Skip to main content

What is SAMA Diagram?

 SAMA is an acronym of Scientific Apparatus Makers Association, in some plants, there has been greater adoption of SAMA diagrams which provide more detailed process diagrams which constitute various process symbols.


SAMA drawings are sometimes referred to as “control functional diagrams”.


SAMA symbols are rarely used on P&IDs. Rather, they are generally used to diagram control systems at a detailed functional level. They provide no information about the device’s location or function, nor about the technology used to implement it.


SAMA Diagram

Usually, SAMA symbols show the control system without reference to the processing equipment or piping details. Still, for complex control systems, because they can show greater functionality compared with other documentation formats, they are often preferred for presenting control strategy details in some industries.


Because of the complexity of their control strategies, SAMA symbols are extensively used in the power generation industry. SAMA methods tend to be used for boiler functional diagrams due to the higher level of control-element details and the visualization they provide.


The newer ANSI (American National Standards Institute) symbols have similarities and differences and are used in many industries. The International Society of Automation (ISA) standards are another choice for putting forward control diagrams.


Many manufacturers of control equipment, particularly distributed control systems (DCS), document their library of control algorithms using something similar to SAMA symbology.


The below figure shows the basic control loop that illustrates SAMA symbols.

In the above drawing, the three diamonds grouped together represent the adjustable setpoint (left A), the adjustable manual output (right A), the auto/manual transfer switch (T). 


 
The square-shaped box is a controller. The diamond-shaped enclosures denote that these are all manual functions performed by the operator.

The figure below is an abbreviated list of some of the commonly used symbols.

ISA and SAMA Diagrams
The below figure shows a simplified example using both ISA and its equivalent SAMA functional diagram.

Generally, the ISA symbology tends to be better suited for piping and instrumentation diagrams (P&IDs), while the SAMA diagrams are better suited to indicate complex logic functions and control.
Three Element Drum Level Control
A three-element control loop is an important application in boiler control. Boiler drum level is a critical process variable (PV) in the safe operation of a boiler.

The below figure is a SAMA diagram of the cascade plus feedforward control application approach.

The three transmitters are the three elements referred to in the name of the control system. The feedwater flow setpoint is automatically by the steam flow signal to keep the feed water supply in balance with the steam demand. This is the feed water component of the control methodology.

The drum level controller trims the feedwater flow setpoint to compensate for errors in the flow measurements or any other unmeasured load disturbances such as blowdown that may affect the drum level. This is the cascade component of the control scheme.

The summing function is employed to combine these two components. The square root functions on the flow transmitters linearize the relationship between the flow and differential pressure flow meters.

Interest to read more example and symbols of SAMA? then download the below document.



Comments

Popular posts from this blog

PLC Program for Mixing Tank

 Create a ladder diagram for controlling a batch mixing process. Implement a PLC program for mixing tank or Mixing Process using PLC Ladder Logic. PLC Program for Mixing Tank Fig : Mixing tank A tank is used to mix two liquids. The required control circuit operates as follows: A. When the START button is pressed, solenoids A and B energize. This permits the two liquids to begin filling the tank. B. When the tank is filled, the float switch trips. This de-energizes solenoids A and B and starts the motor used to mix the liquids together. C. The motor is permitted to run for 1 minute. After 1 minute has elapsed, the motor turns off and solenoid C energizes to drain the tank. D. When the tank is empty, the float switch de- energizes solenoid C. E. A STOP button can be used to stop the process at any point. F. If the motor becomes overloaded, the action of the entire circuit will stop. G. Once the circuit has been energized, it will continue to operate until it is manually stopped. Solution...

Ferrules and Cross Ferruling

 Ferrules are identification labels provided for every wire terminations in an instrument, equipment, or electrical/instrumentation control panels. These tube-shaped sleeves can be inserted easily on each individual wire in a multi-core cable. In earlier days fixed digits/letters are used as ferrules, but now Instrumentation engineers/technicians prints out desired ferrules by using a ferrule printing machine. Typical Ferrule The numbers/ letters on the ferrules will be given as per the approved electrical hook up or loop diagrams. This helps technicians to easily identify a particular loop/wiring from a series of terminal blocks and to troubleshoot the desired terminal connection. Separate numbers on the ferrules distinguish the positive and negative polarities of wires, thus ensure the polarity protection of the instrument. Cross Ferruling  As a wire is connected on its both ends, it is quite useful to use a cross reference method for wire identification. Unlike normal ferru...

What is Relay? How it Works? Types, Applications, Testing

 We use relays for a wide range of applications such as home automation, cars and bikes (automobiles), industrial applications, DIY Projects, test and measurement equipment, and many more. But what is Relay? How a Relay Works? What are the Applications of Relays? Let us explore more about relays in this guide. What is a Relay? A Relay is a simple electromechanical switch. While we use normal switches to close or open a circuit manually, a Relay is also a switch that connects or disconnects two circuits. But instead of a manual operation, a relay uses an electrical signal to control an electromagnet, which in turn connects or disconnects another circuit. Relays can be of different types like electromechanical, solid state. Electromechanical relays are frequently used. Let us see the internal parts of this relay before knowing about it working. Although many different types of relay were present, their working is same. Every electromechanical relay consists of an consists of an Elect...