Please enjoy these pages from our January 2012 calendar

 

 

 

 

 

 

If your OEM, factory repairs are returned with this label…….

We have realized a huge increase in the number of pieces of equipment coming to us from new clients with this label affixed to their equipment hoping that we can help them with their repairs. The vast majority of this equipment is deemed legacy or obsolete and repair or replacement parts are difficult or impossible to locate. Delta Automation has a huge inventory of surplus equipment and an equipment “bone-yard” to obtain used pieces and parts for repair or exchange.

In addition to locating refurbished parts, we have designed and manufactured many specific substitute assemblies for dozens of pieces of equipment to allow for a seamless repair experience for our clients. A few of the part numbers that we have received recently that were labeled unrepairable that we were able to repair successfully are:

AS-M84A-001,  AS-M84A-002, MM-32SD-000, AS-P190-112, 100-258, AS-P145-000 & MM-PM10-300C

So, if you have been told that your equipment is no longer supported for repair or exchange, please give us a call or just send us the equipment to repair!

Temporary Remote I/O Cable Replacement Causes an Unexpected Issue

During a recent Modicon remote I/O service call at a large oil refineries tank farm which had been having intermittent communication, an unusual problem was discovered. The system had been having communication drop-outs intermittently for several weeks. During that time, several F connectors, taps, J890s and sections of trunk cable had been replaced attempting to fix the problem. Unfortunately, none of these parts repaired the problem. Delta had serviced this system several years ago and is familiar with the system layout. The system is a very large system with over 5000 feet of RG-11 cable. It is a splitter type system. Delta suggested utilizing a set of fiber optic modems to isolate the two legs of the split system to increase the signal levels and assist in any future troubleshooting. Delta was commissioned to design and build a panel containing the necessary components. It was completed and shipped to the client. They mounted the panel and notified Delta that they were ready for the unit to be installed and certified. Once on-site, the Delta engineers set out to first discover the issue that initially caused the failure. A TDR was placed on the system and immediately an anomaly was noticed on the first section of trunk cable. This cable was installed overhead on telephone poles utilizing messenger cable. There was no time to properly hang the replacement cable before production had to be resumed, so the cable was installed in a temporary fashion by attaching it to a chain-link fence that was nearby. New connectors were installed and the cable connected to the system. The fiber optic panel was connected as well. The system was then ready to be certified. The TDR test was completed, then the loss measurement and attenuator tests were to be completed. Both of these were being done in an alternating fashion to save time. As the testing progressed, it was noticed that some of the test data was out of specification. The remote drops were still having retries and drop-outs. The TDR was used to reinspect the cable structure and all was found to be correct, with the exception that there was a small amount of AC on the data stream. Since the routing of the temporary cable was different from the original cable, electrical noise was suspected. A ground was installed on the tap at one end of the new cable. The AC disappeared and the errors were gone as well. Testing was resumed and all was found to be within specification. The system was returned to full production with no errors. In the process of replacing the defective cable, and choosing to install a temporary cable in a different routing location, noise was inadvertently introduced into the system. Fortunately the Delta engineers are experienced in these systems and quickly located the introduced problem.

Please enjoy these pages from our December calendar

Triple Threat Failure

As you can see, this small VFD has failed. Quite spectacularly too!  This small unit had not been properly maintained. It had a blocked and failed cooling fan plus a loose power lead. This caused the unit and terminal to overheat and fail. To compound the issue, the unit was not fused which allowed the unit to actually catch fire. The breaker did not open until two of the power leads came together causing a direct short circuit.

A low cost P.M. (preventive maintenance) service would have discovered the blocked and failed fan and the loose connection. Thus preventing this unit from premature failure. Adding fuses to protect the unit would have been recommended as well.

Buss Capacitors are a heat related casuality.

These capacitors were removed from a failed VFD. The cooling fans had failed and the unit was running very hot. These capacitors failed violently, as you can see from the photos.  This repair was compounded by the fact that the capacitors were sandwiched between two buss bars and were a very special physical size. This made the replacements difficult to locate within any reasonable amount of time. Substitutions were impossible due to the size requirements. This unit was critical to the plants production and the cabinet dimensions made a complete VFD replacement a lengthy project as well. The decision was made to repair the unit if at all possible. While waiting for the exact replacements, Delta technicians devised a method for substituting the capacitors using several other capacitors of the proper value and voltage, but a much larger physical size. These units were linked to the buss via a tethered set of cables, which placed the temporary capacitors OUTSIDE of the VFD! This allowed the VFD to function in its application until the exact capacitors were received and installed.

This failure may have been avoided by an inspection and a preventive maintenance visit. This would have identified the failed fans which would have kept the VFD temperature from rising, causing the premature failure of these capacitors. Ask about Deltas P.M plan for your VFDs!

Please enjoy these pages from our November Calendar

Please Enjoy these Pages from our October Calendar

Modbus Plus Super Tap: Features and a ‘Gotcha’

The Modbus Plus Super Tap is a vast improvement over the previous several designs that have been in service since the mid-eighties. The first connector to be used was the MBKT type. It had split type compression connections and used the continuous daisy chain type ground scheme. The next was the Tee type which used the At&T type type of press on connector and an isolated grounding scheme. This was the first type to utilize a “drop cable”. The also is a third-party tap manufactured by Phoenix. This uses screw type terminals, has a switch for the terminations, uses a drop cable, and has a jack for connecting a programming terminal. There is also a ruggedized tap. It uses screw terminals and a drop cable in a small square cast metal enclosure. AVOID this ruggedized unit!!

The latest is the Super Tap. It utilizes screw terminals on removable connectors for the trunk cables as well as the drop cable. This makes it very easy to wire, install and troubleshoot. It has a switch to allow the drop cable not to be installed, such as in a spare location. The switch is either in the “drop”(drop cable installed) or the “short” (no drop cable installed) position. This switch also can be used for troubleshooting if the drop cable is suspected as faulty.

However the switch should NOT be placed in the short position if the drop cable is present and installed, other than for temporary troubleshooting purposes. At D.C. levels this does not present an issue, but at higher frequencies, such as the frequency of the MB+ data, it appears as a short tuning stub. This may alter the wave shape of the data and ultimately cause errors. This anomaly presents itself on a TDR as a sight downward transition, or short. This is indicated below, in the screen shots from a TDR on a system with the switch in both positions. These traces were taken from an actual MB+ system that Delta Automation was performing a network certification.  This was on a spare tap located in a very remote hard to reach location.  The fix was simply to remove the unused drop cable.

Tap with the drop cable removed and the switch in the short position.

Tap with the drop cable installed and the switch in the short position.

Another issue with these units is the auxillary programming port. In normal conditions, there is a protective shorting plug that should be installed. Be certain that it is installed and never take it out! The simple act of plugging and unplugging this shorting plug, whether to use it as a programming access point or some other function actually opens the Modbus Plus trunk line and may cause system errors or a complete network crash. DO NOT use this plug port! There have been many occasions where the port receptacle has stuck in the open position and the entire network goes down. If you need system access, install a spare tap.

The President comes to Town

When the President of The United States of America visits any town, it’s quite the affair. Just last week the President visited our fine city, Richmond, Virginia to speak at the University of Richmond.

Delta had been called to service several failed VFDs on a chiller at the utility complex that was caused by power surges from another recent, famous visitor, hurricane Irene. We had visited the site and determined what had indeed failed and placed the parts on order. At this time there wasn’t an emergency to get the unit back up and running. Unfortunately, the parts were delayed at the factory by the same hurricane aftermath effects. However we were not aware of the delay until the urgency was ratcheted up by the Presidents upcoming visit. His visit created a lock-down time constraint for the service area. The correct parts just would not arrive in enough time to get them installed. We began to rummage and scour our surplus equipment for a similar replacement or substitute part. Fortunately one was located and was rushed over to the site and installed just as the lock-down time was beginning. With the chiller up and running everyone relaxed as much as one can with the President arriving soon.

This is just one example of the detours and hurdles that Delta faces in providing timely, efficient and thorough on-site service to our clients.