Now that the project is designed and financed all that is left is to build it. Well not quite. You see there are stages to engineering. This is the one thing we engineers have learned from the lawyers – a mild form of entrapment. Feasibility design is conceptual and guys in big black medieval-looking masks waving blue tipped torches need something more than a few paragraphs on a page to do their work. For example, “The bathroom will have enough stalls to satisfy the bladder concerns of a small army” has insufficient detail to allow a contractor to build the bathroom. “Small army” needs some definition.

To make the drawings there is a need to have basic standards understood by everyone on the design team. It is always embarrassing when the piping designer in one area of the plant uses Imperial units and the designer in an adjoining area uses metric units. That is why all engineering companies write a project document called the Design Specification Manual which standardizes the basis for the design.

The process of making drawings goes through several stages. The first drawings are for client review and there are always a few mistakes left as sacrificial “gimmees”. The ego needs of clients must always be taken into consideration during a capital project. It is important to remember where the mistakes are because sometimes clients won’t find them all and you don’t want the boss to find them instead. When the client approves the drawings they are issued for quotation. Most projects are competitively bid which means that several construction companies will estimate the cost and supply a bid on building the plant or widget. When all the bids are in and the contractor is chosen he will then tell the engineer how the drawings should really look. You see many engineers don’t ever actually work in the plants they design so they can miss the little nuances like putting in pipe hangers every 4 feet instead of every 400 feet. The engineer goes back to the computer and pops out the construction drawing. There is another set of drawings that should be but are rarely produced. These are the as-built drawings and reflect the twin realities of engineers who design plants they’ll never work in and tradespeople who were afraid to admit they never really understood that last drawing. The result is a plant that looks surprisingly like the original design. The issue of as-built drawings never arises until five years into operation when a smart young engineer proves to management that production can be increased by fifteen percent with the addition of a stub T fly-over return line. The engineering for this award winning and cost saving idea is done on the basis of the old construction drawings and when the welders go to install the new piping they discover that the slurry line to be tapped into is nowhere to be found because a) the design engineer put it in the wrong place and the pipefitter moved it to where it should have been or b) the pipefitter couldn’t read the drawing and it became a vertical riser instead of a horizontal lateral. In either case the economics of the great idea have been ruined and the bright young engineer is left to tell the boss why the plant was shut down and nothing was done. There is something to be said for up-to-date as-built drawings.

The engineering drawings are often similar to the drawings in the feasibility study but they are always more complex and detailed. It is amazing how much detail there can be in a regular mining facility. Toilets and pipes and windows and doors all have to be specified according to applicable building codes. Wires of the proper dimension have to be routed and measured, lights have to be located and selected so that there will be no explosions when the coal dust swirls around them. Cool stuff like that. This is called the detailed design stage and in a big project it can involve hundreds of people staring for long hours into computer screens drawing lines and weird symbols that have meaning to everyone but the project sponsors and the mining engineers. Who would ever have thought that a circle with an arrow through it would indicate a clock thingy. Like a non-technical friend of mine once said, “A plant eh. Isn’t that the building where you make the pipe thing happen?” It doesn’t get more basic than that.

All that has really been done to this stage is define the project conceptually and in enough detail to ensure it will actually work. Someone has thought a little bit about the market and so a cash flow model has been developed that says in numbers, “This is the best thing since sliced bread and only a fool would not invest in it.” The problem is that most projects that advance to a feasibility study come out with this conclusion and not all projects are successful so you kind of have to be careful. But when the innards of the sacrificial chicken are read and the portents are good, the project owner raises sufficient money to do definitive or detailed engineering and then construct the mine. 

I have previously discussed the process flow diagram (PFD) and from it a whole lot of other diagrams are developed. There are piping and instrumentation drawings (P&ID’s) that define the sizes and types of all piping used as well as the location of the temperature and pressure measuring devices. There are electrical drawings that only have meaning to engineers who were born wearing glasses with white tape on the bridge and there are layout drawings that show the location of the major pieces of equipment to be used in the process.  Most field changes in mining plants are due to inadequate attention to the plant layout so real dollars can be saved during this part of the design. In very complicated industrial plants accurate three dimensional computer or physical models are often built to ensure that the layout is correct. The question of whether to build a computer model or scale model is a tough one. Often the cost is about the same for either one and the scale model gives you a very cool coffee table piece d’art at the conclusion of the project. However, during construction it will always attract a crowd of welders, pipefitters and mining engineers who can’t read drawings and they generally hang around too long drinking management’s coffee.

The development of engineering drawings and construction are interleaved activities. It is rare for a project to complete all the engineering , then procure all the equipment and contractors, then do the construction. Even engineers are capable of some level of multi-tasking allowing the procurement and construction to start in advance of the conclusion of engineering. Of course, less engineering means higher risk and so there is a trade-off between “fast tracking” the project by starting construction sooner and completing all the engineering. On smaller projects fast tracking works but if the project is large some amazingly expensive mistakes can be made giving all the engineers the opportunity to say, “See, we told you so!” But let’s talk a bit about construction.