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D1066-18 – Standard Test Method Technical Guide
📐 Scope and Applicability of D1066-18
This standard, designated D1066-18, provides a comprehensive practice for the sampling of saturated and superheated steam. It is applicable to steam produced in fossil fired and nuclear boilers, or by any other process means that is at a pressure sufficiently above atmospheric to establish the flow of a representative sample. The practice also extends to steam at lower and subatmospheric pressures, for which specific means must be provided to ensure the sample remains representative. For specialized sampling equipment or methods of analysis, reference should be made to the Annual Book of ASTM Standards, Vols 11.01 and 11.02.
⚙️ Isokinetic Sampling Principles and Procedure
The fundamental requirement for accurate steam sampling is the principle of isokinetic sampling. As formally defined in the standard, this condition requires the sample entering the port (tip) of the sampling nozzle to have the same velocity vector (both speed and direction) as the main steam stream being sampled.
💡 Critical Concept: Isokinetic sampling ensures a representative sample of dissolved chemicals, solids, particles, chemicals absorbed on solid particles, and in the case of saturated and wet steam, water droplets are extracted from a process stream. Failure to maintain isokinetic conditions can lead to significant sampling bias.
Following the extraction, the sample must be delivered in a representative manner for analysis. This typically involves passing the steam through a sample cooler, defined as a small heat exchanger designed to provide cooling and condensing of the process sampling stream. Additional guidance on flow control and temperature control is found in Practice D5540.
📊 Key Specifications and Equipment
D1066-18 specifies several key components and references critical material standards for constructing a reliable steam sampling system. The definitions for terms used in this practice are provided in Terminology D1129, with specific terms for steam sampling clearly defined within D1066-18 itself.
| 🟦 Referenced Standard | 📐 Full Title | ⚡ Typical Application in Sampling |
|---|---|---|
| A269 | Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service | Sample lines and cooling coils in sample coolers. |
| A335/A335M | Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service | High-temperature steam sampling probes and primary piping. |
| 📏 Term | 📖 Definition from Standard |
|---|---|
| Saturated Steam | A vapor whose temperature corresponds to the boiling water temperature at the particular existing pressure. |
| Isokinetic Sampling | A condition where the sample entering the port of the sampling nozzle has the same velocity vector as the stream being sampled. |
| Sample Cooler | A small heat exchanger designed to provide cooling/condensing of process sampling streams of water or steam. |
| Standard Unit System | SI units are regarded as the standard. Inch-pound units are mathematical conversions for information only. |
⚡ Regulatory Context: Since the 1949 adoption, D1066-18 has been approved for use by agencies of the U.S. Department of Defense. The standard adheres to internationally recognized principles on standardization established by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
❓ Frequently Asked Questions
🔍 What is the definition of Isokinetic Sampling according to D1066-18?
Isokinetic sampling is defined as a condition wherein the sample entering the port (tip) of the sampling nozzle has the same velocity vector (velocity and direction) as the stream being sampled. This is essential for extracting a representative sample of both dissolved and particulate matter.
💡 What types of steam are covered by this standard?
This practice specifically covers the sampling of both saturated and superheated steam. It is applicable to steam produced in fossil fired and nuclear boilers, as well as other process means.
⚡ What is the function of a Sample Cooler as defined in the standard?
A sample cooler is defined as a small heat exchanger specifically designed to provide cooling and condensing of process sampling streams of water or steam, allowing for safe and accurate sample collection and analysis.
📌 What unit system is considered standard in D1066-18?
The values stated in SI units are to be regarded as the standard. The values given in parentheses (inch-pound units) are mathematical conversions provided for information only and are not considered standard.