Identify cooling valves and isolation points

Examples are fictional local conventions. Unless another location is shown, the scope is DC01 / H1. Keep that scope with shortened identifiers.

When to use#

Use this guide when a valve carries no tag, carries a tag nobody can resolve, or carries a tag that names a segment the valve no longer isolates. The output is a valve and isolation-point register. Guide 16 identifies the pipe segment's fluid system and service role; this page records which individual valve sits in that system and exactly what it closes off.

What to gather#

Gather the controlling mechanical drawing and its revision, the existing valve schedule, the observed tag on each valve, the upstream and downstream segment references, and the equipment or space served by the segment.

ASME publishes A13.1 for piping system identification. Its public scope describes marking piping systems; it is not a valve-numbering scheme and it does not state what a given valve isolates. ASME source

Identification workflow#

These steps are this library's recommended recordkeeping method.

1. Fix the drawing reference first. Record the controlling drawing and its revision before reading any tag. A valve schedule without a drawing revision cannot show whether the isolation boundary is current.
2. Separate the tag from the valve. Record the observed tag text, the tag's condition, and the valve's position in the segment as three distinct observations. A missing tag and a wrong tag are different findings with different corrections.
3. State the isolation claim exactly. Name the segment or equipment the record says this valve isolates, and name the two segment references on either side of it. Avoid a room-level or loop-level phrase where a segment reference is required.
4. Record uncertainty precisely. Flag an unreadable tag, an unlocatable valve, and a valve absent from the schedule separately. Refer the resolution to the mechanical owner; this survey operates nothing.
5. Link the boundary to its change history. When a repipe, tie-in, or equipment replacement moved a boundary, connect the former and current isolation claims through the change reference rather than overwriting the earlier one.

The expanded procedures and fictional case below are original editorial recordkeeping guidance to adapt to the site's approved process.

Decide which part of the valve identity is uncertain#

Start by separating the valve as a physical object from the isolation function the record assigns to it. A valve may carry a perfectly readable tag while the segment named on that tag was re-routed two revisions ago. A valve may be correctly positioned in a current drawing while carrying no tag at all. A schedule may list an isolation point that no longer exists because a tie-in removed it. Each of those needs a different finding, and none of them should be repaired by copying a neighbouring valve's tag because the pipe looks similar.

If the controlling drawing revision is uncertain, resolve that reference before accepting any isolation claim built on it. If the drawing is established but the valve cannot be located or reached, keep the valve unconfirmed and record the access limitation as the evidence gap. If two tags in the same segment carry the same number, preserve both observed faces with their exact locations rather than deciding which one is the original. A register row that looks complete can otherwise conceal that the physical valve, its tag, and the drawing position have never been positively associated with one another.

Define the included valve population before starting. A survey may cover one loop, one mechanical room, one tie-in package, or the isolation points for a single equipment replacement. Record the full site and hall scope and identify any valve that sits outside the inspected area but appears in the same isolation claim. Distinguish this task from the pipe-marker survey in guide 16. The valve register describes discrete isolation points and their boundaries; it should not expand into a general fluid-system map that loses the individual valve's identity and position.

Establish the isolation boundary before tagging#

An isolation point is only meaningful against a stated boundary. Record the segment reference upstream of the valve and the segment reference downstream of it, then name what that downstream portion serves. A tag reading CHW ISOL identifies a service but not a boundary; the same text on four valves in one room tells a responder nothing about which one to close. Use the segment references established by the controlling drawing rather than a description of what the pipe appears to feed.

Keep the valve's own identity separate from the boundary it creates. The valve has a position, a type, a size, and usually a schedule number; the boundary has two segment references and a served scope. Recording them in one merged field makes the row unusable when a repipe keeps the valve but moves the boundary, or keeps the boundary but replaces the valve. Preserving both relationships lets the register answer the two different questions people actually bring to it: where is valve V-014, and what closes when I close it.

Record observation limits honestly. If a tag is painted over, describe the visible characters and cite the schedule entry separately rather than reconstructing the full number from context. If a valve sits above a ceiling or behind a panel, record that the position was taken from the drawing and not observed. Any new or replacement tag should follow the site's accepted tagging method and material while keeping existing information readable. The examples here show identity content only. They are not a tagging specification, a valve-selection method, or permission to operate anything.

Describe what the valve actually isolates#

The served scope is the field people rely on under time pressure, and it is the field most often written loosely. AHU-G31-301 names a unit. The segment between SEG-G31-014 and SEG-G31-015 names a boundary. Recording served scope as "the east row" invites a responder to assume a room-level effect that the valve does not have. Where a valve isolates several items, list them rather than summarising them, and state whether the list is complete against the drawing or only against what was observed.

Keep the isolation claim distinct from any statement about what the valve will achieve when operated. A register can establish that the drawing shows this valve bounding this segment. It cannot establish that the valve seats fully, that the segment is drained, or that closing it produces a safe condition for work. Those belong to the mechanical owner's energy-control and commissioning processes. Where a site's procedure requires isolation points to be identified before work, the register supplies the identification input to that procedure; it does not replace it or satisfy it.

Record the valve's normal position when the controlling document states one, and keep it plainly marked as a documented value rather than an observation. A valve found in a position different from its documented normal position is a finding to refer, not a discrepancy for the surveyor to correct by operating the valve. Note the observed position separately if the site's procedure asks for it, with the date and the limitation that a handle orientation is not proof of internal state.

Worked case: the tag survived a repipe that moved the boundary#

In this fictional DC01 / H1 case, valve VLV-G31-014 carries tag text reading CHW-R2-ISOL and the current schedule lists it as isolating SEG-G31-015, which serves CRAH-G31-302. Tie-in package TIE-G31-301 added a branch upstream of the valve two revisions ago. Survey VCASE-G31-301 records the observed tag, the schedule claim, and drawing MECH-G31-301 revision 5 as three separate values. The first finding is that the register's served scope predates the tie-in, not that the tag is wrong.

The mechanical owner reviews the tie-in package against revision 5. In fictional decision DEC-G31-014, the owner confirms that VLV-G31-014 still bounds SEG-G31-015, but that the branch added by TIE-G31-301 means the downstream portion now also serves CRAH-G31-303. The accepted served scope becomes both units. The tag text itself remains correct and is not reprinted; what changes is the register's served-scope field and its link to the tie-in reference. The former served scope is retained with its effective revision so an investigation covering the earlier period still resolves correctly.

Closeout records the corrected served scope under EV-G31-307, links TIE-G31-301 and DEC-G31-014, and reviews the other valves named in the same tie-in for the same stale-scope pattern. Two of them are found to be correct and are recorded as reviewed rather than left unstated. The completed case explains which isolation claims were reconciled to which drawing revision. It does not assert that closing VLV-G31-014 isolates either unit in practice, and it does not substitute for the energy-control procedure that governs the actual work.

Variations to keep visible in the register#

Some sites tag the isolation position rather than the valve body, so the tag stays with the location through a valve replacement. Preserve both meanings where that is the approved policy. The position keeps its boundary references while different physical valves occupy it over time, and each association carries its own effective event. Without that distinction an investigation can find the right boundary but be unable to say which valve was installed during the period under review.

Paired valves that isolate a segment from both ends need their relationship recorded explicitly, not implied by adjacent schedule numbers. Record each valve's own row and the reference that binds them, so a partial closure is visible as a partial closure. The same applies to a valve with a bypass around it: the bypass valve's own isolation claim is different from the valve it bypasses, and a register that omits the bypass will overstate what the main valve closes.

Where a valve serves both a mechanical function and a documented safety or emergency role, keep those references separate and follow the distinction in guide 15. OSHA's accident-prevention signs and tags provision addresses tags that warn of hazards; an operational identification tag has a different function and a different owner. OSHA source Recording both roles in a single free-text field tends to produce a tag that satisfies neither purpose.

Failure patterns and closeout evidence#

Look for duplicate schedule numbers within one system, served scopes written at room level, tags that name a service but no boundary, and valves present in the field but absent from the schedule. A further recurring failure is a correct tag paired with a stale served scope after a tie-in, which reads as complete and is the hardest to detect by inspection alone. Review the valves named in a change package together rather than only the one in front of you. A useful closeout names the valve, its two segment references, the served scope, the controlling drawing revision, and the change event that made the claim current.

Final evidence should separate what was observed from what was accepted through records. Keep the original conflicting values, the mechanical owner's decision, and the final comparison together. Record any valve whose position was taken from a drawing rather than observed, and name the follow-up required to close that gap. Enter the actual review date for the supported scope only. A completed tie-in notice does not establish that every affected isolation claim in the register was reviewed.

Worked example#

Example only: invented valve and segment names.

SCOPE: DC01 / H1
VALVE V-014      TAG READS: CHW-R2-ISOL
Upstream        SEG-014
Downstream      SEG-015
Serves          CRAH-02, CRAH-03
Drawing         Example MECH-301 rev 5

V-014 and SEG-015 are fictional designations, not an ASME scheme or an instruction to operate.

Common mistakes#

• Recording a service name where a boundary reference is required.
• Writing served scope at room level instead of naming equipment.
• Reusing a schedule number after a tie-in removed the original point.
• Treating a handle position as proof of internal valve state.

Verification#

• The controlling drawing revision is recorded with the claim.
• Each valve has upstream and downstream segment references.
• Served scope names equipment, not an area description.
• Unobserved valve positions are marked as drawing-derived.
• Change references link superseded isolation claims.

Worksheet: Cooling valve and isolation-point register#

Filled example row - fictional; no live verification.

FAQs#

Does tagging a valve establish an isolation point for work?#

No. The register identifies which valve the controlling drawing shows bounding a segment. Establishing an isolation for work belongs to the site's energy-control procedure and the mechanical owner, who determine drain, verification, and acceptance steps that a label review cannot supply.

Should the tag name the valve or what it isolates?#

Record both, in separate fields. Tag text is preserved exactly as observed because it is what a responder reads. The boundary is recorded as two segment references plus a served scope, because that is the question the tag text alone usually cannot answer.

What if a valve in the field is missing from the schedule?#

Record it as an observed valve with no schedule entry and refer it to the mechanical owner. Do not assign it the next unused number. An unscheduled valve may be a legitimate addition from a change package or an indication that the controlling drawing revision is not the one installed.

Can one tag cover a pair of valves isolating the same segment?#

Keep a row for each valve and record the reference that binds the pair. A single shared tag hides partial closure, which is exactly the condition a responder needs to see. State in the served scope whether the isolation depends on both valves or either one.

How should a bypass around a valve be recorded?#

Give the bypass valve its own row and its own isolation claim. A main valve's served scope is only accurate when the bypass position is accounted for, so record the relationship between the two rather than assuming the bypass is normally closed.

Does a normal position in the record mean the valve is in that position now?#

No. Normal position is a documented value carried from the controlling document, and the register marks it as such. If the observed position differs, record that as a finding for the mechanical owner. A handle orientation is not evidence of internal seating, and the survey does not operate the valve to check.

More worked label examples

Two additional ways to apply this guide. Keep the exact identifiers and relationships consistent with your own approved records.

SCOPE: DC01 / H1; valve VLV-G31-101
DRAWING: MECH-G31-101 r3, revision recorded with the claim
UPSTREAM:   SEG-G31-101
DOWNSTREAM: SEG-G31-102  -> serves CRAH-G31-101

VALVE TAG FACE
+------------------------------+
| VLV-G31-101                  |
| CHW RETURN / ISOLATION       |
+------------------------------+

REGISTER ROW (what the face cannot carry)
SEG-G31-101 ==[ VLV-G31-101 ]== SEG-G31-102 -> CRAH-G31-101
Normal position: open (record value, not observed)

SCOPE: DC01 / H1; tie-in TIE-G31-201
VALVE: VLV-G31-201 (tag text unchanged and correct)
DRAWING: MECH-G31-201 r4 -> r5

BEFORE r5: SEG-G31-202 -> serves CRAH-G31-201
AFTER  r5: SEG-G31-202 -> serves CRAH-G31-201, CRAH-G31-202

SERVED-SCOPE HISTORY
r4 scope -> retained, effective to TIE-G31-201
r5 scope -> current, accepted under DEC-G31-201
Tag face: not reprinted; text remains accurate
Evidence: EV-G31-207; other TIE valves reviewed

Sources and applicability

• ASME: A13.1 piping identification ↗

  Public scope overview only; no complete color or placement specification was accessed.

  Read scope and linked guides
• OSHA: 29 CFR 1910.145 ↗

  US accident-prevention signs and tags; operational identifiers have a different function.

  Read scope and linked guides

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