analysis system (SWAS) is used for online monitoring of Steam/ Water samples from Boilers and Turbines. These samples are at very high pressure and Temperatures.

In next generation Ultra-supercritical power boilers, Feed water pressures can be as high as 350 Bar and Temperatures of superheated steam closed to 600 Deg C. These samples hold very high energy in terms of Hydraulic pressure and Temperature. Any exposure to these samples can cause serious hazard for human working around. Also during startups samples need to blow down to ensure clean samples are taken in system to avoid clogging of sample lines.These valves are first active component of sample handling system before primary sample coolers which are directly exposed to High pressure and Temperature samples.

Important aspects of Valve Design

Body and Seat:

As Samples are with very high pressure as well as temperatures these valves must be designed to isolate high energy of samples. As everyone aware at elevated temperatures strength of material reduces. Thus metallurgy of valve bodies is first important aspect to handle high pressures at elevated temperatures. As these samples are at very high temperature Globe Valves with metallic seat is most recommended. Valve must be designed to isolate small sample flow rates for sampling applications

Glands and bonnets:

In case of sample isolation valves for steam application valve parts are exposed to high temperature differences. To avoid sample leakages through glands it is recommended to use metallic braided Graphoil packing rings. These glands must be packed in Welded bonnets with Top pressure plate on glands. Pressure plate can be tightened using bolts to ensure leak tight glands once valves exposed to steam.

Spindle:

Long spindles ensure good isolation from High temperature surface of valves. Also there are less chances of conduction of heat from samples to handles for better isolation.

In many cases, particles are trapped in glands No- rotating spindle designed with thrust bearing helps

Forbes Marshall made Sample Isolation valve is specially designed for Steam application

• Robust Forge Body for high pressure and temperature steam application
• Sample Isolation and Blow-down valves are designed in line with ASME PTC 19.11-2008 and ASME B16.34 standards
• Non-rotating spindle design ensures easy operation
• Braided Grafoil gland packing rings of high pressure and temperature applications in SWAS.