How Long Does A P51 Vac Diaphragm _Really_ Last?

[PDW]

I keep reading that a vac diaphragm lasts 3-4 years and then needs replacement. Given that a lever/button filler sac can last 20-30 years this seems a very short time between major services. So, what is your experience of diaphragm life, especially on the P51?

 

As a supplementary question, can you tell in normal use if a diaphragm is getting towards the end of its life, and if so how do you do it?

[OldGriz]

I don't know where you are reading that, but the modern diaphragms that I use and are in my Vacumatics and P51 last a lot longer than that

My 51s and Vacs have diaphragms that are over 10-15 yrs old ....

Generally you can tell if a diaphragm is going south by the fact it feels stiff or strange when you depress the plunger or it is not drawing ink as it did..

Also look out for ink dripping out of the pen at the nib and/or the plunger... both signs of a diaphragm that has holes in it

[Ron Z]

My answer is that it depends on what ink you use in the pen, and how much the pen is used. I have seen sacs and diaphragms die in a surprisingly short time with some inks. There is in my opinion no absolute answer.

 

A diaphragm is subject to more stress than a sac because it is unrolled, and then rolled back again each time the pump is pressed down. Unlike a sac, which is simply squeezed, the action of the filler pulls on the diaphragm and flexes it as it is unrolled, which places unusual stress on it. Therefore the diaphragm is not likely to last as long as a sac in a lever or pneumatic (i.e. TD or snorkel) pen.

[PDW]

My answer is that it depends on what ink you use in the pen, ...

 

Sounds sensible - but what are the least damaging inks?

[Glenn-SC]

I have a First Year Vac found in an antique store 7 years ago that still works just fine.

 

Who knows when (or if) the diaphragm was ever replaced.

Nor do I know how much or with which types of inks the pen was used.