Typical Calibration Procedure of Displacer (Buoyancy) Level Transmitter

Operating Principle

The displacer level transmitter (or any other buoyancy level transmitter) uses the effect of buoyancy. When the displacer is immersed in the process fluid, this buoyancy effect will make the displacer lighter than the non immersed displacer. This change of displacer weight is then detected by the sensor (whether use torque tube or LVDT) and then translated as a fluid level.

2 Wires, 3 Wires, or 4 Wires RTD (Resistance Temperature Detector)?

RTD is a temperature sensitive metal. The resistance of the RTD metal is gradually changed with the changed of temperature. In applications there are 2 wires, 3 wires, and 4 wires RTD. 2 wires RTD means that the RTD only connected to the transmitter by using 2 wires, 3 wires means its connected by 3 wire and 4 wire means its connected by 4 wires. So what it should be, 2 wires, 3 wires, or 4 wires RTD?

The Difference Between API and ASME Pressure Safety Valve (PSV)

In the vendor data sheet, calculation sheet, and or catalogue of the PSV, it was stated two different terms which is API and ASME PSV that usually makes confusion to a young engineer. Some times it is stated as API area, ASME area, actual area, etc. So actually what is the difference between this API and ASME pressure safety valve (PSV)?

Flow Direction of Control Valves

Flow direction of control valves has a relationship with a failure action, High Delta Pressure, Cavitation, and % opening of the valve. There are 2 type of control valve flow direction: Flow to Open (FTO, or Tending to Open), Flow to Close (FTC, or Tending to Close).

Marshalling Cabinet or Marshalling Panel

As discussed in the Typical Architecture of Instrumentation and Automation System, the automation architecture of the plant is having a marshalling cabinet in between the junction box and the system cabinet.  This marshalling cabinet function is to interface the incoming field cable (which is normally a multipair cable) and the I/O (Input/Output) card connection. Without marshalling cabinet, we can sure (for large number of I/O) that there will be a trouble for operation personnel to maintain and operate the cabling.

Typical Architecture of Instrumentation & Automation System

In general application, the instrumentation and automation architecture is consist of field instruments, individual & multicore cable, junction boxes, marshalling cabinet, and system cabinet. Each of them is combined together so that the control loop application can be performed correctly.

End Connection of Control Valves

The control valve end connection may have flange connection, threaded, or even welded end. Flange connection is the most common control valve end connection in the oil & gas application. Other connection such as threaded or welded end is only used in particular application.