Solutions for vacuum and pressure measurements - HMP4 - HMT314 - HMP8 - HMPX - HMT318 - HMP7 - HMM170 - HMT317

Humidity Probes for Vacuum and Pressure Processes Technical Note
Product status
Document code
M213243EN-A
ft:locale
en-US
Product
HMP4
HMT314
HMP8
HMPX
HMT318
HMP7
HMM170
HMT317
Document type
Technical note

Vaisala HUMICAP® humidity sensor is suited for measurements in vacuum and pressurized conditions. When considering vacuum and pressure measurements, it is essential to take into account the following aspects:

  • Ensuring using a pressure-tight probe head. Vaisala recommends using the humidity probes and tightening methods described below.
  • Achieving proper probe sealing by using suitable mounting accessories when installing the probe into the process.
  • Selecting the right filter and probe configuration to ensure quick and reliable measurements.

The following tables describes the vacuum and pressure measurement solutions recommended by Vaisala.

Pressure tightness

Vaisala has conducted pressure tests with the humidity probes listed below. The leak rates from these tests are presented in the following table.Pressure tightness
Property HMP4/HMT314 HMP7/HMT317/HMM170 HMP8/HMT318
Pressure range < 100 bar, absolute and vacuum < 10 bar, absolute and vacuum < 40 bar, absolute and vacuum
Pressure leak test rejection limit 5×10-6 mbar l/s, test conducted in high pressure 3×10-7 mbar l/s, test conducted in vacuum 2×10-4 mbar l/s, test conducted in high pressure
Tightening

Tighten the nut a 50 … 60° (1/6 turn) with a wrench.

With a torque wrench, tighten the nut to max. 45 ±5 Nm (33 ±4 ft-lbs).

For more information, see the probe's user documentation at docs.vaisala.com.

 See SWG12ISO12 Swagelok® Connector Assembly Drawing (DRW218087).

Tighten the nut a 50 … 60° (1/6 turn) with a wrench.

With a torque wrench, tighten the nut to max. 45 ±5 Nm (33 ±4 ft-lbs).

For more information, see the probe's user documentation at docs.vaisala.com.

Probe sealing

To ensure proper probe sealing, it is essential to select the correct mounting options for the setup. If any uncertainty regarding which thread to use, a standard third-party thread test plug can be utilized to test the setup. Additionally, using vacuum grease or PTFE tape (not provided by Vaisala) may improve the tightness.Probe sealing
Property HMP4/HMT314 HMP7/HMT317/HMM170 HMP8/HMT318
Mounting options

Fitting body M22×1.5, 17223SP

Fitting body NPT 1/2", 17225SP

Swagelok® NPT 1/2", SWG12NPT12

Swagelok® ISO 3/8", SWG12ISO38

Swagelok® ISO 1/2", SWG12ISO12

Fitting body NPT 1/2", 212810SP

Fitting body ISO 1/2", for HMP8 DRW212076SP

Filters and probe configurations

Example filters and probe configurations for vacuum and pressurized conditions
Property HMP4/HMT314 HMP7/HMT317/HMM170 HMP8/HMT318
Filter for vacuum

HMP4:

Stainless steel grid HM47453SP

HMT314:

Plastic grid DRW010276SP

HMP7:

Stainless steel grid HM47453SP

HMT317:

Plastic grid DRW010276SP

HMM170:

Stainless steel filter HM47453SP

HMP8:

Stainless steel grid HM47453SP

HMT318:

Stainless steel filter DRW010276SP

Filter for high pressure Sintered filter recommended
Condensation prevention in vacuum - OFF -
Condensation prevention in high pressure - In condensing environments ON -
Example probe configuration for vacuum

HMP4:

HMPX4B1D0A0A0D0

HMT314:

HMT3104B5A1BCA14AEAB1K2

HMP7:

HMPX7E1A0A0A0G0

HMT317:

HMT3107B5A1BCA14APAB1G1

HMP8:

HMPX8G1D0A0A0M0

HMT318:

HMT3108B5A1BCA14ASAB1M1
Example probe configuration for pressurized conditions

HMP4:

HMPX4B1B0A0A0D0

HMT314:

HMT3104B5A1BCC14AEAC1K2

HMP7:

HMPX7E1B0A0A0G0

HMT317:

HMT3107B5A1BCA14APAC1G1

HMM170:

HMM1701AAA1A2A

HMP8:

HMPX8G1B0A0A0M0

HMT318:

HMT3108B5A1BCA14ASAC1M1