Introduction:-
In industrial
environments, pneumatic lines can pose significant hazards to workers and
associated equipment both the lines themselves and the moving components they
operate.
We are going with the
most important dust collector part called Pulse
Diaphragm Valve. It is responsible for the continuous flow of air and
collects dust in a bag filter. Its unique springless design provides fast
opening and closing of the Pulse Valve with the saving of compressed air. Long
life, High flow, and fast diaphragm operation produce reliable and economical
operation.
Systems have been
developed to help minimize these hazards and to comply with two ISO safety
standards (EN ISO 13849 and ISO 13118:2000), which mandate the dissipation of
pneumatic energy to prevent unintended start-up or movement in a machine. Design
engineers can utilize a pneumatic safety, such as Pulse Diaphragm Valve into an
air preparation system to comply with these standards and increase levels of
plant safety.
Maniks pulse diaphragm
valves are operated by integral solenoid pilot operator. When the valve is
energized, the trapped air above the pulse valve diaphragm is quickly exhausted
causing the fast opening of main diaphragm valve. When the pilot-operated valve
is de-energized, air escapes through the bleed hole of main pulse valve to
balance the diaphragm pressure and instantly closes the valve.
Several important
points should be considered when specifying a pulse diaphragm valve:
1. Measure the Operation
Time to Faulted Condition
Take the time to
understand the worst-case scenario as when safety of pulse diaphragm valve is
in faulted condition, standard exhaust times (assuming normal stop) do not
apply. In this situation there is a failure in the valve or control system and
the exhaust flow may be restricted, thereby increasing exhaust time.
2. Working Time is Important
The faster a machine
can stop, the closer to the machine that the guards, light curtains or other
presence-sensing devices can be installed. The Working off impacts your
calculations for safe stopping distance and your switching time on impacts the
lag time to fill the machine.
3. Product design
Adopting a safety of pulse
diaphragm valve with a series-parallel flow design means benefiting from
the best of both series and parallel arrangements, ensuring that both valve
elements (redundant design) must shift to supply air downstream. If particular
valve element has to be out of position with the other, then the downstream air
will be dumped to exhaust in parallel.
This arrangement
allows for higher exhaust flow capability and ensures very low residual
pressure during a fault, eliminating the danger of residual energy making its
way into the machine. Consequently, if two pulse diaphragm valves are used in
series, the air supply to the first valve flows through to the second and then
downstream. When in exhaust mode, this design flows most of the exhaust through
the second valve creating a lag in exhaust time.
4. Know the B10 value
The valve’s B10 value
is its life expectancy in switching cycles and is based on B10 testing (the
point at which 10% of a sample has failed). It’s an important consideration
when determining the MTTFd. The higher the quality of the components is, the
longer the B10 life of the machine into which they are built will be. This is
an important consideration for Category 4 applications where a high diagnostic
coverage is needed.
5. Monitoring
To achieve the highest
level of diagnostic coverage, it’s critical to employ all the best aspects of
safety circuit architecture - redundancy (dual-channel circuits) and monitoring
to detect faults or failures in control systems and check for short circuit
faults. The measuring portion of the safety system must check to see if both
sides of the valve are shifting together every time. This is generally done
with most versions of safety relays and safety PLCs that can also perform pulse
test monitoring.
These types of safety
relays and safety PLCs make for very reliable systems with high diagnostic
coverage – especially short circuit faults in dual channel systems. The use of
sophisticated controls and monitoring ensuring the valve is functional.
Safety allows no room
for error. If the risk assessment requires a safety rating of PLc or higher for
the pneumatic system, then a dual redundant safety exhaust valve offers a
simple-to-implement and cost-effective way to attain the required safety level.






