exit festo – your world-wide partner in factory and ... safety afternoon/2_pm... · f-be/...
TRANSCRIPT
26.10.16 Slide 1© Festo Didactic, Training and ConsultingF-Be/ [email protected]
Festo – your world-wide partner in factory and process automation
• Paul Verbist, 1992->..• 2016-10-20
1
Exit
26.10.16 Slide 2© Festo Didactic, Training and ConsultingF-Be/ [email protected]
Facts and figures
26.10.16 Slide 3© Festo Didactic, Training and ConsultingF-Be/ [email protected]
Top ten of the bestDo & don’t using pneumatics,
in relation with safety.Paul Verbist
26.10.16 Slide 4© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 5© Festo Didactic, Training and ConsultingF-Be/ [email protected]
10: Soft start valve
• Target: prevent fast movement, when pressurization.
• Fact: most of the slow start valves on the market switches automatically, when pressure reaches 50% of the nominal pressure
• Means: cylinders must be at least over dimensioned with 70% otherwise they shouldn't move until the valve switches to the maximum flow, generating immediately the maximum pressure, and highest speed!
• Others kind of valves exist also on the market: the PLC decides when to turn on the High flow!
26.10.16 Slide 6© Festo Didactic, Training and ConsultingF-Be/ [email protected]
10: Soft start valve
26.10.16 Slide 7© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 8© Festo Didactic, Training and ConsultingF-Be/ [email protected]
9: Soft start valve.
• Target: prevent fast movement, when pressurization.
• Means: When exhaust, once the pressure falls below 50%, the valve switches back to the low flow, making the exhausting very slow.
• Due to the fact that actuators are over-dimensioned, this creates a dangerous situation, due to the long exhausting time, and residual pressure
• C:\Users\be0vbi\Documents\Snagit\2016-09-06_13-45-14.gif
26.10.16 Slide 9© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 10© Festo Didactic, Training and ConsultingF-Be/ [email protected]
8: General Exhaust
• Venturi
• Vertical movement
• Inertia: moves will continue
• Valves may not react as expected..(detailledlater)
26.10.16 Slide 11© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 12© Festo Didactic, Training and ConsultingF-Be/ [email protected]
7: Non return valve
• Non return valves – pilot check valves: danger is still there!
• Monday morning effect: every pneumatic component has leaks!
26.10.16 Slide 13© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 14© Festo Didactic, Training and ConsultingF-Be/ [email protected]
6: Speed reduction
In normal operation, it’s a good idea,
But:
if something blocks the movement, speed is no more under controle..
26.10.16 Slide 15© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 16© Festo Didactic, Training and ConsultingF-Be/ [email protected]
5: Work with a lower pressure
• Double working cylinder: force is based on a pressure difference!
• Speed control is not more possible. Speed increases!
26.10.16 Slide 17© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 18© Festo Didactic, Training and ConsultingF-Be/ [email protected]
4: 2 valves serial mounted = 2 channel to exhaust
• Take care of the “third state”: some valves may stay “closed” between “exhaust” and “open” position:
• In the fact, if the second valve has this problem, nothing should be vented
• This is only a way to prevent “unexcepted start”
26.10.16 Slide 19© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 20© Festo Didactic, Training and ConsultingF-Be/ [email protected]
3: Cylinder must stop!
• Yes, but..
• The problem is here to put afterward the machine in a running state!• Clamps reacts at a pressure around 2,5 Bars : Slow start valve shouldn’t help• Chambers are exhausted: speed cannot be controlled when restart• Choice the good clamps! Some are intended to stop during movement, some not (parking brake
>< brake pedal).• Check the lifetime! MTTFd is sometime difficult to reach..
26.10.16 Slide 21© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 22© Festo Didactic, Training and ConsultingF-Be/ [email protected]
2: Wrong choice of the valve
• Poppet or spool valve ?• Norm EN 13849-2 says “use spool valve, because you know where you will have pressure..”• Poppet valve have the advantage that it will always leaks and never allow pressure build-up.
• Pilot air and piloted valves• Be careful with slow start valves and mechanical springs.
• Pneumatic springs:• when exhausting the machine, it can be that this kind of valves shouldn’t return to his rest
position, and stays closed, trapping air in the machine.
26.10.16 Slide 23© Festo Didactic, Training and ConsultingF-Be/ [email protected]
26.10.16 Slide 24© Festo Didactic, Training and ConsultingF-Be/ [email protected]
1: 5/3 closed in central position
• Goal: stops the cylinder during movement.
• Pseudo: the killer !
• The solution:
• difficult to explain to programmer ;o)
+32 497 585779
26.10.16 Slide 25© Festo Didactic, Training and ConsultingF-Be/ [email protected]
Paul Verbist: [email protected] 02 702 32 44
Training and consulting: [email protected]