Trace Moisture Gas Standards Generators

Trace concentration moisture is an extremely important parameter in gases used in a wide range of processes. But there is no absolute analytical method that can be used in all applications.

For most sensing methods, the response to moisture is affected by the background gas and most current methods are subject to “poisoning” by certain contaminants. Basically, all trace moisture sensing systems require calibration to external standards and they must be frequently challenged with standards to demonstrate continued accuracy.

The KIN-TEK Span Pac™ H₂O Instrument Series [brochure] provides an economical solution to every moisture calibration problem.

Span Pac H20 Instrument Series - Trace Moisture Gas Standards

H₂O concentration adjustable over 10:1 range with single oven; 100:1 with dual oven
High ppm to 0.1 ppm H₂O range
Welded models (W series) can go down to about 10 ppb H₂O
Industrial models have NEMA 4 cabinets and optional purge capability
Simple to operate

Click here to see our Trace Moisture Gas Standards models.

Overview
There are three special problems associated with trace moisture calibration:

At the lowest concentration levels, there is no real zero reference point for moisture. Standards prepared by simply adding water vapor to a dry gas actually have unknown uncertainty.
Water interacts readily with almost all materials, so changes in pressure or temperature can appear as transient concentration changes and may take a very long time to stabilize.
Water is pervasive in our atmosphere, so even the most accurate standard may be contaminaed in the delivery process.

The Span Pac™ H₂O systems work on a differential principal. Calibration is based on the change in analyzer response caused by the addition of a known water vapor concentration from a Trace Source™ H₂0 permeation tube to a flowing stream of background gas (which may also contain some moisture). This differential method overcomes the "no zero” problem, and the problem of the background gas affecting the response. Water vapor flow from the permeation tube is measured gravimetrically, and is traceable to NIST. This technique provides a close approximation to a primary standard, even in situations where primary standards are not available.

Special care in design, construction and choice of components minimizes errors due to atmospheric contamination and interactions with other materials in the system.

As listed below, several Span Pac™ H₂O models are offered to insure an economical solution to every moisture calibration problem.

Span Pac™ 61-H₂O and 261-H₂O (Single & Dual Oven Models)
These single and dual-oven instruments are the basic H₂O models. The 61-H₂O single-oven model can produce concentrations over a 10:1 range and from over 1000 ppm down to 0.1 ppm in nitrogen and other inert background gases. The dual-oven 261-H₂O model that can generate a concentration range of 100:1. An internal purge of dry gas is used to minimize contamination from atmospheric moisture in low concentration service.

Span Pac™ 61-W-H₂O and 261-W-H₂O (Welded Instruments)
The welded (W) single-oven instrument is used where the minimum concentration required is below 0.1 ppm (100 ppb). These systems are used for concentrations down to about 10 ppb in inert background gases. (The minimum concentration is actually set by the minimum practical permeation rate.) They feature all electropolished 361L seamless stainless steel tubing, orbitally-welded joints, VCR® connections at service access points and special components for high purity service.

Span Pac ™ 61-W-H₂O-SD (Welded with Secondary Dilution)
The welded single-oven instrument with secondary dilution (SD) is our most versatile moisture system. This instrument provides an internal secondary dilution step that allows addition of extremely low concentrations, production of a very wide concentration range (up to 20,000:1), and the production of variable concentrations in a fixed total flow.

Reactive Gases Model (Span Pac ™ 61-R-H₂O )
The reactive gases (R) model is used to produce moisture standards in reactive gases.

Industrial-grade Models (Span Pac 61-I-H20 and 261-I-H20)
Single and dual-oven industrial-grade (I) models are available in NEMA 4 cabinets for use in harsh, nonhazardous environments. These units contain all electropolished 316L seamless stainless steel tubing. Optional capabilities include X-purge for Class 1, Group C or D, Division I, or Z-purge for Class 1, Group C or D, Division II.