Marine Glass Thermometer and Metal Case Thermometer

Product Overview

A marine glass thermometer lives or dies on the protection around the tube, and this one carries its own. A glass tube with a printed scale sits inside a cast aluminum case, so spray, dust and the occasional knock land on the case instead of the glass. The sensing bulb is carried in a brass thermowell — stainless steel where the medium calls for it — and the thermowell is the part that threads into the pipe, tank or duct. Compact and rigid, the assembly is built for the vibration, shock and salt air of an engine room, and it behaves the same way bolted to a plant line.

There is no bracket, no stand and no remote display to wire in. The unit screws straight into the pipe or vessel wall through its thermowell, and the length of the upper body keeps the scale clear of pipe lagging so the reading stays visible after the line has been insulated — a small detail that decides whether a gauge gets checked on every round or only when something goes wrong.

The scale spans chilled cooling water at one end and steam or hot process lines at the other. Most shipboard cooling work sits near the cold end of that span, which is why the same unit is often chosen as a ship cooling system temperature measurement thermometer on seawater and fresh-water cooling headers, while boiler feed and hot-water lines use the upper part of the scale.

We supply this model as a marine thermometer supplier to chandlers, repair yards and plant maintenance teams. Before an order is packed we check the thread, the working range and the body shape against the point where the gauge will sit, because those three details decide whether a thermometer fits on the first attempt.

Specifications

Metal Case, Thermowell & Glass Element

• Cast aluminum case with gold plating — the case takes the knocks and the spray before they reach the glass, and the plated finish keeps the body looking serviceable in salt air. The wider metal-case range is offered in both iron and aluminum bodies; this model uses the cast aluminum version.
• Glass tube with a printed scale — a marine glass thermometer reads directly from the liquid column, with no pointer, linkage or battery between the bulb and the number you write in the log.
• Brass thermowell, stainless steel on request — the thermowell is the wetted part and the part that carries the connection. Brass is the standard choice and covers most water, steam and oil service; stainless steel is specified where the medium is more aggressive.
• Blue sensitive liquid — the column is dyed blue so it holds contrast against the scale under the dim, uneven light of an engine room, where a pale column tends to disappear against a bright window.
• Threaded hex fitting — the body has flats for a spanner, so the unit seats square in the tapping instead of being forced in by hand.
• Generous upper body — long enough to hold the scale above lagging and insulation and to keep the window in the operator's line of sight without a step or a ladder.
• Liquid-filled dial versions in the same family — the dial thermometers in this range read through a pointer dial or a digital display, and some use silicone oil or glycerine as a damping and heat-transfer fluid. This unit is the glass-tube type: no filling to check, no pointer mechanism to drift.

Temperature Range & Scale Reading

The scale runs from -50 to 600 °C, wide enough for chilled cooling water, hot-water and lube-oil lines, boiler feed and steam in one body style. Rather than buying the whole span, tell us the band you actually work in — the scale can be built around your requirement, and a scale that covers only what you need is easier to read than a crowded one.

Read with the window square to your eye. Looking at the column from above or below shifts where it appears to meet the graduations, and on a finely divided scale that offset is easily larger than the change you are trying to detect. Contrast between column and scale matters as well when the only light comes from a bulkhead lamp behind you, and reading from the side of the window rather than straight on will cost you a division or more.

Accuracy for this class of thermometer is generally quoted as one to two scale divisions. What you see in service also depends on the ambient temperature around the case, the vibration of the line and the properties of the medium, so treat the reading as a practical indication rather than a laboratory value. A periodic check against a known reference — an ice-water bath at 0 °C, or a calibrated comparator — tells you whether the column still tracks; if it has shifted, replace the unit rather than adjusting your logs around it.

Lag is the other thing that affects what you record. Heat has to travel through the brass thermowell before the column moves, so a thermometer put into a line that has just changed duty will keep reading the old value for a while. Give it time to settle, then write the number down.

Installation & Commissioning

1. Check the unit before it goes in — glass intact, column continuous, scale legible, thermowell clean and undamaged.
2. Choose the head orientation first. A straight head suits a vertical tapping with clear space above it; a 90° head suits a horizontal pipe run, or a position where a deckhead or cable tray leaves no room for a straight body.
3. Match the connection and seal it. Confirm the thread against the tapping, use the hex flats with a spanner rather than the case as a lever, and seal with a thread compound suited to the medium.
4. Put the bulb where the medium actually flows — away from dead legs, away from the bottom of a pocket where sediment settles, and away from the stretch downstream of a closed valve.
5. Keep the window readable. Face it toward the walkway, platform or engine-room floor, and check that valve handwheels, lagging or pipe clamps will not obscure it once the line is back in service.
6. Bring the line up to temperature and check for leaks at the thread. If the thread or the body shape is still an open question, send a photo of the tapping to our team — as a marine thermometer supplier we match thread and body shape to installation points like this every week.
7. Guard against mechanical and chemical damage. Keep the case clear of direct contact with hot surfaces, avoid mounting points where a hose or chain will catch the head, and check that the medium is compatible with the brass or stainless steel thermowell.
8. Record the fit — tag number, range, date fitted and location — so the next survey or replacement does not start from a photograph again.

Applications

• Cooling systems and central air-conditioning — seawater and fresh-water cooling headers, chiller connections and the pipework of a ship's air-conditioning plant. This is the classic ship cooling system temperature measurement thermometer duty, where a gauge reading high is the first sign of a fouled heat exchanger or a lazy pump.
• Engine room machinery — diesel engines, boiler feed and hot-water lines, lubrication systems and oil tanks, where a direct glass reading is wanted without adding a sensor, a cable run and a display.
• Cargo holds and tanks — checking the temperature of liquids, gases and vapours in spaces where the gauge is read on a round rather than monitored from a control room.
• Plant and process lines — manufacturing plants, energy and mining sites, machinery repair shops and construction works, on water, steam, oil and air lines that fall inside the stated range.
• Food, beverage and hospitality — food and beverage factories, restaurants and hotel plant rooms, where a simple direct-reading thermometer on a hot-water or steam line is all the measurement the job needs.
• Maintenance and fault diagnosis — during a repair or a survey, the reading on the line tells you whether a circuit is actually cooling or heating before anything is dismantled.

Ordering & Delivery

1. Send the connection details — thread size and standard, plus a photo or sketch of the tapping. A photo of the failed gauge is often the quickest way to identify what you need.
2. State the working range and the medium — the band you actually operate in, and whether it is water, steam, oil, air or something more aggressive. That shapes the scale and the thermowell material together.
3. Confirm the head shape and the upper body length against the space at the installation point, including any lagging that has to be cleared.
4. Ask for the dimensional drawing and specification sheet, so the fit can be checked against your pipework before the unit is packed.
5. Confirm packing, quantity, lead time and freight with your sales contact — as a marine thermometer supplier we quote these against the order and the destination rather than publishing one number that fits nobody.
6. Keep the agreed specification on file for repeat orders: same range, same thread, same body shape. That is what makes the second order a short email instead of a new enquiry.

Technical Support & Model Matching

Buying instrumentation for a vessel or a plant usually comes down to matching the part to the job. Our team at Jiangmen Jiexi Machinery Equipment Co., Ltd. has worked with buyers worldwide since 2013, and we start before the order: confirming the range, thread, connection and mounting you need, checking a model or part number against the equipment on site, and saying plainly where a standard unit stops and custom work begins. After delivery we stay reachable for installation, commissioning and fault-finding, with quality control that includes two extra testing steps beyond industry standard.

FAQ