A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A
Adapter
A type of fitting which provides a method of joining two components of
differing thread types or systems.
Analytical column
A long narrow tube packed or coated with one of many available chemically diverse
compounds that can separate the components in a sample according to their boiling point,
polarity, molecular size, or combination thereof. A column of some kind is used with most
chromatographic techniques.
B
Backflush
The use of valving to reverse the flow through a column in order to "backflush" or purge
heavier components from the column.
See application demonstrating backflush.
Biocompatibility
Defines the materials used in a system (i.e. fittings, tubing, and valves) that do not change
the bioactivity of the biological substances that come into contact with the surface of these
materials. Note that in chromatographic systems, the tubing and column contribute over 99%
of the surface area and the valves and fittings are insignificant.
Bore
The diameter of the minimum orifice through the fitting.
See definitions for
capillary bore,
through-type bore, and
large bore.
Bulkhead fitting
A type of fitting in which the fitting body is inserted through an instrument panel or mounting
bracket, to which it is affixed with a mounting nut. The Valco fitting body is uniquely
undercut so that it "bites" into the panel when the mounting nut is tightened, eliminating the
need for a lock washer.
Butt connection
A type of connection in which the two tube ends are directly and squarely in
contact, usually effected with a through-type union. Typically used with fused
silica connections, or small bore metal tubing.
C
Cap
A cap is used to dead-end a piece of tubing with a nut and ferrule attached.
Ref: Valco metal caps;
Cheminert 1/4-28 caps.
Capillary bore
The smallest available standard orifice in a given fitting design
(usually 0.25 mm). Typically denoted by suffix "C" in the product number.
Clamp ring
Adjustable ring for clamping the valve or standoff assembly onto an actuator,
knob, or instrument panel.
Closemount hardware
All the hardware required to mount a valve directly onto the fac of an air, standard
electric, or microelectric actuator, providing the most direct, shortest
attachment of valve to actuator.
Ref: Closemount hardware for manual valves and
actuators.
Compression fitting
A style of fitting in which a threaded nut compresses a tapered ferrule onto tubing as the
nut is tightened. Valco metal ferrules cut a ring into the tubing wall while polymer types rely
on surface compression to form a seal.
Connecting volume
The volume between two or more connections. This may be cleanly swept, thus not
contributing to peak distortion, or may be "dead volume" such as that found in fittings with
larger bores than the connecting tubing.
Cross
A type of distribution fitting which connects four pieces of tubing, arranging
them in the pattern of a cross.
Ref: Valco standard and
microvolume crosses;
Cheminert high pressure and
1/4-28 low pressure crosses.
D
Dead volume
Any volume which a component introduces to a system that is not cleanly swept and relies on
diffusion to clear the space. See connecting volume.
Detail
See fitting detail.
Distribution fitting
A generic term for tees, crosses, and manifolds, used to provide multiple access points to
"distribute" a gas or liquid through a system. CAUTION! Using a distribution fitting in
reverse to coalesce multiple streams may create dead volume. Special manifolds are
available for this application.
E
External fitting
A type of compression fitting in which the fitting body has male threads; an external nut has
female threads.
F
FIA
Flow Injection Analysis.
A simple and versatile analytical technique for automating wet
chemical analyses based on the manipulation of a sample zone formed from the injection of
the sample into a continuous stream of fluid used as a carrier. For more information, view
a tutorial
by our friends at Global FIA.
Ferrule
One of the components of a compression fitting; the conical piece of metal or plastic that
compresses onto the tube as it is forced into a tapered seat. Valco metal ferrules are
unique in that they attach to and seal at the tube by cutting a shallow ring into it, instead of
by actually swaging it. This is preferable since it introduces no flow restriction.
Filter
A type of union or reducing union which traps the particulates in a stream. The filtering
element is typically a mesh screen or sintered frit.
Ref:
Valco filters;
Cheminert mobile phase,
biocompatible, and
in-line filters.
Fitting detail
One of the components of a compression fitting; if the tube, nut, and ferrule comprise the
male part of the fitting, the fitting detail is the female part. It includes the threads for the
nut, the tapered ferrule seat, and the pilot.
Flanged fitting
A type of fitting used with fluoropolymer tubing (PTFE, FEP) in which a flange is made at the
tube end. Connections are made at the flange either by compressing the flange into a flat
detail (typically 1/4-28 threaded) or by butting two flanges together. A special flanging tool
forms the flanges.
Ref:
Cheminert 1/14-28 flanged fittings.
Flangeless fitting
Similar in application to the flanged fitting, but the flange is not required. A ferrule system
is used which grips/compresses the tube. This fitting type can be used with virtually any
polymeric tubing since the tube end does not have to be formed, but simply square cut.
Typically used in 1/4-28 threaded fittings, it is usually interchangeable with flanged
fittings.
Ref:
Cheminert 1/14-28 flangeless fittings.
Frit
A filter element typically made of stainless, Hastelloy, Titanium, or polymers, usually 0.75 mm
or 1 mm thick. Nanovolume frits, at 0.25 mm (.010") thick, add minimum volume for
nanovolume filtration.
Frits may provide better filtration than screens, but because they are thicker
there is greater mixing potential, and they typically result in increased pressure drop.
Ref:
Valco frits for filters,
frits for column end fittings, and
frits for nanovolume fittings.
G
GC
Gas Chromatography.
An analytical method incorporating an injection system, analytical column, controlled
temperature zone, and detector. An inert carrier gas moves the sample through the column,
which separates the sample components into discrete bands which are measured as they pass
through the detector.
Guard column
A column used in series between the injector and analytical column to prevent certain types
of components from entering the analytical column.
Ref:
Valco pre-columns.
H
HPLC
High Performance Liquid Chromatography.
An analytical system consisting of an injector, pump, analytical column, and detector. Using a
liquid mobile phase, the sample is pumped through the column, where it is separated into
discrete sample component bands which are detected and measured as the bands elute from
the column.
I
ID
Internal diameter.
Inert
Technically, unreactive with other substances; however, in the instrumentation field, "inert"
is a relative term. Often polymers are termed inert but are soluble in some fluids and can
react with some compounds.
Internal fitting
A type of compression fitting in which the fitting body has female threads; an internal nut
has male threads.
K
Keyed
The design which enables multiposition microelectric actuators to self-align.
A specially designed clamp ring and standoff assembly key together with the
microelectric actuator and the valve to locate position 1.
L
LC
Liquid Chromatography.
Any of a variety of low to medium pressure techniques
which use a liquid mobile phase as the carrier to move sample.
Similar to HPLC .
Large bore
A bore that is larger than the standard for a given fitting; a fitting ordered with a large
bore will have a larger flow orifice than the standard or capillary bore fitting of the same
design. Denoted by suffix "L" in the product number.
Luer adapter
An adapter that connects a tapered luer fitting (square nib) of a syringe to a tube
or tube fitting.
Ref:
Valco female luer adapters;
Cheminert 1/4-28 luer adapters and
luer adapter bulkhead unions.
M
Make up
The point at which a ferrule, nut, and tube are assembled in the fashion which will effect a
leak-free seal. In most compression fittings, that is accomplished by compressing the tube
with the small end of the ferrule. With Valco metal ferrules, the ferrule usually makes up
on the tube by cutting a shallow ring in it.
Manifold
A type of distribution fitting in which a single source is directed to
multiple outlets, or vice
versa. Caution! Using a common distribution fitting in reverse
to merge multiple
streams may create dead volume. Special manifolds are available
for this application.
Ref:
Valco 1/16" and 1/8" manifolds;
Cheminert manifolds.
Microbore column
A liquid chromatography column of narrow bore (typically 2 mm or less) for improved
resolution.
N
NPT
National Pipe Thread; a standardized tapered pipe fitting.
See pipe thread.
Nanobore
Nanobore generally refers to components with bore sizes less than 250 µm (0.010").
Nanovolume®
The registered trademark referring to VICI Valco's line of nanobore
fittings and injectors.
Nut
The tensioning component of a compression fitting. As the threaded nut is
tightened into the fitting detail, it pushes the ferrule forward into the
tapered ferrule seat, causing it to make up on the tube.
Ref:
Valco stainless internal or
stainless external nuts;
and
high pressure PEEK internal nuts
(For Cheminert low pressure nuts, see flanged and
flangeless fittings.)
O
OD
Outside diameter.
P
Pilot
The tubing which extends beyond the ferrule in a made-up fitting,
or the integral portion of a ZRF internal reducing ferrule which extends
beyond the ferrule. See also pilot depth, below.
Pilot depth
The length of the tubing diameter cavity beyond the tapered ferrule
seat within a fitting detail. Valco fitting pilot depths are tightly
controlled to facilitate the interchangeability of
components without the risk of leaks or dead volume.
Pipe thread
The external or internal threads of a fitting designed to effect a metal-to-metal seal on the
conical thread faces. This type of fitting does not "bottom out" in the detail. Typically used
with Teflon tape or other compound to lubricate the threads; however, since the diffusion
rate of air components through the Teflon tape is considerable, pipe fittings should not be
used in systems where leakage rates are critical.
Port
The connection, orifice, seal, or septum, etc. through which sample may be added
(injected) or withdrawn.
Position feedback
Hardware which provides a contact closure for the remote start of a chromatograph
or data system.
Ref: Position feedback for manual injectors and
air actuators.
R
Reducing ferrule
A ferrule which allows a smaller tube to be used in a fitting detail designed for a
larger tube. Caution should be taken if standard reducing ferrules (RF) without integral
pilots are used, since dead volume may be created in the fitting pilot depth.
Reducing union
A fitting which joins two tubes of different ODs.
The bore of the fitting should typically match the ID of the smaller tube.
Ref:
Valco reducing unions;
Cheminert
high pressure PEEK,
1/6" internal to 1/32" external, and
1/8" to 1/4" (1/4-28 to 1/2-20)
reducing unions.
Rotor
The internal rotating part of a Valco or Cheminert valve. It contains the engraved slots
which connect the ports on the stator or cap.
S
SFE
Supercritical Fluid Extraction.
An extraction technique using a fluid in its supercritical state as the extraction medium.
Some liquids and mixtures maintained above a critical temperature and pressure exhibit
properties of both the liquid and gas phases of the element. These are defined as
supercritical. CO2 is a common supercritical fluid.
Extreme caution must be used with supercritical CO2,
since uncontrolled expansion (leaks) can be very hazardous due to the substantial stored
energy.
SFC
Supercritical Fluid Chromatography.
An analytical technique using a supercritical fluid (see SFE) as the mobile
phase/carrier.
Screen
A replaceable filter element generally made of Type 316 stainless steel,
usually 0.003" thick. Screens clog less frequently than frits, and because
they are thinner there is less mixing; however, they are less effective filters.
Ref:
Valco replacement screens for filters.
Sideloading
Any force on the valve rotor other than the proper rotational force along the axis of the
rotor, often resulting in leakage or increased wear. It is typically caused by actuation
misalignment, over-rotation, or improper mounting of the valve.
Standard bore
A bore which was chosen as the standard for a particular fitting, typically
based on the most common tubing ID used with that fitting.
Standoff
An extension between a valve and actuator which allows the valve to be installed in a
different temperature zone from the actuator. Standoffs come in several different
lengths.
Standoff assembly
All the hardware required to allow a valve to be mounted in an oven or heated
zone while the actuator or knob remains outside the heated zone. Standard lengths
are 2", 3", 4", and 6".
Ref: Standoff assemblies for actuators and manual actuation.
Standoff mounting hardware
The clamp ring and screws necessary to mount a valve and standoff assembly
onto an actuator.
Stator
The stationary component of a valve. Typically, it contains the fittings as
well as one of the fluid sealing surfaces. In Valco valves, the stator is
called the valve body.
T
Tee
A type of distribution fitting which connects three pieces of tubing, arranging
them in the pattern of a "T".
Ref:
Valco tees;
Cheminert Nanovolume® tees with
360 µm PEEK fittings or
1/32" fittings; and Cheminert
high pressure PEEK tees and
1/4-28 low pressure tees.
Through-type bore
A bore which is slightly larger than the OD of the tubing which is used with the given fitting.
A union with a through-type bore allows the tube ends to butt directly together, or for one
tube to run completely through the fitting. Denoted by suffix "T" in the product number.
In order to assure correct pilot lengths, we recommend that ferrules be made up on the
tubing in a standard union.
U
Union
A fitting for connecting two pieces of tubing of the same OD.
Ref:
See Valco unions.
We make a wide variety of Cheminert unions:
Nanovolume® 360 µm,
Nanovolume® 1/32",
for fused silica,
high pressure PEEK, and
1/4-28 low pressure.
Unswept volume
The volume of any portion of a fitting which is in the flowpath but which is a different
diameter than the primary flow orifice through the tubing/fitting assembly, or any area not
directly swept by the fluid flow. This can also be known as "dead volume" if it is very poorly
swept.
V
VICI
VICI® is an acronym for Valco Instruments Company Inc.
VICI now defines multiple
companies which manufacture various products for the analytical industry.
W
Wetted surfaces
The surfaces which are contacted by the sample stream.
Y
Y ("Wye")
A type of distribution fitting which connects three pieces of tubing, arranging them in the
pattern of a "Y". Occasionally referred to as a "wye".
Ref:
Valco microvolume and
Nanovolume Y connectors.
Z
ZDV
Zero dead volume. See definition below.
Zero dead volume
Describes a connection which does not add volume to the system beyond what an extension
of tubing would in its place.
Zero volume
While often used interchangeably with zero dead volume, it ideally describes a fitting design
in which there is no internal volume, such as a through-type union designed to butt-fit two
pieces of tubing.
