Safety Shield Selection Guide | Pressure, Temperature & Chemical Compatibility

Learn how to select a flange safety shield using pressure, temperature, chemical compatibility, inspection needs and installation conditions.

Selecting a Safety Shield Requires More Than Matching the Pipe Size

Safety shields, flange guards and spray shields are secondary protective devices fitted around mechanical pipe connections. Their purpose is not to stop a gasket from leaking, but to help contain, diffuse or redirect an unexpected release so that a concentrated jet or spray is less likely to reach nearby personnel and equipment.

The correct shield depends on the actual service conditions. A product that performs well on a low-temperature chemical line may be unsuitable for high-temperature steam, while a mechanically robust metal shield may not provide the chemical compatibility or visual inspection features needed elsewhere. For most applications, selection begins with three primary factors: pressure, temperature and chemical compatibility.

Selection factor	What to establish	Why it matters
Pressure	Flange class, normal operating pressure, upset conditions and connection geometry	Influences sizing, construction and the energy of a potential release
Temperature	Normal and maximum operating temperature, including start-up and shutdown conditions	Determines whether fabrics, fasteners, windows and seals remain suitable
Chemical compatibility	Process fluid, concentration, phase and possible reaction products	Prevents degradation and supports suitable visibility, drainage and containment features

1. Pressure: Distinguish Flange Class From Shield Performance

Flange pressure class and safety-shield performance are related, but they are not the same measurement. ASME flange classes such as Class 150, 300, 600, 900, 1500 and 2500 describe a flange system whose allowable working pressure varies with material and temperature. The class also changes the flange outside diameter, thickness and bolt arrangement, which affects the physical size of the shield.

A shield therefore has to fit the connection geometry and also be suitable for the energy and characteristics of a possible release. Specifying a shield only as "for a Class 300 flange" does not confirm suitability for every Class 300 application. The actual operating pressure, temperature, fluid and potential upset conditions still need to be considered.

Independent testing and product-specific limits

Performance claims should be based on the relevant product construction and supporting test evidence. RAMCO® fabric shield materials have been assessed using independent laboratory methods, including Mullen burst testing to ASTM D3786 where applicable. RAMCO® Spray Control™ stainless steel shields have also been independently spray-tested by TREO in Germany at pressures up to 300 bar. Certain stainless steel constructions are additionally covered by DNV Type Approval for SOLAS applications.

These tests provide useful evidence, but they do not create a single universal rating for every shield, fluid or installation. The applicable product data sheet, certificate scope and operating conditions should be checked during specification.

Key distinction: flange class determines connection geometry and pressure-temperature capability. The shield's own suitability depends on its construction, test evidence and the real service conditions.

2. Temperature: Consider the Full Operating Cycle

Safety-shield materials have defined temperature limits. Selection should be based on the highest and lowest temperatures the shield may experience, not only the usual steady-state temperature shown on an operating screen.

Normal process temperature during stable operation.

Start-up, shutdown and cleaning temperatures.

Steam-out, heat tracing or nearby radiant heat.

Cold or cryogenic service, including embrittlement and condensation effects.

The temperature resistance of the complete construction, including fabric, window, thread, fasteners and closures.

Fabric shields can be suitable across a wide range of chemical applications, but the exact polymer and construction must remain within its stated limits. Stainless steel shields are commonly selected for high-temperature steam, hot oil and other mechanically demanding services. Even then, the complete assembly and installation method must be assessed rather than assuming that stainless steel alone makes the shield suitable for any temperature.

3. Chemical Compatibility: Assess the Actual Process Medium

Chemical compatibility is usually assessed against the process fluid, concentration and operating temperature. A current chemical-resistance chart should be used, supported by application-specific advice where mixtures, contamination or unusual conditions are involved.

Acids and caustics - select a polymer, thread and window construction compatible with the specific chemical and concentration.

Hydrofluoric acid - avoid shield constructions containing fibreglass where contact with HF is possible. RAMCO® PPL Spra-Gard™ is designed without fibreglass for this type of application.

Hydrocarbons, hot oils and fuels - consider temperature, fire risk, mist formation and the need for a robust metal construction.

Fluids that crystallise or leave deposits - RAMCO® Clear Teflon (ETFE) VUE-GARD™ shields allow early visual identification of leakage or residue build-up without removing the shield.

Neutral-pH fluids - pH-indicating patches may not change colour, so direct visibility through a clear shield can be more useful.

Matching the shield material to the piping material can be a useful initial reference, but it should not replace a proper compatibility assessment. The shield may contain several different materials, and all wetted or potentially exposed components need to remain suitable.

PTFE-Based or Stainless Steel: Which Construction Is Appropriate?

Construction	Often selected for	Points to check
PTFE / TFE-based fabric shields	Broad chemical resistance, acids, alkalis and general chemical processing	Temperature limit, UV exposure, closure materials, pressure evidence and whether visibility or drainage is required
Stainless steel shields	Steam, hot oils, fuels, offshore service and mechanically demanding installations	Grade, mesh or diffusion layer, clasp design, corrosion environment, drain arrangement and certificate scope
Transparent inspection shields	Applications where routine visual monitoring is required	Chemical and temperature suitability of the clear section, UV exposure and whether deposits may obscure visibility

Additional Selection Factors That Are Often Overlooked

Indoor, outdoor and offshore exposure

Outdoor shields may be exposed to ultraviolet light, weathering, salt and temperature cycling. TFE Spra-Gard™ contains a natural UV inhibitor and can provide a longer service life than less weather-resistant fabric constructions in exposed locations. Offshore and marine applications may additionally require corrosion-resistant materials and evidence aligned with the project specification or classification requirements.

Pedestrian areas and drains

Where flanges are located above walkways, access routes or working areas, controlling the direction of a release is especially important. A drain connection can channel collected liquid towards suitable containment and help reduce pooling or slip hazards. The drain route itself must be compatible with the process fluid and must not create a new exposure point.

Inspection and leak visibility

A shield should not hide developing leakage from operators. Transparent designs, inspection windows, drain indicators or compatible leak-detection coatings can help preserve visual inspection. This is particularly relevant where the process medium is neutral in pH, where a colour-changing pH patch would not activate, or where a crystallising fluid may leave a visible deposit.

Connection type and installation access

Flanges are not the only potential spray points. Valves, expansion joints, hoses, pump connections and threaded or socket-weld components may require different shield geometries. Clearance around the connection, nearby instruments, insulation and the ability to install or remove the shield safely should be considered before ordering.

Common Safety-Shield Selection Mistakes

Selecting by nominal pipe size without confirming flange class, outside diameter and connection geometry.

Treating the flange pressure class as though it were the shield's guaranteed pressure rating.

Checking the main shield material but overlooking thread, window, fastener or closure compatibility.

Using a pH-indicating feature for a neutral fluid without providing another means of visual inspection.

Ignoring outdoor UV exposure, salt atmosphere, wash-down chemicals or nearby heat sources.

Installing a shield without considering where a captured or redirected liquid will drain.

Assuming a safety shield prevents leakage rather than recognising it as a secondary consequence-control measure.

Safety-Shield Selection Checklist

Confirm	Information required
Connection	Type, nominal size, standard, flange class and outside dimensions
Process medium	Chemical name, concentration, phase and possible contaminants
Pressure	Normal operating pressure, maximum pressure and credible upset conditions
Temperature	Normal, minimum and maximum temperatures, including cleaning and start-up
Location	Indoor, outdoor, offshore, pedestrian area or restricted-access zone
Inspection	Need for clear visibility, indicator patch, leak-detection coating or drain
Certification	Customer specification, test evidence, DNV/SOLAS or other project requirements
Installation	Available clearance, orientation, insulation, obstructions and safe access

Frequently Asked Questions

How do I choose the correct flange-guard material?

Start with chemical compatibility, operating temperature and the characteristics of a possible release. Then consider pressure, flange geometry, location, inspection requirements and any applicable test or certification requirements.

Does flange pressure class determine which safety shield is required?

It determines the physical flange geometry and contributes to the operating envelope, but it does not determine suitability on its own. Actual pressure, temperature, fluid and shield construction must also be assessed.

What type of safety shield is generally used for steam?

Stainless steel shields are commonly selected for high-temperature steam because of their temperature resistance and mechanical durability. The selected construction should still be checked against the actual pressure, temperature and project specification.

Can PTFE safety shields be used outdoors?

Suitable TFE-based constructions can be used outdoors, but UV exposure, weathering, temperature cycling and expected service life should be considered. Product-specific outdoor suitability should be confirmed.

What shield should be used for hydrofluoric acid?

The complete shield construction must be compatible with HF, and fibreglass-containing constructions should be avoided where HF contact is possible. RAMCO® PPL Spra-Gard™ is a non-fibreglass option intended for this type of service.

When is a transparent safety shield useful?

It is useful where routine visual inspection is required, where leaking media may crystallise or stain, or where a neutral-pH fluid would not activate a pH indicator patch.

Should a flange guard include a drain?

A drain may be appropriate above walkways or where collected liquid needs to be directed to containment. The drain material, route and receiving system must be suitable for the process fluid.

Do safety shields prevent flange leaks?

No. They are secondary protective devices intended to help manage the consequences of leakage. Correct design, installation, gasket selection, inspection and maintenance remain the primary controls.

Summary

Correct safety-shield selection is application-specific. Pressure, temperature and chemical compatibility form the starting point, but flange geometry, environmental exposure, inspection needs, drainage and certification requirements can be equally important. The safest specification is based on the complete operating environment and supported by product-specific technical data and independent test evidence.

How to Select the Correct Safety Shield