MTNW Service Bulletin

Sweating Manikin Fluid System Storage and Flushing Procedures

Long-term storage of water systems, even with high purity water, can result in bacterial growth and a resulting biofilm on all wetted surfaces. Studies have demonstrated significant bacterial activity within 7 days in a high-purity closed system. The large number of variables affecting this phenomenon, including supply water purity, existing bacterial content of water system, ambient temperature, and wetted materials, can make each location unique.

MTNW’s sweating manikin systems meet many of the criteria for promoting bacterial growth. The sealed design of MTNW’s fluid system does not permit reliable purging of the internal tubes, so the system remains wetted throughout its service life. The flowrates are low and often stagnant during non-sweating operation. Water recirculates through the system, so any bacterial content developed in the manikin tubes gets returned to the reservoir. Adding more high-purity water to the reservoir does not eliminate any existing biological activity.

The maintenance procedures outlined below are intended to minimize/reduce bacterial growth, and also offer a shock treatment to systems for periodic cleaning. NOTE: All supply water should be deionized or distilled high purity water.

If you will be USING the manikin sweating system AT LEAST ONCE PER WEEK:

1. Fully drain and rinse out the manikin fluid reservoir with supply water
2. Refill reservoir with supply water
3. Unplug recirculation (black) tube from reservoir and route it to a drain or collection bucket
4. Turn on the fluid pump and allow it to run for 10 minutes to purge the old water from the system
5. Top off the reservoir and resume testing

If you will be STORING the manikin or not operating the fluid system (re: non-sweating tests) for MORE THAN ONE WEEK:

1. Remove the wicking fabric sweating suit
2. Add 5 liters of supply water to empty reservoir
3. Add 1 ml of unscented household bleach and shake the reservoir to mix and coat the inside surfaces (this will result in approximately 10 PPM sodium hypochlorite solution)
4. With the manikin tubing fully connected, turn on the fluid pump and allow it to run for 10 minutes, recirculating this solution through the closed system.
5. Set all the manikin sweat rates to 2000 ml/hr/m2, and allow the system to sweat for 10 minutes.
6. The system can now be stored for up to 2 months containing this solution
7. Prior to running sweating tests, repeat this procedure with fresh supply water to purge chlorine from the system

Every TWO MONTHS as preventative maintenance or as a special one-time shock treatment after storage:

1. Very important – Long-term exposure to sodium hypochlorite can degrade internal manikin system components. Do not allow bleach solution to remain inside the manikin system for more then 10 minutes.
2. Caution – This process uses bleach with a concentration which could possibly discolor fabrics or cause staining. Use colorfast or white absorbent pad and towels for this procedure. Wear eye protection.
3. Remove the wicking fabric sweating suit and place an absorbent pad beneath manikin to catch runoff
4. Add 5 liters of supply water to empty reservoir
5. Add 100 ml of unscented household bleach and shake the reservoir to mix and coat the inside surfaces (this will result in approximately 1000 PPM sodium hypochlorite solution)
6. With the manikin tubing fully connected, turn on the fluid pump and allow it to run for 5 minutes, recirculating this solution through the closed system.
7. Set all the manikin sweat rates to 2000 ml/hr/m2, and allow the system to sweat for 5 minutes.
8. Set sweat rates back to 0 ml/hr/m2 and quickly blot the manikin dry with a colorfast cloth and turn off fluid pump
9. Immediately drain and rinse reservoir, and refill with clean supply water
10. Unplug recirculation (black) tube from reservoir and route it to a drain or collection bucket
11. Turn on the fluid pump and allow it to run for 5 minutes to purge the system
12. Set all the manikin sweat rates to 2000 ml/hr/m2, and allow the system to sweat for 5 minutes.
13. Set sweat rates back to 0 and blot manikin dry with colorfast cloth
14. Allow the pump to run for an additional 10 minutes, flushing water out the recirculation (black) tube.
15. Begin using the manikin for sweating tests within one week, or follow the previously mentioned storage procedure

Our engineers love custom projects, and for this application they envisioned a waterproof thermal hand system where the hand form was attached to a sealed control enclosure box not much bigger than the manikin’s forearm diameter. Exiting this box would be one or two cables for power and serial communications. In use, the glove being tested would be placed on the hand, and the whole assembly – manikin and control enclosure box – would be immersed in the test tank with cables exiting the water and connecting to the system’s power enclosure and laptop computer.

No word yet if we’ll have the chance to build this device, but I mention it as an example of our interest in custom projects. If you’ve got a project or know of a project that falls outside the standard range of thermal testing equipment – let us know. MTNW got its start back in 1986 creating customized thermal systems, and we still look forward to those opportunities that either push the envelope or lead us in new directions.