Valves Flashcards
What is the first thing that you should do prior to working on a valve?
Communicate with operations to determine the function of the valve and any affects of valve movement.
Why is it important to completely read through a job plan prior to starting to work?
An understanding of hazards and an inventory of any tools or spare parts required should be obtained before starting the work.
Where would you find safety critical procedures?
OMS - Standard Operating Procedures.
How do you determine whetehr you have a smart or analog device?
Name plate, model number.
WHat type of test devices are needed for analog vs smart devices?
4-20mA source or Hart communicator.
How do you know what the bench set is of an actuator?
Manufacturer’s label.
When would you need to adjust the bench set of an actuator?
When the process pressure may overcome the spring pressure of the actuator. Process change or trim change.
What is important to look for when coupling a valve to an actuator?
Mounting, fail open vs. fail close, bench set.
How do you tell if a valve is fail open or fail close?
Air on top (fail open) or air on the bottom (fail closed).rotation for 90 degree valves.
What is the difference between a dual acting and a spring return valve.
Dual acting valves are driven by air both open and closed. Spring return are only driven one direction with air.
What potential failures might be found when trouble shooting a control valve?
Control wiring damage, blown fuse, leaking seals, leaking gaskets, broken spring, valve corrosion, positioner mechanical failure, IP failure, worn trim…
How would you troubleshoot a valve?
Remove valve from service. Inspect, check voltage, check pressure, stroke valve with amperage source.If neccesary, obtain parts and inspect internals.
When all calibration is complete and the valve still leaks by, what is left to check?
Valve internals. Process pressure.
Where would you find information for replacement parts?
Manufacturer’s manuals.
How do you isolate a valve from the process without causing an upset?
If possible, work with operations to by-pass the control valve.
When working on a valve when would you need to isolate and LOTO? How?
There are trapped energy in the process connections and the air connections. Double block and bleed and LOTO valves. JSEA, LOTO forms, verification.
What are the steps taken to replace an I/P?
Isolate valve from process upset. Disconnect airlines, pull fuse. Replace I/P. Test. Return to service.
Why would you use a manual overide/hand-jack? What position should the manual overide / hand-jack be in when the work is complete?
When work needs to be performed on the vale controller or control loop and the process will not be shut down. The override should be placed in the mid position when work is complete.
How is a DVC (Digital Valve Controller) calibrated?
Connect a HART communicator to the control loop. Follow prompts. Refere to manufacturer’s docs.
Who would you contact to test operation of a valve?
Operations.
What is the local indicator on the side of the actuator used for?
Estimate of valve position.
Explain how you would pressure test a valve.
Using a pressure source and a pressure indicatore, I would pressurize one side of the valve and wait to see if the pressure bleeds through the valve.
What are potential sources of leaks from process or from pneumatics?
Gaskets, diaphram, stem packing, airline tubing.
