Flow Safe F84L Series

Need help?

Do you have a question about the Flow Safe F84L Series and is the answer not in the manual?

Overview

Function Description
Important Technical Specifications
Usage Features
Maintenance Features

The FLOW SAFE F84L Series Liquid Relief Valve is a direct-acting, spring-loaded relief valve designed for liquid service. It features plastic seating with elastomeric seals, ensuring reliable performance in various applications.

Function Description:

The primary function of the F84L Series valve is to protect systems from overpressure by relieving excess liquid. When the system pressure exceeds the valve's set pressure, the valve opens to discharge the liquid, preventing damage to equipment and ensuring safe operation. The valve is balanced against superimposed backpressure, meaning its set pressure will not change due to variations in backpressure.

Important Technical Specifications:

Orifice Sizes: Available in -2, -3, -4, -8, -G, and -J.
Set Pressure Range:
- Minimum Set Pressure (All Body Sizes): 50 psig (3.45 barg) for -2, -3 orifices; 30 psig (2.1 barg) for -4, -8, -G, -J orifices.
- Maximum Set Pressure:
  - 2-pc. Micro body: 24,277 psig (1674 barg)
  - C, D, E Body w/ small bonnet: 720 psig (49.6 barg) for -2, -3, -4, -8 orifices; 668 psig (46 barg) for -G orifice; 298 psig (20.5 barg) for -J orifice.
  - C, D, E Body w/ XL bonnet: 4292 psig (296 barg) for -2, -3, -4, -8 orifices; 3705 psig (255 barg) for -G orifice; 2700 psig (186 barg) for -J orifice.
  - C Body w/ XXL bonnet: 8382 psig (578 barg) for -2, -3, -4, -8 orifices.
Blowdown: Nonadjustable. Designed to be a maximum of 20% for -3, -4, -8, -G, and -J orifices. For the -2 orifice, blowdown may approach 30-35% at low flow rates or when the valve partially opens.
Soft Goods (Seats) Temperature Range:
- PI / PAI / Vespel: MAX 500°F (260°C), MIN -65°F (-54°C)
- PEEK: MAX 525°F (273°C), MIN 0°F (-18°C)
- Teflon (PTFE): MAX 400°F (204°C), MIN -65°F (-54°C)
- Kel-F (PCTFE): MAX 400°F (204°C), MIN -65°F (-54°C)
Soft Goods (Spindle Seals) Temperature Range:
- Buna-N: MAX 275°F (135°C), MIN -30°F (-34°C)
- Viton: MAX 400°F (204°C), MIN -30°F (-34°C)
- EPR: MAX 325°F (163°C), MIN -65°F (-54°C)
- Kalrez: MAX 525°F (273°C), MIN 0°F (-18°C)
- Polyurethane: MAX 225°F (107°C), MIN -65°F (-54°C)
- Note: Minimum temperatures for spindle seals should be confirmed with the factory for specific service/applications.
Set Pressure Adjustment Tolerances:
- 70 psig: ± 3% of specified set pressure
- < 70 psig: ± 2 psi
Seat Tightness: ZERO leakage at or below:
- For F84L -3, -4, -8, -G, -J: 0.90 x set pressure (if set pressure > 100 psig); 0.80 x set pressure (if set pressure < 100 psig).
- For F84L-2: 0.90 x set pressure (if set pressure > 500 psig); 0.80 x set pressure (if set pressure < 500 psig).

Usage Features:

Installation: The valve should be installed in an upright position, as close as possible to the pressure source to minimize pressure losses. Inlet piping pressure losses should not exceed 3% of the set pressure when the valve is flowing, in accordance with API 520 Part II. The discharge pipe must be sufficiently large to prevent backpressure from exceeding system design conditions. Inlet piping/flanges should have an opening equal to or greater than the valve's inlet diameter, free of obstructions. Wrench flats on the valve inlet bushing should be used for tightening, avoiding the cast body or bonnet.
Startup: Before installation, piping should be thoroughly cleaned to prevent foreign particles from damaging the valve. Inlet and outlet connections should be protected if the valve is not installed immediately. Pressure can be applied gradually, and the valve seat tightness should be verified.
Lift Lever Operation (Optional): If equipped, the lift lever allows for verification that the valve spindle and seat can open freely. It should only be operated when the inlet pressure is at least 75% of the nameplate set pressure. The handle is rotated clockwise or counterclockwise until resistance is met, then slowly rotated further until flow is indicated. The lift lever does not verify set pressure.

Maintenance Features:

Regular Maintenance Schedule: FLOW SAFE recommends placing all valves on a regular maintenance schedule, including routine replacement of softgoods every three years. However, customers should determine their own schedule based on use and environment.
Inspection: During routine maintenance, internal components should be inspected for damage, abnormal wear, and excessive corrosion. A corrosion allowance of 0.06" (1.5 mm) is designed into carbon steel components; operating with corrosion exceeding this allowance is not recommended.
Cycling: Cycling the valve at least once a year is considered good practice to verify operation and confirm that parts are not seized.
Disassembly: The valve must be removed from service or adequately blocked from incoming pressure before disassembly. Steps include removing lockwire, lift lever (if present), pressure adjusting screw cap, loosening the PA screw lock nut, and then disassembling the bonnet, spring, and spindle assembly. Specific instructions are provided for bolted-bonnet valves and F84L-2 two-piece micro bodies, including seat and O-ring removal.
Reassembly: Reassembly is the reverse of disassembly, with careful handling of softgoods. Inspection of nozzle seating and spindle guide surfaces is crucial, with polishing or replacement as needed. Lubricants (Neverseez or DuPont Krytox for oxygen service) should be applied to straight threads. The seat, seat retainer, and retainer screw (for bolted-bonnet valves) or push-in seat (for F84L-2) must be installed correctly. New drag seals and spindle seals should be carefully installed and lubricated with Desco 600 grease or Dow Corning Molykote 33, depending on the valve type and pressure. Bonnet bolts should be torqued to specified values. The PA screw and lock nut are reinstalled, and the valve is then ready for testing.
Testing and Adjustment: After maintenance, set pressure and seat tightness must be tested and adjusted. Setting the valve on water or other suitable liquid is recommended; setting on air may damage the seat.
Troubleshooting Guide: A comprehensive guide is provided to address common issues such as leaks (around bushing, through outlet, through atmospheric vent), valve not closing, valve opening below/above set point, and valve chattering or rapid-cycling. Possible causes and remedies are detailed, including tightening, cleaning, replacing damaged parts, adjusting pressure, and checking piping.
Softgoods Kits: Replacement softgoods are available in specific kits (Standard SG Kit and Lift Lever SG Kit) tailored to orifice size and valve type. These kits include items such as seats, bushing seals, rear seals, drag seals, spindle seals, shaft crush rings, and bushing crush rings.