Glass-Lined Pipe, Fittings and Equipment
Glass-lined steel is the oldest corrosion-resistant lining still in everyday service, and in pharmaceutical, fine chemical and specialty chemical plants it is still the reactor-train standard: a borosilicate glass lining fused to a carbon steel shell gives a surface that most acids, halogens and solvents cannot touch, that cleans to a visual standard, and that adds nothing to the product. Marspec Technical Products supplies glass-lined pipe and fittings, glass-lined process equipment and reglassing of existing equipment, alongside the PTFE-, PVDF- and polypropylene-lined pipe spools we fabricate. Call 251-625-4949 or contact us online with a nozzle schedule, a drawing or a vessel to be reglassed.
This page covers what we supply, where glass lining is the right choice, where it is the wrong one, and how it pairs with fluoropolymer-lined pipe in the same plant.
What glass lining is
A glass-lined vessel or pipe starts as a carbon steel fabrication. Several coats of borosilicate glass enamel are applied and fired at high temperature until they fuse to the steel, building a continuous glass layer typically one to two millimeters thick that is bonded to the metal. The glass carries the chemical resistance; the steel carries the pressure, the vacuum and the nozzle loads. The lining is smooth, non-porous and non-catalytic, which is why it is specified where product purity and cleanability matter as much as corrosion. Every glass-lined part is spark tested at high voltage to prove the lining is continuous, the same discipline we apply to fluoropolymer liners.
What we supply
Glass-lined pipe and fittings
Glass-lined steel pipe spools, elbows, tees, reducers and reducing flanges with split-ring (loose) flanges, so the glass flare on each piece seats on the next with a PTFE-enveloped gasket between and the steel flange ring floats free to align bolt holes. Flange drilling to ASME B16.5 class 150 or 300, or DIN 2873 for European equipment. Glass-lined pipe is the normal connection between glass-lined vessels in a reactor train: the overhead to the condenser, the bottom outlet to the receiver, the transfer line to the Nutsche filter. The size and flange standard are chosen to match the vessels, and the quote form on our contact page has a glass-lined category for exactly that.
Glass-lined process equipment
Glass-lined reactors with jackets or half-pipe coils, agitators and baffles; distillation and stripping columns; receivers and storage tanks; shell-and-tube and coil heat exchangers; and Nutsche filters and filter-dryers for isolating a product cake under nitrogen. Nozzle counts, manways, sight and light glasses, bottom outlet valves and agitator seals are specified to your process. We quote new equipment to your data sheet and reglassing of equipment you already own; the Other Products page summarizes the range.
Reglassing
A glass-lined vessel whose lining has reached the end of its life can be stripped, repaired and reglassed, returning a shell with known history to service for a fraction of the cost of new equipment. Send photos, the original data sheet and the inspection report and we will quote the reglass and the lead time with it.
Where glass lining is the right choice
Glass lining resists hydrochloric, sulfuric and nitric acid across the concentration range, bromine and chlorine chemistry, organic acids and nearly all solvents, and it does so at the temperatures of a jacketed reactor. That covers the halogenation, acid chloride, nitration, esterification and solvent recovery steps of active pharmaceutical ingredient, advanced intermediate and agrochemical synthesis, which is why the reactor train in a fine chemical plant is glass-lined by default. The second reason is cleanability: a glass surface rinses clean between campaigns, shows residue to the eye, and leaves no iron or nickel in a product that will be measured in parts per million. The third is inertness; glass does not catalyze side reactions the way a metal surface can. Our pages on pharmaceutical and fine chemical plants and on chlor-alkali and chemical plants describe the processes, and the service pages on hydrochloric acid, nitric and mixed acids and solvents cover the chemistry.
Where it is the wrong choice
Glass has three enemies, and a specification that ignores them fails quickly. Hydrofluoric acid and any fluoride-bearing stream dissolve glass; there is no glass-lined service for HF, fluosilicic acid, ammonium bifluoride or nitric-hydrofluoric pickling acid, and our hydrofluoric acid page explains what to use instead. Hot strong alkali attacks glass; caustic above roughly pH 12 at elevated temperature etches the lining, so a caustic hydrolysis or a hot caustic clean belongs in fluoropolymer-lined or alloy equipment, and hot concentrated phosphoric acid is in the same category. Thermal shock and mechanical impact crack glass: a vessel has a limit on how fast its contents and jacket can change temperature, and a dropped tool or a hard object in a Nutsche filter can chip the lining, which is why glass-lined equipment is inspected and spark tested on a schedule and repaired with tantalum plugs and patches when a chip is found.
Glass-lined vessels, fluoropolymer-lined lines
The most common arrangement in a fine chemical plant is glass in the vessels and PTFE in the pipe. Reactors, columns, receivers and filters are glass-lined; the transfer lines, charge lines, vent headers and solvent recovery piping between them are PTFE-lined steel spools and fittings, with PTFE- or PFA-lined ball, plug and diaphragm valves. The two systems bolt together at an ANSI B16.5 flange, the PTFE flare of the lined pipe against the glass flare of the nozzle with an enveloped gasket between, and neither puts metal in the wetted path. Fluoropolymer-lined pipe is lighter, tolerates thermal cycling and vibration better, is easier to field-fit and reconfigure, and handles the caustic and fluoride services glass cannot. Glass wins inside the vessel on cleanability, visibility and the sheer surface area it protects. Specify each where it is strongest, and ask us for both from one source: lined pipe and fittings, lined valves, and the glass-lined pipe, fittings and vessels to go with them. Liner temperature limits and flange data for the fluoropolymer side are on our technical details page.
Specifying and quoting
For pipe and fittings, send the sizes, the flange standard (ASME class 150 or 300, or DIN 2873) and a sketch or isometric; for vessels and filters, the data sheet or the process conditions, nozzle schedule, jacket and agitation requirements, and the glass specification if your plant has one; for reglassing, the original nameplate data and the inspection findings. Our lined pipe products comply with ASTM F1545 and the fluoropolymer-lined fittings conform dimensionally to ANSI B16.5; glass-lined equipment is supplied to the applicable pressure vessel code and the manufacturer's glass standard, with the test certificates your quality system needs. We ship nationwide from Fairhope, Alabama. Call 251-625-4949 or contact us online.
FAQ: Glass-Lined Pipe and Equipment
When should I choose glass-lined pipe over PTFE-lined pipe?
Between glass-lined vessels in a reactor train, where the connection matches the vessel nozzles and the whole wetted path stays glass and PTFE gasket. For transfer lines, vent headers, utility chemical lines and anything that will be re-routed or cycled hard, PTFE-lined steel is lighter, tougher and handles the caustic and fluoride services glass cannot.
Can glass-lined equipment handle caustic or hydrofluoric acid?
No to both. Hydrofluoric acid and any fluoride stream dissolve glass, and hot strong caustic above roughly pH 12 etches it. Those services go in fluoropolymer-lined or alloy equipment; the reactor can still be glass-lined if the caustic step is cool and dilute, which we will confirm against the glass manufacturer's data.
What flange standard does glass-lined pipe use?
Split-ring loose flanges drilled to ASME B16.5 class 150 or 300 for North American plants, or DIN 2873 for equipment of European origin. Tell us which your vessels carry and the pipe and fittings will match; adapters are available where a train mixes the two.
Is reglassing a vessel worth it compared with buying new?
Usually, when the steel shell, nozzles and jacket are sound. Reglassing restores the lining to new condition at a fraction of the cost and lead time of a new vessel. Send the nameplate data, photos and the last inspection report and we will quote both options so you can compare.