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Storage
If valves are not put into service within three months after factory shipment, long term storage measures should be initiated to preclude valve deterioration. Contact Pacific Valves for details regarding long term storage procedures.
Installation
HANDLING—Valves should always be installed in clean lines. Use lifting lugs where provided. If lugs are not provided, slings should be used. VALVES MUST NEVER BE LIFTED BY HANDWHEELS OR STEMS.
WELD END VALVES—Weld end valves should be installed using proper welding practices similar to procedures covered in ANSI B31.1 through B31.8. Care must be taken not to overheat valve bodies. Temperatures exceeding 400oF in the seat area of the valves during welding may cause seat distortion and leakage. During the welding operation, the valve should be assembled and in the closed position for maximum support and protection of seating surfaces. Weld debris should be cleaned from line and valve internals before operating valves.
Maintenance
FLANGED BONNET JOINT—Valve bonnet joints are assembled to design specifications at the time of factory assembly. However, because of the flexible nature of joint materials, varying applications can affect bolt stress and cause bonnet leakage problems. Internal pressure, temperature and external piping loads can affect the bonnet seal and certain precautions must be taken to prevent joint leakage. Line pressure tends to relieve gasket loads during operation. All bolted joints should be inspected periodically and retorqued as needed.
Factory assembly takes place at ambient temperatures. However, many actual service conditions are at elevated temperatures. For conditions where bolting creep (elongation under stress—increasing with higher temperatures) can occur, it is recommended that bonnet bolting be retorqued after the first shutdown of the system. For services over 500oF, retorque bolts during the first 100 hours regardless of whether or not shutdown has occurred.
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Because valve assemblies are often stored for long periods before installation, the above considerations are also applicable. This means torquing before start-up is required if prolonged storage occurs.
Distortion of valves, especially lower ANSI pressure classes, can occur when piping loads become excessive. To prevent this situation, inspect valve and piping assemblies to insure against piping misalignment. External pipe supports should be used to eliminate misalignment.
Bonnet maintenance should, whenever possible, be accomplished without disassembling the valves. Retorquing bolts is the most effective means of insuring against leaks. However, as pointed out in the chart notes, special conditions may require torque modifications. Consult Pacific Valves when more exacting means are required. NEVER DISASSEMBLE VALVES COVERED BY FACTORY WARRANTY WITHOUT PREVIOUSLY
CONTACTING NVF VALVES. FAILURE TO DO SO MAY VOID WARRANTY. Bonnet
gaskets, other than undamaged ring joint type, should not be reused if valves are disassembled.
PACKING—Valve packing should be checked periodically to prevent leakage. Tightening adjustments may be sufficient, but care should be taken not to over compress packing, which may cause excessive valve operating torque. From time to time packing may need to be added or replaced.
LUBRICATION—Where lube fittings are provided, valves should be lubricated periodically. Stem threads must be bushed with lubricant to avoid damage and excessive torque from developing.
Valves should never be operated with unlubricated stem threads or yoke sleeves.
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Precautions
Before installing a valve check the data on the permanently affixed metal nameplate and any other attached tag against the purchase order, to assure that the valve is of the design and material required for the intended service. Make sure that the valve is new and in the factory as built condition prior to use. All new Pacific valves carry a limited warranty against defects in workmanship and materials at time of factory shipment, but such warranty is voided when valves are changed in any way. Please see scope of limited warranty as set forth in the quotation.
While all NVF valves are tested at the factory to insure compliance with industry standards and purchase specifications, they will eventually experience deterioration or wear which could cause leakage or malfunction. A preventative maintenance program, including periodic inspection of packing, gaskets and seats is a key to reducing the occurrence of these problems. Factors that affect valve service life include but are not necessarily limited to, the following:
- Selection of proper design and materials for the intended service.
- Frequency of opening and closing.
- Corrosive and/or erosive properties of the contained fluid.
- Service pressure and temperature.
- Reasonable care in operation (e.g., avoidance of overtightening of the handwheel).
- Degree of leakage, if any, that the user’s system can tolerate.
- Proper installation and maintenance,
For specific recommendations on maintenance or service consult NVF Valves.
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Bolt Dia.
In. |
Torque-Ft/lbs
+/-6% |
Bolt Dia.
In. |
Torque-Ft/lbs
+/-6% |
1/2
9/16
5/8
3/4
7/8
1
11/8
11/4 |
65
95
135
230
360
535
815
1125 |
13/8
11/2
15/8
13/4
2
21/2
23/4 |
1525
1900
2540
3240
4990
8525
10525 |
- Bolts should be progressively tightened in a star pattern to prevent cocking of the flange and uneven gasket pressure.
- Torque values listed are typical or alloy steel bolts (approximately 100,000 psi yield strength) used with carbon or intermediate alloy steel valves.
- Final torque required to pull up joint may vary greatly due to effects of temperature, corrosion, lubrication and thread finish.
- Torque requirements for a given bolt diameter may not be the same when used on valves of different material or special design. For best results consult Pacific Valves for recommendation.
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