www.cranecpe.com
2
NOZ-CHEK
®Cryogenic
Installation, Operation & Maintenance
1.0
INTRODUCTION AND BACKGROUND
1.1 HIGH PERFORMANCE NON-SLAM CHECK VALVE
Crane Stockham Valve has been an innovative leader
in non-return valve design since 1960. The design of
modern compression and pumping installation and
certain other process applications have a requirement for
low pressure drop, rapid response, non-slam check valves.
The Noz-Chek® product is the result of a two year project
undertaken by Crane Stockham Valve Engineers in
conjunction with Queen’s University, Belfast. During this
development many hydrodynamic flow and surge tests
were performed at their flow laboratory.
Final testing was successfully conducted in the hydraulic
machinery laboratory of the Industrial Technology
Division of Delft Hydraulics, at Delft Netherlands.
The product of this development is a precision non-return
valve which can be placed in critical locations to ensure
predictable, non-slam closing times in applications where
extremely quick flow reversal is anticipated.
The Noz-Chek® valve range has been designed to meet
ASME B16.34 and API 6D specifications. The Crane
Stockham Valve manufacturing facility in the UK is
approved to ISO 9001, and the Pressure Equipment
Directive 2014/68/EU.
The Noz-Chek® is a high performance non-return check
valve offering four major benefits for critical service
applications:-
•
Minimises water hammer in liquid service.
•
Removal of chatter associated with conventional
valves in reciprocating compressor service.
•
Protects rotating equipment from damage due to
flow reversal.
•
Minimises the pressure loss in the piping.
It optimises the performance between low pressure loss
and quick dynamic response, keeping the reverse velocity
to a minimum.
Further development and testing of the valve, including
updating to state of the art machining techniques and
refined material selection, means the Noz-Chek® now fully
complies with BS 6364 cryogenic leak rates.
1.2 CRYO NOZ-CHEK ® FEATURES
Cryogenic Service
The Cryo Noz-Chek® valve is capable of achieving reduced
leak rates of less than 300cc/min/inch at -196°C which
fully complies with BS6364 and ISO 28921-1.
Low Pressure Loss
Axial movement of the valve disc allows an ideal
streamlined flow path. The valve geometry creates a
controlled reduction in flow area, resulting in an increased
flow velocity through the valve. The venturi effect allows
maximum valve capacity and minimises pressure loss.
Long Valve Life
The Crane Stockham Valve Noz-Chek® is a simple,
compact, reliable, well engineered valve. The only moving
part is the disc, which has a stem, positively guided
through a low friction bearing. Noz-Chek II ® components
are designed to have a long quiet and dependable life.
Non-Slam Characteristics
Flow velocity into the valve inlet causes the disc to move
axially and compresses the valve spring. The valve is fully
opened when the inlet velocity has reached the critical
velocity. The valve is designed to be in the fully open
position with the smallest possible axial movement.
When inlet velocity is reduced below critical velocity the
compressed spring initiates valve disc closure.
The short stroke, spring assisted disc design minimises
valve slam and water hammer.
Spring Options
The Crane Stockham Valve Noz-Chek® is available with
different strength springs. The choice of different
springs effects critical velocity and valve response. Crane
Stockham Valve engineers review each application
and make the correct spring selection for each specific
application.