Cylinder Position Sensors: Reed Type vs Solid State

I oversee the maintenance of a few imported automatic assembly machines. Each machine has 40-70 Festo air cylinders, and each cylinder has two to four 3-wire Festo reed type cylinder position sensors. The machine produces about 30,000 parts per day. I have found that these cylinder position sensors are the source of many of our previously unexplainable intermittent breakdowns. The sensors fail despite the status indicator reporting all is good. I have also determined that their mechanical nature might be negatively affected by the rough operation the sensors experience. The machine manufacturer likes to have cylinders operate line pressure, at high speeds and without cushions at the end of their stroke. I refer to the setup as "everything set to kill"

As a test, I recently switched a few sensors to Sick and Balluff solid-state cylinder position sensors. These appear to function flawlessly. My question is, other than to have a dry contact, why would someone specify the reed type over solid-state? Cost and not needing to stock both NPN and PNP are the only reasons I have received when asking vendors & peers.
Are there other reasons to select one type over the other?

Thanks
Andrew
 
Other considerations might be availability and rated environmental conditions.

At my previous job, we had machines with Festo cylinder sensors that kept failing in the field but when they were bench tested, they worked perfectly. The problem was the heat & humidity inside the machine (automated ultrasonic parts washers). We replaced the sensors with units rated for the environment and didn't have further issues. I don't remember if the originals or replacements were reed or solid state, but both were Festo branded sensors.
 
Other considerations might be availability and rated environmental conditions.

At my previous job, we had machines with Festo cylinder sensors that kept failing in the field but when they were bench tested, they worked perfectly. The problem was the heat & humidity inside the machine (automated ultrasonic parts washers). We replaced the sensors with units rated for the environment and didn't have further issues. I don't remember if the originals or replacements were reed or solid state, but both were Festo branded sensors.
Interesting experience, thanks for the reply.
I unintentionally singled out Festo as that's the brand on my most troublesome machines. I have also experienced issues with three packaging lines where someone installed reed switches on the machine guarding. The switches look like industrial versions of magnetic security alarm switches. The three machines all experience random stoppages which I attribute to the machine slamming violently with every cycle and disturbing the switch contacts. Switching to true safety switches resolved the stoppages.

Our environment is indoor ambient air with a significant amount of carbon dust.
 
I would be asking the manufacturer of the machine why they specified / used reed switches instead of solid state switches.
I've had no issues with solid state switches from Festo (aside from operators adjusting their positions all the time).
A reed switch is a mechanical device - so any the end stroke impacts could cause them to have a decreased lifespan.
 
I would be asking the manufacturer of the machine why they specified / used reed switches instead of solid state switches.
I've had no issues with solid state switches from Festo (aside from operators adjusting their positions all the time).
A reed switch is a mechanical device - so any the end stroke impacts could cause them to have a decreased lifespan.
Thanks, I began this conversation with the manufacturer, they weren't very forthcoming.
 
There are many different types of cylinder switches, including actuators, pneumatic relays, solid state and reed switches. Some types have LED (Light Emitting Diode) indicators. The type of switch may affect the rated voltage and voltage drop, so it should be selected according to the requirements of the device.
The reed switches have magnetic proximity sensors that open when an aligned magnetic field is applied. The poles of the aligned magnets are adjacent to each other in the axial plane. When a magnet approaches a reed switch, it creates a magnetic field parallel to the reed switch. A reed switch consists of a pair of ferromagnetic metal reeds enclosed in a sealed glass tube. In the absence of a magnetic field, the metal reeds separate and the sensor turns itself off. When used with a cylinder, a reed switch is mounted on the cylinder tube to detect the presence of the magnetic field generated by the magnet on the cylinder piston. This action draws the metal reeds together, signaling the circuit to turn on the magnetic sensor.
 
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