Sealant or Stacking

Your questions are too broad. It sounds like homework.

And, it's staking, not stacking. I assume you mean attaching components to boards?

There are many robotics suppliers that can help you, but you need to give details.

staking applly for components to pcb.the importance of this process is at the time of vibrations don't damage the components and don't get mall function from the component due vibration.my company producing railway products so in railway too much vibrations r there so we want protect components from vibrations.

The next question is, do you need to stake all components, or just the heavy ones? Have you performed a vibration analysis?

Can you dip coat the boards, to protect from moisture and vibration?

we stake required components only,they r like capaciotrs,transformers,relays,high wattage resistors,terminal blocks.we performed vibration analysis for proto type cards only.

for protect from moisture and vibration we r doing conformal coating(poly urthene material)

You stake, and coat?

Have you considered using a thick (thixotropic) coating that will also act as a staking material. We used to do this on stuff we launched into outer space on rockets.