MAINTENANCE & REPAIR
BY GREG JOHNSON
Just Read the Instructions
Although the situation might change ventually, it’s a reality that most
people working in the valve repair
industry today are men. It is also a reality that many men hate to read instructions or rely on a map. However, when
repairing critical pressure-containing
equipment such as valves, a little glance
at the words now and then can be
important. And when it comes to valve
repair instructions and standards,
sometimes it takes a little digging to
find the right paragraphs of wisdom.
For commodity valve repair, a thorough repair document is published by
the American Petroleum Institute (API)
entitled API Recommended Practice
(RP) 621, “Reconditioning of Metallic
Gate, Globe, and Check Valves.”
RP621 is a 15-year-old document created by a joint team of valve repair
companies and end-users to standardize
the process of valve repair. Prior to
RP621, commodity valve repair standards were created and maintained by
each individual end-user as well as
many repair facilities themselves. This
consolidation of valve repair standards
has helped to create a level playing
field.
The detailed procedures and standards found in RP621 are designed for
gate, globe and check valves, but many
of the principles are easily adaptable to
other valve types. If RP621 has a drawback, it is that repairing valves in accordance with its requirements is relatively
expensive. Because inexpensive import
cast steel valves have emerged, repairing smaller sizes to any standard, much
less RP621, is not feasible. However,
the repair of larger, higher pressure and
critical application valves—such as
those in the American Society of
Mechanical Engineers (ASME) B31.3,
category M Lethal Service—under the
RP621 standard, is still cost effective.
Even if all the tenets of the standard are
not followed, enough good information
exists to create a less detailed, but relevant valve repair procedure. RP621 can
also be used as a starting point for creating valve repair procedures for other
valve types.
API has another repair document for
upstream valves, API 6DR, “Repair and
Remanufacture of Pipeline Valves.” The
6DR document is not as extensive as
RP621, but it does outline the major
requirements of pipeline valve repair.
Both API RP621 and 6DR require
the repair practitioner to possess cur-
rent editions of the parent documents
under which the valves were originally
manufactured. For API RP621, those
documents are: API 600, “Steel Gate
Valves—Flanged and Butt-welding
Ends, Bolted Bonnets”; API 602,
“Steel Gate, Globe and Check Valves
for Sizes NPS 4 (DN 100) and Smaller
for the Petroleum and Natural Gas
Industries”; API 603, “Corrosion-
resistant, Bolted Bonnet Gate Valves—
Flanged and Buttwelding Ends”; and
API 594, “Check Valves: Flanged, Lug,
Wafer and Butt-welding.” For the API
6DR standard, the parent document is
API 6D, “Pipeline Valves.” In addition
to these parent documents, any facility
performing repairs on these types of
valves should have copies of the refer-
enced ASME, Manufacturers Standard-
ization Society and American Society
for Testing and Materials (ASTM) docu-
ments as well.
GREG JOHNSON, a contributing editor to Valve Magazine, is president of United Valve (
www.unitedvalve.com), Houston, TX. Reach him at
greg1950@unitedvalve.com.
