Main stop valves

Driving units shut down by closing the main stop valve and the steam turbine regulating valves and at the same time closing the butterfly valve upstream of the expander (closing time 2-3 sec)... 

Main Valve Main Stop Valve 4 Every Outage 4 4 4 4 4... 

A variety of valves are required on a sprinkler system. There must be a main stop valve which on a wet system must be locked open, conveniently placed and fitted with an approved sign. Downstream of this is an alarm valve which opens when a demand is put on the system and also provides a flow to actuate the alarm. Other valves include a drain valve which allows the system to be drained and tests to be carried out on the system and a test valve which simulates the operation of a sprinkler head and enables the operation of the alarm valve and the alarm to be tested. Dry systems and alternate wet/dry systems require further valves. The principal valves in the control units of various types of sprinkler installation are summarised in Table 25.8. 

A main stop valve An alarm valve A main stop valve An air valve Compressed air supply A main stop valve An alarm valve An air valve Compressed air supply A main stop valve A pre-action valve A pre-action control panel Compressed air supply... 

All systems require at least two pressure gauges, one above and one below the main stop valve. 

Control systems generally contain many automatic protection and alarm systems. A typical protection system includes a main stop valve which is spring-loaded to close and is mounted ahead of the turbine inlet valve. Hydrauhc oil keeps this valve open if several protection devices all indicate safe operation. These include an overspeed governor, bearing oil pressure relay, a manual trip relay, and where apphcable, a low-vacuum relay and nonreturn valve relays. 

Turbine control valve quickly closed Main stop valve closure Earthquake acceleration large Loss of offsite power... 

Main stop valves closure MSIV closure (90%)... 

Since the function of the AFS is to keep the main coolant flow rate in the event of the unavailability of the RCPs, its actuation signals should be released by detecting an abnormality in the RCPs or a decrease in the main coolant flow rate. Reactor coolant pump trip and main coolant flow rate low are taken as the AFS signals. Loss of offsite power, condensate pump trip, turbine control valves quickly closed, main stop valves closure, and MSIV closure are also taken as the AFS signals because these abnormalities cause a trip of the RCPs. 

The pressure gauge and associated shut-off valve, the boiler vent cock valve, main steam stop valve, and safety valve can be observed rising above the crown sheet of a FT boiler (the highest point of the boiler), normally in a line running the length of the boiler. 

Stop valves are fitted to each main or auxiliary discharge steam outlet, close to the boiler (but not in front of a safety valve or superheater connection). They are employed to place a boiler in or out of service. Gate-type stop valves of outside stem and yoke valve (OS Y) design often are employed because they indicate whether they are open or shut by the (out/in) spindle position. 

A steam heating line used to warm up the main steam line and equalize the pressure around the main steam stop valve. 

Bush(Flame Bush). A slang term used at proving grounds to signify the pecularly-shaped flame that emerges and arises from the nozzle exit of some thrust chambers of rocket motors after the main control valves have been closed and the primary combustion stopped Ref RocketEncycl(1959), 65... 

If gas is leaking around the neck of the cylinder where the valve screws into the cylinder, you will not be able to stop this. You should take action to remove the cylinder to the outside if it is a small leak and you can do this safely. You may want to call your EHS department to assist in taking care of this problem. The leak can only be repaired by the supplier and they will need to be called to retrieve the leaking cylinder. Similarly, if there is a leak around the pressure relief device that is on the main cylinder valve, you will not be able to fix this. Nevertheless, it will need to be moved outside. In some cases, there may be leaks in small cylinders that can be placed in a laboratory hood—a lecture bottle, for example. 

Overpressure protection for the shell side of the steam generators and the main steam line up to the inlet of the turbine stop valve is provided by the secondary safety valves. 

A pressure relief function is used to control large pressure transients. This system will operate safety/relief valves following closure of the main steam isolation valves or the sudden closure of the turbine admission or stop valves and failure of the turbine bypass system to relieve the excess pressure. For this fimction, the safety/relief valves discharge steam from the steam lines inside the drywell to the suppression chamber. Each safety/ relief valve is operated from its own overpressure signal for the relief fimction, and by direct spring action for the safety function. 

Steam is removed from the steam generator sections by four DN90 pipelines equipped with double pneumatically actuated stop valves, enters the main steam line and then the turbine generator. 

HP cylinder inlet steam temperature - the main steam temperature before the turbine stop valves (or in the main steam line) at the rated turbine power. The actual value should be... 

Implement a plan for evacuation and quickly contact the local fire department if unignited and uncontrolled leakage is encountered that cannot be stopped by shutting off the closest appropriate valve or main supply valve without risk. 

The purification stop valves are normally open, motor-operated valves located inside containment. They close automatically on a low pressuriser level signal from the protection and safety monitoring system to preserve reactor coolant pressure boundary and to prevent uncovering of the heater elements in the pressuriser. However, they can also be manually operated from the main control room and the remote shutdown workstation (Section 9.3.6.3.7 of Reference 6.1). 

This system consists of the pipes and valves that take the steam from each steam generator to the stop valves of the high-pressure turbine. It diverts a proportion of the steam to the to the moisture-separator reheater (Section 6.6.5) and a small amount of steam to seal the low-pressure turbine glands (Section 6.6.7). There is also a turbine bypass coimection, which allows the steam to be dumped directly into the main condenser (Section 6.6.8) without passing through the turbine. 

The flow of main steam entering the high-pressure turbine is controlled by four control valves. The turbine control valves are adjusted automatically by electrohydraulic servo actuators. These actuators control the turbine speed when it is starting up, and for load control after the turbine-generator unit is synchronised. In series with each control valve is a stop valve, whose function is to shut off and isolate the steam flow to the turbine when required. 

Main steam stop valve Turbine control valve... 

Water hammer (also known as hydraulic shock) occurs in two distinct ways when the flow of liquid in a pipeline is suddenly stopped, for example, by quickly closing a valve [13], and when slugs of liquid in a gas line are set into motion by movement of gas or condensation of vapor. The latter occurs when condensate is allowed to accumulate in a steam main, because the traps are too few or out of order or in the wrong place. High-pressure mains have been ruptured, as in the following incident. 

Valves have two main functions in a pipeline to control the amount of flow, or to stop the flow completely. There are many different types but the most commonly used are the gate valve and the globe valve. The gate valve contains a disk that slides at right angles to the flow direction. This type of valve is used primarily for on-off control of a liquid flow. Because small lateral adjustments of the disk cause e.xtreme changes in the flow cross-sectional area, this type of valve is not suitable for adjusting flow rates. 

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