Posted by boilerguru on July 09, 2000 at 11:43:01:
In Reply to: Safety/Relief Valves posted by Jack on June 03, 2000 at 21:41:58:
: So tell me what you think about hand lifting safety or relief valves on a periodic basis while under pressure to ensure a positive flow path.
: I have a State Safety Engineer in California telling us we should be doing this "frequently",but wouldn't define this what frequently was. He hinted that shiftly or daily would sufice. We have two 150 BHP scotch marine fire tube boilers.
: Now I'm not saying he's wrong, bcause I know what his intentions are, but there are negative consequences to this which may only compound the problem and or create problems for you.
: The code isn't necessarily clear on this, it suggests you should do it, but could cause wire drawing across the seats.
: In the 10 years I was in the Navy I never heard of this nor had this done in any plant that I was in.
As a boiler inspector, I routinely direct folks to either remove the valves periodically(annually is recommended) and having them lift tested at a valve shop or performing an onsite boiler system pressure test(not recommended by me though, as safety controls are bypassed and require supervision and a qualified test procedure). The NBIC suggests this, but also suggests "routine"(defined to be every 2 months) hand lifting while under pressure. The important thing to remember when hand lifting the valves is that the boiler should have AT LEAST 75% of the valve's lift pressure on the unit BEFORE lifting, or damage could incur to the valve. I too was in the Navy, and we had routine(every 5 years) PM on our valves where we had to remove them and take them to a lift-test site on base. This method is the best I think if the cost associated is cheaper than purchasing new valves.