NOAA Standard Specification AMC-505-1B_Valve Overhaul and Tests.pdf
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This is a Standard Specification document for valve overhaul and testing services for the National Oceanic and Atmospheric Administration (NOAA) Atlantic Marine Center, issued in August 1995 (superseding the September 1990 version AMC-505-1A).
The specification establishes general requirements for overhauling and testing valves on NOAA ships and boats. Contractors must remove specified valves to a suitable machine shop for overhaul unless welded ends prevent removal or other specifications apply, in which case in-place overhaul is acceptable. Standard overhaul procedures include complete disassembly with matchmarking, thorough cleaning to bright metal, stem straightening to within 0.002 inch total indicator runout with 32 RMS finish on packing surfaces, visual inspection of all parts and fasteners, and cleaning and truing of gasket mating surfaces. Contact fit requirements vary by valve type: globe valves require 360-degree continuous contact with bluing transfer lines not exceeding 1/16-inch width; gate valves require 360-degree continuous contact with transfer lines not exceeding 3/16-inch width in the lower 50-percent of seating surface; plug valves require minimum 80-percent plug-to-bore surface contact; and swing-check valves require 360-degree continuous disc-to-seat contact. All gaskets, fasteners, rubber seals, and non-metallic seats must be renewed, with specific packing requirements for different valve types per MIL-P-24503, DOD-P-24583, and MIL-P-24396 Type B standards.
Additional requirements address sea valve fastener materials (nickel-copper preferred with condition reporting required), interior steel valve coating with epoxy primer, waster and spool piece removal and inspection, and special handling for transducer sea chest valves. Hydrostatic testing must use clean water at 150-percent of maximum operating pressure (minimum 50 psig), with no leakage allowed in open position tests. Seat leakage limits are specified by valve type and diameter. Quality assurance requires preliminary inspections and tests by the Contractor before COTR witnessing of final bluing contact inspection and acceptance hydrostatic tests. Any valve failing seat leakage testing must be renewed or reworked and retested until acceptance.
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Text version
AMC-505-1B
AUGUST 1995
SUPERSEDING
AMC-505-1A
SEPTEMBER 1990
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION (NOAA)
ATLANTIC MARINE CENTER
STANDARD SPECIFICATION AMC-505-1B
VALVE OVERHAUL AND TEST
1. SCOPE. This specification contains the general requirements for overhaul and test of valves on and for NOAA ships and boats.
2. REFERENCES.
None
3. REQUIREMENTS.
3.1 Standard Overhaul. Overhaul all specified valves as
follows:
3.1.1 Except for valves which have welded ends preventing
removal without cutting the welds, or unless otherwise specified in the detail specification or other applicable procurement document, remove all specified valves from the ship or boat to a suitable machine shop for overhaul and tests. Specified valves which are not removed from the ship or boat shall be overhauled in place. See paragraph 3.2 for special requirements for sea valve removals.
3.1.2 Tag each valve prior to removing from the ship or
boat.
3.1.3 Completely disassemble each valve. Matchmark valve
parts. Thoroughly clean bonnets, stems, discs, gates, globes, seats, bodies, and other metal parts to bright metal.
3.1.4 Deleted.
3.1.5 Clean and chase all valve stem threads. Check stems
for straightness. Straighten stems to within 0.002 inch total indicator runout (TIR). Polish stems to a 32 Root-Mean-Square (RMS) finish in way of packing surface and remove all raised edges.
3.1.6 Visually inspect all parts, including all fasteners, for deterioration and other defects. Clean, dress, and true gasket mating surfaces.
3.1.7 Check the disc-to-seat, globe-to-seat, and plug-to-
bore contact fits using the bluing transfer method. Machine, grind, lap, spot-in, and recheck contact fits as necessary to obtain the following contacts:
a. Globe, globe angle, and globe stop-check valves shall have a 360-degree continuous globe-to-seat contact with a bluing transfer line not exceeding 1/16-inch width.
b. Gate valves shall have a 360-degree continuous gate-to-seat contact with a bluing transfer line which does not exceed 3/16-inch width. The transfer line shall appear within the lower 50-percent of the gate seating surface at the top and bottom of the gate.
c. Plug valves shall have a minimum 80-percent plug-to-bore surface contact, evenly distributed over 100-percent of the area.
d. Swing-check valves shall have a 360-degree continuous disc-to-seat contact.
3.1.8 If unable to obtain the above specified contact fits
by machining, grinding, and lapping, renew the globes, plugs, discs, gates, and renewable seats. Contractor may, at their option and at no additional cost to the Government, renew globes, plugs, discs, gates, and renewable seats after initial inspections and before machining, grinding, or lapping the existing parts to obtain the required contact fits.
3.1.9 (Modified and relocated to section 3.2)
3.1.10 Reassemble each valve. Insure that discs, gates, and plugs are in the half-open position during reassembly to avoid damaging seats or bending stems. Renew all gaskets, fasteners, rubber seals, and non-metallic seats. In butterfly valves, renew boots, o-rings, o-ring fasteners, and teflon bushings. Renew valve stem packing in feed water, condensate, and steam valves with packing conforming to MIL-P-24503 and DOD- P-24583. Renew valve stem packing in all other valves with packing conforming to MIL-P-24396, Type B.
3.1.11 Prior to disassembling and overhauling a valve, the
Contractor may, at their option and at no additional cost to the Government, renew the valve with an identical valve. If this option is exercised, the new valve must be tested and meet the same acceptance criteria as prescribed herein for overhauled valves. If a valve is determined after disassembly to be nonrepairable, the Government will negotiate an equitable cost adjustment, limited to the difference between the cost of the new valve and the costs which would have been incurred had the valve been overhauled. For valves of 3-inch IPS size and below, the cost adjustment will be limited to the costs incurred associated with disassembling the valves.
3.2 Additional Sea Valve Requirements.
3.2.1 Inspect all studs, bolts, and nuts in line and bonnet
flanges of non-ferrous sea valves to determine the material. If the fasteners are not nickel-copper (Monel), submit a Condition Report giving the actual material, condition, and recommendations.
3.2.2 Coat the interior of each steel valve, excluding
seating and polished surfaces, with the same epoxy primer used on the underwater body.
3.2.3 Remove all waster pieces and spool pieces installed
between the sea valves and the ship's hull. Thoroughly clean the waster and spool pieces, and inspect for deterioration or other defective conditions. Inspect all fasteners and submit a Condition Report same as specified above for sea valves.
3.2.4 Whenever a transducer sea chest valve is required to
be removed for overhaul, extreme care must be taken to prevent damaging the transducer assembly. Remove and reinstall the transducer assembly in accordance with the transducer manufacturer's technical manual, a copy of which will be provided by the COTR within 48 hours after requested.
3.3 Tests. After reassembling or renewing, conduct hydrostatic tests of each valve as follows:
3.3.1 All tests shall be performed using clean water as the
test medium. Unless otherwise specified, the test pressure shall be 150-percent of the maximum operating pressure of the system from which the valve was removed, but not less than 50 pounds-per-square-inch-gage (psig).
3.3.2 With the valve in the open position, test each valve
body for 10 minutes. No leakage is allowed.
3.3.3 Seat each plug and butterfly valve with hand force.
Seat all other valves using the torque values listed in the following table as the maximum allowable seating force applied to the handwheel.
Total Tangential Force Handwheel Diameter (pounds) on Rim of Handwheel
2 inches and below 90 3 inches 98 4 inches 106 5 inches 112 6 inches and greater 118 plus 3 pounds for each inch above 6, not to exceed 150 pounds.
3.3.4 Test each globe, angle globe, and globe stop-check
valve by applying test pressure in the direction tending to open the valve. Test each butterfly, gate, and plug valve by applying test pressure alternately on both sides of the disc, gate, or plug. Hold test pressure for a minimum of 3 minutes if there is no evidence of leakage. If there is evidence of leakage, hold the test pressure and measure the leakage rate.
3.3.5 Test each globe stop-check valve and swing-check
valve by applying test pressure in direction tending to close the valve (back pressure) for a minimum of 5 minutes. If leakage occurs, hold the test pressure and measure the leakage rate.
Globe stop-check valves shall be tested with stems in the open position. The test back pressure for valves having a pressure rating of 150 psig and below shall be 50 psig, and for valves having a pressure rating over 150 psig shall be 100 psig.
3.3.6 The seat leakage shall not exceed the following:
a. Check valve back pressure tests -- For valves up to and including 2 inches, the leakage rate shall not exceed 25 cc/hour/inch diameter. For valves 2-1/2 to 10 inches, the leakage rate shall not exceed 50 cc/hour/inch diameter. For valves over 10 inches, the leakage rate shall not exceed 100 cc/hour/inch diameter.
b. Soft-seated valves -- No leakage shall be permitted.
c. Metal-to-metal seated valves -- For valves less than 1 inch, the leakage rate shall not exceed 10 cc/hour. For larger valves, the leakage rate shall not exceed 10 cc/hour/inch of nominal pipe size.
3.3.7 Any valve which fails a seat leakage test shall be
renewed or overhauled and retested until an acceptable test is performed.
3.4 Reinstallation. After tests have been accepted by the COTR, reinstall each valve, using new flange gaskets.
4. QUALITY ASSURANCE.
4.1 Prior to requesting the COTR to witness the final bluing
contact inspection or the final acceptance hydrostatic tests of a valve, the Contractor shall perform preliminary inspections and tests which meet the acceptance criteria stated above.
4.2 After acceptable preliminary inspections and tests have been conducted, the Contractor shall notify the COTR and conduct final acceptance bluing contact inspection and final acceptance hydrostatic tests of each valve in the COTR's presence.
END OF SPECIFICATION
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