Wednesday, December 12, 2018

Happy Holidays from Piping Specialties / PSI Controls

From all of us at Piping Specialties/PSI Controls, we wish our customers, partners and vendors a safe and happy holiday season and a wonderful 2019!


Sunday, December 9, 2018

What Are Trunnion Mount Ball Valves?

Trunnion ball valve design. Trunnions highlighted.
Ball valves are well understood in process control and industrial piping systems. Their simple 1/4 turn operation, compact form factor, bidirectional sealing, and tight shutoff make them a very popular choice for a wide range of applications.

Although there are many varieties of seat designs, body styles, and flow patterns, ball valves can be separated in to two main groups, distinguished by a primary design element - the mounting method of the valve ball.

The two groups are:
  • Floating ball
  • Trunnion mounted ball
Floating ball valves use the body and valve seats to position and hold the ball in the media flow path, allowing the flow force to lodge the "floating" ball firmly against the downstream seat. In this style, the ball is not mechanically held in place, thus the term "floating". Floating ball valves are, in general, limited to applications with smaller sizes and lower pressure ranges because, at some point, the fluid pressure on the ball may exceed the seat and trim's ability to hold the ball properly in place.

Trunnion mount valves, on the other hand, employ a "trunnion" in their design. A trunnion is a pin, or a pivot, forming one of a pair on which ball is mechanically connected and supported. The valve shaft and the trunnion connect at the top and bottom of the valve and create the vertical axis of rotation for the ball. The trunnion also prevents the ball from moving or shifting with changing pressures.

Due to their structural integrity, trunnion mount ball valves are generally well suited for all pressure ranges and valve sizes. Their design is used by many manufacturers for severe service. They provide excellent sealing properties over an extensive range of temperatures and pressures. Trunnion mount valves are available in both full and reduced bore designs with a wide range of materials, sizes, and pressure classes offered. The vast range of sizes, styles, pressure classes, and materials together with conformance to ANSI, API, and NACE specifications make these valves suitable for virtually all industrial, petrochemical, refinery, and oil and gas services. Finally, there may be an advantage to actuate trunnion ball valves due to lower torque requirements compared to similar floating ball valves whose torque increases with increasing flow pressure.

For more information on floating ball or trunnion mount ball valves, contact Piping Specialties, Inc. at 800-223-1468 or visit https://psi-team.com.

Monday, December 3, 2018

Process Refractometers Used in Black Liquor Recovery Boilers

recovery boiler
The recovery boiler plays a central role in the chemical cycle of a modern pulp mill. The recovery boiler is a chemical reactor, which is used for recovering chemicals from spent kraft liquor and generating energy at the same time.

In the recovery boiler, the organic matter is burned. The dry solids liquor content required for firing is at least 60 %, but preferably more than 65 %. Black liquor is concentrated by evaporating water from the liquor. When the concentration of black liquor is maximized, so is the energy production. Before entering the burners, sodium sulfate decahydrate, or glauber salt, is added to cover chemical losses.

Application
Black liquor
Chemical curve: R.I. per Black
liquor Conc% at Ref. Temp. of 20 ̊C

The liquor should have a high content of combustible dry solids in order to minimize flue gas emissions and maximize boiler efficiency.

Too low concentration of dry solids fed to the burners may result in a steam explosion with consequent damage or destruction to the boiler. Therefore, it is essential to utilize a refractometer to monitor the black liquor feed to the recovery boiler to ensure a safe operation.

Instrumentation and installation

The K-Patents Digital Divert Control System DD-23 complies strictly with all recommendations of the Black Liquor Recovery Boiler Advisory Committee (BLRBAC).

The DD-23 system includes two SAFE-DRIVE Process Refractometer sensors in the main black liquor line, two indicating transmitters and a divert control unit in an integrated panel.

The sensors are installed using K-Patents patented SAFE-DRIVE Isolation valve. This allows for safe and easy insertion and retraction of the refractometers under full operating pressure, without having to valve off the liquor piping or having to shut down the process. The SAFE-DRIVE Isolation valve contains a steam wash system for automatic prism cleaning. The system contains a SAFE-DRIVE Retractor Tool SDR-23 for safe sensor insertion and retraction.

For more information about refractometers used on blacl liquor recovery boilers, contact Piping Specialties by calling 800-223-1468 or visit https://psi-team.com.

Friday, November 30, 2018

The Drexelbrook USonic Non-contact Level Transmitter


The Drexelbrook USonic level transmitter provides a level measurement utilizing a non-contact ultrasonic sensor. Measurements of level, distance, volume and open channel flow is easily configured through the menu driven display. The Usonic level transmitter is offered with a two wire 4-20 mA, Hart output signal and is suitable for all Class I Div. 1, Zone 0, I.S. or XP locations.

For more information contact PSI Controls / Piping Specialties by calling 800-223-1468 or visit https://psi-team.com.

Tuesday, November 20, 2018

Level and Pressure Instrumentation for Pulp & Paper Production

Pulp and paper
Pulp and paper applications create a notoriously harsh, high moisture and chemical-laden environment; coupled with extreme vibration in many of the processes. The following document outlines an array of level, pressure, and position applications and solutions for the pulp & paper industry.

Download a copy of the Measurement Solutions for the Pulp & Paper Industry here.


Piping Specialties, Inc / PSI Controls
800 223-1468
https://psi-team.com

Wednesday, October 31, 2018

Process Flow and Process Instrument Diagrams

To show a practical process example, let’s examine three diagrams for a compressor control system, beginning with a Process Flow Diagram, or PFD. In this fictitious process, water is being evaporated from a process solution under partial vacuum (provided by the compressor). The compressor then transports the vapors to a “knockout drum” where they condense into liquid form. As a typical PFD, this diagram shows the major interconnections of process vessels and equipment, but omits details such as instrument signal lines and auxiliary instruments:
Process Flow Diagrams
One might guess the instrument interconnections based on the instruments’ labels. For instance, a good guess would be that the level transmitter (LT) on the bottom of the knockout drum might send the signal that eventually controls the level valve (LV) on the bottom of that same vessel. One might also guess that the temperature transmitter (TT) on the top of the evaporator might be part of the temperature control system that lets steam into the heating jacket of that vessel.

Based on this diagram alone, one would be hard-pressed to determine what control system, if any, controls the compressor itself. All the PFD shows relating directly to the compressor is a flow transmitter (FT) on the suction line. This level of uncertainty is perfectly acceptable for a PFD, because its purpose is merely to show the general flow of the process itself, and only a bare minimum of control instrumentation.

Process and Instrument Diagrams

The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming in” of scope from the whole evaporator process to the compressor as a unit. The evaporator and knockout vessels almost fade into the background, with their associated instruments absent from view:

Process and Instrument Diagram

Now we see there is more instrumentation associated with the compressor than just a flow transmitter. There is also a differential pressure transmitter (PDT), a flow indicating controller (FIC), and a “recycle” control valve allowing some of the vapor coming out of the compressor’s discharge line to go back around into the compressor’s suction line. Additionally, we have a pair of temperature transmitters reporting suction and discharge line temperatures to an indicating recorder.

Some other noteworthy details emerge in the P&ID as well. We see that the flow transmitter, flow controller, pressure transmitter, and flow valve all bear a common number: 42. This common “loop number” indicates these four instruments are all part of the same control system. An instrument with any other loop number is part of a different control system, measuring and/or controlling some other function in the process. Examples of this include the two temperature transmitters and their respective recorders, bearing the loop numbers 41 and 43.

lease note the differences in the instrument “bubbles” as shown on this P&ID. Some of the bubbles are just open circles, where others have lines going through the middle. Each of these symbols has meaning according to the ISA (Instrumentation, Systems, and Automation society) standard:

Instrument bubbles


The type of “bubble” used for each instrument tells us something about its location. This, obviously, is quite important when working in a facility with many thousands of instruments scattered over acres of facility area, structures, and buildings.

The rectangular box enclosing both temperature recorders shows they are part of the same physical instrument. In other words, this indicates there is really only one temperature recorder instrument, and that it plots both suction and discharge temperatures (most likely on the same trend graph). This suggests that each bubble may not necessarily represent a discrete, physical instrument, but rather an instrument function that may reside in a multi-function device.

Details we do not see on this P&ID include cable types, wire numbers, terminal blocks, junction boxes, instrument calibration ranges, failure modes, power sources, and the like. To examine this level of detail, we must turn to another document called a loop diagram (not in this post).





Reprinted from "Lessons In Industrial Instrumentation" by Tony R. Kuphaldt – under the terms and conditions of the Creative Commons Attribution 4.0 International Public License.