As I'm sure you know grounding the vac.sysyem must be done right
This is just my 2 cents but I would run unshelded copper wire down the pipe ( inside all the pipe because you are using PVC) then ground it to one out let box for the vac.power plug in.
It can be to the frame of the vac. motor because it should be a grounded type plug.
The cheap way to get the job done is to buy some standrard house wire like 14/3 take off the cover and strip the wire to the copper, grounding copper wire is not cheap and the stantard wire will do just fine.
If you get to a gate just use a bolt and fix the wire to both sides of the bolt then with a small hole in the PVC/hose keep moving on with the wire. ( a little auto type PVC seal on the hole will plug the hole)
The dust going down the pipe will setup a CHARGE and can start a fire inside the pipe.
It's always a long shot but if it comes about it will blow the pipe right off the wall.
It's like a flour mill going up with a 2lb. block of C4 under it.
You may want to make your own gates, they are easy to make and you should have one at all the opening/equipment if you want I will post a snapshot of the ones I make for my small vac. system.
A good way to check your vac. system is start up the vac. system and take a hand full of saw dust and throw in on the PVC pipe, if it sticks (stands up) you need to fix the grounding system.