Gate valve - fully open

For the isolation valves, take gate valves fully open, one for each vessel, two for the pump and two for the control valve ... 

Gate valve fully open Gate valve V4 open Gate valve V2 open Gate valve V4 open... 

A typical control loop contains three components — sensor, controller and final control element — and failure of any one component can cause the loop to fail in a particular mode, for instance with a control valve fully open. Thus the failure rates of the three components combine through OR gates and the failure rate for the whole loop is the sum of the component failure rates. 

Gate valve (wedge disc plug disc) Fully open 13... 

A pipeline connecting two tanks contains four standard elbows, a plug valve that is fully open and a gate valve that is half open. The line is commercial steel pipe, 25 mm internal diameter, length 120 m. 

The distillation column operates at a pressure of 500 mmHg (500 mm of mercury, absolute). The feed point to the column is 12 m above the base of the tank. The tank and column are connected by a 50 mm internal diameter commercial steel pipe, 200 m long. The pipe run from the tank to the column contains the following valves and fittings 20 standard radius 90° elbows two gate valves to isolate the pump (operated fully open) an orifice plate and a flow-control valve. 

A gate or ball type valve that is fully opened in normal operation should be used, where a valve in the feed line near the separator cannot be avoided. 

Globe or stainless steel ball valves with Teflon trim are recommended where throttling is desired. Gate valves are suitable only in locations where the valve operations are either fully open or fully closed. Valves should have all-metal seats and disks. The use of aluminum is not recommended. 

The simplest functionality of a gate valve is a linear stem that raises and lowers a plate across the ports of the valve. FuU conduit valves such as expanding and slab gates provide protection for the seat in the fully open position. Knife and wedge gates permit circulation across the seats in the open position. Valves are available with pressure preferences for fail open or fail closed requirements. 

Moller and Elmqvist presented the head loss data for water, for thermomechanical pulp at two concentrations, and for kraft pulp at two concentrations for range of flow rates through fully open and partly closed gate valves, elbows, bends, expansions, and contractions [48], They observed that the head losses for pulp suspensions across these fittings were proportional to the square of the flow velocity in the pipe. 

The internal design of process-control valves has a direct impact on the flow characteristics of the gas or liquid flowing through the valve. A fully open butterfly or gate valve provides a relatively straight, obstruction-free flow path. As a result, the product should not be affected. 

Slide gates and butterfly valves are the most common discharge valves, while in some applications a pin gate is used. Whatever the type of valve that is chosen, it should generally be used only for maintenance purposes, i.e. operated fully open or fully closed, and not used to control the rate of discharge. 

A storage tank is connected to a pond (at atmospheric pressure ) by a length of 3 in pipe and two gqte valves. From previous operating experience, it has been found that when the tank is at a pressure of 3 atm the flow through the pipe is 12.5 m /h, when both gate valves are fully open. If the pressure in the tank increases to 5 atm, what will be the maximum discharge rate from the tank ... 

Isolation valves being considered include gate valves, butterfly and ball valves. These valve types minimize system pressure drops when in the fully open position. The selected valve would need to be completely sealed from the space environment to prevent system leakage, with an external actuator to position the valve. A redundant actuator could be used to improve valve reliability and both actuators could be operated in parallel to free a sticking valve. The NRPCT does not have experience with solenoid operators on either the size valves proposed for the SNPP or at the temperatures proposed. Both valve performance, with respect to pressure drop (check valves), and valve actuation remain development challenges. 

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