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ASME B19.3b-1995 — Safety Standard for Compressors for Process Industries (1995 Addenda)
📐 ASME B19.3b-1995 is the second addenda to the Safety Standard for Compressors for Process Industries (ASME B19.3-1991), following the first addenda (B19.3a) issued in 1994. In line with the ASME addenda system, this document is published as replacement pages that incorporate revisions directly into the affected pages of the 1991 edition. Approved by the American National Standards Institute (ANSI) on August 17, 1995, and issued on May 31, 1996, this addenda goes beyond scattered point changes: several safety-technology sections were rewritten in their entirety. This article reviews the standard’s scope and safety framework and focuses on what this second addenda changed.
💡 Changes introduced by this addenda are identified on the page by the margin note (b), while the 1994 first addenda (B19.3a) is marked (a). A page carrying both (a) and (b) notes has been revised twice in succession — check it against the replacement-page lists of both addenda.
1. Overview and Scope 📌
The core objective of ASME B19.3 is to prevent compressor accidents. Its specific recommendations cover requirements for safety devices and protective facilities that guard against excessive pressure, destructive mechanical failures, internal fires or explosions, and leakage of toxic or flammable fluids. General safety practices and hazards unique to compressors are also covered.
The Standard applies to the compressor and its auxiliaries: drivers, intercoolers, surge chambers, disengaging drums or scrubbers, interconnecting piping, and the lubrication, seal oil, and jacket water systems. Its requirements apply to all types of compressors — centrifugal, axial, rotary, and reciprocating — that are an integral part of facilities processing petroleum, petrochemicals, or chemicals, including air separation plants. This addenda’s revision of the scope provision makes explicit that the Standard does not apply to plant utility air compressors.
Two matters remain outside the provisions: (1) the basic mechanical design of compressor components, assumed to be performed by qualified engineers in accordance with recognized standards and specifications; and (2) the design and operation of connected process facilities. The Standard again reminds users that its safety principles are not restricted to new systems: all compressor systems should be reviewed in light of the revised requirements to identify possible changes.
⚠️ B19.3b-1995 revises para. 1.2(a) (scope). Always reference the latest replacement pages and note the explicit exclusion of plant utility air compressors — such machines are governed by ASME B19.1 (Safety Standard for Air Compressor Systems), not by B19.3.
2. Technical Requirements and Specifications 🔧
The revisions in this addenda concentrate on Chapter 3 (Safety Requirements). Unlike the more scattered changes of the first addenda, B19.3b rewrites several safety provisions in their entirety, which means the affected pages are replaced wholesale — engineers must reread the complete replacement sections rather than compare individual sentences.
| Section | Content Revised | Type of Change |
|---|---|---|
| 1.2(a) | Scope statement | Revised |
| 3.2 | Safety Devices | Revised in its entirety |
| 3.3.1 | Fire and Explosion Protection — general | Revised in its entirety |
| 3.3.2(a) | Fire and Explosion Protection — specific measures | Revised in its entirety |
| 3.4.4 | Flammable Material — related provision | Revised |
The overall technical framework of the base standard should be read alongside these changes. Chapter 2 sets general safety considerations for design: compressor piping shall comply with ANSI/ASME B31.3; the use of cast-iron valves and fittings in the process stream is restricted; block valves are intended only for isolating shutdown equipment and must be confirmed open before startup; and positive displacement compressors shall be protected with pressure-relieving devices between the discharge and block valves, without exception. Chapter 3 specifies that relief devices should preferably be spring-loaded valves of the type described in the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, and defines requirements for the selection, capacity, and setting of safety devices.
🚨 This addenda rewrites Section 3.2 (Safety Devices) in its entirety. Safety devices — relief valves, interlocks, alarms, and emergency shutdown systems — are the last line of defense against overpressure and accidents; recalculating relief capacity and set pressures against the new requirements is the highest-priority task when implementing this addenda.
3. Engineering Practice Essentials 🛠️
- 📑 Implementation checklist: the replacement pages cover pages 1, 6–8, 9, and 9.1 (plus the 3.4.4 revision in the page-13 range). Work through the “SUMMARY OF CHANGES” page by page, retain the original pages and the title/copyright pages of both addenda for reference.
- 🔧 Safety device settings: against the fully rewritten Section 3.2, verify the set pressure, relieving capacity, and back-pressure effects of every relief valve; spring-loaded relief valves are the preferred type, with design basis traceable to the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1.
- 🔥 Fire and explosion protection: the rewritten 3.3.1 and 3.3.2(a) update the requirements for hazardous-area classification, ignition-source control, and flammable-media handling. Electrical installations should follow the area-classification approach of API RP 500A and comply with NFPA 70 (National Electrical Code).
- 📊 Operation and monitoring: centrifugal and axial compressors shall not run below the surge point; vibration shall be monitored against the Section 3.5 limits. Toxic fluids require seal systems, leak monitoring, and emergency isolation procedures.
- 🧭 Existing-plant review: the Standard recommends reviewing installed compressor systems against the revised provisions. Fold the addenda changes into the scope update of your plant’s HAZOP / SIL assessments and close out improvements.
💡 Both addenda (a, 1994 and b, 1995) modify the same 1991 base edition. If a plant’s records hold the 1991 edition, keep the complete package — base edition plus all replacement pages of addenda a and b; missing any piece makes the referenced text diverge from actual practice.
4. Frequently Asked Questions ❓
❓ Q: What is the difference between B19.3b-1995 and B19.3a-1994?
A: Both are addenda to ASME B19.3-1991. B19.3a (1994) is the first addenda with scattered changes; B19.3b (1995) is the second, with Sections 3.2, 3.3.1, and 3.3.2(a) rewritten in their entirety — a much larger revision. Their ANSI approval dates are May 23, 1994 and August 17, 1995, respectively.
A: Both are addenda to ASME B19.3-1991. B19.3a (1994) is the first addenda with scattered changes; B19.3b (1995) is the second, with Sections 3.2, 3.3.1, and 3.3.2(a) rewritten in their entirety — a much larger revision. Their ANSI approval dates are May 23, 1994 and August 17, 1995, respectively.
❓ Q: Why was this addenda issued in 1996?
A: Its Date of Issuance is May 31, 1996, while the 1995 version year in the designation reflects the year the work was completed and approved, consistent with ASME addenda naming conventions. Reference the number printed on the document cover.
A: Its Date of Issuance is May 31, 1996, while the 1995 version year in the designation reflects the year the work was completed and approved, consistent with ASME addenda naming conventions. Reference the number printed on the document cover.
❓ Q: Does the Standard apply to plant utility air compressors?
A: No. Para. 1.2(a) — itself revised by this addenda — excludes plant utility air compressors; their safety requirements are addressed by ASME B19.1, Safety Standard for Air Compressor Systems.
A: No. Para. 1.2(a) — itself revised by this addenda — excludes plant utility air compressors; their safety requirements are addressed by ASME B19.1, Safety Standard for Air Compressor Systems.
🔍 Q: How does “revised in its entirety” differ from an ordinary revision?
A: An ordinary revision changes individual sentences or provisions. “Revised in its entirety” means the whole section is replaced — the previous text no longer applies, and engineering documents and design calculations must be rechecked against the new section as a whole, not just at marked change points.
A: An ordinary revision changes individual sentences or provisions. “Revised in its entirety” means the whole section is replaced — the previous text no longer applies, and engineering documents and design calculations must be rechecked against the new section as a whole, not just at marked change points.
