Photograph via snooOG

Process Control


2,878 Subscribers



Hi everyone! I am relatively new to process control. Anyone here know the difference between BCAS (backup cascade) and CAS (cascade) in Honeywell DCS? Thank you!

11:12 UTC


Level Gap Controller

I currently have a process with a Gap Controller connected to a level tank that controls an on off valve. When the level reaches SP, valve opens to dump liquid content from the tank and then closes. Leaving the valve open however results in the system stripper pressure it’s connected to to always increase. We want to replace the Gap Controller with a PID to make the process continuous and make the valve run in auto. Need to come up with a design solution for this. What all will I need to check to make sure implementing a PID is even feasible for this process?

05:44 UTC


Process Control Lab

I started my career working for Emerson designing the underlying infrastructure (networks /hypervisors / servers) for their DeltaV product. I used to love it however I slowly drifted into pure IT and I now want to look to drift back into the OT side of things.

I now run my own IT consultancy company and have partnered with a couple of vendors that also offer OT variants of their network/security products. I would like to try and get my head back into the land of OT and redevelop my skills. I would like to put together a small (cheapish) eBay shopping list of network based SCADA components where I could potentially take input from 4-20mA rosemount temperature probe into a Analogue Input device, fire it over the network to some sort Digital Output device to trigger a strobe or something like that?! I potentially may also want to have a little bit of Modbus TCP thrown in there for good measure. I know with Emerson this would have been almost impossible without a 'golden key' or a spending a lot of money on licenses. Does anybody have any good suggestions to point me in the right direction?

17:25 UTC


Retrofitting analog wine press

I am a winemaker and my backup wine press is a beautiful Italian unit in pristine condition... but it's from 1990 and has analog controls which don't allow sufficient "programming" (setting of timers) to press grapes in the modern way. I'm asking for some advice on retrofitting digital, automatic controls.

A bladder press does three things (and has three corresponding motors)- inflates the bladder with an air compressor, deflates with a vacuum blower, and spins the drum that contains the bladder and the grapes. It relies on two sensors- a pressure sensor and a position sensor (to make sure the perforated side of the drum is facing down when grapes are being squeezed). The pressure ranges from -3 psi to 29 psi.

The manufacturer can retrofit the unit... for $16,000! It seems like a simple enough system that I could do it myself for a lot less. Typically, presses are full of PLCs, but why can't I just use a computer? The programming I need is very simple, ex:

deflate to -3 psi rotate to position, inflate to 6 psi and hold for 3 minutes, deflate, rotate three times, inflate to 9 psi etc...

I would need multiple programs for different applications, but its never more complicated than pressure, time, and number of rotations.

My idea is to install motor controls (VFD) on each motor and control them via relay from a computer. I haven't started down the arduino rabbit hole, but I would just need to send current from the relay to a control terminal on the VFD at programmed times/sensor feedback . This would also let me install manual switches to the vfds for loading and cleaning. I'm way outside my area of expertise, but it seems to me that the VFDs would protect the motors and some simple circuitry would prevent contradictory commands.

I have no idea what to do for computing/programming/interface, but I thought I'd ask ya'll first if this is worth attempting.

02:21 UTC


Trying to define a role for the team- newb

I’m a new leader in our organizing and we have a big gap that I am trying to fill in data analitics, tools and systems and I don’t know where to start.

We have delta v and osi pi, LIMS, and a home made PIMS, no erp.

I need to define a role to bring together the data and the systems to drive the business better. To find tools and set digital strategy for our org. But we are small and scrappy <150 people. We have lots of systems but no way to tie them all together. Any ideas what to call the role or where to look?

12:35 UTC


Struggling to find a 3-phase voltage monitor

Hey all

Im looking to install a 3-phase voltage monitor on a series of linear accelerators im working with, as theyre super sensitive to noise in the power line. To integrate this into the current system, i have a few requirements that i am struggling to meet, so i was hoping you might have some ideas!

I need:
- an output that can be read by my current setup (analogue signal, modbus, serial whatever)
- Only voltage input, not out (tapped onto power line, not in series)

Everthing seems to be either power meters (in series) or voltmeter but only with relay output.

Maybe im looking in the wrong place?

Help please! Thanks

1 Comment
01:05 UTC


OPC HDA ABB problem

Hi All,

i am new here and i need your help.

i have need to connect ABB Tenore OPC to second system.

OPC DA and AE works fine with live data (Realtime). but when i want to take data from history ( OPC HDA) i got problem with analog raw points (measurements from the field not calculated), digital and calculated analog work fine.

For those points i received "0" value instead actual value from historian.

i cannot figure out where is the problem.

20:03 UTC


Super green process control engineer

Good morning all, I recently got hired for a process control engineer position, And they are willing to invest what is needed to get me up to speed. Currently looking for valuable training and certification to look into, but don't know where to start. I recently signed up for the ISA AEST boot camp, and looking into the CAP cert (which I lack the requirements for) My background is far from adequate for this position but I was hard saying no to such a great offer. For my background: I hold a mechatronics engineering degree from an institution outside the US which is not ABET accredited I have a year experience in mechanical design 4 years in high voltage mostly maintenance, testing, and troubleshooting field equipment (120v-34kv, SEL relays, mechanical relays, breakers, transformers testing, etc.) 3 years of SCADA experience( mostly dnp3, modbus IO mapping, and communication troubleshooting fiber& copper, serial, TCP/IP, etc.)

Hope this helps clarifying what my background and intent is, and thanks for the help in advance!

Let me know if I am missing something and if I misspelled something let me know will correct it or clearly it! English is not my first language Position is in the US btw

16:07 UTC


Pneumatic cylinder stutter

2 questions

1: I have a pneumatic tamper cylinder, operated by solenoid, that intermittently stutters/chatters in the retracted state. If i apply pressure to the tamper plate with my hand, it stops and immediately starts again after letting go. I haven't encountered this before and Google keeps giving me hydraulic results. No indicator light on solenoid to suggest issue is electrical, kind of narrows it down to solenoid or cylinder but I'm not sure what to look for

2: any other industrial process maintenance subs out there?

08:58 UTC


When should a pressurised LPG tank have two temperature probes?

1 Comment
15:45 UTC


Graduated from an Instrumentation program not too long ago and this is my tribute. Digital. Me

23:25 UTC


Need help displaying data stream

I hope that someone here can help me out. I have a computer that is sending a CSV stream of 1 number that updates every second on Port 2001. I can Telnet to IP Address:2001 from another computer on the network and see the data updating.

I want to be able to display the number dynamically in a web page, to make it easier to read. Anyone have an idea on how to do that? I tried Googling it, and all I could ind was displaying a CSV file in HTML.

Any help, or pointing me in the right direction, would be much appreciated.

04:34 UTC


Help with a Transfer function problem

Hi guys, so I have the following problem which I couldnt solve:

A system, whose open chain transfer function is first order, has an
improper gain constant and a pole equal to 6 and -2, respectively.
A processing engineer then decides to place this system under unitary
negative feedback, aiming to make the system faster.
What is the value of the new system time constant?
A) 0,125
B) 0,25
C) 0,5
D) 1
E) 3

I never seen the term 'improper gain' before but I just assumed it was my regular 'K' and with some simple maths to determine the time constant I found the following Transfer Function:

tau*(-2)+1=0 → tau=0.5

Calculating the Closed loop Transfer I did


And got


So the new Gain constant would be 6/7 (instead of 6) and the new time constant would be 1/14, instead of 1/2.

However this isnt the answer. What did I do wrong and how would one solve this? Thanks in advance

12:56 UTC


Pneumatic control question

I don’t know how many of you are still using pneumatic controllers but we have a topic of date in my shop and I’m wanting to expand the amount of amount of people in the discussion. We have a PI Fischer controller. In the VTD it says to close the reset knob to the slowest setting than to start to balance the controller. Some old timers say you have to lock in 9psi in the reset bellows instead of doing that. What does everyone think?

These are from the instructions for reference. They old timers say at step three to lock in 9psi to the reset bellows

  1. For C1P and C1B controllers with anti-reset windup record the direction of the arrow on the anti-reset windup assembly (key 190, in figure 22).

Remove the assembly and install the two O-rings (key 81), and cover (key 80) supplied with the controller. Secure the cover with the two machine screws (key 82) provided. 2. Connect regulated supply pressure to the controller. Do not exceed the normal operating pressure in table 5. 3. Rotate the reset knob to CLOSED (slowest setting). 4. Rotate the proportional band adjustment knob to 1.5 (15 percent proportional band). 5. Verify that the calibration adjuster screws (key 48) are at mid-position in the calibration adjuster (key 36) slots. Depending upon the controller action, perform one or the other of the following procedures.

For reverse-acting controllers: 6. Apply an input pressure equal to the sensing element upper range value. 7. Rotate the pressure setting knob to the maximum value. 8. Adjust the nozzle (key 54) until the controller output pressure is between 0.6 and 0.7 bar (8 and 10 psig). 9. Apply an input pressure equal to the sensing element lower range value. 10. Rotate the pressure setting knob to the minimum value.

1 Comment
18:41 UTC


Work got us a new computer for our processing plant

17:19 UTC


Energy Consumption Monitoring Simulation

Need help interpreting our simulation results. Our control system is to monitor the energy consumption in a room. Once it reaches the set point energy consumption: 5.7kWh per day, a smart plug cuts off the electric supply and will reset at 12 am. We used rectangular pulse function. We get that it rises up to 5.7kWh due to consumption and returns back to 0 after 24 hrs. Why is it at steady-state though? What does it entail? Is there another input function we can try to show the gradual energy consumption in a day then back to 0 after 24 hrs?


03:27 UTC


Have you guys/gals ever seen a breaker trip itself to the off position?

We have a 24v solar/battery system that operates our remote pipeline station.

The controls cabinets have tamper switches in them that will show when someone opens the cabinets and it will log the tamper in our data historían.

Three weeks ago, we lost communications with the station, we go investigate and there’s a Siemens 24VDC breaker in the off position (not in the tripped position). Another tech thought that was odd but switched it back on, everything came back on, the tech monitored for an hour and it held.

For three weeks.

Yesterday, we lost it again. Head to the valve station today and it was just as reported before: Not tripped but in the off position.

No tamper recorded previous to the loss of comms.

There was a spare breaker next to it so we hooked up on that one. We’re seeing if we might have a bad breaker or a bad component.

I am aware that there are some breakers that trip off and to be completely honest I’ve never seen one of these Siemens breakers trip.

Just seeing if you guys might’ve seen this before.

19:55 UTC


Does an LPG tank releases pressure when left open?

I read that the pressure inside the tank will decrease when the gas cylinder is left open. Does it mean that when an LPG tank is in use or if there's a gas leak, the LPG tank will release pressure? Is there a way to measure the magnitude of the gas pressure output for leakage monitoring system in the kitchen?

11:53 UTC


does anyone know what the 40 A and 25 A on the right side refer to? operation current and thermal current maybe?

22:09 UTC


Control System Design

Hi! Undergraduate student here. Was tasked to design a basic control system for home improvement. My options are (a) kitchen temperature monitoring and alarm (b) device for continuous glucose monitoring and (c) automatic door lock system. I'm leading towards (a) but we have no background in designing a control system. Among those, which do you think can be done by a student? (Feel free to suggest if you have a better idea. Badly needed) Thank you!

14:57 UTC


Running a bin empty or close to it

Not sure if this belongs in this sub.

I have recently started at a new site and product waste is ridiculous. At the end of each run on the 7 packing machines, the bin above is left with roughly 120lbs of product that gets scrapped. This is due to only having Vega level transmitters and no low level probe for true low level detection.

I have fairly extensive process experience. In my previous plant, we'd mark a bin empty if LIT was <5% and Low level probe was off for some short period of time. This was fairly reliable unless the LIT went crazy.

I looked into the program on these machines and basically they're doing some calculations once it's the end of the run and LIT is <2%. They're trying to calculate the product weight and figure out how many more packages can be produced. While my immediate recommendation is to calibrate the LIT's, ensure they're long enough and then I'll look to get the calculations better afterwards (product density will still be an issue here).

I also recommended adding a low level probe, but I was told that due to quality concerns it can't be added. Would need to re-validate the wash sequence and will never get buy in for this.

Has anyone ever dealt with this problem? Is there some type of non contact or flush mount sensor that would help here or a different method I can apply that quality will possibly allow? We can't run the bin completely empty due to the way the machine functions, so just running until the weights on the check weigher go down isn't an option either. It would cause issues with the line.

Also in my previous plant, I was able to shift the business to load cells on every new project, but this may be difficult due to needing a flexible 300psi pipe for isolation. Most pipes I've seen are flexible and would allow product to remain trapped in the veins too.

Sorry if this is too long and as always I appreciate the wealth of knowledge in this forum.

20:28 UTC


I searched everywhere but I was unsuccessul in finding information for marked parts.

Some Metainformation to understand the snippet of this drawing better;

supply top : a mix of excess process and fresh water.
supply bottom : pipe which feeds LIC has cleaned water. Pipe who goes to pulper is seal water, fresh water.

1rst Question: When is is necessary to open the impurity discharge gate valve on the bottom of the pulper (right now it is displayed in closed position)

2nd Question: What does the abbreviation EV mean at the gate valves?

3rd Question: Why is the valve placed there below the pulper?

I would be elated if someone knows the solutions :)


12:57 UTC


Hello All! I know there is a pneumatically operated valve, but how can I describe this valve also there? And what is this other symbol?

12:41 UTC


what is meant by DN150/63 on a control valve?

i know the nominal diameter is 150 mm, but what does the 63 mean? does it mean that the input and output diameters are different?


I was mistaken , it's 150/65 not /63

technical drawing of the valve in question

12:12 UTC


Need help designing simulator

I am needing to control a 120v a/c signal in proportion to a 4-20ma signal to build a simulator for my plant. Does anyone have any recommendations of what might work?

20:58 UTC


Does anyone have any suggestions for pH probes to use in a high temp, high solids process. Need to control the stream between 7-8.

15:33 UTC


RTD question

Hey guys. Random question. I am an I&C tech at a nuclear power plant. I had a 4 year apprenticeship with the company and had 5 years as a tech before transitioning to a training position.

I am teaching the new apprentices the course work and ran Into a topic I can’t find my answer too.

When speaking about RTDs I know the broad overview. How they work. How to describe their operation. How to wire they them. Ect. However I am required by the training course to speak about the equation of an RTD to find resistance and the tables.

My issue I’m running into is when I explain the RT = Rref (1+ alpha (T-Tref)] equation and then compare the result to an RTD table. The results never match. Seems to be off by more than a few degrees when we do them. Seems to be further off in F than C.

Will this equation only work in C accurately?

Is this a valid exercise to do? Or do the tables not complete compute the the equation. We didn’t go very in-depth in my apprenticeship about this. Our trainer at the time wasn’t very good. Any help is appreciated.

I know the equation photo and rtd tables coefficient doesn’t match. I attached the equation for reference and the data tables for reference as well. The equation should work for whatever coefficient you have but it doesn’t seem to.

Edit : I think you simply can’t do the equation in F. Since Alpha is a unit of Celsius the Fahrenheit numbers don’t come out right. But if you convert to C and then do the math and concert back it works.

02:52 UTC


what actually the process control engineer will do? what is the scope and responsibilities?

06:30 UTC


What are these?

Let's see who knows the basics


Name 2 systems:

- Elements

Name the following:




- Variables

Name the following:


How does CV relate to PV?

Name the following:


Give examples of different PV:

Give examples of Independent/Dependent:

Name the following:


MV - Different from previous MV



What does URV-LRV equal?

Give examples of the following:





!- Systems!<

!Open loop/Closed loop!<

!- Elements!<

!CE - Control element!<

!FE - Final element!<

!PE - Primary element!<

!- Variables!<

!CV - More or less CV will control my PV !<

!PV - Flow/ Level/ Temperature/ Quantity    Independent/ Dependent/ Range!<

!Manipulated V - The PV that's changed to allow CV to reach SP!<

!Measured V -!<

!SP - Desired value of controlled variable!<


!Range = URV-LRV!<

!Signals - Voltage/Current!<

!Indicators - Audible chimes/ Visual lights!<

02:05 UTC

Back To Top