Sanitization of the AquaWIT V integrity test system with steam

The sanitization of the AquaWIT system can be performed by either hot water or steam. For the selected program (steam sanitization or hot water sanitization), different settings can be predefined in the respective program settings. The testing was performed using steam for sanitization and the respective settings are presented in Table 1.

Table 1. Sanitization settings¹

¹ Note: With the previous AquaWIT IV System, it was possible to set the opening times and time between opening for the steam supply valve. With the AquaWIT V, this parameter setting is fixed.

During the sanitization cycle, the temperature in the water storage tank was elevated to a preset sanitization temperature for a preset sanitization time. The different phases followed by the system during a steaming-in-place (SIP) program are as follows:

• System check: the system checks that the maintenance manifold is attached and operating. A pressure hold test is included to confirm steam-path closure.
• System filling: the system fills the flow path and the water tank with steam and continues until the defined sanitization temperature is maintained for 10 min. Note: The system does not monitor the pressure of the steam supply. The pressure must be constant to run a SIP procedure successfully.
• Sanitization loop:

1. The system flushes steam through the flow path for the duration of the sanitization time. If the sanitization time is not reached or unstable for 30 min, the system aborts the SIP procedure and displays an error in the test result.
2. When the system temperature drops below the sanitization temperature, the Sanitization time timer pauses, and the Sanitization reset timer starts. If the Sanitization reset timer is reached, the Sanitization time is reset to 0.
3. To avoid overheating of the system, the inlet valve AV08 closes when the system temperature exceeds Target sanitization temperature + 10°C. The inlet valve AV08 opens again when the temperature has decreased to the target sanitization temperature + 6°C.

• System depressurizing: The system is vented slowly until the system pressure reaches 200 mbar (0.2 bar, 2.9 psi, 0.02 MPa). If the system pressure does not reach 200 mbar, an error message appears on the screen.
• System air flush:

1. The Palltronic Flowstar V instrument pressurizes the flow path with air to drain water from the flow path through port F to the waste line.
2. The system drains steam and condensate from the water tank. The air is flushed through the system during air flush time.
3. If the system does not cool down to the default system cooling target temperature after the air flush time, a warning is included in the test result.

During the sanitization loop, the AquaWIT V sanitization program uses two configurations (configuration 1 and configuration 2) to circulate the steam inside the system piping. Each configuration corresponds to certain valves of the AquaWIT being open or closed (V1 to V9 and V14, see Fig 1). For the initial testing, the program used a valve opening sequence timing of 10 s for configuration 1 and 5 s for configuration 2.

Fig 1. The AquaWIT V system sanitization loop alternates between configuration 1 and configuration 2.

All components in the flow path can be sanitized with steam up to 135°C. For efficient steaming, we recommend keeping the steam temperature and the setpoint as close as possible to allow optimal regulation (within 10°C delta). The steam pressure supply was 1.8 to 2.0 barg, approx. 130°C to 135°C depending on the steam demand from other installations during the test.

For the thermal mapping, either heat-resistant aluminum tape was used to secure the thermocouples (sensors) on the stainless-steel piping and outer surface of the system, or the sensors were inserted in cut sanitary clamp seals to be positioned inside the system. Table 2 describes the position of the sensors.

Table 2. Sensor placement

We connected the thermocouples to a Kaye validator 2000 system v2.01.

For three positions, we inserted sensors inside the piping using cut seals (nr. 04, 07, and 08). Figure 2 displays the temperature mapping, where the thermocouples are attached on the AquaWIT V system.

Fig 2. AquaWIT V system setup for sanitization testing, sensor placement. Sensors marked orange: System surface. Sensor marked yellow: Inside system.

We calibrated the thermocouples used for temperature recording before testing. Once a sanitization program was initiated, data from the thermocouples were recorded every 2 s using the Kaye validator system 2000. We manually recorded TT01 internal sensor-displayed temperature (AquaWIT V thermocouple installed in the water tank) every 5 min.

We performed all sanitizations using a condensate trap installed after port F.

Three sanitization runs are reported below:

• A: Initial run, condensate trap installed at port F.
• B: Run started when we filled the system tank with water (room temperature) and emptied it twice.
• C: Run similar to run B, condensate trap installed 1 m down from port F (1 m of ¾” PTFE tubing installed between port F and steam trap).

Each sanitization went through the different sequences:

(a) Setup verification, initialization sequence (approx. 3 min).

(b) Steam entrance over port E into the AquaWIT V system and heating up (10 min).

(c) Steam/sanitization cycle (20 min)—this is where configurations 1 and 2 are combined to steam the system.

(d) System venting.

(e) System air flush.

Table 3 presents the temperature averages of each run. The data selected for the average calculation include the temperatures measured during the sanitization/steam cycle (20 min) only, from the sanitization starting time and ending time as reference (time indicated on the test ticket). The detailed results are presented in Appendix 2. We measured ambient temperatures 1 m away from the AquaWIT system.

Values in columns other than 04 and 08 indicate an average temperature above the set point (125°C). The values in columns 04 and 08 indicate a temperature between 121°C and 125°C. For all tests, the TT01 internal sensor indicates average temperatures above the respective setpoint.

Table 3. AquaWit V system average temperature during sanitization (20 min) in °C for each sensor

01: Tank top

02: Tank bottom

03: Tank drain

04: Tank drain (inside piping)

05: Port E (steam entry)

06: Port B inside cabinet

07: Port B (inside piping)

08: Port V (inside piping)

09: Ambient temperature

Regarding the sensor placement on the outer surface, temperatures from the TT01 internal sensor can be used as a reference for the temperatures measured at sensor 01 (top of the tank) and at sensor 02 (bottom of the tank). The difference in temperature between TT01 and sensor 01 is approx. 3°C to 4°C and sensor 02 is approx. 4°C to 5°C lower.

Comparing sensor 03 (piping out of tank drain) and sensor 04 (inside piping, close to 3), the temperature inside the piping was measured at 2°C to 3°C lower compared to the surface.

Figure 3 gives an overview of the average temperature measured during the steam-sanitization phase (20 min) for each run.

The target temperature (125°C) refers to the AquaWIT TT01 internal sensor, where the temperatures we measured were above the target.

For all sensors, average values lay above 121°C, the lowest average being measured on the inside of the bottom pipe (sensor 04, Run B, 122.5 ± 0.6°C), which is expected to be the coldest point due to its location. The temperature at the same point, but on the surface, was higher (sensor 03, Run B, 125.1 ± 0.5 °C). This may be attributed to condensate, which lowers the temperature inside the pipe at the bottom of the system.

Run B shows the lowest temperature averages. However, based on the standard deviations, the differences are not significant compared to the other two runs.

Fig 3. Temperature averages during sanitization phase (20 min). Error bars represent standard deviation.

The temperature of the steam supply is critical. The difference between the steam temperature and the set point needs to be as close as possible to allow optimal regulation (within 10°C delta). The steam pressure supply was 1.8 to 2.0 barg, approx. 130°C to 135°C) depending on the steam demand from other installations during the test.

If the temperature measured by the TT01 is more than 10°C above the set point, the steam admission (valve 08) closes (here 135°C). If the temperature drops below 6°C above the setpoint (131°C), the admission valve opens again.

Lionnel Lueginbuehl, Team Manager, SLS MSAT Filtration was the R&D team leader for this project.

Appendix 1: AquaWIT filter integrity system schematic

Appendix 2: Steam cycle temperature averages (°C) per sensor including standard deviations (°C)

1 bar = 14.5 psi = 0.1 MPa

Appendix 3: Steam temperatures over time, runs A, B, and C