Should You Connect Your Steam Autoclave To Your Building’s Boiler?

Even the rattly steam systems heating older university buildings can do a fine job generating the needed heat to operate today’s efficient steam autoclaves. But by the same token, some brand-new buildings suffer vexingly persistent HVAC issues, including balky boilers.

If your building has a reliable steam supply, then switching to house steam should lead to:

  • Increased Efficiency
  • Decreased Maintenance
  • Lowered Costs

But if the building steam system has erratic pressure or inconsistent performance, an in-chamber heater offers:

  • Greater Reliability
  • Greater Independence
  • Steam On-Demand

The Benefits of House Supplied Steam Autoclave

The primary benefit of running your autoclave off of “house steam” is efficiency: By taking advantage of the building’s existing steam generation, you greatly reduce your autoclave’s water and energy consumption. In fact, if you have building-wide steam generation and metal drain pipes (as opposed to PVC), your steam sterilizer can operate with zero additional fresh water. (For more on issues of water conservation with steam autoclave design, please download our free whitepaper).

And this efficiency isn’t just an environmental victory—it brings with it cost savings. This shows up first in utility bills: Supplied by house steam, your autoclave will only draw a few watts per day—hardly a blip on the electric meter—and no additional water. As for maintenance, a research-grade unit running just a few cycles per day puts little additional strain on a building-wide boiler system. Since the building’s steam supply is maintained as a part of overall facility management, this responsibility doesn’t fall to an individual lab or research group (or their budgets).

In the absence of house steam, many autoclaves are supplied by independent “bolt-on” steam generators. These have earned a bad reputation among many lab managers. Although they do supply ample steam at a moment’s notice, over time these units often become a burden. They must stay hot 24/7 in order to operate properly, consuming electricity and fresh water even while idle. Constant operation means constant wear and tear, and regular maintenance by a licensed technician. All of this adds up—by some accounts, up to 50 percent of a lab’s funding is sucked up by utility and maintenance costs1.

Possible Pitfalls of House Steam

Shifting the cost of steam off your balance sheet also shifts it out of your control. If there’s a problem in the building’s boiler or steam system, it will likely cause irregular cycles with your steam autoclave.

Some labs find that the steam pressure in their building fluctuates fairly widely. This doesn’t have an impact on the building’s heat (and likely passes entirely unnoticed by occupants), but will lead to failed cycles. Similarly, building steam systems may take time to come up to temperature in the morning. This can again lead to erratic steam autoclave performance (for example, one lab found that their first cycle every morning always failed because of an aging boiler that struggled to come up to steam).

Although overall maintenance costs on house-steam supplied autoclaves are generally lower than those for autoclaves with their own steam generation, the initial installation will be somewhat more complicated.  Steam autoclaves must be supplied with “dry steam” (steam with few or no water droplets held in suspension in the heated vapor). Independent and in-chamber steam generators always produce dry steam, but most house steam systems will need a “steam filter” (described in the next section) as described below.

For labs where these are concerns, in-chamber heating may be preferable. Generating steam inside the chamber avoids the cost and maintenance pitfalls that come with independent steam generators, while providing the lab quick, reliable access to steam, and a degree of independence from building maintenance issues.

Steam Filters for Steam Autoclaves

A simple “steam filter” will ensure that excess moisture is shunted out of the steam supply, and offers the added benefit of eliminating grit that might get picked up as the steam traverses the building. Depending on your needs, suitable filters may include the Balston 23/75R Steam Filter and Eaton “Type T” and “Type ST” Gas/Liquid Separators.

In either case, the filter’s theory of operation is the same: The steam from the building’s supply enters through the filter’s narrow inlet, then passes into an expansion chamber. The sudden shift in pressure and velocity forces the excess water vapor to condense into droplets–trapping particulate matter in the process–and collect in a trap beneath the unit, from which it can either be flushed or captured and recirculated. The dry steam then flows through a physical filter (usually in the .1 to 10 micron range, depending on the final application), which eliminates any lingering impurities.

To learn more about using existing building steam generation systems to run your steam autoclave, contact us for a free consultation.

1In a 2017 interview with the Campus Energy and Sustainability Podcast Allison Paradise of My Green Lab told host Dave Karlsgodt: About 50 cents of every dollar that gets donated to research, or given to research, is taken off the top and goes to paying … the utility bills.”