Refineries and petrochemical
VOC · hydrocarbons · API 622 / API 624
Control of fugitive emissions of volatile organic compounds in hydrocarbon lines. Compliance with API 622, API 624, ISO 15848-1.
Belleville Washers
for valves
Live loading on the gland packing of the stuffing box: they keep the sealing pressure constant despite packing wear, thermal cycling and relaxation.
Temperature range
−240 °C → +800 °C
Reference standard
MSS SP-143
Engineering support
In-house engineering team since 1974
01
What valve live loading is
Live loading consists of inserting one or more stacks of Belleville washers between the nut and the gland follower of the valve. As the studs are tightened, the washers are partially compressed and remain in a preloaded elastic state.
While the valve operates, the packing wears, flows or relaxes due to temperature. Without live loading, the sealing force drops until it causes leakage and requires periodic manual retightening. With Belleville washers, the stack releases its stored deflection at the rate of packing wear, keeping the closing force within the useful range for thousands of cycles.
The benefits are measurable: the sealing stress stays within the admissible range even as the packing flows or wears, manual retightening is reduced, it helps comply with fugitive emission regulations (API 622, API 624, ISO 15848-1, TA-Luft), it absorbs thermal cycling of the stud-body-packing assembly and it dampens vibration, preventing the loosening of the fasteners.
The reference standard for live loading packing systems is MSS SP-143 · Live-Loaded Valve Stem Packing Systems.
FIG · stuffing box section with Belleville stackswashers → highlighted in green
Technical section → the assembly includes the stem, the stuffing box studs and the Belleville stacks under each nut. The packing (cross-hatched, bottom) receives the axial force through the gland follower.
Dynamic cycle → as the packing wears, the washer releases its stored deflection and restores the closing force without manual retightening.
02
When to use Belleville washers in a valve
Live loading with Belleville washers is especially recommended when one of the following conditions is met. The more conditions are met, the greater the benefit of live loading.
Industry data indicates that between 50% and 80% of leaks in industrial bolted joints are caused by loss of preload, and a very significant share of fugitive VOC emissions in petrochemical plants comes from valves and flanges with poor sealing.
They are not used in valves with a metal bellows seal (bellows-sealed), where there is no packing on the stem. Nor in valves with no load-maintenance requirement (static service without thermal cycling).
Packing
Valve with packing
Applicable to all valves with packing on the stem. Does not apply to valves with a metal bellows seal.
Frequency
High number of cycles
Control valves with constant modulation or frequent ON/OFF service — where packing wear is accelerated.
Actuation
Motor-operated valve (MOV)
Electric or pneumatic actuators where manual stuffing box adjustment is hard to coordinate with operation.
Access
Costly maintenance
Valves in hard-to-reach areas, insulated lines or cryogenic insulation where each retightening requires a plant shutdown.
Service
High temp. or high pressure
Wide thermal cycling between start-up and steady state — the stud-body-packing assembly expands differentially.
Criticality
Safety and continuity
Lines critical for process safety, fire control or plant continuity — where a leak means a shutdown or a hazard.
History
Recurring leaks
Valves with a history of packing leaks — the first candidate for conversion to live loading.
Regulation
Emissions regulation
Applications subject to LDAR, EPA, IED or TA-Luft — where fugitive leakage is subject to a measurable legal limit.
PHOTO · valve with live loading installed
Assembly in service · stacks visible on each stuffing box stud.
— Operational benefit
Keeps the sealing stress within the admissible range even as the packing flows, wears or the assembly undergoes wide thermal cycling.
Live loading reduces manual retightening, dampens vibration, helps comply with fugitive emission regulations and extends the service life of the packing.
Source · MSS SP-143 · API 622 · ISO 15848-1
03
Stacking configurations
The load capacity and total deflection of the spring are tuned by combining several washers in different orientations. There are four basic configurations — the choice between series, parallel or a mixed configuration is one of the most important design decisions in a live loading system.
parallelSame orientation
The washers are stacked directly in the same orientation. The total travel equals that of a single piece; the force is multiplied by the number of units. There is friction between the discs → curve with hysteresis.
seriesFacing opposite
The washers are placed alternating their orientation. The resulting force equals that of a single piece; the travel is multiplied by the number of units. No friction between washers → clean curve.
parallel-seriesCombination
k groups in parallel stacked in alternating series. Allows fine tuning of the trade-off between load and travel. The most common configuration in medium and large valves.
FIG · stacking configurations
FIG · side diagram · orientation of each washer
— Practical rules for sizing
Recommended minimum pretension
≥ 15% of the total travel — avoids hysteresis and working in the soft zone
Recommended maximum dynamic load
≤ 75% of the total travel — F(0.75 h₀), prolonged fatigue zone
Loss from initial relaxation
~ 5% during the first two weeks after assembly
Mixing thicknesses
Allowed in series — produces an F/s curve with sections of progressive stiffness
The recommended working deflection for prolonged fatigue is between 15% and 75% of the total travel of the individual spring.
— Data needed to define the stack
- Stud diameter of the stuffing box.
- Target preload (torque or force) calculated by the packing supplier.
- Radial clearance (RC) available around the stud — defines the maximum external diameter of the spring.
- Axial clearance (AC) available between the nut and the stuffing box — defines the maximum stack height.
Let's talk about your project
Tell us about your use case and our engineering team will help you choose the optimal solution.
04
Materials for Belleville washers in valves
The material defines the temperature range, the corrosion resistance and the fatigue behaviour. Surisa works with five alloys that cover virtually all industrial applications. The selection depends on the service temperature, the working atmosphere and the frequency of thermal cycling.
17-7 PH
X7CrNiAl17-7 · 1.4568 · AISI 631
−240 → +300 °C
Rm up to 1,700 N/mm²
De facto standard for industrial valves: high mechanical strength, good corrosion resistance and stable fatigue behaviour.
In marine environments or with aggressive chlorides it may require an additional silver-nickel coating.
Inconel 718
NiCr19NbMo · 2.4668 · AMS 5596
−240 → +600 °C
Non-magnetic · stable creep
Cryogenics (LNG, liquid H₂), severe corrosion, continuous high temperature. Replaces 17-7 PH above 350 °C or in aggressive atmospheres.
Reference material for services where the seal allows no retightening: petrochemical, LNG, severe chemical.
H-13
X40CrMoV5-1 · 1.2344
up to +500 °C
Hardness retained at high temp.
Hot-work tool steel, 5% Cr base. Common application in superheated steam and non-corrosive high-temperature process lines.
Not stainless — limited to dry atmospheres without corrosive agents.
Inconel X-750
NiCr15Fe7TiAl · 2.4669 · AMS 5598
up to +600 °C
Prolonged service
Precipitation-hardenable nickel alloy. Prolonged continuous service at high temperature without significant loss of elastic load.
An alternative to Inconel 718 when long-term dimensional stability is the priority.
Nimonic 90
NiCr20Co18Ti · 2.4632 · AMS 5829
up to +800 °C
Extreme cases
Nickel-cobalt-based superalloy. Reserved for extreme cases: refineries with severe service, turbines, hot gas lines.
The final-choice material when no other one retains its elastic properties in service.
17-7 PH is the default material in most industrial valves: it combines high mechanical strength (Rm up to 1,700 N/mm²), good fatigue behaviour and enough corrosion resistance for typical environments.
In marine environments or with aggressive chlorides it may require an additional silver-nickel coating. For cryogenic service (LNG) or steam above 350 °C it is replaced by Inconel 718; in oxidising service at very high temperature, Nimonic 90 retains its properties up to 800 °C.
The ranges are indicative for preliminary design. The admissible service temperature also depends on the load, the frequency of thermal cycling and the atmosphere.
FIG · service temperature ranges by material
05
Valve types compatible with live loading
Belleville washers are used in practically any valve with packing subject to cycling. The most common configurations:
GateGate
Isolation valves with packing on a rising stem. Live loading is common in process lines at temperature.
GlobeGlobe
Regulating valves with a linear stem. Most common application — high cycle frequency and packing wear.
BallBall
Quarter-turn valves with stem packing. Live loading on the seal of the obturator shaft.
ButterflyButterfly
Shaft sealed by packing in large-diameter valves. Common application in water and air treatment lines.
ControlControl
Continuous automatic modulation — the packing works in a permanent cyclic regime and demands live loading.
MOVMotor-operated
Motor-operated valves in hard-to-reach installations. Manual retightening is not operationally viable.
— Exception
They are not used in valves with a metal bellows seal, where there is no packing on the stem. In these cases sealing relies on the welded bellows and the Belleville washers have no function.
06
Industrial sectors and applications
Belleville washers for valves are the standard when a packing leak has critical consequences — safety, plant shutdown, environmental penalty — and the environment makes the loss of initial preload inevitable.
Oil & Gas (upstream · midstream)
Wellheads · manifolds · transport
Valves in wellheads, manifolds and transport lines where prolonged service without accessible maintenance is the norm.
LNG · FLNG
Cryogenics down to −160 °C
Cryogenic valves where the thermal contraction of the assembly compromises sealing. Standard solution with Inconel 718.
Chemical and pharmaceutical industry
Aggressive fluids · high purity
Valves in contact with corrosives or in high-purity service, where a leak is unacceptable for safety or cross-contamination reasons.
Power generation
Steam · thermal · nuclear
High-temperature steam valves in thermal and nuclear power plants, within reliability and maintenance-reduction programmes.
Water treatment
Regulating · high cycling
Regulating valves with a high number of daily cycles where packing wear is the main cause of leakage.
07
Frequently asked questions
01 Which Belleville washer material is most used in industrial valves?
The most widely used material is 17-7 PH stainless steel (X7CrNiAl17-7 / 1.4568 / AISI 631), which works between −240 °C and +300 °C. It combines high mechanical strength, good corrosion resistance and a competitive cost, which makes it the de facto standard for general-service valves in petrochemical, chemical and industrial installations. For temperatures above 350 °C it is replaced by Inconel 718, H-13 or Nimonic 90 depending on the range.
02 Which stacking configuration should I use in my valve?
It depends on the force and deflection required. As a general rule: parallel multiplies force without increasing travel, series multiplies travel without increasing force, and the parallel/series combination lets you tune both. To define the stack you need the stud diameter, the target preload (calculated by the packing supplier), and the available radial and axial clearances. Our engineering team can size the stack from that data.
03 Do Belleville washers help comply with fugitive emission standards?
Yes. Live loading with Belleville washers is one of the recognised methods to reduce fugitive emissions in industrial valves and helps comply with API 622 (packing testing), API 624 (rising stem valves for low emissions), ISO 15848-1/2 and TA-Luft VDI 2440. The specific standard for live loading packing systems is MSS SP-143, Live-Loaded Valve Stem Packing Systems.
04 What is the difference between live loading and a conventional stuffing box?
In a conventional stuffing box the force on the packing depends on the initial tightening torque and is progressively lost through wear, creep and thermal expansion, requiring periodic manual retightening. In a live-loaded system, the Belleville washers store elastic energy on installation and release it progressively at the rate of wear, keeping the sealing force constant for thousands of cycles without intervention.
05 Can Belleville washers be used in cryogenic or LNG valves?
Yes. For cryogenic service (down to −240 °C), the recommended materials are Inconel 718 and, in specific cases, 17-7 PH, which retains its mechanical properties at very low temperatures. In LNG/FLNG installations the thermal contraction of the valve-packing assembly is one of the main leakage factors, and live loading with Belleville washers in Inconel 718 is the standard solution to keep the seal under those thermal gradients.
06 What data does Surisa need to size the stack for my valve?
Four parameters that the process engineer or the packing manufacturer normally provides: (1) the stuffing box stud diameter, (2) the target preload in torque or force calculated by the packing supplier, (3) the radial clearance available around the stud — defines the maximum external diameter of the spring, and (4) the axial clearance between the nut and the gland follower — defines the maximum stack height. With that data we select the material and configuration.
07 Does live loading apply to bellows-sealed valves?
No. Metal bellows valves do not have packing on the stem, but a welded bellows that acts as the primary seal. There is no packing on which to apply load, so the Belleville washers have no function. In this case sealing relies solely on the integrity of the bellows.
Let's talk about your project
Tell us about your use case and our engineering team will help you choose the optimal solution.