Pump and Valve Castings: How to Specify Pressure-Boundary Components

A pump or valve casting is not simply a shaped piece of metal.

It forms part of the pressure boundary.

That changes how the component should be specified, manufactured and inspected.

A specification that simply says:

“Ductile iron valve body”

or:

“WCB pump casing”

leaves too many unanswered questions.

What pressure and temperature must the component withstand?

What fluid will it contain?

Which flange standard applies?

Which surfaces must be machined?

What surface finish is required at the gasket interface?

Is hydrostatic testing mandatory?

Which casting zones require NDT?

Is weld repair permitted?

When these requirements are unclear, problems often appear later as:

• Leakage
• Premature corrosion
• Machining rework
• Gasket failure
• Dimensional mismatch
• Pressure-test rejection
• Field failure

For engineering and procurement teams, a good pump or valve casting specification should function as a measurable manufacturing contract.

It should define:

Material → Pressure class → Geometry → Machining → Sealing surfaces → Testing → NDT → Traceability

before tooling and production begin.

Why Pump and Valve Castings Need More Detailed Specifications

Pumps and valves combine several engineering requirements in one casting.

The component may need to:

• Contain pressure
• Resist mechanical load
• Resist corrosion
• Maintain sealing surfaces
• Support internal components
• Hold dimensional relationships
• Survive pressure and temperature cycling

A casting may pass basic dimensional inspection and still fail because of:

• Interconnected porosity
• Shrinkage in a pressure wall
• Poor flange-face finish
• Misaligned bores
• Inadequate material selection
• Improper repair
• Incomplete pressure testing

The casting drawing therefore needs to describe more than external geometry.

Step 1: Define the Fluid and Service Conditions

Material selection should begin with the actual process fluid.

Before selecting grey iron, ductile iron, carbon steel or stainless steel, define:

• Fluid chemistry
• Chloride content
• Sulphides where relevant
• Solids or abrasives
• Operating temperature
• Maximum temperature
• Normal pressure
• Maximum pressure
• Thermal cycling
• Water hammer or pressure shock
• External environment

Material suitability cannot be determined correctly from pressure alone.

For example, a casting that performs adequately in treated water may not be appropriate for:

• Seawater
• Aggressive chemicals
• High-temperature steam
• Hydrocarbon service

without different material, corrosion allowance, coating or specification requirements.

Step 2: Select the Correct Casting Material

The supplied source discusses four important pump and valve material families:

• Grey cast iron
• Ductile iron
• Carbon cast steel
• Austenitic stainless cast steel

Each solves a different service requirement.

Grey Cast Iron

The source uses examples including:

IS 210 FG260

and

ASTM A48 Class 40.

Grey iron offers useful characteristics such as:

• Good machinability
• Vibration damping
• Cost-efficient casting
• Dimensional stability

This can make it suitable for selected pump and valve applications where:

• Pressure is moderate
• Impact loading is limited
• The fluid is compatible with the material
• The design provides suitable safety margin

The principal limitation is lower ductility compared with ductile iron.

Applications involving severe impact or cyclic mechanical loading may therefore require another material.

Ductile Iron

Relevant examples in the source include:

IS 1865 SG 500/7

and

ASTM A536 65-45-12.

Ductile iron provides an improved combination of:

• Tensile strength
• Elongation
• Toughness
• Fatigue performance
• Castability
• Machinability

compared with conventional grey iron.

That can make it attractive for:

• Waterworks valves
• Pump casings
• Industrial fluid-control components

where greater mechanical resilience is required.

But the drawing should specify the exact material grade rather than simply stating:

“SG iron.”

Carbon Steel Castings

The source identifies:

ASTM A216 WCB

and an IS 1030 carbon-steel grade family as relevant examples.

Carbon steel is widely used where pump or valve bodies require combinations of:

• Strength
• Toughness
• Pressure containment
• Weldability

and suitable temperature capability.

Typical applications can include:

• Hydrocarbon systems
• Steam service
• Industrial process valves
• Pump casings
• Pressure-containing housings

depending on the governing equipment standard.

The material specification should be combined with the required:

• Heat treatment
• NDT
• Pressure testing
• Repair procedure

where applicable.

Stainless Steel Castings

The source also discusses CF8/CF8M-type stainless castings for corrosive fluid service.

These materials may be appropriate where corrosion resistance is a major design driver.

However, stainless casting capability should not be assumed to be a confirmed Technocast capability from this source alone.

For any RFQ involving CF8, CF8M or another stainless grade, buyers should first confirm the foundry’s current approved material capability.

Step 3: Define Pressure Class and Temperature Together

One of the most common specification errors is writing only:

PN16

or:

Class 300

without considering temperature or the applicable material group.

Pressure class is not simply a maximum pressure number that applies under every operating condition.

Allowable pressure can change with:

• Material
• Temperature
• Governing standard

The supplied source references standards such as:

• ASME B16.34
• ASME B16.1
• ASME B16.42

for different valve/flange applications.

The drawing or RFQ should therefore clearly identify:

Material + Pressure class + Design temperature + Governing standard

rather than leaving the supplier to infer them.

Steel Valve Applications

For relevant steel and stainless valve applications, ASME B16.34 is commonly used to establish pressure-temperature relationships according to material group and class.

The important engineering point is not the specific numerical rating quoted in a generic article.

It is that:

Class 150, 300, 600, etc. cannot be interpreted independently of material and temperature.

Cast Iron and Ductile Iron Flanged Systems

The source also references:

• ASME B16.1
• ASME B16.42

for relevant cast-iron and ductile-iron flange applications.

Again, use the applicable standard for the actual equipment design.

Do not copy a pressure rating from an unrelated material or flange family.

PN Systems

Metric systems may use PN designations.

The same principle applies:

PN rating + material + temperature must be considered together.

Step 4: Separate As-Cast and Machined Requirements

A pump or valve drawing should clearly distinguish between:

as-cast surfaces

and:

functional machined surfaces.

Critical machined regions can include:

• Flange faces
• Seat pockets
• Bearing bores
• Stem bores
• Shaft bores
• Gasket rails
• O-ring interfaces
• Bolt circles

The foundry needs adequate machining allowance to clean up these features after casting variation and distortion.

But adding excessive stock everywhere increases:

• Casting weight
• Machining time
• Tool wear
• Cost

The machining allowance should therefore follow the manufacturing process and actual functional requirement.

Step 5: Define Flange Facing

A statement such as:

“Machined flange face”

is incomplete.

The specification may need to identify:

• Raised face or flat face
• Applicable dimensional standard
• Surface finish
• Serration pattern
• Flatness/runout requirement

depending on the joint design.

The source highlights flange-facing geometry and sealing-surface finish as critical pump/valve specification items.

Why Flange Surface Finish Matters

Gasket performance depends partly on surface texture.

A surface that is too rough may create leakage paths.

A surface that is too smooth may also perform poorly with certain gasket designs because the gasket may not grip correctly.

The source cites a 3.2–6.3 µm Ra range as a common example for certain gasketed raised-face applications.

Treat that as an application example—not a universal Technocast specification.

The correct finish should follow:

• Flange standard
• Gasket supplier requirement
• OEM specification
• Fluid/service condition

Serration Pattern Can Matter

For some gasketed flange systems, the machining pattern is functionally important.

The drawing may therefore need to specify whether the required finish is:

• Concentric
• Phonographic/spiral
• Another approved pattern

according to the joint design.

This is more meaningful than providing only a generic roughness value.

Step 6: Control Critical Dimensional Features

Pump and valve castings may contain multiple functional interfaces.

These can include:

• Impeller bores
• Shaft positions
• Bearing locations
• Seat pockets
• Stem bores
• Flange faces
• Bolt circles

General casting tolerances should not be applied blindly to these features.

Instead, define:

General as-cast tolerance

separately from:

Final machined CTQ dimensions.

Fits such as H7/H8 may be used for certain machined bores where the design requires them, but the exact fit must come from the equipment design.

Step 7: Specify Pressure Testing Clearly

Writing:

“Hydrotest required”

is not a complete specification.

A production pressure-test requirement should define:

• Test standard
• Test medium
• Test pressure
• Hold time
• Acceptance criteria
• Gauge/instrument requirements
• Traceability

The source specifically recommends making testing mandatory and measurable rather than leaving it to unspecified “standard practice.”

Valve Hydrostatic Testing

The source references API 598 for relevant valve testing.

It cites examples such as:

• Shell test around 1.5× applicable cold rating
• Seat testing at a lower multiplier according to method

for relevant API 598 test conditions.

These should not be copied automatically into every pump or valve drawing.

The actual test requirement should follow the governing valve standard and OEM specification.

Pump Casing Pressure Testing

The source also references ANSI/HI guidance for pump-casing testing.

Again, the important sourcing principle is:

Define the actual test requirement contractually.

Do not allow:

“Pressure tested according to our normal procedure.”

to replace an agreed test specification.

Pressure-Test Documentation

For production components, the test report may need to identify:

• Part number
• Heat or lot number
• Serial number where applicable
• Test pressure
• Hold duration
• Test medium
• Gauge/instrument ID
• Result
• Inspector

This allows the test result to remain connected to the physical component.

Step 8: Select NDT According to Risk

A common specification mistake is either:

no NDT requirement

or:

require every NDT method everywhere.

Neither is good engineering.

Inspection should target the actual failure risk.

Visual Inspection

Visual inspection remains the first line of defence for obvious surface defects and finishing problems.

Magnetic Particle Testing

For suitable ferromagnetic castings, MT/MPI may be appropriate for surface and near-surface discontinuities.

Potential areas include:

• Fillets
• Pressure transitions
• Machined regions
• Repair locations

where specified.

Dye Penetrant Testing

PT/DPI can detect surface-breaking indications.

It may be appropriate for:

• Machined sealing surfaces
• Stainless/non-magnetic materials
• Specific repaired or critical regions

depending on specification.

The source recommends DPI for particular surface-critical areas.

However, in-house dye penetrant capability should not automatically be presented as a confirmed Technocast capability unless documented internally.

Ultrasonic Testing

For appropriate thick ferrous sections, UT may be used to evaluate internal discontinuities.

Technocast’s established capability information includes UT.

The coverage and acceptance criteria should still be specified by component risk.

Radiographic Testing

Radiography can be useful when internal porosity or shrinkage needs to be evaluated in pressure-sensitive sections.

The source recommends RT for selected applications.

But RT should not be described as a confirmed in-house Technocast capability based solely on this draft.

Where required, confirm:

• Availability
• In-house vs external execution
• Technician qualification
• Acceptance standard

during RFQ qualification.

Step 9: Match the Moulding Process to the Casting

Pump and valve castings vary significantly in:

• Size
• Wall thickness
• Core complexity
• Volume
• Dimensional requirement

The moulding route should therefore be selected for the component rather than from one fixed company process.

The source focuses particularly on shell moulding and no-bake moulding.

Shell Moulding

Shell moulding can offer advantages such as:

• Better surface finish
• Improved repeatability
• Reduced as-cast variation
• Potentially lower machining stock

for suitable medium-sized components.

It can therefore be attractive for repeatable pump or valve parts where geometry fits the process.

No-Bake Moulding

No-bake moulding is well suited to:

• Larger pump casings
• Large valve bodies
• Complex core packages
• Heavy sections
• Lower/medium-volume programs

where mould flexibility is more important than achieving the finest as-cast surface.

Pump Volutes Need Core Control

A pump volute is a good example of why core capability matters.

The internal flow geometry affects hydraulic performance.

Core variation can influence:

• Passage geometry
• Wall thickness
• Machining stock
• Flow path consistency

The RFQ should therefore include sufficient information about:

• Internal geometry
• Core complexity
• Minimum wall
• Machining requirement

for the foundry to evaluate the process correctly.

Step 10: Prevent Porosity and Shrinkage Before Inspection

NDT can find defects.

It does not prevent them.

Defect prevention begins with:

• Gating
• Feeding
• Risering
• Melt quality
• Core control
• Section transitions

The source identifies gas porosity/inclusions and shrinkage cavities as recurring pump/valve casting concerns.

Porosity

Porosity can become particularly serious when it connects:

• Internal fluid cavity

to:

• External casting surface.

A casting may appear acceptable until machining exposes the defect.

This is why pressure-casting DFM should identify high-risk areas before tooling.

Shrinkage

Thick pressure sections and abrupt section transitions can create shrinkage risk.

Feeding strategy needs to be designed around those hot spots.

Simply increasing every wall thickness can sometimes make the problem worse.

Step 11: Define Weld-Repair Rules

Steel casting repairs may be permitted under controlled conditions depending on the component specification.

But the RFQ should clearly state whether weld repair is:

• Allowed
• Restricted
• Requires customer approval
• Prohibited

and what qualification is required.

Repair requirements may need to address:

• Procedure qualification
• Preheat
• Filler material
• Post-weld treatment
• NDT
• Documentation

Do not allow weld repair to become an undocumented supplier decision.

Step 12: Require Material Traceability

A pressure-boundary component should be traceable to relevant production records.

Depending on program requirements, traceability may include:

• Heat number
• Chemistry result
• Mechanical testing
• Heat-treatment record
• NDT report
• Pressure-test report
• Final dimensional inspection

Traceability is especially important when investigating a production or field issue.

Supplier Qualification for Pump and Valve Castings

Before approving a casting supplier, evaluate the complete system.

Material Control

Can the supplier produce and document the required material grade?

Metallurgy

Can chemistry be linked to production heats?

Foundry Engineering

Can the team explain:

• Gating
• Feeding
• Riser strategy
• Pressure-wall risk
• Machining allowance?

Moulding

Is the selected process appropriate for:

• Casting size
• Volume
• Geometry
• Core complexity?

Machining

Can the required:

• Flange faces
• Bores
• Seats
• Datums

be produced consistently?

Inspection

Does the supplier have access to the required:

• Dimensional inspection
• UT
• Other NDT

according to the specification?

Pressure Testing

Where required, can the supplier execute or coordinate the specified test with traceable records?

Quality System

Verify the supplier’s current:

• ISO 9001 certification
• Scope
• Calibration
• Non-conformance system
• Corrective-action process
• Traceability

rather than relying only on a certificate copy.

Technocast Foundry for Pump and Valve Casting Programs

For pump and valve programs, the most useful foundry relationship is one that combines foundry engineering with machining and quality control.

Technocast’s established capabilities relevant to this sector include:

• Grey iron
• Ductile iron
• Carbon steel
• Shell moulding
• No-bake moulding
• Heat treatment
• CNC machining
• Spectrometry
• CMM inspection
• Ultrasonic testing

For an individual pump or valve program, the exact manufacturing route should be selected according to:

• Material
• Component size
• Pressure boundary
• Wall thickness
• Core complexity
• Production volume
• Machining content
• Inspection requirement

For additional materials such as CF8/CF8M stainless steel, or inspection/testing methods such as radiography, dye penetrant testing or in-house hydrostatic testing, confirm Technocast’s current capability before including those claims in the commercial offer or website content.

Pump and Valve Casting RFQ Checklist

A strong RFQ should include the following.

Material

Specify:

• Exact grade
• Standard
• Heat-treatment condition
• Corrosion allowance where applicable

Fluid

Identify:

• Fluid type
• Chemistry
• Solids
• Corrosive constituents

where relevant.

Pressure and Temperature

Define:

• Operating pressure
• Design pressure
• Operating temperature
• Design temperature
• Pressure class or PN
• Governing standard

Casting Geometry

Provide:

• Controlled drawing
• 3D model where available
• Wall thickness
• Internal core geometry

Machining

Identify:

• Flange faces
• Bores
• Seats
• Bolt circles
• Datums
• Machining allowance

Sealing Surfaces

Define:

• Facing type
• Surface finish
• Flatness
• Runout
• Serration pattern

where applicable.

Pressure Testing

Specify:

• Test standard
• Test pressure
• Test medium
• Hold time
• Acceptance

NDT

Define:

• Method
• Inspection zones
• Sampling
• Acceptance criteria

Weld Repair

State explicitly whether repair is:

• Permitted
• Restricted
• Approval-controlled
• Prohibited

Traceability

Define required heat/lot or serial-level documentation.

Conclusion

A reliable pump or valve casting specification should remove ambiguity before production starts.

The drawing should not simply tell the foundry:

what shape to cast.

It should define:

what material the pressure boundary must be

what pressure and temperature it must withstand

which surfaces control sealing

what must be machined

how integrity will be tested

which defects are acceptable

how the result will be documented

The strongest specifications therefore connect:

Material + Pressure class + Temperature + Casting design + Machining + Surface finish + NDT + Pressure testing + Traceability

That gives engineering, procurement and the foundry the same measurable definition of an acceptable component.

Request a Pump or Valve Casting Technical Review

For a new or re-sourced pump or valve component, send Technocast:

• Component drawing
• 3D model where available
• Material grade
• Fluid/service information
• Design pressure and temperature
• Single-piece weight
• Annual volume
• Machining requirements
• NDT requirement
• Pressure-test specification

The component can then be reviewed for material feasibility, moulding route, casting DFM, machining and quality requirements before tooling release.

Frequently Asked Questions

Which material is best for pump and valve castings?

There is no universal best material. Grey iron, ductile iron, carbon steel and stainless cast materials serve different pressure, temperature, corrosion and mechanical requirements.

When should ductile iron be used instead of grey iron?

Ductile iron can be preferable when greater strength, toughness, impact resistance or fatigue performance is required.

Why is ASTM A216 WCB commonly used for valve bodies?

WCB is a recognised carbon cast-steel grade used in many pressure-containing applications. Final suitability depends on the applicable pressure-temperature and equipment standard.

Why does flange surface finish matter?

The gasket interacts directly with the machined flange face. Surface roughness and machining pattern can influence gasket seating and leakage behaviour.

Does every pump or valve casting require radiography?

No. NDT should be selected according to material, geometry, criticality and the applicable customer or equipment specification.

Should hydrostatic testing be stated on the drawing?

Where required, yes. The specification should clearly identify the test method, pressure, hold time and acceptance criteria rather than leaving testing to unspecified supplier practice.

What is the difference between shell moulding and no-bake for pump and valve castings?

Shell moulding can offer better repeatability and surface finish for suitable components. No-bake provides flexibility for larger castings and complex core packages such as large pump volutes.

What should I send for a pump or valve casting quotation?

Provide the drawing, material grade, pressure and temperature requirement, fluid information, component weight, annual volume, machining details, NDT and pressure-test requirements.