The Relief Valve is Leaking!

"The valve keeps leaking. I can't keep steam. Help!" the text message read.

Rather than get in an extended text message conversation, I called the person. In his usual animated way, he said, "That stupid valve on top of the boiler keeps opening, and I lose all my steam. It ruins my batch. I thought you said this was a good boiler."

"It is an excellent boiler. I can order a replacement pop safety valve." I said.

"While you are at it, get me one of those pressure controls. That's not working either."

"It's not? Which one?" I asked, now starting to sense there was an underlying problem.

"The one with the button on the front." He continued.

"I'll be out in a bit." I offered.

There was a recent repair done in the asphalt parking lot which looked a pipe was replaced as it was a straight line. When I walked into the boiler room, I gasped. There was a wire connected to the safety valve and the pipe, preventing it from opening.

"Fixed it," he said proudly of himself like he was MacGyver.

"You can't do that." I gulped.

"Why not?" he asked with his hands on his hips.

"The pop safety valve is the last line of defense against a catastrophe. It has to be able to operate freely." I explained.

I also noticed the black iron pipe which was initially on the safety valve was replaced with a copper tube piped to and inside the floor drain. He saw me noticing it and said, "That old pipe was leaking all over the floor. Steam and water were going everywhere, so I piped it into the drain." He said proudly.

The pressure control setting was 14 ½ Psig. "Who turned this up?" I asked.

"Oh, I did. This expert online said I would get a better batch if I ran the pressure that high." He said. I reminded him of one of my rules, The out of town or online expert may not always be an expert. I adjusted the pressures down to where they were when I started the boiler, 10 Psig.

"I saw the parking lot was recently ripped up. Did you replace the drain by any chance?"

"How did you know?" he asked.

"The temperature of steam at 14 psi is about 248 Degree F, and the temperature rating of PVC plastic which most new drains use is 140 Degree F." I said. He was discharging temperatures over 100 Degrees F hotter than the temperature rating of the drain pipe. He essentially turned the drain pipe into cooked spaghetti.

I also showed him the tag on the pop safety valve. The manufacturer stipulates the following:

The minimum pressure differential between the pressure relief valve set pressure and the boiler operating pressure is 5psi. Under no circumstances should this margin be less than five psig.

That would make the maximum boiler setpoint at ten psig. I also explained the warmest temperature allowed in a drain is 140 degrees F. Be careful operating the boiler too close to the upper limit.

Would you like to learn more from Ray Wohlfarth? Check out his seminars, books, and blog about brewing with steam.