Need source for DP transmitter

[OkiePC]

Bad power supply damaged the output of DP transmitter measuring flow at a customer site.

After a storm rolled through, they had multiple failures. I got all of it working again ... except this last item ... after replacing a bad power supply, two signal isolators and some 'puter stuff needed to be reset.

I was reading 60+ vac on top of what was supposed to be 24vdc supplying loop power to two devices, and now the transmitter puts out 50mA all the time.

It looks like this one:

http://www.lesman.com/unleashd/cata...-ST800/180-HW-Smartline-ST800-transmitter.jpg

Only it is all blue and has an analog gauge in the window. There was no mfg. name on the data plate, and I have no idea how old it is (the plant was built in the 1920s).

I need something similar to install in its place at a reasonable cost. The old one was 0-150IWC and 4-20mA I am assuming WC means inches of water column.

If I can find one that has the same range, it will save me the trouble of having to rewrite the math in the DL06 PLC. A similar mechanical design will be helpful too, so I do not have to spend too much time pretending to be a plumber.

I have never even worked on one of these before, so I do not know if the electronics can be replaced. I did not find isolation valves, but I also did not crawl down in the pit where the lines attach to the main water line, so shutting them down to work on this thing might be a wet mess.

So who and where is a good source for one of these things?

Thanks,
Paul

EDIT: I forgot I had a picture of the data plate in my phone. p/n is 1151DP4E22B3M1
Rosemount might be right ... We thought we had one located for around $1000 from Omega, but it was discontinued. I already got approval to spend that much from the customer.

 

[Mickey]

Rosemount (Emerson) transmitters are blue. But

reasonable cost

they are not.

https://www.google.com/search?q=ros...0CDYQsARqFQoTCJ21qdzdxccCFcrTgAod6lABig&dpr=1

http://www2.emersonprocess.com/en-u...s/3051-pressure-transmitters/pages/index.aspx

 

[danw]

That 1151 was an analog transmitter that was ranged by applying a pressure from a calibration source and making adjustments to the electronic output.

Modern smart transmitters talk digital HART for configuration, but HART requires ancillary configuration equipment (handheld or PC/HART modem/Software) either of which are costly and not something you want to mess with for a onesie replacement.

The alternative to the HART headache is to make sure that you arrange to have whomever sells you the transmitter to range it 0-150 inches water column (yes, you're right about wc) (real distributors do that without a 2nd thought) or get a DP with pushbuttons and a display that can be used to configure the range.

You'll kill the replacement transmitter, too, if you don't get rid of that 60Vac on the 24Vdc line.

Why were there signal isolators there in the first place?
Do they need replacement?
Did the isolators the analog input that the DP was connected to ?

 

[OkiePC]

That 1151 was an analog transmitter that was ranged by applying a pressure from a calibration source and making adjustments to the electronic output.

Modern smart transmitters talk digital HART for configuration, but HART requires ancillary configuration equipment (handheld or PC/HART modem/Software) either of which are costly and not something you want to mess with for a onesie replacement.

The alternative to the HART headache is to make sure that you arrange to have whomever sells you the transmitter to range it 0-150 inches water column (yes, you're right about wc) (real distributors do that without a 2nd thought) or get a DP with pushbuttons and a display that can be used to configure the range.

You'll kill the replacement transmitter, too, if you don't get rid of that 60Vac on the 24Vdc line.

Why were there signal isolators there in the first place?
Do they need replacement?
Did the isolators the analog input that the DP was connected to ?

Thanks for the detailed info, Dan!

The power supply problem is fixed. The isolators are necessary at least for one device of the three feeding a 4 channel analog card in the PLC which has a single common. Yes, two of the isolators also got zapped, and they have already been replaced. Both of them were fed from that old linear supply hiding in the corner of the control panel. Another switching supply is now feeding a solid steady 24vdc to all the transmitters and one analog output. It would not surprise me if that supply was the main cause of the analog woes experienced by this facility in the past. The previous operator told me that they keep spare isolators because "we go through them like crazy during storm season." I now suspect that brownouts or surges during storms might have been making that old supply go goofy at times.

The signal from the DP transmitter is about 150' away in a different building. Lightning seems to wipe out these signal isolators occasionally, so it is probably good that they are there, since they are cheaper and easier to replace than that analog input card.

If I have to alter the code in the PLC it is not a huge problem. I already had to rewrite it once since the old logic was way wrong, so I have gotten some practice with DirectSoft.

A modern transmitter may be able to take the burden of scaling flow away from the PLC, but I am not sure if that will be any easier to set up. Now that I have all the square root math working properly, I'd just as soon not have to touch it. We don't have any HART hardware here, but it might be an inevitable purchase at some point.

It seems that 0-150WC is not a common ready to ship item. We'll find out what we can get quickest and may have to get permission to spend more. The customer will have to decide how long they are willing to run without flow totals and manual CL2 adjustments. Without that flow signal, the PLC can't properly pace the chlorine supply.

 

[danw]

A new, smart, DP typically comes from the factory ranged 0-100 in wc.
They can be ranged up to 400-600in wc, depending on mfg; or down to about 10-25 in wc, depending.

Ranging one with pushbuttons takes about 3 minutes, half of which is unscrewing and screwing back on the EXP screw covers.

About the same time configuring the range with a HART handheld. Another minute to put it back in the shipping carton.

If there's a smart DP in stock, it's not a big deal.

 

[OkiePC]

Okay, so I will still just be setting up a linear scaling of pressure, not trying to put the square root (flow) curve into the thing with three buttons and an LCD display...

Thanks again Dan!

 

[danw]

The square root function should be enabled on either the transmitter or the PLC, not both. If the PLC does the square root function, then transmitter is 'Linear'. If the transmitter 'transfer function' is square root, then the PLC is linear.

If you get one with push buttons to do the setup yourself, make sure that the pushbuttons and display do numerical entry of the range, eng units (in wc), tag number, and linear/square root function.

Although you don't care about the tag number, some brands/models have pushbuttons that are used to set the range by using applied pressure: when the applied pressure for low range (LRV) is correct, push the left button; when the applied pressure for the high range (URV) is correct, push the right button.

That limited zero/span button function typically can't numerically enter a tag name (or a numerical LRV or a URV). If the push buttons and display can enter a tag name like LIT-101, then they're functionally capable of entering a URV of 150.0 and selecting inches from a list of units.

 

[boneless]

Hey Okie,

Have you found something yet? We use Yokogawa for similar applications, again not really cheap, but cheaper than Rosemount.

Let me know if you need to borrow my HART device .

 

[boneless]

Also the pic you posted, kinda looks like one I've seen before. From Fuji.

http://www.fujielectric.com/products/instruments/products/transmitter/top.html

 

[TWS]

The pic OkiePC posed is a Honeywell ST-700 transmitter

 

[rdrast]

This by any chance? With the analog option?
Endress-Houser PMD75 We use them on everything from water to steam with very few issues. Again, not cheap.

 

[OkiePC]

Thanks, guys. I have to hit the road again today, so if I can pick one and get it ordered this morning that would be great.