Here at ACI, one of our products is the DCR (digital chart recorder). This system consists of a small control panel with proprietary software mounted on a cart with a laptop, usually a ruggedized computer but that's left up to the customer to decide.
The digital chart recorder (DCR) monitors pressure and performs calculations for pressure testing requirements. The system is contained within a NEMA4/12 enclosure with industrial bulkhead connectors for the pressure sensor cable connector and an ethernet connection for a computer running the graphical user interface.
As an option an abrasion resistant pressure transducer cable can be manufactured based on the site requirements. Transducers can also be provided that can range from 100 to 60,000 psi. The system provides the following features:
Easy to use graphical interface (Windows operating system)
Predictive leak detection algorithms
Automatic and periodic calibration capability
Adjustable testing and pressure loss thresholds
Operator real-time instruction for testing sequence
Configurable alarms and test shutdowns notifications
Trending and datalogging for different ranges (other options configurable upon request)
Ruggedized or standard laptop computer
Reporting (configurable upon request)
Recently we had an order placed for a DCR that would be used on an offshore oil rig off the coast of Africa. With only a few minor hardware mods, we were able to make this product safe to use in a Class 1 Div 2 location, provided the actual control panel and laptop be operated from a secured control room. Now, lets dive into the fabrication of ACI's DCR!
First we start with the panel layout. Here we cut and secure the wire way and din rail, then we attach all the devices according to the design specs. After all the hardware is attached and properly secured to the backplane, we cut the wire way covers and test fit for any necessary adjustments. As we work through the panel layout, we are constantly checking that the measurements/spacing are in accordance with the drawings and specs. Then we apply the terminal block markers, jumper bars, ground lugs and any other miscellaneous components the drawings require.
Next, we move to wiring the panel. Before we start though, we go through the drawings and print out all the wire labels needed and neatly arrange them so they are easily accessible while we terminate the panel. If any cables are required for the internal wiring, those lengths are approximated, cut and the ends prepared for termination. Preparation is key during the wiring process. Constantly moving from wire terminations to other things that could of been done before slows done the completion of the panel and is easily avoided with a little bit of planning. We usually start with the power wiring first. This DCR has been modified for 220v as well as 120v. Supply power is terminated to all necessary terminals and devices such as DC power supplies. Then the outgoing DC power is terminated to its respective terminal blocks or wired directly to the device. On this panel, since the only 5VDC device is the Opto22 rack we run the power supply output directly to the rack, eliminating distribution terminal blocks and saving space. After the power wiring is completed, me move to the IO wiring.
Care must be taken when terminating the IO wires. Routing these wires near 120/220v power wires will produce EM noise and effect the function of the panel. Consideration is also needed when terminating to the IO modules on the rack. You want the wires to look clean and not interfere with the neighboring card. Sometimes these cards need to be swapped out so keeping each card in a neat and orderly footprint ensures that any required maintenance is easy and fast. Also, a properly terminated IO card will have the wire labels in a neat and legible fashion to further facilitate troubleshooting and maintenance. When the backplane terminations are completed, we move over to preparing the enclosure.
Here we cut the enclosure for the incoming power cord, the ethernet bulkhead to communicate with the laptop, the power switch on the door and the sensor cable bulkhead connector. After all necessary cuts are made per the drawings and deburred then we prepare the bulkhead connector.
An appropriate length of cable is cut and prepared for pin attachment. Then we strip the wires and crimp on the pins. We check for a proper crimp before inserting into the bulkhead connector. Although it is possible to extract an incorrectly placed pin from the connector, damage to the connector is pretty much guaranteed if extreme care is not taken. Even being careful isn't good enough because the pin retaining collars are small and delicate and can be easily damaged when trying to extract a pin, rendering the connector useless. These connectors have a minimum of a couple weeks lead time so its critical that great caution is exercised during connector fabrication. Triple checking wire colors and connector markings before fully seating pins is just standard procedure. After the bulkhead connector is finished, we use some epoxy heatshrink to cover the wires going into the back of the connector. Then its time to drop in and secure the completed backplane so we can move onto the finishing step. Finishing consists of attaching the cable gland for power cord, the panel power switch on the door, the ethernet bulkhead and the sensor bulkhead connector. All of these devices and the power cord are terminate to their required locations. Use of sticky backs and spiral wrap is needed for power switch wires and panel door ground wire. After finishing is completed, we move to the sensor cable fabrication.
Since this DCR will operate on an offshore oil rig, the requirements for the sensor connection are Class 1 Div 2, explosion proof. So the connectors at the sensor end are EX rated and the pressure transducer also has an EX rating. Since the transducer has flying leads and not a connector on it, it is necessary for us to attach one of the EX rated connectors and protective sheath to the leads to interface with our cable. The actual sensor cable is a robust, armored cable usually used on continuously moving robotics. It is more than capable of enduring the harsh industrial environment that it will be utilized in. Though it is more expensive (~$5 per/ft) than our regular sensor cable, there is a much smaller chance of down time due to damage when using the armored cable in applications such as this. Remember, everything can be damaged, so care should be taken when using any industrial control product to ensure the longest lifespan possible. Once the cable is finished, we move on to Quality Control (QC).
First we print out all required QC documents that we need to fill out. Referring to the Panel Serial Number and Cable Serial Number spreadsheet, we add panel and cable then assign serial numbers. Then we note the project number, panel and cable serial numbers on all the documents used for QC. After all documents have been prepared, we work our way through the QC checklist. One of those steps is ringing out every termination, end to end, with a multimeter. The cable goes through its own QC checklist first then its connected to the panel and rung out from end of cable to the termination points at the terminal blocks. Then we move on to power checks and function testing. We call it the 'smoke' test (if you don't see smoke when you flip the breaker then its prolly good). Once the control system passes QC, the proper stickers & tags are securely attached, Photos are taken and properly documented, copies made of all QC documents and filed in project folder, necessary drawings are placed inside the panel and its ready for testing.
During the final testing, we confirm the sensor is reading correctly, run calibrations then we go through a simulated pressure test with the sensor attached. We also make sure the HMI is operating as it should and is configured for the specific customer.
If any issues are found, they are fixed and we retest. During this time, we also get the laptop configured with all the required software and programs. Once the DCR has passed all the testing and configuration, it is time to say goodbye and send it on its way to Africa.
In all, we only had one issue during the QC process and that was a defective bulkhead connector. We ordered a replacement part immediately and had the new one installed the next day without any further issue. You can read about that defective part here:
If you are interested in our DCR system, please contact us to discuss your project today! There are different ways to build this system depending on customer preferences and site requirements.
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