Ulvac UHE10F User manual

D/N. ME30007E, 2019MY03 ULVAC CRYOGENICS INCORPORATED
4K CRYOCOOLER
Instruction Manual
Original Instructions
Export Control Policy
When applying a refrigerator to a cryocooler for optical sensors, the
cryocooler falls under row 6.A.2.d.2 of the control list established by
The Wassenaar Arrangement, which is equal to row 10(2) of
appended table 1 of Japan’s Export Trade Control Order.
Customers must follow all related rules and regulations such as
Foreign Exchange and Foreign Trade Act and take appropriate
procedures when exporting or re-exporting our refrigerators.
UHE10F
UHE12F
UHE15F

MZ0F001E,2013OR03 ULVAC CRYOGENICS INCORPORATED F-1
Introduction
Thank you for choosing our products. This instruction manual gives
information and precautions on handling, installation, operation, and
maintenance of the product.
This product is intended for use by qualified personnel who recognize shock
hazards and are familiar with the safety precautions required to avoid possible
injury. To ensure proper use of this product, read this instruction manual
carefully and keep this manual close at hand so that you can use for reference
during operation.
If you purchased our other products and/or optional devices with this product,
read relevant instruction manuals carefully.
1. About the personnel who are involved in handling our products
All personnel involved in handling our products should take a general safety
education and training that is officially accepted in the country where our product
is used. The personnel are also required to have specialized knowledge/skills and
qualification on the electricity, the machinery, the cargo handling, and the vacuum.
Especially, the personnel should be familiar with handling a cryopump in order to
use it safely. Since we offer a training session (which is subject to fees) as needed
for people who use cryopumps for the first time, please do not hesitate to contact
our Service Engineering Division to join the training session.
2. Warranty
2.1 Gratis warranty period and Warranty coverage
【Gratis warranty period】
Note that an installation period of less than one year after installation in your
company or your customer’s premises or a period of less than 18 months (counted
from the date of production) after shipment from our company, which is shorter, is
selected.
【Coverage】
(1) Failure diagnosis
As a general rule, diagnosis of failure should be done on site by customer.
However, ULVAC CRYOGENICS or our service network can perform this service
for an agreed fee upon the customer’s request. There will be no charge if the cause

F-2 ULVAC CRYOGENICS INCORPORATED
of the breakdown is found to be a fault of ULVAC CRYOGENICS.
(2) Damage during transportation
When damage by delivery/transportation is admitted, the product will be
repaired free of charge within the range of the guarantee expressed in the sales
contract.
(3) Breakdown repairs
There will be a charge for breakdown repairs, replacements and on-site visits
for the following seven conditions. In those cases the cost shall be your own
expense even though the product is within the warranty period.
①Breakdowns due to improper storage or handling, careless accident, software
or hardware design by the customer.
②Breakdowns due to modifications of the product without consent of the
manufacturer.
③Breakdowns due to maintenance of the product without authentic parts or
breakdowns resulting from using the product outside the specified
specifications of the product.
④Breakdowns due to contamination or corrosion caused by user’s use
conditions.
⑤Breakdowns due to natural disasters (such as fire, earthquake, flood,
lightning, salt damage, and so on) , environmental pollution, irregular voltage,
and /or usage of undesignated power source.
⑥Breakdowns that are outside the terms of warranty.
⑦Consumables and/or replacement service.
Since the above services are limited to within Japan, diagnosis of failures, etc are
not performed abroad. If you desire the after service abroad, please contact
ULVAC CRYOGENICS and consult us for details in advance.
2.2 Exclusion of opportunity loss from warranty liability
Regardless of the gratis warranty term, compensation to opportunity losses
incurred to your company or your customers by failures of ULVAC CRYOGENICS
products and compensation for damages to products other than ULVAC
CRYOGENICS products and other services are not covered under warranty.

MZ0F001E,2013OR03 ULVAC CRYOGENICS INCORPORATED F-3
2.3 Repair period after production is discontinued
ULVAC CRYOGENICS shall accept product repairs for seven years after
production of the product is discontinued.
3. Service Form
After the products are delivered, please fill out the following information in the
blanks. If you have any questions or technical problems, please feel free to contact
the nearest Customer Support Center or headquarters. Please refer to “Service
Network”.
Cryopump／Super trap Model ：
Cryopump／Super trap Serial No. ：
Refrigerator Model ：
Refrigerator Serial No. ：
Compressor Model ：
Compressor Serial No. ：
Temperature controller／Thermal display Model ：
Temperature controller／Thermal display Serial No. ：
Option Part Model ：
Optional Part Serial No. ：
4. Notes for repair and maintenance requests
We may decline your request for the repair or the maintenance of our products if
you refuse to give us information about the presence of the hazardous substance
and/or contaminant.
Also, please be aware that we do not accept liability for damages by the
contaminant, which might be caused during transportation to our office or the
nearest customer support center. To avoid such accident, please pay careful
attention to packing of the product
5．In case of breakdown and accident
When breakdown or accident occurs, we may ask for keeping the product on site
as it is or retrieving the product to investigate its cause. Also we may ask for
reporting the detailed process and/or the operating condition. When unidentified
malfunction was generated, please contact our Service Engineering Division or

F-4 ULVAC CRYOGENICS INCORPORATED
the nearest customer support center with reference to the chapter of Service
Network. We ask for cooperation about the above.
6．General Precautions
(1) It is strictly prohibited to duplicate, open, and transfer this instruction
manual or any of its parts to a third person without written permission from
ULVAC CRYOGENICS.
(2) Information in this document might be revised without a previous notice for
the specification change and the improvement of the product.
(3) If you have any questions or comments on this document, please do not
hesitate to contact us. The phone numbers of local customer support centers
are listed at the end of this manual.

MZ0F001E,2013OR03 ULVAC CRYOGENICS INCORPORATED F-5
Safety Considerations
Our products have been designed to provide extremely safe and dependable operation
when properly used. Following safety precautions must be observed during normal
operation and when servicing them.
CAUTION
WARNING
A warning describes safety hazards or unsafe practices
which could result in severe injury or loss of life.
Acaution describes safety hazards or unsafe practices which
could result in personal injury or equipment damage.
Toxic gas or chemicals used.
There is a risk of severe injury upon contact.
Corrosive chemicals used.
There is a risk of severe injury upon contact.
Flammable gas used.
There is a danger of fire or burn injury.
Explosive gas used.
There is a risk of fire or explosion.
Hazardous voltage .
Electric shock may cause severe injury or loss of life.
Hot heating part present.
There is a risk of burn injury.

F-6 ULVAC CRYOGENICS INCORPORATED
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4K Cryocooler Instruction Manual
ULVAC CRYOGENICS INCORPORATED I
Table of Contents
Safety Instructions...............................................................................................................S-1
Disposal Considerations....................................................................................................IW-1
1. INTRODUCTION..........................................................................................................1-1
1.1. General .................................................................................................................1-1
1.2. Specifications........................................................................................................1-3
1.3. Vacuum Chamber Specifications..........................................................................1-4
1.4. Regulations applicable (Cryocooler).....................................................................1-5
2. INSPECTION ...............................................................................................................2-1
2.1. Shipping List..........................................................................................................2-1
2.2. First Inspection of 4K Cryocooler..........................................................................2-2
3. INSTALLATION ...........................................................................................................3-1
3.1. Auxiliary Equipments Required.............................................................................3-1
3.2. Mounting the 4K Cryocooler to the Vacuum Chamber.........................................3-3
3.3. Connecting Roughing Pump.................................................................................3-4
3.4. Connecting Cooling Water Pipe............................................................................3-4
3.5. Connecting 4K Cryocooler to Compressor Unit (Connecting Flexible Hose) ...... 3-4
3.6. Connecting Remote Wiring...................................................................................3-5
3.7. Connecting Electrical Cables................................................................................3-5
4. OPERATION ................................................................................................................4-1
4.1. Prior to Startup......................................................................................................4-1
4.2. Mounting Samples (load)......................................................................................4-1
4.3. Rough Pumping....................................................................................................4-1
4.4. Startup and Cooldown...........................................................................................4-2
4.5. Normal Operation..................................................................................................4-2
4.6. Shutdown Procedures...........................................................................................4-3
4.7. Handling of Hazardous Materials..........................................................................4-4

Troubleshooting
II ULVAC CRYOGENICS INCORPORATED
5. Disconnection and Storage.......................................................................................5-1
5.1. Disconnecting Flexible Hose ................................................................................5-1
5.2. Storage..................................................................................................................5-2
6. MAINTENANCE...........................................................................................................6-1
6.1. Scheduled and Unscheduled Maintenance..........................................................6-1
6.2. Charging Helium Gas............................................................................................6-2
APPENDICES
A. Troubleshooting............................................................................................................A-1
B. Flexible Hose.................................................................................................................B-1
C. Principles of Refrigerator Operation ..........................................................................C-1
D. Dimensional Drawing...................................................................................................D-1
E. Self-Certification ...........................................................................................................E-1
SERVICE NETWORK.............................................................................................................CS-1

4K Cryocooler Instruction Manual
ULVAC CRYOGENICS INCORPORATED III
Figures
Figure 1-1 Typical Diagram of 4K Cryocooler System ............................................ 1-2
Figure 3-1 Recommended Mounting Flange for UHE10F,UHE12F and UHE15F.. 3-1
Figure 3-2 Maintenance Space for UHE10F, UHE12F and UHE15F...................... 3-3
Figure 3-3 Connecting helium flexible hoses correctly............................................3-6
Figure 3-4 Flexible hoses connection order............................................................3-7
Figure 3-5 Using two spanners to connect / disconnect flexible hoses .................. 3-8
Figure 5-1 Disconnecting Flexible Hose..................................................................5-1
Figure 6-1 Charging helium gas ..............................................................................6-3
Figure C-1 Principle of Refrigeration ......................................................................C-1
Figure C-2 Principle of G-M Crycle Operation.........................................................C-4
Figure C-2 Two-stage Refrigerator...........................................................................C-4
Figure D-1 External Drawing UHE10F.....................................................................D-2
Figure D-2 External Drawing UHE12F.....................................................................D-3
Figure D-3 External Drawing UHE15F.....................................................................D-4
Tables
Table 1-1 4K Cryocooler System Standard Composition....................................... 1-3
Table 1-2 4K Cryocooler Standard Capacity.......................................................... 1-3
Table 1-3 4K Cryocooler Composition Standard Specifications.............................1-4
Table 2-1 Shipping List for 4K Cryocooler System ................................................2-1
Table 2-2 Shipping List for 4K Cryocooler..............................................................2-1
Table 6-1 Maintenance Intervals............................................................................ 6-2
Table A-1 Fault Diagnosis.......................................................................................A-1

Troubleshooting
IV ULVAC CRYOGENICS INCORPORATED
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4K Cryocooler Instruction Manual
ULVAC CRYOGENICS INCORPORATED S-1
Safety Instructions
This chapter describes safety information for the customer when using our cryocooler.
Before designing cryostat or other systems incorporating our cryocooler, or before
using the cryocooler, read this section carefully for using the product safely.
When using a cryogenic device such as a cryostat, heat transfer by gases is blocked
normally by making the surrounding area of the cooling section vacuum. Customers are
requested to supply a vacuum chamber around the cooling section (coldhead).
If gas is introduced into the vacuum chamber during the operation of the cryocooler, the
gas is condensed and accumulated in the low-temperature section of the cryocooler. When
the cryocooler is suspended operation, the gas condensed in the low-temperature section
finally returns to the room-temperature gas as the cryocooler warms up. Accordingly, the
pressure in the vacuum chamber increases. Positive pressure (pressure greater than
atmospheric pressure) may be created in the vacuum chamber depending on the volume
of the condensed gas. If it occurs, there is a potential risk of burst and shattering of a
vacuum gauge attached on the vacuum chamber or a glass window for observation.
Be sure to attach an appropriate pressure relief valve to the vacuum chamber so that the
pressure can be released immediately even in case the pressure of the vacuum chamber
becomes positive (Figure 1).
☆
When flammable, explosive, combustion enhancing, toxic, or corrosive gas is
pumped, connect a dedicated duct on the exhaust side of the pressure relief
valve to prevent gas leak from the pressure relief valve to indoor
circumference while the Cryocooler is suspended. (Refer to “5. Shutdown and
warm up cryocooler after pumping flammable, explosive, or combustion
enhancing gas.”)
1. Pressure relief valve must be attached to the
cryostat and other cryogenic devices.
Cryocooler
Vacuum pump
Pressure relief valve
Roughing valve
Vacuum chamber
Cylinder
Figure 1 Attaching a pressure relief valve to the vacuum chamber

Safety Instructions
S-2 ULVAC CRYOGENICS INCORPORATED
Some gases would be secondarily generated in vacuum processes. They might
contain flammable gas, explosive gas, toxic gas, or combustion enhancing gas.
For example, moisture in vacuum chamber, which comes from the atmosphere or the
substrate, dissociates into hydrogen and oxygen in plasma. Those gases may be also
discharged in large amounts from some evaporants or sputtering targets. Oxygen is one
of the gases which increase the susceptibility to burn, and hydrogen is flammable
and explosive. At atmospheric pressure, the mixed gas of hydrogen of 4% or more and
oxygen of 5% or more are sure to cause the explosion momentarily if there is a cause (refer
to “3.When flammable or explosive gases pumped”).
In addition, ozone might be secondarily generated when oxygen (O2 )or carbon dioxide
(CO2 ) is resolved in plasma. Ozone is toxic gas，and moreover liquid ozone might explode
by the reaction with organic substances or any impact when it is in high concentration.
Therefore, it is necessary to check the safety of the secondarily generated gas as well as
that of process gases.
For handling flammable or explosive gases, refer to “3.When pimping flammable or
explosive gases”and“4.When pumping oxygen” in this chapter. Implement safety
precaution and preventive maintenance as necessary.
For handling toxic gases, specific safety measures to the gases are sometimes required
in addition to the safety measures for flammable or explosive gases, for example, purge of
pump or dilution of exhaust duct with inert gases.
The customers are requested to take appropriate safety measures for managing the
cryocooler operation in a safe manner appropriate for the system hardware or
processes.
2. Check the safety of secondary-
generated gases in process

4K Cryocooler Instruction Manual
ULVAC CRYOGENICS INCORPORATED S-3
Table 1 Combustion range and detonation range of major gases
(Volume percentage against air)
Gas
Molecular
Weight
Specific
Gravity
0
℃
, 1atm
Boiling
Point
K
Combustion
Range
Vol. %
Detonation
Range
Vol. %
Hydrogen
Carbon
Monoxide
Hydrogen
Sulfide
Silane*
Arsine*
Phosphine*
Diborane*
Ammonium
Methane
Ethane
Propane
Etylene
Acetylene
H
2
CO
H2S
SiH4
AsH3
PH3
B2H6
NH3
CH4
C2H6
C3H8
C2H4
C2H2
2.016
28.01
34.08
32.14
77.94
34.00
27.67
17.03
16.04
30.07
44.10
28.05
26.04
0.070
0.970
1.190
1.107
2.692
1.146
0.955
0.590
0.555
1.040
1.550
0.978
0.907
20.3
81.7
213.6
161.2
210.7
185.5
180.7
239.8
111.6
184.6
231.1
169.5
198.2
4.0-75.0
12.5-74.0
4.3-45.0
0.8-98
0.8-98
1.3-98
0.8-98
15-28
5.3-14
3.0-12.5
2.2-9.5
3.1-32
2.5-100
18.3- 59
4.2- 50
(*): Hikaru Harada; "Handotai-gas Anzen-ka Souran 1st Edition" (The 1st edition of
Semiconductor gas safing comprehensive manual) published by Science Forum Inc.
1984Except (*): The high pressure gas safety institute of Japan; "Koatsu-gas Kogyo Gijyutu"
(High pressure gas industrial technology) published by Kyoritsu Shuppan Co., Ltd. 1977
Table 2 Combustion range and detonation range of
mixture of oxygen and inflammable gas
Gas
Combustion Range
(Vol. %)
Detonation Range
(Vol. %)
Hydrogen
Acetylene
Methane
Propane
Carbon Monoxide
Ammonium
4- 94
2.3 - 94.5
5.1 - 61
2.3 - 55
15.5 - 94
15 - 79
15 - 90
3.5 - 93
-
3.7 - 37
38 - 90
25.4 - 75
The high pressure gas safety institute of Japan; "Koatsu-gas Kogyo Gijyutu"
(High pressure gas industrial technology) published by Kyoritsu Shuppan Co., Ltd. 1977

Safety Instructions
S-4 ULVAC CRYOGENICS INCORPORATED
When flammable or explosive gas is pumped with the cryocooler, it must be
done safely from the vacuum chamber while the cryocooler is suspended. Be
sure to take the following safety measures.
(1). Control and manage the process condition, the time period and method of
regeneration in order to keep the concentration of the hazardous gases
discharged to the exhaust duct below the allowable level.
(2). Eliminate ignition factors completely from the vacuum chamber and ducts.
(3). Make sure that the safety measures mentioned above to be conducted in
case of abnormal events.
Possible causes of ignition in the vacuum chamber are as follows;
Ignition by a vacuum gauge filament being turned on
Ignition by a heater with heating element(s) exposed into the process
circumstance or the like
Ignition by static electricity
Ignition by liquid ozone
If a roughing pipe or exhaust line is made of plastic such as vinyl chloride, static electricity
is likely to be generated.
Ozone is occasionally generated under the process utilizing plasma with oxygen or COX
gas. Captured and condensed ozone in the vacuum chamber liquefies in the warm-up
process of regeneration. Note that liquid ozone is regarded as so unstable that it might
explode by impact or ignition resulting from the reaction with organic matter.
When pumping flammable or explosive gas(es), appropriate safety precaution must be
taken with reference to “5. Stop and warm up cryocooler after pumping flammable,
explosive, or combustion enhancing gas”.
It is very dangerous to mix oxygen and flammable gases.
Oxygen is the gas that enhances combustion. Use the Cryocooler after
confirming the safety precautions or measures when pumping the mixture of
oxygen and flammable gas. In particular, the mixture of oxygen and hydrogen,
which has a broad range of combustion/detonation, is extremely dangerous.
3. When pumping flammable or
explosive gases
4. When pumping oxygen

4K Cryocooler Instruction Manual
ULVAC CRYOGENICS INCORPORATED S-5
The mixes gas with hydrogen of 4% or more and oxygen of 5% or more at atmospheric
pressure could cause explosion momentarily (refer to “3.When flammable or explosive gases
pumped”).
Therefore, when oxygen is used as a process gas the appropriate safety precautions must be
taken with reference to “5. Stop and warm up cryocooler after pumping flammable,
explosive , or combustion enhancing gas”.
Oxygen may generate ozone.
Ozone may be unknowingly generated in plasma production process (e.g.,
sputtering, etching, glow discharge, EB deposition).
Captured and solidified ozone in the vacumm chamber liquefies in the warm-up process of
regeneration. The liquid ozone at high concentrations might explode by impact or ignition
by the reaction with organic matter.
In case that a remarkable amount of ozone is generated in the process and accumulated in
the Cryocooler, the following phenomena could be occurred around the Cryocooler at the
initial stage of regeneration:
1) Cracking/popping sounds (as in electrical arching) occurring within the first few
minutes of regeneration.
2) Gases exhausted from vacuum chamber during regeneration has a pungent odor,
similar to that produced in arc welding operation.
A large volume of ozone causes an intense explosion, and is very dangerous.
In case of pumping ozone by the cryocooler, following safety measures must be taken.
1. Make sure that the amount of captured of ozone in the vacuum chamber is below an
allowable level by increasing the frequency of regeneration. A required regeneration
cycle differs depending on the flow rate of oxygen and other process conditions.
2. Reduce the flow rate of oxygen to the minimum as far as it does not influence the
process performance.
3. Reconfirm the safety required if the process condition is changed, as it might
increase ozone generation.
When using oxygen as a process gas, appropriate safety precaution and measures must
be taken with reference to “5. Stop and warm up Cryocooler after pumping flammable,
explosive, or combustion enhancing gas”.

Safety Instructions
S-6 ULVAC CRYOGENICS INCORPORATED
When pumping flammable, explosive, or combustion enhancing gas, those
gases must be safely vaporized again and exhausted. Following safety
measures on the method of stop and warm up method are extremely
important for operating Cryocooler safely. Please take proper safety
measures on both hardware and process software. Also, be aware that there
is a risk that some hazardous gas would be secondarily produced in the
vacuum chamber as a result of plasma reaction or the like.
1. Safety measures for normal shutdown and warm up
Following are the safety measures which customers are requested to take in the
regeneration process after pumping flammable, explosive, or combustion enhancing
gas. Refer to figure 2 and take necessary measures. In addition, you may have to
take additional safety measures depending on the kind of the gas used, the process
conditions, or the environment used.
1) Both the purge of the cryopump and the dilution of the exhaust duct with inert
gas are required to reduce the concentration of flammable gas or explosive gas
and keep it under a certain level where the gas does not burn or explode even
when it evaporates when the Cryocooler has been stopped or during warm-up
time. For inert gas use nitrogen gas that its dew point temperature is -40ºC or
below or argon. (In this instruction manual, the terms “inert gas” or “dry nitrogen
or argon” mean “nitrogen gas that its dew point temperature is -40 ºC or below
or argon”.)
Please determine the purge flow rate, the dilution flow rate, and shutdown and
warm up cycle (which depends on the pumping capacity of flammable gas) and
take appropriate safety measures before operation.
2) Eliminate ignition factor. Make sure that there are no sources of ignition (refer to
“3. When pumping flammable or explosive gases”) while the cryocooler is
suspended or being warmed up.
3) Be sure to use metallic pipes for the roughing system and exhaust lines in order
to prevent generation of static electricity. Ground the pipes with the grounding
resistance of 100 Ωor less.
5. Shutdown and warm up the cryocooler after
pumping flammable, explosive, or
combustion enhancing gases

4K Cryocooler Instruction Manual
ULVAC CRYOGENICS INCORPORATED S-7
Figure 2 Dilution of oxygen/inflammable gas
4) In case that the gas to be exhausted is hazardous and lighter than the dilution
gas (such as hydrogen gas), design and install the exhaust pipes so that its
lighter gas should not be accumulated in the pipes.
5) Perform inert gas purge into the exhaust line in order to reduce the flammable
gas concentration below its combustion range before exhausting them away to
atmosphere.
6) Perform inert gas purge as the stop and warm up start.
7) Assuming the pressure relief valve would work, connect the pressure relief
valve to the exhaust line in order to dilute the gases which might spout out from
the valve.
8) Be sure not to rough pump the vacuum chamber without inspecting the state of
the chamber just after power failure. Reduce the concentration of hazardous
gases in the chamber and exhaust line by adding inert gas before rough
pumping. It helps to exhaust the vaporized gas safely out of the chamber in
case power failure occurred.
9) When adopting a oil-sealed rotary pump as a roughing pump, change
lubricating oils with Fomblin grease which is insensitive to oxygen. Instead, a
drypump will be fully recommended.
2. Safety measures in emergency
If the cryocooler stops due to an abnormal event such as power or water supply
failure or compressed air shutoff, pumped gas evaporates and fills the vacuum
chamber as the temperature of the Cryocooler rises. The chamber filled with high
concentration of flammable, explosive, or combustion enhancing gas may
Cryocooler
Vacuum pump
Pressure relief valve
(Opens at an atmospheric
pressure or more)
Roughing valve
Vacuum chamber
Exhaust line
Use metallic pipe and
grounding
≦
100
Ω
Purge with inert gas
(such as N2)
Inert gas for dilution
(such as N2)
Outside
Exhaust valve
(Opens at atmospheric
pressure)
Pressure gauge
(other than filament type)

Safety Instructions
S-8 ULVAC CRYOGENICS INCORPORATED
immediately cause an explosion or high-temperature combustion by any ignition
factor (refer to “3. When pumping flammable or explosive gases”). To prevent these
hazards, install UPS, and make sure that inert gas purge into the vacuum chamber
and dilution in the exhaust duct described in the previous item 1. can be performed
even in case of an abnormal event.
UPS (Uninterruptible Power Supply system) installation
In case that the Cryocooler stops because of blackout etc, hydrogen explosion or
high-temperature combustion which may occur if high concentration of O2 or H2 is filled
up in the chamber with some source(s) of ignition such as O3.
UPS is necessary to prevent those hazards.
Toxic or corrosive gases must be appropriately detoxified or made inert before they are
exhausted outdoors from the duct. Ask the safety manager for appropriate instructions.
Major components of the cryocooler cylinders are stainless steel and copper.
Special precautions must be taken when pumping corrosive gas which may be
produced by plasma reaction, sputtering, etc. in chamber, and corrodes cylinder
materials.
For maximizing performance of the Cryocooler, the stainless steel cylinder thickness is very
thin. During normal operation, the pressure of helium gas in the Cryocooler is
approximately 2 - 2.5 MPaG and if the corrosion develops, the cylinder may rupture at
weak portion.
☆If the cryocooler is used to pump corrosive gases, periodic pressure proof test is
recommended.
☆ULVAC CRYOGENICS INC. conducts the pressure proof test of cylinders by applying
gas pressure of 1.5 times as high as the normal operating pressure.
6. When pumping toxic and
corrosive gases
7. Rupture of cylinder by corrosion