Flange Spray Shields
Spray Shields for Lined Pipe in Acid and Caustic Service
A lined pipe protects the pipe. A spray shield protects the people beside it. The flanged joint is where a lined line will leak if it leaks at all, and a shield wrapped around the joint catches the spray, shows it, and drains it or turns it into a drip, which gives maintenance the time to isolate the line. We supply Drake Specialties safety spray shields with our lined piping systems: for every flange on the line and for the valves, expansion joints and unions between them. Spray shields are also called flange guards, splash guards or flange safety covers.
On hydrofluoric acid lines the shield is part of the specification rather than an afterthought: HF permeates PTFE, so HF spools are built with heavy-wall liners and vented housings, and the flanges get shields. The same logic applies to chlorine, hypochlorite, bromine and hydrogen peroxide, where a venting ball valve and a shielded joint go together. Our hydrofluoric acid page covers the piping side.
Shields are quoted line by line with the pipe and fittings and valves they protect, on the same quote, and ship with the order from Fairhope.
Choosing a Shield
Fabric shields for most chemical service; 316 stainless for steam, flammables, high temperature and high pressure. Name the fabric, or send the chemical, concentration and maximum temperature and we will pick it with Drake.
Fabric shields
| Fabric | Maximum temperature | Inspection and leak indication | Notes |
|---|---|---|---|
| Clear PTFE | 400 °F | Clear FEP center strip for inspection; optional ½" PTFE drain nipple | PTFE-coated glass cloth sides; the usual choice on lined pipe in acid and caustic service |
| Standard PTFE | 450 °F | Solid cloth, leak-indicating patch | PTFE-coated glass cloth, reinforced 3-ply with a fourth protective insert; fire resistant |
| Premium PTFE | 450 °F | Solid cloth, leak-indicating patch | Highest PTFE content, 3-ply, for extreme service and long life; fire resistant |
| Single-ply PTFE | 450 °F | Solid cloth, leak-indicating patch | One-layer economy version of the premium fabric |
| 100 % woven PTFE | 500 °F | Solid cloth, leak-indicating patch | Woven PTFE with no glass cloth, 100 % PTFE thread and cord; for the most severe service |
| Polypropylene | 200 °F | Solid cloth, leak-indicating patch; clear-center model available | Solid woven polypropylene, 3-ply with a fourth insert; the fabric Drake's guide gives for hydrofluoric acid |
| PVC | 170 °F | Clear-center or all-clear models; color-changing patch | Reinforced vinyl, 3-ply, safety orange or other colors; new plant start-ups, water treatment, food plants |
| Polyethylene | 170 °F | Transparent; optional leak-indicating patch | Reinforced 3-ply, the economy choice for milder service |
All fabric shields close with hook-and-loop fastening and a draw cord and are fitted by one person without tools. Solid-cloth shields carry a replaceable pH-indicating patch: toward red for an acid leak, toward green for an alkali. The PTFE fabrics are the ones Drake rates fire resistant. Source: Drake Specialties flange shield pages at drakespec.com and the fabric spray shield brochure, 2019 edition.
316 stainless shields and band protectors
316 stainless, 24 gauge; 304 to order. Valve shields fit ball, butterfly, plug and check valves and gate and globe bonnets with the handle or handwheel still usable. Source: Drake Specialties metal spray shield and flange band protector brochures, 2019 editions.
Chemical resistance guide · maximum shield temperature, °F
| Medium | Polyethylene | PVC | Polypropylene | Clear PTFE | PTFE | 316 stainless |
|---|---|---|---|---|---|---|
| Ammonia | 170 | 170 | 200 | 200 | 450 | 500+ |
| Ethylene dichloride | n/r | n/r | 75 | 75 | 450 | 500+ |
| Hydrochloric acid, to 35 % | 140 | 140 | 200 | 400 | 450 | 500+ |
| Hydrofluoric acid, to 85 % | 75 | 75 | 200 | n/r * | n/r * | 500+ |
| Nitric acid, to 30 % | 150 | 150 | 150 | 300 | 450 | 500+ |
| Oleum | n/r | n/r | n/r | 75 | 450 | 500+ |
| Sodium hydroxide, to 50 % | 170 | 170 | 200 | 300 | 450 | 500+ |
| Sulfuric acid, to 30 % | 170 | 170 | 200 | 300 | 450 | 500+ |
Shield exposure limits for the media listed, not a piping material guide. n/r = not recommended. * Hydrofluoric acid attacks the glass cloth under the PTFE coating: use polypropylene or 316 stainless. Other media: send the chemical, concentration and maximum temperature. Source: Drake Specialties fabric spray shield brochure, 2019 edition.
Shields for Every Joint
- Flange shields, fabric or 316 stainless, for every flange size and rating: ASME, API, DIN and PN, JIS and others, and non-standard sizes to dimensions.
- Valve shields for ball, check, butterfly, gate, globe, plug, diaphragm and control valves; bonnet shields let gate and globe stems travel.
- Expansion joint shields for rubber, stainless and PTFE bellows of any make, allowing the lateral movement; clear PTFE for watching the bellows.
- Fitting and union shields for elbows, tees, unions and couplings, including hammer unions.
- Pipe end covers in vinyl or PTFE fabric for safety relief valve and rupture disc vent outlets, straight or angled, any diameter.
- Specialty covers for actuators, pumps, camlocks, gauges and instruments, standard and custom.
What to tell us
- Flanges: size and rating
- Valves: size, rating, type, make and model, and whether flanged, socket-weld or threaded
- Expansion joints: size, make and model, number of convolutions or overall length
- Fittings: size and type
- Fabric: name it, or give the chemical, concentration and maximum temperature
- Options: drain nipple, clear window, pH patch, color
Ask about spray shieldsSpray shield datasheet (PDF)
Or call (251) 625-4949. The quote form takes shields line by line with the rest of the system.
FAQ: Spray Shields on Lined Pipe
Do I need a spray shield on every flange?
On lines carrying acid, caustic or anything that would hurt someone standing beside the joint, the usual practice is a shield on every flanged joint at working height or above a walkway, and on the valves, expansion joints and unions in the same line. Many plants shield the whole line; the cost of a shield is small against one spray-out.
Will a shield hide a leak?
No. A clear PTFE shield shows the joint through its window, and a solid shield carries a pH patch that turns toward red for an acid leak and toward green for an alkali. Either way the leak shows at a glance, and the shield has already contained it.
What happens to the liquid a shield catches?
A fabric shield holds it; the clear PTFE shield can be ordered with a PTFE drain nipple, so a caught leak drains to a safe place instead of pooling against the flange. Stainless shields disperse the spray to a drip and can take a drain nipple too.
Can a shield be reused after a leak?
Yes. The pH patch is replaceable: fit a new patch, refit the shield. The fabrics are chemical, UV and weather resistant, and the PTFE fabrics are also fire resistant; they are meant for years outdoors.
Which fabric for hydrochloric acid, and which for hydrofluoric?
For hydrochloric acid to 35 % Drake's guide rates the clear PTFE shield to 400 °F and the solid PTFE shields to 450 °F. For hydrofluoric acid to 85 % the guide does not recommend the PTFE-coated shields, because HF attacks the glass cloth under the coating, and gives polypropylene to 200 °F and 316 stainless to 500 °F and above. Drake also makes a 100 % woven PTFE shield with no glass cloth; ask us about it for an HF line.
Do you stock spray shields?
Shields are made to the flange size and rating, so we quote them with the pipe, fittings and valves they protect and ship them with the order. Send the sizes, the media, the concentration and the temperature and we will come back with the fabric and the price.
Spray shields by Drake Specialties, Lafayette, Louisiana, supplied by LinedPipe.Com with lined piping systems. Product data from Drake Specialties literature as cited; confirm sizes and ratings with the order acknowledgement.