ASME B29.17M-1998 (2018) — Hinge Type Flat Top Conveyor Chains and Sprocket Teeth

⚙️ ASME B29.17M-1998 (reaffirmed 2018), Hinge Type Flat Top Conveyor Chains and Sprocket Teeth, is the American National Standard defining dimensions and interchangeability requirements for hinge type flat top conveyor chains. Chains of this type were first introduced in the late 1930s and met with considerable success on material conveying applications. They consist of a series of links each having a flat top plate (carbon or stainless steel) with hinge-like barrels on each side: the barrels of adjacent links interlace, and pins inserted through the holes formed by the barrels connect adjacent links, forming a continuous flat top conveyor chain free to flex in one direction. Pins are retained by press fit and/or heading in the barrels of one link while being a free or slip fit in the interlaced barrels of the adjacent link. The chain is driven by meshing the curl outside diameters with sprocket teeth. In 1973 a subcommittee of American National Standards Committee B29 was appointed to draft the standard; the previous edition was approved by ANSI on June 21, 1983, and reaffirmed in 1995. The 1997 modification added two straight-running nonmetallic chains (24P26 and 24P86), and this edition received ANSI approval on September 9, 1998, and was reaffirmed in 2018.

1. Scope and Construction 📌

The Standard covers steel and plastic hinge type flat top conveyor chains and their sprocket teeth, including general link dimensions, M.U.T.S., measuring load, chain length tolerance, top plate width, and sprocket tooth form. Each link has a flat top plate with hinge barrels on both sides; top plate width is a parameter specified separately from the chain number. To allow products from different manufacturers to interconnect, the Standard publishes controlling dimensions (maximum/minimum limits) for chain components — not manufacturing dimensions but an envelope within which components must fit for interchangeability.

In drive terms, the chain is driven by the curl outside diameter engaging sprocket teeth, which keeps the chain accurately positioned and running smoothly on the conveyor line. Plastic flat top chains have links molded from plastic material, with pins usually of stainless steel retained by press fit or knurls, offering corrosion resistance, low noise, and easy cleaning.

2. Chain Numbering System 📏

B29.17M chain numbers consist of two pairs of digits separated by a letter: the first two digits are the number of sixteenths of an inch in one pitch; the letter designates material — A = austenitic stainless steel (link and pin), C = carbon or alloy steel (link and pin), P = plastic; the last two digits equal the hinge width in sixteenths of an inch. For example, 24A26 designates an austenitic stainless steel chain of 1.5 in. pitch (24/16) having a nominal hinge width of 1.625 in. (26/16). Top plate widths are available in various sizes and must be specified independently from the chain part number.

Note: the table illustrates the numbering rule; actual pitch, curl diameter, top plate thickness, and M.U.T.S. for each chain number are given in Tables 1 through 3 of the Standard. The plastic chains 24P26 and 24P86 are the straight-running nonmetallic chains added in 1997.

3. Performance Parameters and Key Definitions 🔧

3.1 Minimum Ultimate Tensile Strength (M.U.T.S.)

M.U.T.S. is the minimum force at which an unused, undamaged chain could fail when subjected to a single tensile loading test, performed by slowly applying a uniaxial force to the chain sample. The Standard warns that M.U.T.S. is not a “working load” — it greatly exceeds the maximum force that may be safely applied, and the tensile test is destructive. Even if the chain does not visibly fail at the M.U.T.S., it has been damaged and is unfit for service.

3.2 Measuring Load and Chain Length Tolerance

The measuring load is approximately 2% of the minimum ultimate tensile strength (Table 1), the load under which a chain should be measured for length. New chains may exceed the theoretical length by up to 0.38 in. per 120 in. (9.7 mm per 3048 mm) but must not be shorter. Length tolerance ensures uniform tension across parallel lines and correct sprocket meshing.

4. Sprocket Tooth Forms (Type A and Type B) 🔩

To reflect common usage, the Standard records two sprocket tooth forms:

• Type A — Radius Tooth Form: one tooth form cutter covers the full range of teeth, suited to the normal range of sprocket tooth counts (Table 4);
• Type B — Straight Face Tooth Form: optimizes load absorption and allowable chain elongation; the full range requires several cutters, with five cutters covering the 12 through 41 teeth shown in the Standard (Table 5).

Other sprocket data — pitch diameter, maximum outside and bottom diameters, pressure angle limits, and maximum eccentricity and face runout tolerances — are given in Fig. 9 and Tables 5 and 6.

5. Engineering Practice Essentials 🛠️

• 🔍 Selection workflow: determine conveyed product, load, and line speed → choose material (A/C/P) and pitch → determine hinge width from the chain number → select top plate width separately → choose Type A or Type B sprocket tooth form.
• 🔧 Material selection: choose austenitic stainless (A) for wet or hygienic areas; carbon steel (C) for high-temperature or general industrial duty; plastic (P, subject to temperature limits) for beverage and light-duty wash lines.
• 📊 Cleaning and lubrication: flat top chains are common in wet areas — clean regularly and use food-grade lubricants; inspect curl and pin wear to prevent joint seizure.
• 📋 Interchangeability management: only links and sprockets made to B29.17M are guaranteed interchangeable; top plate width is specified separately, so state both the chain number and plate width when ordering.

6. Frequently Asked Questions ❓