Broken pressure gauge

Pressure gauge failure can be attributed to one or more of these eight reasons: mechanical vibration, pulsation, extreme temperature, pressure spikes, overpressure, corrosion, clogging, and mishandling/abuse.

Pressure gauges are an integral part of an application’s warning system. By constantly measuring pressure, these instruments allow users to see how a process is doing. Gauges are sturdy and can handle challenging conditions. However, even the hardiest instruments will experience failure if they weren’t designed for a specific application or condition.

At WIKA USA, our customers often ask us why their gauges are damaged or stopped working properly. With decades of pressure experience, we have seen all the causes of pressure gauge failure.

Inner workings of a Bourdon tube pressure gauge

diagram of a Bourdon tube pressure gauge

How A Pressure Gauge Works

Before getting into why things go wrong and how to troubleshoot the problem, it’s important to first understand the inner workings of a mechanical gauge, the most popular of which is the Bourdon tube pressure gauge.

The Bourdon tube is a hollow C-shaped spring element within the case. As the tube is pressurized from the media entering it, it starts to move – like a balloon trying to equalize. This movement is translated through the connecting link, attached to the Bourdon tube via the end piece, into a pressure measurement that the pointer indicates on the dial.

8 Causes of Gauges Failure

When a pressure gauge doesn’t work as expected, the cause can be traced back to at least one of these eight reasons:

1. Mechanical vibration

Numerous studies have shown that vibration is the main cause of pressure gauge failure in manufacturing facilities. Vibration has a negative impact on gauge accuracy in two ways. First, it is difficult to read the pointer on a dial when a gauge is vibrating. Second, incremental damage to the pointer mechanism from vibration can eventually move a pointer off zero, producing inaccurate readings.

Visible signs of mechanical vibration

  • Metal filings/dust, like a halo, inside the gauge window from worn pinion and segments gears
  • Detached pointer if the vibration is severe
Effects of mechanical vibration on pressure gauge

(left) halo inside gauge window; (right) detached pointer


Risks posed by mechanical vibration

  • Wear and tear of internal components
  • Loss of accuracy/functionality
  • Pressure system failure

(left and center) worn pinion gears; (right) worn segment gear

 

Diaphragm seal with flanged process connection

model 990.28 diaphragm seal

Solutions for gauges experiencing mechanical vibration

For most situations, a liquid-filled case is the most convenient and cost-effective way to protect pressure gauges from vibration. The glycerin or silicone-oil case fill acts as a damper to slow down the movement. It also lubricates the pinion and segment gears, thereby reducing wear and prolonging the life of a gauge.

A second solution is to move the gauge away from the source of the vibration. How? Use a diaphragm seal with capillary connection, like the 990.28 cell-type (sandwich) seal. A diaphragm seal can be mounted practically anywhere in the application, and the line allows for remote reading. (See this video and blog for more info on how diaphragm seals work.)

2. Pulsation

Effect of pulsation on pressure gauge

pointer flutter

Vibration refers to regular oscillation of mechanical parts. Pulsation, on the other hand, is regular instances of rapid pressure increases and decreases of the media.

Visible signs of pulsation

  • Pointer flutter
  • Loose or broken pointer in extreme cases

Risks posed by pulsation

  • Difficulty in obtaining an accurate reading
  • Wear and tear of internal components
  • Loss of accuracy/functionality
  • Pressure system failure
Snubber and restrictor

(left) snubber; (right) socket restrictor

Solutions for gauges experiencing pulsation

As with mechanical vibration, a liquid-filled case is an easy solution. So are valves and protective devices like a socket restrictor. This small device has a small orifice to restrict and slow down the pressure of the media before it encounters the gauge. Restrictors are cost-effective and easy to install. Several gauges, like model 111.11 for compressed gas regulators, come standard with a restrictor already threaded into the bore.

For more extreme pulsation, use a snubber or needle valve. Snubbers function like restrictors but come in more material choices, orifice sizes, and psi ratings. Snubbers are also less prone to clogging and are more adjustable in the field, thanks to interchangeable pistons or adjustment screws. Needle valves also throttle the media, thereby reducing the impact of pulsations. These pulsation dampeners are commonly found in pump discharge and boiler house applications.

3. Extreme temperature

Different gauges have different tolerances for extreme temperatures. We look at both ambient temperatures, such as what is found in the Arctic or around a furnace, and the temperature of the process media.

Effect of extreme temperature on pressure gauge

gauge discoloration

Visible signs of extreme temperature

  • Dial and/or liquid fill is discolored, usually yellow, orange, brown, or black
  • Dial, case, or window is melted – usually because the media is too hot

Risks posed by extreme temperature

  • Difficulty in obtaining an accurate reading
  • Loss of accuracy/functionality
  • Pressure system failure

Solutions for gauges in extreme temperatures

Cooling adapter

model 910.32.250 mini cooling adapter

A diaphragm seal with capillary allows pressure measurement to occur away from extreme ambient or media temperatures. The longer the run, the more heat is dissipated before the pressure reaches the gauge. Or attach a cooling adapter like the 910.32.200 (up to 500°F/260°C) or 910.32.250 (up to 700°F/370°C). With fins to increase the surface area, these adapters are very effective at radiating and dissipating heat. They’re also extremely easy to retrofit using threaded connections. Pigtail, coil, and mini (rod and cap) siphons use the same principle to dissipate heat.

Glycerin is the typical fill fluid for pressure gauges. For extremely hot or cold ambient temperatures, silicone oil is the better choice as it will not discolor in heat over time or freeze in sub-zero environments.

4. Pressure spikes

Spikes occur when the pressure sharply increases and then suddenly drops. This condition can cause all sorts of problems for gauges not designed for this condition.

Effect of pressure spikes on mechanical gauges

bent pointer

Visible signs of pressure spikes

  • Bent pointer, like a fishtail or fish hook, from hitting the stop pin too often
  • Nicked or broken pointer from hitting the stop pin too hard
  • Broken stop pin

Risks posed by pressure spikes

  • Increased wear on movement and components
  • Loss of accuracy/functionality
  • Split Bourdon tube, leading to released media
  • Pressure system failure

Solutions for gauges experiencing pressure spikes

As with pulsation, good solutions for dampening the effects of pressure spikes are to use a liquid-filled gauge and/or accessories like restrictors, snubbers, needle valves, or diaphragm seal with capillary. Another way to prevent damaged pointers and internals is to replace the gauge with one that has a higher pressure range. A good rule of thumb is to choose a gauge that is two times the expected pressure maximum. So, if a process typically reaches 500 psi, use one that goes up to 1,000 psi.

For greater reassurance that a gauge never exceeds a certain maximum, attach an overpressure protector to the instrument. This unique option allows the user to changing the maximum pressure setting. If the pressure ever reaches that value, the protector’s spring-loaded piston valve will automatically close, preventing the gauge from experiencing the spike. And when the system pressure drops approximately 25% below pre-set maximum, the valve with automatically reopen.

5. Overpressure

Effect of overpressure on mechanical gauges

pointer buried against stop pin

This situation is very similar to pressure spikes, but occurs when the gauge regularly measures pressures near or at the maximum range. We typically see this condition in water/wastewater treatment and gas lines.

Overpressure can cause the Bourdon tube to deform and split. This is major problem because a rupture allows caustic media, such as the hydrofluoric (HF) acid in alkylation units, to escape. In pharmaceutical manufacturing, a rupture event ruins very expensive product and leads to shutting down the line, quarantining the product, and re-sterilizing the process.

Visible signs of overpressure

  • Pointer buried against stop pin
  • Pointer dislodges stop pin

Risks posed by overpressure

  • Increased wear on movement and components
  • Overpressure protector

    model 910.13 overpressure protector

    Loss of accuracy/functionality
  • Split Bourdon tube, leading to released media
  • Pressure system failure

Solutions for gauges experiencing overpressure

As overpressure is similar to pressure spikes, so is the fix: use a gauge with a higher pressure range, and attach an overpressure protector.

6. Corrosion

Corrosion on a pressure gauge

corroded pressure gauge

Many industries work with harsh chemicals: hydrofluoric acid in refineries, flocculants and chlorine in wastewater treatment, chlorinated gases in fiber optic production, and so on. These media find their way into gauges.

Visible sign of corrosion

  • Discoloration and deterioration of the gauge case, pointer, connection, and dial

Risks posed by corrosion

  • Loss of accuracy/functionality
  • Pressure system failure

Solutions for gauges in corrosive environments

Isolate the gauge from harsh chemicals by using a diaphragm seal made of the appropriate corrosion-resistant materials. WIKA’s diaphragm seals come in a variety of standard and exotic alloys for both the wetted and non-wetted parts: 316L and 316 TI stainless steels, Hastelloy®, Monel®, Inconel®, tantalum, and titanium. The metals can be left as-is or, for extra protection, lined with Teflon® or plated with gold. When deciding on the materials for your diaphragm seals, look at what the existing wetted parts are made of, and choose those.

Clogged pressure gauge

clogged pressure gauge

7. Clogging

Clogging is an issue for paper plants, wastewater plants, pharmaceuticals, and other industries, as slurry, pulpy, viscous, and high-particulate media can gum up the system.

Visible sign of clogging

  • Gauge at or near zero when the system is operating

Risks posed by clogging

  • Loss of accuracy/functionality
  • Possibility of overpressure

Solutions for gauges measuring clogging media

Again, use a diaphragm seal to separate the gauge from the challenging media. An excellent solution is WIKA’s All-Welded System (AWS), an assembly comprising an XSEL® industrial process gauge permanently welded to a bell-shaped diaphragm seal.

As the AWS still has a small orifice that the media can enter, customers can opt for versions with a flushing port. This component allows operators to clear away media either when clogging occurs or during regular maintenance.

Another solution is WIKA’s INLINE™ diaphragm seals, which has smooth walls for full flow-through. By eliminating dead spaces, there’s no risk of media buildup.

8. Mishandling/abuse

Gauges look sturdy, especially the larger process gauges, but they are not designed to be handles or footholds! During site visits, we often see evidence of gauge mistreatment. Operators might grab on to a gauge as they move around process skids on wheels, or step on them as they climb scaffolding. Not only is this practice unsafe, it increases the chances of gauge damage and failure. 

Effects of mishandling and abuse on a pressure gauge

pressure gauges with broken window (left) and cracked case (right)


Visible signs of mishandling/abuse

  • Cracked case
  • Broken window
  • Loss of case filling
  • Crooked or bent gauge and/or process connection

Risks posed by mishandling/abuse

  • Loss of functionality

Solutions for gauge mishandling/abuse

Training is the best prevention. Employees should be aware of the dangers of mishandling gauges. They should also know how to properly connect gauges. For example, when threading the gauge onto the process, some people tighten it by hand, which risks torquing the case. When the NPT or G connection has a wrench flat area, use a wrench to tighten the gauge.

WIKA USA’s pressure specialists have decades of experience diagnosing why gauges fail, and then coming up with solutions so that instruments last longer. When the causes aren’t obvious, we encourage customers to take advantage of our Instrument Failure Analysis (IFA) program. Send the failed gauge to our facilities in Lawrenceville, Georgia, and our engineers will conduct a full evaluation on the nonfunctioning gauge – all free of charge. Contact WIKA USA for more information about why pressure gauges fail and what you can do to solve the problem.



One Response to
  1. Rupali Mhaske

    Good information put together


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