Warning: Hydrostatic Testing of Systems with Valves Containing Thermodiscs May Damage the Valves

Safety valves that contain a Thermodisc, such as the Consolidated 1811 series or the Consolidated 1700 series (Maxiflow), are designed for steam service only.

If the valve is opened even slightly with water, it may, at minimum, damage the Thermodisc. If the valve is lifted with water and then closes with the neck and nozzle full of water, the hydraulic effect will not only damage the disc, but can also fracture the nozzle and could possibly render the valve unrepairable. Because of this, precautions must be taken prior to performing hydrostatic testing, high-pressure boiler wash, or any service that may force any liquid to contact the valve seats.

Valves that contain a Thermodisc may be installed in power plants, refineries, paper mills, sugar plants — pretty much anywhere you find a boiler or steam service. These valves are not intended for fluid service.

After doing maintenance or repair on a boiler, it’s common practice to perform hydrostatic testing to make sure the welding and repairs will hold pressure. However, if the testing is even remotely close to the valve’s set pressure, the valve could open, causing damage to the valve. Exposing the valve to water through high-pressure washing can have the same result.

  • At a minimum, opening any valve containing a Thermodisc with a liquid (e.g., water) may damage the Thermodisc. This damage could be so severe that the valve may be unrepairable.
  • In addition, if you open a valve containing a Thermodisc using liquid (e.g., water), you will void the valve’s warranty.

So if there’s even the slightest possibility that this will happen, take steps in advance to protect your valves.

Before performing hydrostatic testing or high-pressure washing of your system, you need to do one of three things:

  1. Remove the valve and install a blind flange, which will seal the system.
  2. Gag the valve so that it cannot be open by fluid. Be sure to follow the manufacturer’s instructions to avoid damaging the valve during gaging.
  3. NOTE: This should be done by a qualified technician. Install a hydro plug in the valve’s inlet. After the testing or wash is complete, have the qualified technician remove the plug prior to starting the equipment. The plugs can be saved and reused during the next service.

Again, DO NOT allow valves with Thermodiscs to come into contact with water. Reliable valve operation depends on it.

If you have any questions about this or about any of the valves in your facility, please contact us. We’re here to help.

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