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ASME B29.27-2002 (2016) — Single-Pitch and Double-Pitch Hollow Pin Conveyor Chains and Attachments
🧷 ASME B29.27-2002 (2016) is the American National Standard for single-pitch and double-pitch hollow pin conveyor chains and their attachments. It establishes the dimensional limits required for chain interchangeability on sprockets and defines the construction of connecting links, hollow pin chains, pin links, and roller links. The Standard was developed by the ASME Standards Committee B29 (Chains, Attachments, and Sprockets for Power Transmission and Conveying). For many years roller chain manufacturers furnished substantial volumes of a limited series of hollow pin chains for specific conveying applications. Such chains are usually rollerless bushing chains having cylindrical pins; the pin bores are essentially the same as the bushing bores for equivalent pitch chains in ASME B29.1 or ASME B29.4. They are often used in parallel strands with detachable cross-rods fitted through the pin bores of the two parallel strands of chain. Around 1990 the B29 Committee suggested that a standard was needed; in 1995 the Roller Chain Technical Committee of the American Chain Association established a subcommittee to develop it. The Standard was approved by the American National Standards Institute on March 20, 2002, and reaffirmed in 2016.
💡 The unique value of hollow pin chain is “a hole in the pin”: laid out in twin parallel strands, cross-rods pass through the pin bores to form a continuous or spaced carrying platform — a classic solution for flour, grain, feed, and bulk-material conveyors as well as pallet and workpiece transport.
1. Scope 🔍
The scope is explicit: the Standard covers the dimensional limits required for chain interchangeability on sprockets. It does not provide for interconnectability of chains or individual links from different manufacturers. The body has three sections — Scope, Hollow Pin Chains, and Sprockets — supported by eleven figures and one general dimension table.
⚠️ Interchangeability and interconnectability are different things: B29.27 guarantees correct engagement with standard sprockets (interchangeability) but does not guarantee that links from different manufacturers can be assembled into one chain. Mixing brands can cause pitch mismatch and premature wear.
2. Construction and Terminology 🛠️
Standard components and terminology:
- Connecting link: an outside link consisting of a pin link plate E, two hollow pins G-G, a detachable pin link plate D, and two retainers H-H (Figs. 1 and 2), used to close the chain into an endless loop.
- Hollow pin chain, double-pitch: a series of alternately assembled roller links and pin links in which the hollow pins articulate inside the bushings; the pitch of the link plates is twice that of the base-series chain. Pin link plates and roller link plates have identical straight-edged contours. Chains may have large rollers intended for use when the conveyed load is carried by the rollers (Figs. 3 and 4).
- Hollow pin chain, single-pitch: a series of alternately assembled roller links and pin links in which the hollow pins articulate inside the bushings (Fig. 5).
- Pin link: an outside link consisting of two pin link plates E-E and two hollow pins F-F (Figs. 6 and 7).
- Roller link: an inside link — double-pitch large roller series consists of two roller link plates A-A, two bushings B-B, and two rollers of the large series CL-CL (Fig. 8); double-pitch small roller series has two roller link plates A-A and two bushings B-B (Fig. 9); single-pitch roller link has two roller link plates A-A and two bushings B-B (Fig. 10).
💡 The economy of double-pitch design: link plates are twice the pitch while bushings and pins stay comparable to the base series, halving the number of link plates per unit length — lower cost and lighter chain for medium-load, long-distance conveying; the large roller series carries the load directly on rolling rollers.
3. General Proportions and Dimensions 📏
Section 2.2 sets general proportions in terms of pitch P:
- Single-pitch: the roller diameter is approximately 0.625P, with width and other parameters established relative to the base series (see the proportion formulas in the Standard).
- Double-pitch: separate proportions for small and large roller series ensure correct engagement on ASME B29.4 double-pitch sprockets.
The centerpiece is Table 1, “General Chain Dimensions, Limiting Dimensions for Interchangeability, Measuring Loads, and Ultimate Tensile Strengths,” which lists by chain number: pitch, pin/bushing bore diameters, link plate contours, the measuring load (the tension used when measuring chain length after assembly), and the minimum ultimate tensile strength, in U.S. customary inch-pound units with metric conversions per ASME Guide SI-1.
| Item | Content | Purpose |
|---|---|---|
| General dimensions | Pitch, pin diameters, link plate contours | Unified manufacture and interface |
| Interchangeability limits | Upper/lower deviation limits | Guarantee engagement with standard sprockets |
| Measuring load | Specified tension for length measurement | Standardized length verification |
| Ultimate tensile strength | Minimum ultimate tensile strength (M.U.T.S.) | Strength acceptance criterion |
🚨 Chain length must be measured under the measuring load: lengths taken at different tensions can differ by several pitches. Without measuring at the standard load and method, the installed chain may have accumulated length error and poor sprocket engagement.
4. Sprocket Matching and Attachment Applications ⚙️
Section 3 defines sprocket matching: single-pitch hollow pin chains run on ASME B29.1 roller chain sprockets, and double-pitch chains run on ASME B29.4 sprockets — directly linked to bushing diameter, roller diameter, and chain width selection. For attachments, chains may be assembled with modified design attachment pin link plates or roller link plates to adapt to more versatile conveying operations; the most typical arrangement is twin parallel strands with detachable cross-rods through the pin bores forming a continuous or equally spaced carrying surface.
💡 Note the sprocket family: single-pitch and double-pitch hollow pin chains belong to the B29.1 and B29.4 sprocket systems respectively. Do not mix sprockets between the two pitch systems — engagement mismatch leads to skipping teeth and premature chain failure.
5. Engineering Practice Essentials 🛠️
- Selection workflow: determine chain series by conveying pitch (single/double reference) and speed → check M.U.T.S. against material weight and cross-rod spacing → confirm the sprocket comes from the B29.1 or B29.4 system → choose the roller series (large rollers for load carrying vs small rollers for guidance).
- Installation: close the chain with a connecting link and fit retainers correctly; orient the open side of detachable pin link plates consistently for easy maintenance.
- Lubrication and maintenance: hollow pin chain joints are commonly drip- or bath-lubricated; inspect pin bore and bushing wear, link plate cracks, and cross-rod bending.
- Length control: pre-stretch new chain under the measuring load and check total length so twin strands do not differ and tilt the cross-rods.
6. Frequently Asked Questions ❓
❓ Q: What is the essential difference between hollow pin chain and other conveyor chains?
A: The pins of hollow pin chain are tubular, and the pin bore diameter approximates the bushing bore, allowing cross-rods to pass through to form a parallel twin-strand carrying structure; ordinary roller/bushing chains have no through-bore and cannot take cross-rods directly.
A: The pins of hollow pin chain are tubular, and the pin bore diameter approximates the bushing bore, allowing cross-rods to pass through to form a parallel twin-strand carrying structure; ordinary roller/bushing chains have no through-bore and cannot take cross-rods directly.
❓ Q: Are single-pitch and double-pitch hollow pin sprockets interchangeable?
A: No. Single-pitch chains use ASME B29.1 sprockets; double-pitch chains use ASME B29.4 sprockets. The pitch systems differ and mixing them causes engagement mismatch.
A: No. Single-pitch chains use ASME B29.1 sprockets; double-pitch chains use ASME B29.4 sprockets. The pitch systems differ and mixing them causes engagement mismatch.
❓ Q: Does the Standard guarantee interconnectability between manufacturers?
A: No. It only covers dimensional limits for interchangeability on sprockets; for repair and replacement, use the same chain number from the same manufacturer.
A: No. It only covers dimensional limits for interchangeability on sprockets; for repair and replacement, use the same chain number from the same manufacturer.
❓ Q: How do I choose between the large and small roller series?
A: Choose the large roller series when the load is carried directly on rollers running on tracks; choose the small roller series when the load is carried by link plates or attachments and rollers only guide.
A: Choose the large roller series when the load is carried directly on rollers running on tracks; choose the small roller series when the load is carried by link plates or attachments and rollers only guide.
