dhi recommendations for molbloc installation ユーザーズマニュアル

 

 

Recommendations for 

molbloc-S

®

 Installation 

Instruction Sheet 

The molbloc-S is a high precision metrological 
instrument whose stability over time is a key component 
in the performance of the molbloc/molbox™ mass flow 
calibration system.  molbloc-S, like any high accuracy 
standard, should be handled, operated, and stored 
with care.  Use the following guidelines whenever 
installing and using the molbloc-S. 

Particulate and moisture contamination must be 
avoided.  Potential sources of contamination, such as 
an unclean gas supply or device to be calibrated, 
should not be connected upstream of the molbloc-S 
without the use of a 5 micron sintered metallic filter 
upstream of the molbloc-S. 

With the exception of ambient air, the molbloc-S 
should only be used with dry gases.  Air compressed 
on-site (generally known as instrument air) should be 
filtered to remove oil, moisture and particulates.   
The final dew point temperature of the calibration gas 
should be – 40 °C or lower. 

The molbloc-S elements designated 5E1-S through 
2E3-S have VCR face seal inlet connections and ISO-
KF Style vacuum flange outlet connections.  The 5E3-
S and 1E4-S molbloc-S elements utilize ISO-KF Style 
vacuum flanges for both the inlet and outlet.  See the 
relevant sections for further details. 

In making the molbloc-S flow connections, always use 
soft O-rings.  They allow a leak free connection to be 
accomplished with minimal torque, and they provide a 
source of flexibility between the molbloc-S and 
elements to which it is connected, protecting the 
molbloc-S from mounting stresses. 

Use the following O-ring seals for making molbloc-S 
VCR

®

 connections: 

5E1-S 

and 1E2-S 

1/4 in. 

102070 

2-202 

Fluorocarbon
rubber (FKM),

Viton

®

 

2E2-S 

thru 2E3-S 

1/2 in. 

102912 

2-207 

Fluorocarbon
rubber (FKM),

Viton

®

 

5E3-S and 

1E4-S 

n/a n/a 

n/a 

n/a 

 

  Install the recommended soft O-ring securely against 

the sealing surface in the nut of the mating fitting. 

  Align the mating nut with the molbloc’s male VCR 

fitting and thread the nut onto the fitting.  Hold the 
molbloc-S with your hand, rotate the nut until 
resistance is felt when the O-ring begins to compress. 

  Holding the molbloc-S with your hand, tighten the 

nut an additional 1/2 turn.  A wrench may be used 
on the nut if desired, but do not tighten beyond 
one half turn.  If more than one half turn is needed 
to make a leak free connection, the O-ring may be 
damaged and should be replaced. 

  To break the fitting, hold the molbloc-S with your 

hand and loosen the nut until it is completely 
backed off. 

 

 

The ISO-KF Style vacuum flange fitting utilizes an 
internal centering ring and an external overpressure ring 
clamp.  The seal is affected by the uniform application 
of pressure by the clamp on the 15° surface of the 
mating stainless steel flanges.  These mating flange 
surfaces compress a Viton O-ring that is held in place 
by the centering ring.  The overpressure ring keeps 
the O-ring in place, and maintains a leak free 
connection when the system is subjected to internal 
pressures above vacuum level.  This connection is 
reusable, rotatable, and can operate leak free in 
vacuum applications up to 10

-8

 Torr, and in positive 

pressures of 700 kPa (100 psig).