A pressure gauge looks like the simplest thing on the line, so it's often the last thing anyone thinks about. Then the pointer is pinned against the stop, or it's vibrating so hard nobody can read it, or the case is full of fog. After 20 years in this trade, I can tell you most gauge problems come down to how it was picked, not how it was made. Here's what to look at before you order.
1. Pick the Range First
A good rule of thumb is to choose a gauge whose full-scale range is about twice your normal operating pressure. That keeps the pointer near the middle of the dial, where the gauge is easiest to read and most accurate, and it leaves room for spikes without overpressuring the Bourdon tube.
- Running near full scale wears the tube and can take the gauge out of calibration for good.
- Running near zero on a big range makes small changes hard to see.
- Vacuum or swinging between vacuum and pressure? Use a vacuum or compound gauge, not a standard pressure range.
2. Glycerin Filled or Dry?
Glycerin filled gauges damp pointer flutter from vibration and pulsation, so they're the right call on pumps, compressors and hydraulic units. The fill also keeps the movement lubricated longer. Dry gauges suit steady pressure, and locations where the fill could be a concern. If you're working in cold weather, ask about the fill before you order, since temperature affects how a filled gauge behaves.
3. Dial Size and Accuracy
Small 1-1/2" to 2-1/2" dials fit tight panels, skids and instrument manifolds. When the gauge has to be read from across the room, or the job calls for tighter accuracy, step up to a 4-1/2" process gauge.
4. Mounting and Connection
- Bottom (lower) mount for a gauge threaded straight into a line or tee.
- Center back mount for panels and manifolds where you look at the gauge head-on.
- Panel mount with a U-clamp or front flange for control panels.
Match the connection size, usually 1/8", 1/4" or 1/2" NPT, to what's in the field. Use thread sealant on the NPT threads, hold the gauge by the wrench flats on the socket, and never twist it on by the case.
5. Protect the Gauge
Some service will kill even a good gauge if it's left unprotected:
- Pulsation or pressure spikes: add a snubber.
- Hot steam: use a syphon so condensate, not live steam, reaches the gauge.
- Corrosive, viscous or dirty media: use a diaphragm seal so the process never touches the Bourdon tube.
- Isolation for change-out: install a needle or gauge valve so you can replace the gauge without shutting down the line.
6. Material and Environment
All stainless steel gauges, with a stainless case, stainless wetted parts and a welded case-to-stem, hold up in washdown, offshore, outdoor and corrosive service. Here near the harbor, salt air eats painted and brass gauges fast, so stainless is worth it on any outdoor line.
What to Send Us
Dial size, range and units, mounting, connection size, glycerin filled or dry, and any options like a diaphragm seal, snubber, gauge valve or calibration certificate. With that, we can usually match a gauge from our local inventory of stocked gauges the same day.
A-Best Industrial Inc. Fittings, Valves, and Tubing keeps 1-1/2" to 2-1/2" all stainless steel gauges and 4-1/2" process gauges on the shelf in San Pedro, plus thermometers, thermowells, diaphragm seals, gauge valves and accessories. See our pressure gauges page or download the stocked pressure gauges spec sheet (PDF). For gauge isolation, browse our needle valves.
Not sure which gauge fits your line? Call A-Best Industrial Inc. Fittings, Valves, and Tubing at 310-833-3353 or email sales@abesttube.com. We're here Monday through Friday, 8:00 AM to 5:00 PM Pacific, with after-hours emergency service.