Hi all, I have no way of knowing how old my Optimus 8R is so, as they were first made in the late 60s (as far as I can ascertain), it's possible that mine could be up to approximately 40 years old. This being the case I think it's about time the tank PRV had a service - the condition of the spring and sealing pip checked. Browsing through some of the earlier posts on here I have seen it mentioned that these valves have to be set to an exact 'blow-off' pressure on re-assembly but, looking at the (external) construction of mine, I can't see how this could be. It looks as though the slotted screw is just screwed in until its head seats tightly onto the valve body - mine does not have a pentagonal recess - and this seems to make sense, assuming the spring rating was carefully chosen by the designer. Before I tear mine apart I would really appreciate some advice, from someone who has dismantled and serviced this type of valve, as to whether the above is correct. Dave, Here's a photo of my SRV -
It's OK, I have found a couple of older posts that show the valve stripped down and, as I suspected, there is no way of pre-setting the release pressure on this type of valve - it relies solely on the spring pressure and this is non-adjustable. Dave.
Aye - there is an adjustable type but it's not that one. Some folks like them spot on - some like to guestimate. I fall into the later catagory but don't use petrol much. With the adjustable PRV's I just count the turns when removing the pic & give it the same amount when replacing. Some folks set up rigs to test the psi thy fail at. With these it's down to the spring tension.
