Hole On A Second

Hole On A Second

As we all know, a boiler is a pressurized vessel. After all, that pressure is created by – and necessary for – the production of steam. Something else we all know is, boilers need regular inspection and care to make sure they run safely, and for a long, long time. So how do you get inside a vessel that’s pressure-sealed? Easy. You make a hole.


The openings in a pressure vessel have to be big enough to be useful, but they still have to be able to seal tightly to prevent leakage. That leads us to the first thing you’ll notice about the openings in a boiler: they aren’t all the same size. Some smaller openings, called “hand holes”, are just big enough for… wait for it… a hand. Technicians use hand holes to get a look at the inside surfaces of a boiler tank during inspections. They also allow boiler operators to reach inside to clean the inside of the boiler, as well. 

The larger holes in a pressure vessel are known as “manways”, because man does the lid weigh a lot. Just kidding. They’re used for those instances when a technician has to actually get inside the boiler for inspection or boiler repair


When you’re dealing with heated water and steam under pressure, keeping the media inside is obviously the number one priority. That’s why the plates that seal manways and hand holes, known as “manway plates” and “hand hole covers” (bet you saw that coming), are made of metal. They’re held in place with either multiple bolts or one large bolt which pulls against a “yoke” outside of the boiler as the bolt is tightened. This sandwiches the vessel shell between the cover plate inside, and the yoke outside. The cover or plate is always inside the vessel, so that pressure adds sealing force, instead of relying only on the bolts.

As we all know, metal-to-metal sealing is a difficult if not impossible task. That’s where gaskets come into play. Some gaskets are made of rubber, some are polymer, some can be fiber, and some are even made of metal or graphite but they all serve one purpose: to maintain the integrity of the seal between the cover and the hole. 

Different types of gaskets are suited for different applications, so it’s always important to know what the boiler’s manufacturer specifies. Using the wrong gasket can cause damage, leaks, and even explosions. Of course, WARE’s online Boiler Warehouse site has pretty much every kind of gasket you could need, and we’re always here to help. If you need an inspection, boiler repair, or if you have a leaking manway or hand hole, the professionals at WARE are standing by to help.

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