was already existing. It equated to taking a skid that would normally be 25 feet long by 8 feet wide and reducing it to only 16 feet long and 6 feet wide by the manipulation of pipe routing and some creative thinking. Alongside the mechanical team, S&S Technical’s electrical team got to work on the controls solution.
At the beginning of the project, it was determined that the system would be controlled from the plant DCS and would only be receiving commands and sending feedback. Without a “canned” controller to accommodate this system, it was up to S&S to design and program the customized controls. As the design began to unfold, it became clear that the customer was beginning to change their mind on the purpose of the skid. After various design meetings, it was determined that the systems controls would now be autonomous and run the skid rather than simply sending and receiving data from the DCS. Even though the change required a different approach, more controls components and quite a bit more programming, S&S knew the promised delivery date still had to be met.
When designing a system, two very important key considerations are safety and ease of maintenance. The safety aspect is inclusive of both personnel and equipment. Items such as Allen Bradley emergency push button stations and Newson Gale grounding units were put in place to help protect personnel. In the event of a serious emergency, the e-stop could be pressed and the entire system would go into a safe mode as well as sound an alarm that could be heard throughout various locations in the plant.
The grounding system helps to ensure the truck is properly grounded to the skid in order to prevent the possibility of a spark caused by static electricity. This has become a grave concern for many facilities around the world as each year multiple accidents, some fatal, occur due to vapor ignition set off by static electricity. As a standard, S&S has used the grounding units as interlocks within the controls so that the system cannot run unless the truck, or rail in some applications, is grounded.
On the equipment protection side of things, various pressure transmitters were installed and logic written in order to avoid damage to the transport trucks. In this particular case, the bladder in the low pressure trucks were only able to handle a fraction of the pressure that could be handled by the high pressure trucks. The skid had a designated inlet for low pressure only and one for high pressure only. Both style trucks were built with the same fittings from the manufacturer. This made it challenging to create a mechanical interlock which forced a design built around an electrical interlock.
Once a truck hooks up to its respective inlet and is set up to offload, there is a pressure transmitter to determine whether it has hooked up to the correct skid inlet. This prevents the possibility of a low pressure truck being over pressurized due to hooking up to the high pressure side. Much like the grounding interlock, the transmitter would not allow the system to run if it sensed the truck was hooked up to the incorrect spot.