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Installation and Maintenance Instructions for
Acid Leak Detection (ALD) Assemblies
1.0 INTRODUCTION
The Acid Leak Detection (ALD) assembly provides multiple
layers of safety when dealing with acid media. In addition to
a diaphragm seal to isolate the pressure sensing elements of
pressure gauge, it also provides a visual indication to leaking
process media, alerting operators to failed instrumentation.
The ALD paint turns bright red when exposed to media with a
pH ≤ 3.0.
2.0 SAFETY INFORMATION
To assure safe operation and maintenance procedures, read
and follow these instructions.
WARNING: Serious injury or equipment damage can result
from failure to properly install, maintain, or operate these components
• Follow all instructions in this document to avoid exposure to
pressurized fluid
• Use proper tools and safety equipment in installing or maintaining components
• Assure that process pressure and temperatures are properly
monitored and maintained, and the process fluid is appropriate and compatible with the wetted materials of the diaphragm system
• Follow all of your company’s safety procedures in the event
an acid leak is detected
3.0 PRODUCT OVERVIEW
Pressure Gauge
with the pressure instrument wetted materials.
The ALD product combines a pressure gauge and a diaphragm
seal into a single assembly, welded together at the socket. The
diaphragm seal, gauge socket, and portions of the gauge case
are coated with an acid-detecting material that turns red when
exposed to acid material.
4.0 ALD SPECIFICATIONS
Accuracy: ±1.0% of span (1259, 1279) or ±1.5% of span (T6500)
Process Connection Size: ½ NPT male or ASME Flanged
Case Style: Solid front with pressure relief back
Pointer: Micrometer, adjustable, aluminum
Weather Protection: Hermetically sealed: IP66
Diaphragm Seal Type: 510 Threaded or DF Flush Flanged
Wetted materials: 316L stainless steel, Monel, Hastelloy-C276
Window Material: Shatterproof glass, acrylic (OPT.)
Tamper Proof Design: Diaphragm seal welded to gauge socket
Pressure Rating (MAWP): Standard: Vac. to 1,500 psi @ 100°F
Optional: 1,500 to 10,000 psi @ 100°F
5.0 SAFETY INFORMATION
Users should become familiar with ASME B40.100 (Gauges
– Pressure Indicating Dial Type – Elastic Element) before specifying pressure measuring gauges. To prevent misapplication,
pressure gauges should be selected considering media and
ambient operating conditions. Improper application can be
detrimental to the gauge, causing failure and possible personal
injury, property damage or death. The information contained in
this I&M is offered as a guide in making the proper selection of
a pressure gauge. For detailed product selection information for
the ALD assembly, see the ALD-2 data sheet.
Acid Detecting Coating
Gauge Socket Welded to Seal
Diaphragm Seal
A diaphragm seal (isolator) is a device which is attached to the
inlet connection of a pressure instrument to isolate its measuring element from the process media. The space between the
diaphragm and the instrument’s pressure sensing element is
solidly filled with a suitable liquid. Displacement of the liquid fill
in the pressure element, through movement of the diaphragm,
transmits process pressure changes directly to a gauge, switch
or any other pressure instrument. When diaphragm seals are
used with pressure gauges, an additional 0.5% tolerance must
be added to the gauge accuracy because of the diaphragm
spring rate. Used in a variety of process applications where
corrosives, slurries or viscous fluids may be encountered, the
diaphragm seal affords protection to the instrument where dual
containment is needed or the process media is not compatible
5.1 SAFETY INFORMATION
The range of the instrument should be approximately twice the
maximum operating pressure. Too low a range may result in
(a) low fatigue life of the elastic element due to high operating
stress and (b) susceptibility to overpressure set due to pressure transients that exceed the normal operating pressure. Too
high a range may yield insufficient resolution for the application.
5.2 LOCATION
Whenever possible, gauges should be located to minimize
the effects of vibration, extreme ambient temperatures and
moisture. Dry locations away from very high thermal sources
(ovens, boilers etc.) are preferred. If the mechanical vibration
level is extreme, consider a pressure gauge with the PLUS!™
performance option.
5.3 GAUGE REUSE
ASME B40.100 recommends that gauges not be moved indiscriminately from one application to another. The cumulative
number of pressure cycles on an in-service or previously used
gauge is generally unknown, so it is generally safer to install
a new gauge whenever and wherever possible. This will also
minimize the possibility of a reaction with previous media.
6.0 ALD INSTALLATION
The ALD Acid Leak Detection Assembly should be installed
© Ashcroft Inc. 2018, 250 East Main Street, Stratford, CT 06614-5145, USA, Tel: 203-378-8281, Fax: 203-385-0357, www.ashcroft.com
All sales subject to standard terms and conditions of sale. I&M008-1026, 04/18
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Installation and Maintenance Instructions for
Ø 5.81
3.36
Ø 5.07
Ø 5.81
[147.6]
[85.3]
[128.9]
[235.4]
3.36
5.20
Ø 5.81
[147.6]
[85.3]
[132.1]
[235.4]
Ø 5.81
[147.6]
H2
H
HEIGHT
Ø D
Acid Leak Detection (ALD) Assemblies
according to the following instructions depending on whether
the threaded (510-type) or flanged (DF-type) seal was selected. It is recommended that the assembly be installed with an
isolation valve that will allow the instrument to be isolated from
the process in the event that the Acid Alert coating has indicated a pressure boundary failure.
6.1 THREADED SEALS
Torque should never be applied to the gauge case. Instead, an
open end or adjustable wrench should always be used on the
wrench flats of the diaphragm seal to tighten the assembly into
the fitting or pipe. NPT threads require the use of a suitable
thread sealant, such as pipe dope or PTFE tape, and must be
tightened securely to ensure a leak tight seal.
6.2 FLANGED SEALS
The following steps must be followed to ensure a leak-tight
connection between the mating flange and the flanged diaphragm seal supplied as part of the ALD assembly.
1. Select nuts, bolts, washers, gasket and thread lubricant in
accordance with process requirements and ASME PCC-12010
2. Center the gasket between the mating flange and dia-
phragm seal face, lining up the bolt pattern on each flange.
Ensure that the gasket does not cover the active surface of
the diaphragm
3. Thread nuts and washers onto one end of each bolt, and
insert through the bolt holes on the mating flange, passing up through the bolt holes on the diaphragm. Attach
nuts and washers to the opposite end of the bolt and finger-tighten
4. Refer to ASME PCC-1-2010 to determine the necessary
torque based on gasket material and bolt frictions. Using a
torque and a conventional wrench, tighten each bolt to 30%
of the target torque for the flange in a crisscross tightening
sequence. Next tighten to 70% using the same tightening
sequence, then finally 100% of the required torque. After at
least four hours, the bolts should be tightened one final time
to their required final torque value.
7.0 OPERATION AND REPLACEMENT
7.1 FREQUENCY OF INSPECTION
Inspection frequency is application-specific and depends upon
the severity of the service and how critical the accuracy of
the indicated pressure is. For example, a monthly inspection
frequency may be in order for severe service applications.
Annual inspections, or even less frequent schedules, are often
employed in non-critical applications.
7.2 IN-SERVICE INSPECTION
If the accuracy of the gauge cannot be checked in place, the
user can at least look for (a) erratic or random pointer motion;
(b) readings that are suspect – especially indications of pressure
when the user believes the true pressure is 0 psig. Any gauge
which is obviously not working or indicating erroneously, should
be immediately isolated from the process and removed from
service to avoid a possible pressure boundary failure.
7.3 FREQUENCY OF INSPECTION
In the event that exposure to acidic material triggers the Acid
Alert coating on the ALD assembly, the assembly should be
immediately isolated from the process and the source of the
exposure determined. Red ALD coating on the diaphragm
seal could point to a leak nearby, perhaps a loose threaded or
flanged joint or acidic mists or vapors in the atmosphere. In the
unlikely event of reddened Acid Alert coating inside the gauge
case, a serious failure of both the diaphragm and bourdon tube
could be at fault. In this scenario it is critical that the wetted
materials of the assembly be evaluated for compatibility before
it is replaced.
8.0 DIMENSIONAL INFORMATION
1259/510 Assembly
Ø 5.81
[147.6]
1279/510 Assembly
[147.6]
9.27
1
⁄2˝ NPT
Ø 2.26
[57.5]
1279 or 1259/DF Seal Assembly
9.27
3.74
[95]
1
⁄2˝ NPT
1279 or 1259/DF Seal Dimensions
SIZEDNPRESSURE
1˝
1½˝
2˝
CLASSES
150
300
150
300
150
300
Ø D H
4.33
[110]
4.92
[125]
4.92
[125]
6.10
[155]
5.91
[150
6.50
[165]
2.71
[68.8]
2.75
[69.8]
2.75
[69.8]
2.87
[72.9]
2.81
[71.3]
2.93
[74.5]
Ø 2.26
[57.5]
H2
HEIGHT
8.835
[224.4]
8.875
[225.4]
8.875
[225.4]
8.995
[228.5]
8.935
[223.95]
9.055
[230]
MIN
SPAN
1bar
14.5 psi
3.74
[95]
WEIGHT
lbs [kg]
3.3
[1.5]
4.4
[2.0]
4.6
[2.1]
7.7
[3.5]
66
[3.0]
88
[4.0]
9.0 STORAGE
Assemblies should be stored in a cool, dry area. Storage
temperature should not exceed 250°F (150°F for PLUS!
Performance) or drop below -40°F.
™
© Ashcroft Inc. 2018, 250 East Main Street, Stratford, CT 06614-5145, USA, Tel: 203-378-8281, Fax: 203-385-0357, www.ashcroft.com
All sales subject to standard terms and conditions of sale. I&M008-1026, 04/18
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