Double Block and Bleed Valves Opening or Closing Sequence

On processes where the fluid in question is especially dangerous, “double block and bleed” valve manifolds are often used to isolate pressure measuring instruments (like pressure gauge, pressure transmitters, etc) from the process.

Double Block and Bleed Valves

Describe the proper procedure for block and bleed valve opening/closing when removing and replacing an instrument connected to a process through such a manifold.

Answer:

Removing the gauge from service:

Close the “block” valve closest to the process.

Open the “bleed” valve. Monitor the instrument’s pressure indication, to make sure it is changing to register atmospheric pressure. This tells you that the “bleeding” is successful.

Close the “block” valve closest to the instrument.

Close the “bleed” valve.

Place lock-out tags on all three valve handles to notify operators and technicians of the instrument’s removal and pending return.

Remove the gauge from the piping or tubing.

Assuming the process ﬂuid is especially dangerous, there may be some sort of recommended decontamination process for the instrument prior to you connecting it to calibration equipment in the shop. As always, be aware of any special safety considerations on any process you are working around.

Placing the gauge back into service:

Remove the lock-out tags on all valve handles.
Open the “bleed” valve (to relieve any pressure that may have built up between the two closed block valves from a leak in the ﬁrst block valve).
Re-attach the gauge to the piping or tubing.
Open the “block” valve closest to the instrument.
Close the “bleed” valve.
Open the “block” valve closest to the process.

Comments

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...

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...

Chlorine dioxide Analyzer Principle

Chlorine dioxide measurement Chlorine dioxide (ClO2) is an instable, non-storable, toxic gas with a characteristic scent. The molecule consists of one chlorine atom and two oxygen atoms – represented in the chemical formula ClO2. It is very reactive. To avoid the risk of spontaneous explosions of gaseous chlorine dioxide or concentrated solutions, it is generally handled in dilution with low concentrations. ClO2 is soluble in water, but tends to evaporate quickly. Typically it is prepared on site, for example from hydrochloric acid and sodium chlorite. The procedure provides solutions with approx. 2 g/l ClO2 that can be safely handled and stored for several days. Image Credits : krohne Sensor Parts : Reference electrode Applied chlorine dioxide specific potential Current needed to maintain the constant potential Counter electrode Measuring electrode The disinfection effect of ClO2 is due to the transfer of oxygen instead of chlorine, so that no chlorinated byproducts are formed. C...

TILI Automation

Search This Blog