Measure the cage body OD across the outer wire surfaces at an undamaged, straight body location—not across a top flange, roll band, bottom cap, venturi, or obvious bend. Enter the value and unit, then write the distance or ring reference that identifies the location. A recognized field guide notes that some bottom pans differ from the cage body and therefore should not substitute for a body-diameter reading. [4] If roundness is uncertain, record a second direction at the same location and another undamaged body position. Report all readings; do not average away a possible bend or declare a tolerance.

Write the endpoints before writing the length. For example: outermost top-flange face to outermost bottom-cap face, including the integral venturi projection; or cage-body seating shoulder to bottom-cap face, excluding a removable venturi. Photograph both endpoints with arrows on a separate sketch. For a split cage, record assembled overall length as its own field after the section and joint measurements. Do not compare two length values until both records use the same endpoints. A bent cap, unseated joint, or detached top makes the field damaged or incomplete, not nominal.

Choose one longitudinal wire as the start, mark it with a removable blank tag, and count once around the full circumference until returning to that wire. Record the count as observed and add an overall end-view photo that shows the count path. Do not infer the wire count from a product family, an incomplete photo, or a common configuration. Industry references treat longitudinal or stringer-wire count as a cage construction field, but example counts belong to the products or fabric constructions described by those sources—not to every collector.

Use a suitable caliper on a clean, accessible, straight portion of one vertical wire between welds. Record the tool, location, value, and unit. If a coating remains on the wire, state that the reading includes the coating; do not subtract an estimated coating thickness. Repeat on another undamaged wire when corrosion, buildup, flattening, or visible variation could affect the reading. A corrosion-reduced or damaged-wire reading is condition evidence and must not be copied into the intended replacement specification without another reliable reference.

Count every support ring and identify whether the top and bottom structural rings are included in your count. Measure spacing from ring centerline to ring centerline, beginning at a named top reference and proceeding in order toward the bottom. List each interval or identify repeated intervals plus exceptions; do not write “even” from appearance alone. Industry measurement guidance specifically notes that the last interval can differ from the others. [4] Record both end intervals, the unit, and any ring displaced by damage. No universal ring spacing is implied.

Photograph the top straight-on, from the side, and from inside the cage. Describe what is observed—such as a turned or rolled flange, straight flange, roll band, split/rolled collar, detachable top, or another profile—without assuming the supplier's name for it. Measure the body-to-top transition, outside and inside features that mate or seat, groove or shoulder location, overall top height, and any projection, using named reference faces. Note installed direction and whether the top supports, locates, hangs, or seats the cage. A style name or silhouette alone does not establish fit.

Photograph the bottom face, side profile, body-to-cap transition, and wire attachment. Record whether the observed part looks like a cup, pan, disc, rounded cap, open frame, or another construction; then measure the cap outside diameter, height, projection beyond the body, and the reference used. Note whether wires appear welded inside, outside, or into another feature and whether the edge is smooth, distorted, or damaged. Manufacturer literature illustrates different bottom and edge constructions, but those examples are product-specific and do not set a universal requirement.

State present, absent, or unknown. If present, record whether the venturi is integral, welded, detachable/drop-in, or otherwise attached; photograph its orientation and the cage-top mating detail. Measure opening or throat, inlet and outlet diameters where identifiable, overall height, flange or seating geometry, and relevant projection, always with endpoints and units. EPA describes a venturi in a pulse-jet cleaning arrangement, while industry sources show integral and separate versions. [1] [4] Do not conclude that every collector needs one or that matching outer shape proves cleaning compatibility.

Record one-piece or split/sectional construction and the number and installed order of sections. For each section, name its top and bottom endpoint and record its free length. Photograph both joint halves before assembly, during engagement if site procedures permit, and fully assembled on supports. Record joint OD/ID or profile, overlap or engagement evidence, locking or indexing feature, assembled reference, and whether a section can rotate. Also document clean-plenum or access constraints from approved records or safe exterior evidence. Do not prescribe a minimum engagement or assume two joints with similar names interchange.

Copy a material or coating only from an identified drawing, label, certificate, purchase record, or supported test result. Industry literature recognizes low-carbon/plain steel, galvanized steel, stainless materials, and coated cage constructions. [5] Appearance may support an observed description—bright metallic, dark coating, flaking layer, discoloration—but cannot prove alloy grade, stainless grade, galvanizing, coating chemistry, or thickness. Write “material unknown” or “coating unknown” when the evidence is missing, and include dust, moisture, chemistry, temperature, and upset history for project-specific review.

Map corrosion by cage reference: top, ring number, wire number or clock position, joint, and bottom. Photograph an overall view and a close view with a neutral location marker. Describe surface discoloration, coating loss, loose scale, pitting, reduced section, or an uncertain deposit without assigning a mechanism from appearance. Donaldson’s maintenance guidance includes filter/cage condition in periodic review. [6] The source does not provide a universal accept/reject corrosion threshold, and neither does this guide. Route the actual evidence, operating context, and bag marks for competent disposition.

Sight along the supported cage from both ends and rotate only if the handling plan permits. Record any bow, twist, flat area, shifted ring, broken wire, loose wire, or distorted top/bottom/joint by the same location system used for the photos. Keep sharp or loose areas isolated and follow site handling controls. Do not use the distorted OD, length, or joint position as intended geometry. Compare with an undamaged matching cage, an approved drawing, the mating bag and collector evidence, or a retained sample. If no reference exists, mark the intended value unknown and request review.

Use good light and close photographs to review wire-to-ring welds, top and bottom attachments, cap edges, and joint surfaces. Do not sweep a bare hand over a suspected burr or sharp edge. Parker describes polished ring welds and rounded edges as abrasion-reduction features in its cage construction. [5] That is useful inspection context, not a universal weld-quality standard. Record the observed rough area, its location, associated bag wear, and whether the condition affects a measurement; leave acceptance and repair to the controlling specification and competent reviewer.

Lay the documented cage record beside the bag record: bag body size and measurement method, overall-length endpoints, top attachment and seal, bottom construction, seam and wear locations, current media when supported, and installed orientation. Add the tube-sheet opening, seating surfaces, access direction, blowpipe or cleaning relationship, and venturi position when safely documented. One Donaldson LP manual shows its cage seating inside a snap-band bag at the tube sheet, which demonstrates why mating components must be recorded together but is not a universal installation method. [3] Do not calculate a universal clearance from nominal diameters.

Draw one side view, one top/end view, the bottom profile, the venturi detail, and both halves of every joint. Give each field an M/C/O/A/U status, value, unit, endpoint or location, tool or record source, photo filename, and reviewer question. Put damaged readings in a condition layer, not the intended-geometry layer. Add collector maker/model/serial when known, position, bag reference, installed quantity, requested quantity, process and dust, cleaning method, temperature and moisture context, reason for replacement, and sample availability. The drawing is a traceable RFQ record—not a compatibility certificate.