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From: Yaritza Brinker <YBrinker**At_Symbol_Here**FELE.COM>
Subject: Re: [DCHAS-L] Hydrothermal and solvothermal reactor safety
Date: Wed, 28 Aug 2019 22:15:42 +0000
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Message-ID: BL0PR05MB4641E6C8171DCD5EF2C647F9ADA30**At_Symbol_Here**BL0PR05MB4641.namprd05.prod.outlook.com
In-Reply-To


Hi Jeff,

 

I've purchased and used pressure bombs. The models I've used are bigger� 1L vessels with pressure gauge and temp probe. However, I do know that Parr offers PTFE lined small vessels with Safety Blow-Off that can be used as hydrothermal reactors.

 

https://www.parrinst.com/products/sample-preparation/

https://www.parrinst.com/download/37527/

 

Here's what I learned from using the 1L capacity�

  • It is safer to spend the extra money and go for a model with a Pressure Gauge.
    • `This will help you ensure that�
      • you don't over pressurize the system
      • you don't open the system before it is completely cooled
  • A temperature probe is nice to have.
    • If you intend to heat the system, your heat source should have ramp control and temperature readout. If not, then the temp probe basically becomes required.
    • For Teflon lined units, you want to keep your system below the temp/pressure where Teflon softens.
  • Don't use materials that are known to be incompatible with the vessel's interior (goes without saying, but you'd be surprised)
  • Look around the area for any other pieces of equipment that could cause a larger combined hazard if the vessel fails.
    • i.e. if your pressure vessel has water in it, don't use an oil bath as your heat source (you'd be surprised here too)
  • Before each use, inspect
    • the seals for any signs of hardening, cracking, or softening.
    • If PTFE lined, inspect that too.
    • the fasteners for any signs of cracking or elongation.
  • Do not over torque it as this can damage the lip seals and cause elongation (weakening) of the fasteners
  • Ensure the vessel is back to room temperature before opening.
    • This is where the temperature probe comes in really handy.
      • Also, PTFE is a plastic and as such acts as a thermal barrier. Your metal outer may be cool to the touch, but the inside can still be hotter that you'd think.
    • In the past I've routinely let the vessel cool down overnight and also ensured the pressure gauge was back to "0" before opening.
  • For shielding, we used a latched oven. That particular oven had ports we could use to monitor the bomb. We added a containment pan at the bottom of the oven just incase of spillage.
  • Cooling and heating rates should always follow the manufacturer's recommendations� these are tied to the metal alloys used, the metal thickness, and seal design.
  • Always have a lab buddy monitoring from a safe distance when opening the unit� just in case it goes south.

 

 

Hope this helps.

 

Yaritza Brinker

260.827.5402

 

From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Jeffrey Lewin
Sent: Tuesday, August 27, 2019 12:01 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] Hydrothermal and solvothermal reactor safety

 

** External Email **

I'm looking for any information on the safe operation of hydrothermal and solvothermal reaction chambers.  They are sometimes also referred to as "autoclaves" (different than what this biologist thinks of) and "bombs." which might be the best description having recently viewed pictures of one that catastrophically failed (no injuries, plenty of damage).

 

From what I can find Googling - they've been around commercially for some time (10 or more years?); I found very little in written SOP's, but the discussion on researc- gate I've seen several comments that if not handled correctly, the results can be energetically problematic.

 

 

So questions for the group:

 

Does your institution have specific guidance on using these such as limiting the size of reaction chambers?  

 

Do you have minimum engineering controls for containment (blast shielding, etc.)?  

 

Does your institution explicitly prohibit using them?

 

Two critical administrative controls I've seen are:

 

1) not overfilling the reaction chamber, allowing headspace for gas formation.  For hydrothermal reactions, this seems pretty well established since water expands about 25% at the temperatures these are operating at (190-220C).  For solvents, it doesn't seem to be as straight forward.  For example, I've not been able to find an expansion factor for dimethylformamide (DMF).

 

2) not heating and cooling too fast.  The instructions I've seen with reactors say things like don't heat or cool faster than 5C/min.  But I've seen instructions that go outside those guidelines (8C/min) and several that say "cool naturally" i.e. not at 5C/min (I've also seen discussions that specifically advise against quenching them).  

 

Any insight would be appreciated.

 

Jeff

 

 

--

Jeff Lewin

Chemical Safety Officer

Research Integrity Office

Laboratory Operations

207 Advanced Technology Development Complex (ATDC)

Michigan Technological University

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