Ball Valve Rated to 450°F won't open (or close) when heated

[LNGRULES]

We are using 6" Velan ball valves on an asphalt piping manifold. The valves have a max temperature rating of 450°F. We are heating the manifold to 300°F using MI heat trace cable and once they reach temperature they won't move in either direction. Any ideas what's causing this or how I can fix it without removing the valves? There are 6 valves on the same manifold, all of the same model and manufacturer and every one of them is "froze".

 

[SPDL310]

It sounds like it could be a thermal expansion issue. One or more of the following scenarios could be occurring:

1.) The balls and seat are expanding relative to one another causing the ball to be squeezed.

2.) The stem and packing are expanding creating a squeezing action on the stem.


Are these actuated or hand wheel operated valves? Do the valves unfreeze when cooled down? You may need to take one of the valves out of line and return to the manufacturer for a teardown inspection to find the problem.

 

[moltenmetal]

3) The valves are "rated" for 450 F, but have soft seats which have melted and turned into glue, because
4) The asphalt has coked in the cavity of the valves, because the actual temperature the MI trace took the valves to is higher than you're admitting, or

5) The temperature inside the valves is lower than you think it is because you're measuring the temperature of the trace cables NOT the valve bodies much less the valve contents- and hence the asphalt is still a solid, glueing the valves shut

Just guesses here of course, because you haven't provided enough information for us to help further in a meaningful way aside from brainstorming crazy things that might be wrong here. Model numbers would help, as would specs.

A useless suggestion perhaps, but use gates next time! Unless they're actuated, why on earth you'd want the extra complexity and expense of a high temperature ball valve in this service is beyond me. You can't need better than class IV shutoff, and the gate valves will be a fraction of the price of ball valves which are actually suitable for that temperature. And as a bonus, when you try to open them, they'll likely actually open!

 

[LNGRULES]

SPDL310, I'm assuming that is what is happening. I was just wondering if anyone else had had this problem and more importantly was able to fix it without removing the valves. I should have been more specific on the set up. The valves have the MI cable for heat trace and the heat trace is controlled by a watlow controller and dinamite switch. The thermocouple is connected right to the valve body so the valve body is at whatever temperature the watlow is set at. These were new surplus valves I was able to purchase for about half price. The reason for the ball valves vs gate valves is these valves are opened and closed at least 20 times a day during shipping season and the operators requested ball valves for the time saving. We have ball valves in similar situations throughout the terminal but the majority of our valves are gate valves. I would have loved to put actuators or even hand wheels on them but my boss wouldn't let me spend the extra money.

The valves will open if you put enough of a cheater bar on the handle, its just a pain in the butt to do. The piping for the manifold was dry when they initially tried opening the valves and they still were hard to move so I don't think its the AC. This was a new install this winter and we literally just flooded the pipe yesterday. Really the AC should act as a lubricant as long as its up to temperature. I'm hoping with a little more exercise they will loosen up a little bit.

If you have any more thoughts I'd love to hear them. I think in the future I might just tell the operators to suck it up and deal with the gate valves.

 

[SPDL310]

Good additions by moltenmetal. I ruled out number three due to temperature rating, and assumed a metal seated design. I also assumed a trunnion mounted design, but that may not be the case.

Increased torques are a known issue with elevated temperature valves, and I don't have any quick fix for you other than contacting the manufacturer about purchasing gear operator or actuation kits. Changing bonnet packing material and type could also reduce torques but with second hand valves, and an unknown valve standard it may not be an option.

With that large of a diameter and only a lever your valves may not be designed for open/closing under full line pressure.

 

[LittleInch]

Have you actually checked what the operating torque is supposed to be? Like SPDL says, I'm surprised you could get 6" valves with just a handle on them - it could be that they are in spec, just never designed for one person to close them with a bar type actuator.

What type of Velan ball valves - they make a lot so its like saying you own a Ford.

How were they stored and protected if they've been lying around for ages?

Did you lubricate them or "service" them in any way before installing them?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[moltenmetal]

If you can open a 6" metal seated ball valve with an ordinary lever handle, something is wrong!

A 450 F rating might be for the body, not the seats. The seats could be metal or PEEK, in which case a high operating torque is NORMAL.

One solution would be to put gear operators on them, trading a difficult quarter-turn operation for an easier process but requiring multiple turns- i.e. you could turn your ball valve back into a gate valve as far as they're concerned- or you could put an air operator on them if you really want to improve efficiency. Just make sure it's sized for the real torque, otherwise it won't open them either!

We need valve model numbers to comment further.